JP2012182114A - Nonaqueous electrolyte, and nonaqueous electrolyte secondary battery containing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte for a secondary battery and a nonaqueous electrolyte secondary battery, which have excellent discharge characteristics at low temperature and/or cycle characteristics.SOLUTION: A nonaqueous electrolyte is used for a nonaqueous electrolyte secondary battery including: negative and positive electrodes capable of absorbing and desorbing metal ions; and a nonaqueous electrolyte. The nonaqueous electrolyte includes hexafluoro phosphate and a compound which has no aliphatic substituent having an unsaturated bond and has an Si-Si bond, and further includes at least one selected from the group consisting of fluoro phosphate other than the hexafluoro phosphate, fluoro sulfonate and an imide salt.

Description

  The present invention relates to a non-aqueous electrolyte and a non-aqueous electrolyte secondary battery using the same, and more specifically, a non-aqueous electrolyte for a lithium secondary battery containing a specific component and the same. The present invention relates to a lithium secondary battery.

Along with the downsizing of electronic equipment due to the rapid development of modern industry, there has been a strong demand for higher capacity of secondary batteries. Therefore, lithium secondary batteries having higher energy density than nickel / cadmium batteries and nickel / hydrogen batteries have been developed, and up to now, efforts to improve the performance have been repeated.
In recent years, against the background of global issues such as environmental issues and energy issues, great expectations have been placed on the application of lithium secondary batteries to large-scale power sources such as in-vehicle power sources and stationary power sources. However, since such a battery is generally expected to be used in an environment exposed to the outside air, in the development, battery characteristics under a low temperature environment such as below freezing point, particularly low temperature discharge characteristics are regarded as important. In addition to this, a life performance higher than that of a conventional lithium secondary battery is required for its use.

Components constituting the lithium secondary battery are mainly classified into a positive electrode, a negative electrode, a separator, and an electrolytic solution. Of these, electrolytes generally include electrolytes such as LiPF ₆ , LiBF ₄ , LiClO ₄ , LiCF ₃ SO ₃ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiCF ₃ (CF ₂ ) ₃ SO ₃ , Cyclic carbonates such as ethylene carbonate and propylene carbonate, chain carbonates such as dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate; cyclic esters such as γ-butyrolactone and γ-valerolactone; chain esters such as methyl acetate and methyl propionate A non-aqueous electrolyte solution dissolved in a non-aqueous solvent such as a liquid is used.

As one of the efforts for improving the low temperature discharge characteristics of the lithium secondary battery, an attempt is made to suppress reaction resistance in the system in a low temperature discharge state by adding a specific compound to the electrolyte solution.
Patent Document 1 reports that the low-temperature discharge capacity can be improved by adding a silicone-based antifoaming agent to the electrolytic solution.

Patent Document 2 and Patent Document 3 report that adding a phosphazene derivative to the electrolytic solution suppresses the interface resistance of the electrolytic solution and improves the low-temperature discharge characteristics.
Patent Documents 4 to 6 report that the low-temperature discharge characteristics can be improved by using a technique of adding a predetermined phosphoric acid compound to the electrolytic solution.
Patent Documents 7 to 9 report that internal resistance at a low temperature can be suppressed by using a technique of adding a silicon compound having an unsaturated bond to an electrolytic solution.

On the other hand, in Patent Document 10, by using a negative electrode mainly composed of Si, Sn or the like, an ethylene carbonate derivative and a predetermined Si-containing compound are added to the electrolytic solution, thereby suppressing the swelling of the battery and improving the cycle life. Has been reported.
Patent Document 11 and Patent Document 12 introduce a technique of adding hexamethyldisilane as an additive for the purpose of reducing the irreversible capacity at the negative electrode and suppressing the decomposition reaction of the electrolytic solution at the negative electrode. Examples of salts other than lithium hexafluorophosphate include lithium bis (trifluoromethanesulfonyl) imide.

JP 11-185804 A JP 2001-217006 A JP 2002-83628 A JP 2007-141830 A JP 2007-165292 A JP 2010-62164 A JP 2002-134169 A JP 2003-173816 A JP 2003-323915 A US Open 2010-159336 JP 2010-116475 A JP 2010-9940 A

  As described above, various efforts for improving low-temperature discharge characteristics have been studied, but it is not yet sufficient to achieve sufficient battery characteristics, and further improvements are required.

Patent Documents 7 to 9 report techniques for adding a compound containing a predetermined Si—Si bond to an electrolytic solution, thereby improving low-temperature characteristics.
The techniques described in Patent Documents 7 to 9 use a silane compound having an unsaturated bond that easily undergoes self-polymerization to form a stable film by performing a polymerization reaction at the electrode interface at the initial stage of the cycle. It is said that the increase in resistance can be suppressed.

However, when a compound that is easy to self-polymerize is used, the coating film is stabilized, but an excessive coating film is formed, which may be a cause of high resistance.
Patent Document 10 reports a technique for adding a predetermined Si-containing compound to an electrolyte solution. This technique is limited to a negative electrode mainly composed of Si, Sn, or the like, and further provides cycle characteristics. It has been shown not to be excellent.

Further, Patent Document 11 and Patent Document 12 introduce a technique of adding hexamethyldisilane for the purpose of forming a film on the negative electrode surface, but here, it is only introduced as an example of many additives. However, there has been no specific verification of the effect.
Further, Patent Document 11 and Patent Document 12 mention lithium bis (trifluoromethanesulfonyl) imide as a salt other than lithium hexafluorophosphate, but these are introduced only as an example of many lithium salts. However, there is no specific verification about the effect, and furthermore, there is no specific description regarding a technique for combining hexamethyldisilane and lithium bis (trifluoromethanesulfonyl) imide.

Further, according to Patent Document 11 and Patent Document 12, although the effect obtained by adding hexamethyldisilane to the electrolytic solution is said to be reduction of irreversible capacity and suppression of decomposition reaction of the electrolytic solution at the negative electrode. However, it has not been known how it affects the low-temperature discharge characteristics and the cycle characteristics.
This invention is made | formed in view of this background art, and is providing the nonaqueous electrolyte solution for secondary batteries excellent in the low temperature discharge characteristic and / or cycling characteristics, and a secondary battery using the same.

  The present inventors pay attention to a substituent having a relatively low self-polymerizability, and increase the degree of polymerization of the film by using a compound having an Si—Si bond having no aliphatic substituent having an unsaturated bond. Without reducing internal resistance at low temperatures, improving the low-temperature characteristics of the battery, and also using a combination of certain other compounds to greatly improve the low-temperature discharge characteristics and / or cycle characteristics. The present invention has been reached.

That is, the present invention provides the following non-aqueous electrolyte solution.
A non-aqueous electrolyte solution used in a non-aqueous electrolyte secondary battery comprising a negative electrode and a positive electrode capable of occluding and releasing metal ions, and a non-aqueous electrolyte solution, wherein the non-aqueous electrolyte solution is hexafluorophosphate, And a compound having a Si—Si bond having no unsaturated substituent having an unsaturated bond, and further comprising a fluorophosphate other than the hexafluorophosphate, a fluorosulfonate, and an imide salt A non-aqueous electrolyte containing at least one selected from the above.

  The present invention also provides a non-aqueous electrolyte secondary battery comprising a carbon-based negative electrode and positive electrode capable of occluding and releasing metal ions, and a non-aqueous electrolyte, wherein the non-aqueous electrolyte is the non-aqueous electrolyte. The present invention provides a non-aqueous electrolyte secondary battery.

  According to the present invention, it is possible to provide a non-aqueous electrolyte solution that is particularly excellent in low-temperature discharge characteristics and / or cycle characteristics, and a non-aqueous electrolyte secondary battery using the same.

Hereinafter, embodiments of the present invention will be described in detail. However, the description of the constituent elements described below is an example (representative example) of an embodiment of the present invention, and is not specified in these contents. Various modifications can be made within the scope of the gist.
<1-0. Estimation mechanism of effect of the present invention>
The present invention adds a hexafluorophosphate and a compound having an Si—Si bond not having an aliphatic substituent having an unsaturated bond to a non-aqueous electrolyte solution as in Example 1 or 2 described later. Further, by adding at least one compound selected from the group consisting of monofluorophosphate, difluorophosphate, fluorosulfonate, and imide salt, the effect of suppressing the internal resistance of both batteries is synergistic. This is thought to be due to the fact that they acted more effectively than the simple addition.

  The reason for this is that the compound having an Si—Si bond having no unsaturated substituent having an unsaturated bond forms a low-resistance film on the negative electrode, while monofluorophosphate, difluorophosphate, At least one compound selected from the group consisting of a fluorosulfonate and an imide salt has an effect of suppressing the resistance of the positive electrode, but a part of the former negative electrode film diffuses to the positive electrode side. It is presumed that the resistance suppression effect was enhanced.

<1-1. Electrolyte>
There is no restriction | limiting in the electrolyte used for the non-aqueous electrolyte of this invention, The well-known thing used as an electrolyte can be arbitrarily employ | adopted and contained in the target non-aqueous electrolyte secondary battery. When the non-aqueous electrolyte solution of the present invention is used in a non-aqueous electrolyte secondary battery, the electrolyte is preferably a lithium salt.

As a specific example of the electrolyte, for example,
Inorganic lithium salts such as LiClO ₄ , LiAsF ₆ , LiPF ₆ , Li ₂ CO ₃ , LiBF ₄ ;
LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiC (CF ₃ SO ₂ ) ₃ , LiPF ₄ (CF ₃ ) ₂ , LiPF ₄ (C
_{2 F 5) 2, LiPF 4} (CF 3 SO 2) 2, LiPF 4 (C 2 F 5 SO 2) 2, LiBF 3 (CF 3), LiBF 3 (C 2 F 5), LiBF 2 (CF 3) ₂ , fluorine-containing organolithium salts such as LiBF ₂ (C ₂ F ₅ ) ₂ , LiBF ₂ (CF ₃ SO ₂ ) ₂ , LiBF ₂ (C ₂ F ₅ SO ₂ ) ₂ ; lithium bis (oxalato) borate, lithium difluoro Dicarboxylic acid complex lithium salts such as (oxalato) borate, lithium tris (oxalato) phosphate, lithium difluorobis (oxalato) phosphate, lithium tetrafluoro (oxalato) phosphate;
Sodium salts or potassium salts such as KPF ₆ , NaPF ₆ , NaBF ₄ , CF ₃ SO ₃ Na;

Of these, LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , L
iN (C ₂ F ₅ SO ₂ ) ₂ or lithium bis (oxalato) borate is preferred, and LiPF ₆ or LiBF ₄ is particularly preferred.
One type of electrolyte may be used alone, or two or more types of electrolytes may be used in any combination and ratio. In particular, when two types of specific inorganic lithium salts are used in combination, or when inorganic lithium salts and fluorine-containing organic lithium salts are used in combination, gas generation during continuous charging is suppressed, or deterioration after high-temperature storage is suppressed. Therefore, it is preferable.

In particular, the combination and the LiPF ₆ and LiBF _4, and an inorganic lithium salt such as _{LiPF 6, LiBF 4, LiCF 3} SO 3, LiN (CF 3 SO 2) 2, LiN (C 2 F 5 SO 2) _2, etc. It is preferable to use in combination with a fluorine-containing organic lithium salt.
Furthermore, when LiPF ₆ and LiBF ₄ are used in combination, it is preferable that LiBF ₄ is contained at a ratio of usually 0.01% by mass or more and usually 20% by mass or less with respect to the entire electrolyte. LiBF ₄ has a low degree of dissociation, and if the ratio is too high, the resistance of the non-aqueous electrolyte may be increased.

On the other hand, when inorganic lithium salts such as LiPF ₆ and LiBF ₄ are used in combination with fluorine-containing organic lithium salts such as LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , and LiN (C ₂ F ₅ SO ₂ ) ₂ The proportion of the inorganic lithium salt in the entire lithium salt is preferably in the range of usually 70% by mass or more and usually 99% by mass or less. In general, fluorine-containing organic lithium salts have a higher molecular weight than inorganic lithium salts. If the ratio is too high, the ratio of the non-aqueous solvent in the entire non-aqueous electrolyte may decrease and the resistance of the non-aqueous electrolyte may increase. .

  Further, the concentration of the lithium salt in the final composition of the non-aqueous electrolyte of the present invention is arbitrary as long as the effects of the present invention are not significantly impaired, but usually 0.5 mol / L or more, preferably 0.6 mol / L L or more, more preferably 0.8 mol / L or more, and usually 3 mol / L or less, preferably 2 mol / L or less, more preferably 1.5 mol / L or less. If this concentration is too low, the electrical conductivity of the non-aqueous electrolyte may be insufficient. If the concentration is too high, the electrical conductivity will decrease due to an increase in viscosity, and the non-aqueous electrolyte of the present invention will be used. The performance of the existing non-aqueous electrolyte secondary battery may deteriorate.

In particular, when the non-aqueous solvent of the non-aqueous electrolyte is mainly composed of a carbonate compound such as alkylene carbonate or dialkyl carbonate, LiPF ₆ may be used alone, but when used together with LiBF ₄ , capacity deterioration due to continuous charging is suppressed. This is preferable. When these are used in combination, the molar ratio of LiBF _{4 to} LiPF ₆ is usually 0.005 or more, preferably 0.01 or more, particularly preferably 0.05 or more, and usually 0.4 or less, preferably 0.2. It is as follows. If this molar ratio is too large, battery characteristics after high-temperature storage tend to be reduced. Conversely, if it is too small, it is difficult to obtain the effect of suppressing gas generation and capacity deterioration during continuous charging.
When the non-aqueous solvent of the non-aqueous electrolyte contains 50% by volume or more of a cyclic carboxylic acid ester compound such as γ-butyrolactone or γ-valerolactone, LiBF ₄ accounts for 50 mol% or more of the entire lithium salt. It is preferable.

<1-2. Non-aqueous solvent>
The non-aqueous solvent contained in the non-aqueous electrolyte of the present invention is not particularly limited as long as it does not adversely affect the battery characteristics when it is used as a battery, but among the solvents used in the following non-aqueous electrolytes It is preferable that it is 1 or more types of these.
Examples of commonly used non-aqueous solvents include linear and cyclic carbonates, linear and cyclic carboxylic acid esters, linear and cyclic ethers, phosphorus-containing organic solvents, sulfur-containing organic solvents, and the like.
Moreover, there is no restriction | limiting in the kind of chain carbonate, As an example of what is used normally, a dialkyl carbonate is preferable, and carbon number of the alkyl group to comprise is preferable 1-5 respectively, Most preferably, it is 1-4. .

Specific examples include dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl-n-propyl carbonate, ethyl-n-propyl carbonate, di-n-propyl carbonate and the like.
Among these, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate are preferable in terms of industrial availability and various characteristics in the non-aqueous electrolyte secondary battery.

There is no restriction | limiting in the kind of cyclic carbonate, As for what is normally used, 2-6 are preferable, as for carbon number of the alkylene group which comprises a cyclic carbonate, Most preferably, it is 2-4.
Specific examples include ethylene carbonate, propylene carbonate, butylene carbonate (2-ethylethylene carbonate, cis and trans 2,3-dimethylethylene carbonate) and the like.

Among these, ethylene carbonate or propylene carbonate is preferable in that various characteristics in the non-aqueous electrolyte secondary battery are good.
Further, the type of chain carboxylic acid ester is not limited, and examples of commonly used ones include methyl acetate, ethyl acetate, acetic acid-n-propyl, acetic acid-i-propyl, acetic acid-n-butyl, acetic acid-i. -Butyl, acetate-t-butyl, methyl propionate, ethyl propionate, propionate-n-propyl, propionate-i-propyl, propionate-n-butyl, propionate-i-butyl, propionate-t- Examples include butyl.

Among these, methyl acetate, ethyl acetate, methyl propionate, or ethyl propionate are preferable in terms of industrial availability and various characteristics in nonaqueous electrolyte secondary batteries.
Also, the type of cyclic carboxylic acid ester is not limited, but examples of commonly used ones include γ-butyrolactone, γ-valerolactone, δ-valerolactone, and the like.
Among these, γ-butyrolactone is preferable in terms of industrial availability and various characteristics in the non-aqueous electrolyte secondary battery.

Furthermore, although the kind of chain ether is not limited, examples of those usually used include dimethoxymethane, dimethoxyethane, diethoxymethane, diethoxyethane, ethoxymethoxymethane, and ethoxymethoxyethane.
Among these, dimethoxyethane or diethoxyethane is preferable in terms of industrial availability and various characteristics in the non-aqueous electrolyte secondary battery.

Moreover, although there is no restriction | limiting in the kind of cyclic ether, Tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran etc. are mentioned as an example of what is used normally.
Furthermore, the type of the phosphorus-containing organic solvent is not particularly limited, but examples of commonly used organic solvents include phosphate esters such as trimethyl phosphate, triethyl phosphate, and triphenyl phosphate;
Phosphites such as trimethyl phosphite, triethyl phosphite, triphenyl phosphite;
Phosphine oxides such as trimethylphosphine oxide, triethylphosphine oxide, triphenylphosphine oxide;
Etc.

  Further, the kind of the sulfur-containing organic solvent is not particularly limited. Examples of those usually used include ethylene sulfite, 1,3-propane sultone, 1,4-butane sultone, methyl methanesulfonate, busulfan, and sulfolane. , Sulfolene, dimethylsulfone, diphenylsulfone, methylphenylsulfone, dibutyldisulfide, dicyclohexyldisulfide, tetramethylthiuram monosulfide, N, N-dimethylmethanesulfonamide, N, N-diethylmethanesulfonamide and the like.

  Among these, chain and cyclic carbonates or chain and cyclic carboxylic acid esters are preferable in terms of various characteristics in the non-aqueous electrolyte secondary battery, and among them, ethylene carbonate, propylene carbonate, dimethyl carbonate, More preferred are ethyl methyl carbonate, diethyl carbonate, ethyl acetate, methyl propionate, ethyl propionate, and γ-butyrolactone, ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl acetate, methyl propionate, γ- Butyrolactone is more preferred.

These may be used alone or in combination of two or more, but it is preferable to use two or more compounds in combination. For example, it is preferable to use a high dielectric constant solvent of cyclic carbonates in combination with a low viscosity solvent such as chain carbonates or chain esters.
One preferred combination of non-aqueous solvents is a combination mainly composed of cyclic carbonates and chain carbonates. Among them, the total of the cyclic carbonates and the chain carbonates in the entire non-aqueous solvent is 80% by volume or more, preferably 85% by volume or more, more preferably 90% by volume or more, and the cyclic carbonates and the chain carbonates. The cyclic carbonates have a capacity of 5% or more, preferably 10% by volume or more, more preferably 15% or more, and usually 50% or less, preferably 35% or less, more preferably 30% or less. belongs to. Use of a combination of these non-aqueous solvents is preferable because the balance between cycle characteristics and high-temperature storage characteristics (particularly, remaining capacity and high-load discharge capacity after high-temperature storage) of a battery produced using the non-aqueous solvent is improved.

  Specific examples of preferred combinations of cyclic carbonates and chain carbonates include ethylene carbonate and dimethyl carbonate, ethylene carbonate and diethyl carbonate, ethylene carbonate and ethyl methyl carbonate, ethylene carbonate and dimethyl carbonate and diethyl carbonate, ethylene carbonate and dimethyl carbonate And ethyl methyl carbonate, ethylene carbonate, diethyl carbonate, and ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

A combination in which propylene carbonate is further added to the combination of these ethylene carbonates and chain carbonates is also a preferable combination. In the case of containing propylene carbonate, the volume ratio of ethylene carbonate to propylene carbonate is preferably 99: 1 to 40:60, particularly preferably 95: 5 to 50:50. Furthermore, the amount of propylene carbonate in the whole non-aqueous solvent is 0.1% by volume or more, preferably 1% by volume, more preferably 2% by volume or more, usually 10% by volume or less, preferably 8% by volume or less, more preferably Is preferably 5% by volume or less because the charge / discharge load characteristics are further excellent while maintaining the combined characteristics of ethylene carbonate and chain carbonates.

  Among these, those containing asymmetric chain carbonates are more preferable, particularly ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, ethylene carbonate, diethyl carbonate and ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl. Those containing ethylene carbonate such as methyl carbonate, symmetric chain carbonates and asymmetric chain carbonates, or further containing propylene carbonate are preferred because the balance between cycle characteristics and charge / discharge load characteristics is good. Among these, those in which the asymmetric chain carbonate is ethyl methyl carbonate are preferable, and the alkyl group constituting the dialkyl carbonate preferably has 1 to 2 carbon atoms.

  Another example of a preferable mixed solvent is one containing a chain ester. In particular, those containing a chain ester in the mixed solvent of cyclic carbonates and chain carbonates are preferable from the viewpoint of improving charge / discharge load characteristics of the battery. Examples of the chain esters include ethyl acetate and methyl propionate. Is particularly preferred. The capacity of the chain ester in the non-aqueous solvent is usually 5% or more, preferably 8% or more, more preferably 15% or more, usually 50% or less, preferably 35% or less, more preferably 30% or less, More preferably, it is 25% or less.

  Examples of other preferable non-aqueous solvents include one organic solvent selected from the group consisting of ethylene carbonate, propylene carbonate and butylene carbonate, γ-butyrolactone and γ-valerolactone, or two or more selected from the group A mixed solvent composed of an organic solvent occupies 60% by volume or more of the whole. Such a mixed solvent preferably has a flash point of 50 ° C. or higher, and particularly preferably 70 ° C. or higher. A non-aqueous electrolyte using this solvent reduces evaporation of the solvent and leakage even when used at high temperatures. Among them, the total of ethylene carbonate and γ-butyrolactone in the non-aqueous solvent is 80% by volume or more, preferably 90% by volume or more, and the volume ratio of ethylene carbonate and γ-butyrolactone is 5:95 to 45: Or the total of ethylene carbonate and propylene carbonate is 80% by volume or more, preferably 90% by volume or more, and the volume ratio of ethylene carbonate to propylene carbonate is 30:70 to 80:20 In general, the balance between cycle characteristics and charge / discharge load characteristics is improved.

<1-3. Specific Si Compound>
The “compound having an Si—Si bond not having an aliphatic substituent having an unsaturated bond” (hereinafter sometimes referred to as “specific Si compound”) used in the present invention may be one kind or two kinds. Any of the above combinations may be used. Hereinafter, the “specific Si compound” in the present invention will be described more specifically.

  The “specific Si compound” in the present invention is not particularly limited as long as it is a compound having an Si—Si bond not having an aliphatic substituent having an unsaturated bond, but industrial availability and solubility in an electrolytic solution. From the viewpoint, the compound represented by the following general formula (1) is preferable.

(A ^{1 to} A ⁶ may be the same or different, and may have a hydrogen atom, a halogen atom, or a hetero atom, and may have a C 1-10 hydrocarbon group or substituent. Represents a silicic acid group of 1 to 10, and A ^{1 to} A ⁶ may be bonded to each other to form a ring, provided that A ^{1 to} A ⁶ are all aliphatic substituents having an unsaturated bond. Absent.)
Among them, A ^{1 to} A ⁶ are preferably a hydrocarbon group having 1 to 10 carbon atoms or a hydrogen atom, and particularly preferably a hydrocarbon group having 1 to 10 carbon atoms. Examples of the hydrocarbon group having 1 to 10 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-propyl group, a t-butyl group, a phenyl group, and a hydrogen atom. It is preferably a methyl group, an ethyl group, a phenyl group, or a hydrogen atom.

Further, in the present invention, the specific compound having a Si—Si bond does not have an aliphatic substituent having an unsaturated bond because the high-resistance film formed by the self-polymerization of the aliphatic substituent is “ This is to prevent the effect of suppressing the internal resistance of the battery by the “specific Si compound” from being impaired.
Preferable specific examples of the “specific Si compound” include (a) to (p), and the like (a), (b), (e), (g), (i) to (k), (n ) Is more preferable, and (a), (e), (
j), (k), (n) are more preferred, (a) hexamethyldisilane, (e) hexaethyldisilane, (j) 1,2-diphenyltetramethyldisilane, (k) 1,1,2,2 -Tetraphenyldisilane is most preferred.

The reason why the above compound is preferable is that the manufacturing cost of the electrolytic solution can be suppressed due to industrial availability and the “specific Si compound” is easily dissolved in the non-aqueous electrolytic solution. The effect that the internal resistance of the battery is suppressed is more effectively exhibited by the formed high-quality film.
When the “specific Si compound” in the present invention is blended in the electrolytic solution, the blending amount of the “specific Si compound” is arbitrary as long as the effects of the present invention are not significantly impaired, but the lower limit relative to the whole non-aqueous electrolytic solution. The value is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and the upper limit is preferably 10% by mass or less, more preferably 5% by mass or less, and still more preferably 2% by mass. % Or less, most preferably 1% by mass or less. Within the above range, the effect of the “specific Si compound” can be sufficiently obtained, but it is particularly excellent in terms of inhibiting an unnecessary reaction.

<1-4. At least one compound selected from the group consisting of monofluorophosphate, difluorophosphate, fluorosulfonate, and imide salt>
In the present invention, “at least one compound selected from the group consisting of monofluorophosphate, difluorophosphate, fluorosulfonate, and imide salt” (hereinafter sometimes referred to as “specific salt”) is used. 1 type may be used or 2 or more types of arbitrary combinations may be sufficient. Hereinafter, the “specific salt” in the present invention will be described more specifically.

Examples of the monofluorophosphate include lithium monofluorophosphate, sodium monofluorophosphate, potassium monofluorophosphate, magnesium monofluorophosphate, calcium monofluorophosphate, and the like. Examples of the difluorophosphate include difluorophosphate. Examples include lithium, sodium difluorophosphate, potassium difluorophosphate, magnesium difluorophosphate, calcium difluorophosphate, etc., and examples of fluorosulfonate include lithium fluorosulfonate, sodium fluorosulfonate, potassium fluorosulfonate, magnesium fluorosulfonate , Calcium fluorosulfonate, and the like. Examples of imide salts include LiN (FSO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , and LiN (C ₂ F ₅ S
O ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), and the like. Among these, more preferable compounds include lithium monofluorophosphate, lithium difluorophosphate, lithium fluorosulfonate, LiN (FSO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ S
O ₂ ) _{2 and the} like are listed, and are shown below as Chemical Formula 1 to Chemical Formula 6. Among these, chemical formulas 2 to 5 are particularly preferable. This is because they have a high solubility in the non-aqueous electrolyte, and thus the effect of a specific salt can be more effectively exhibited. In addition, by using a salt containing lithium ions as a cation, in a battery such as a lithium ion secondary battery, a reaction in which lithium ions are inserted into and removed from a carbon material generally used as a negative electrode can proceed reversibly. Therefore, there is an advantage that the battery has no particular adverse effect.

  When the “specific salt” in the present invention is blended in the electrolytic solution, the blending amount of the “specific salt” is arbitrary as long as the effects of the present invention are not significantly impaired. Preferably it is 0.01 mass% or more, Preferably it is 0.1 mass% or more, and is 20 mass% or less normally, Preferably it is 10 mass% or less. Within the above range, the effect of the “specific salt” can be sufficiently obtained, but it is particularly excellent in terms of inhibiting an unnecessary reaction.

<1-4. Additives>
The nonaqueous electrolytic solution of the present invention may contain various additives as long as the effects of the present invention are not significantly impaired. In the case where the preparation process is performed by adding an additive, a conventionally known one can be arbitrarily used. In addition, an additive may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

  Examples of the additive include an overcharge inhibitor and an auxiliary agent for improving capacity maintenance characteristics and cycle characteristics after high-temperature storage. Among these, carbonates having at least one of an unsaturated bond and a halogen atom as an aid for improving capacity retention characteristics and cycle characteristics after high-temperature storage (hereinafter sometimes abbreviated as “specific carbonate”) Is preferably added. Hereinafter, the specific carbonate and other additives will be described separately.

<1-4-1. Specific carbonate>
The specific carbonate is a carbonate having at least one of an unsaturated bond and a halogen atom. However, the specific carbonate may have only an unsaturated bond, may have only a halogen atom, and is unsaturated. It may have both a bond and a halogen atom.
There is no restriction | limiting in particular in the molecular weight of a specific carbonate, Although it is arbitrary unless the effect of this invention is impaired remarkably, Usually, 50 or more, Preferably it is 80 or more, Usually, 250 or less, Preferably it is 150 or less. If the molecular weight is too large, the solubility of the specific carbonate in the non-aqueous electrolyte solution is lowered, and the effect may not be sufficiently exhibited.

Moreover, there is no restriction | limiting in particular also in the manufacturing method of a specific carbonate, It is possible to select and manufacture a well-known method arbitrarily.
In addition, the specific carbonate may be included alone in the nonaqueous electrolytic solution of the present invention, or two or more may be combined in any combination and ratio.
Moreover, there is no restriction | limiting in the compounding quantity of the specific carbonate with respect to the non-aqueous electrolyte solution of this invention, Although it is arbitrary unless the effect of this invention is impaired remarkably, Usually 0.01 mass with respect to the non-aqueous electrolyte solution of this invention. %, Preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and usually 70% by mass or less, preferably 50% by mass or less, more preferably 40% by mass or less. Is desirable.

  Below the lower limit of this range, when the non-aqueous electrolyte solution of the present invention is used in a non-aqueous electrolyte secondary battery, the non-aqueous electrolyte secondary battery is less likely to exhibit a sufficient cycle characteristic improving effect. There is. In addition, if the ratio of the specific carbonate is too large, when the non-aqueous electrolyte solution of the present invention is used in a non-aqueous electrolyte secondary battery, the high-temperature storage characteristics and continuous charge characteristics of the non-aqueous electrolyte secondary battery deteriorate. In particular, there are cases where the amount of gas generated increases and the capacity retention rate decreases.

(1-4-1-1. Unsaturated carbonate)
Among the specific carbonates according to the present invention, as a carbonate having an unsaturated bond (hereinafter sometimes abbreviated as “unsaturated carbonate”), a carbon-carbon such as a carbon-carbon double bond or a carbon-carbon triple bond is used. There is no other limitation as long as it is a carbonate having an unsaturated bond, and any unsaturated carbonate can be used. In addition, the carbonate which has an aromatic ring shall also be contained in the carbonate which has an unsaturated bond.

Examples of unsaturated carbonates include vinylene carbonate derivatives, ethylene carbonate derivatives substituted with a substituent having an aromatic ring or a carbon-carbon unsaturated bond, phenyl carbonates, vinyl carbonates, allyl carbonates, and the like. .
Specific examples of the vinylene carbonate derivatives include vinylene carbonate, methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, phenyl vinylene carbonate, 4,5-diphenyl vinylene carbonate, catechol carbonate, and the like.

Specific examples of the ethylene carbonate derivatives substituted with a substituent having an aromatic ring or a carbon-carbon unsaturated bond include vinyl ethylene carbonate, 4,5-divinyl ethylene carbonate, phenyl ethylene carbonate, 4,5-diphenyl ethylene carbonate. Etc.
Specific examples of phenyl carbonates include diphenyl carbonate, ethyl phenyl carbonate, methyl phenyl carbonate, t-butyl phenyl carbonate, and the like.

Specific examples of vinyl carbonates include divinyl carbonate and methyl vinyl carbonate.
Specific examples of allyl carbonates include diallyl carbonate and allyl methyl carbonate.
Among these unsaturated carbonates, as the specific carbonate, vinylene carbonate derivatives, ethylene derivatives substituted with a substituent having an aromatic ring or a carbon-carbon unsaturated bond are preferable, and in particular, vinylene carbonate, 4,5- Diphenyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, and vinyl ethylene carbonate are more preferably used because they form a stable interface protective film.

(1-4-1-2. Halogenated carbonate)
Among the specific carbonates, the carbonate having a halogen atom (hereinafter sometimes abbreviated as “halogenated carbonate”) is not particularly limited as long as it has a halogen atom, and any halogenated carbonate may be used. Can be used.
Specific examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Among these, a fluorine atom or a chlorine atom is preferable, and a fluorine atom is particularly preferable. The number of halogen atoms contained in the halogenated carbonate is not particularly limited as long as it is 1 or more, but is usually 6 or less, preferably 4 or less. When the halogenated carbonate has a plurality of halogen atoms, they may be the same as or different from each other.

Examples of halogenated carbonates include ethylene carbonate derivatives, dimethyl carbonate derivatives, ethyl methyl carbonate derivatives, diethyl carbonate derivatives and the like.
Specific examples of the ethylene carbonate derivatives include fluoroethylene carbonate, chloroethylene carbonate, 4,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4,4-dichloroethylene carbonate, 4,5-dichloroethylene carbonate, 4- Fluoro-4-methylethylene carbonate, 4-chloro-4-methylethylene carbonate, 4,5-difluoro-4-methylethylene carbonate, 4,5-dichloro-4-methylethylene carbonate, 4-fluoro-5-methylethylene Carbonate, 4-chloro-5-methylethylene carbonate, 4,4-difluoro-5-methylethylene carbonate, 4,4-dichloro-5-methylethylene carbonate, 4- (fluoromethyl) Ethylene carbonate, 4- (chloromethyl) -ethylene carbonate, 4- (difluoromethyl) -ethylene carbonate, 4- (dichloromethyl) -ethylene carbonate, 4- (trifluoromethyl) -ethylene carbonate, 4- (trichloromethyl) -Ethylene carbonate, 4- (fluoromethyl) -4-fluoroethylene carbonate, 4- (chloromethyl) -4-chloroethylene carbonate, 4- (fluoromethyl) -5-fluoroethylene carbonate, 4- (chloromethyl)- 5-chloroethylene carbonate, 4-fluoro-4,5-dimethylethylene carbonate, 4-chloro-4,5-dimethylethylene carbonate, 4,5-difluoro-4,5-dimethylethylene carbonate, 4,5-dichloro- 4, - dimethyl carbonate, 4,4-difluoro-5,5-dimethylethylene carbonate, 4,4-dichloro-5,5-dimethylethylene carbonate.

  Specific examples of dimethyl carbonate derivatives include fluoromethyl methyl carbonate, difluoromethyl methyl carbonate, trifluoromethyl methyl carbonate, bis (fluoromethyl) carbonate, bis (difluoro) methyl carbonate, bis (trifluoro) methyl carbonate, chloromethyl Examples thereof include methyl carbonate, dichloromethyl methyl carbonate, trichloromethyl methyl carbonate, bis (chloromethyl) carbonate, bis (dichloro) methyl carbonate, and bis (trichloro) methyl carbonate.

  Specific examples of the ethyl methyl carbonate derivatives include 2-fluoroethyl methyl carbonate, ethyl fluoromethyl carbonate, 2,2-difluoroethyl methyl carbonate, 2-fluoroethyl fluoromethyl carbonate, ethyl difluoromethyl carbonate, 2,2,2 -Trifluoroethyl methyl carbonate, 2,2-difluoroethyl fluoromethyl carbonate, 2-fluoroethyl difluoromethyl carbonate, ethyl trifluoromethyl carbonate, 2-chloroethyl methyl carbonate, ethyl chloromethyl carbonate, 2,2-dichloroethyl methyl Carbonate, 2-chloroethyl chloromethyl carbonate, ethyl dichloromethyl carbonate, 2,2,2-trichloroethyl methyl carbonate , 2,2-dichloroethyl chloromethyl carbonate, 2-chloroethyl dichloromethyl carbonate, ethyl trichloromethyl carbonate.

Specific examples of the diethyl carbonate derivatives include ethyl- (2-fluoroethyl) carbonate, ethyl- (2,2-difluoroethyl) carbonate, bis (2-fluoroethyl) carbonate, ethyl- (2,2,2- Trifluoroethyl) carbonate, 2,2-difluoroethyl-2′-fluoroethyl carbonate, bis (2,2-difluoroethyl) carbonate, 2,2,2-trifluoroethyl-2′-fluoroethyl carbonate, 2, 2,2-trifluoroethyl-2 ′, 2′-difluoroethyl carbonate, bis (2,2,2-trifluoroethyl) carbonate, ethyl- (2-chloroethyl) carbonate, ethyl- (2,2-dichloroethyl) ) Carbonate, bis (2-chloroethyl) carbonate, ethyl- ( 2,2,2-trichloroethyl) carbonate, 2,2-dichloroethyl-2'-chloroethyl carbonate, bis (2,2-dichloroethyl) carbonate, 2,2,2-trichloroethyl-2'-chloroethyl Examples include carbonate, 2,2,2-trichloroethyl-2 ′, 2′-dichloroethyl carbonate, bis (2,2,2-trichloroethyl) carbonate, and the like.

  Among these halogenated carbonates, carbonates having fluorine atoms are preferred, ethylene carbonate derivatives having fluorine atoms are more preferred, and in particular, fluoroethylene carbonate, 4- (fluoromethyl) -ethylene carbonate, 4,4-difluoroethylene carbonate. 4,5-difluoroethylene carbonate is more preferably used because it forms an interface protective film.

(1-4-1-3. Halogenated unsaturated carbonate)
Furthermore, as the specific carbonate, a carbonate having both an unsaturated bond and a halogen atom (this is appropriately abbreviated as “halogenated unsaturated carbonate”) can also be used. There is no restriction | limiting in particular as a halogenated unsaturated carbonate, As long as the effect of this invention is not impaired remarkably, arbitrary halogenated unsaturated carbonates can be used.

Examples of the halogenated unsaturated carbonate include vinylene carbonate derivatives, ethylene carbonate derivatives substituted with a substituent having an aromatic ring or a carbon-carbon unsaturated bond, and allyl carbonates.
Specific examples of the vinylene carbonate derivatives include fluorovinylene, 4-fluoro-5-methylvinylene carbonate, 4-fluoro-5-phenylvinylene carbonate, 4- (trifluoromethyl) vinylene carbonate, chlorovinylene carbonate, 4-chloro Examples include -5-methyl vinylene carbonate, 4-chloro-5-phenyl vinylene carbonate, and 4- (trichloromethyl) vinylene carbonate.

  Specific examples of the ethylene carbonate derivatives substituted with a substituent having an aromatic ring or a carbon-carbon unsaturated bond include 4-fluoro-4-vinylethylene carbonate, 4-fluoro-5-vinylethylene carbonate, 4,4 -Difluoro-4-vinylethylene carbonate, 4,5-difluoro-4-vinylethylene carbonate, 4-chloro-5-vinylethylene carbonate, 4,4-dichloro-4-vinylethylene carbonate, 4,5-dichloro-4 -Vinylethylene carbonate, 4-fluoro-4,5-divinylethylene carbonate, 4,5-difluoro-4,5-divinylethylene carbonate, 4-chloro-4,5-divinylethylene carbonate, 4,5-dichloro-4 , 5-Divinylethylene carbonate, 4-full B-4-phenylethylene carbonate, 4-fluoro-5-phenylethylene carbonate, 4,4-difluoro-5-phenylethylene carbonate, 4,5-difluoro-4-phenylethylene carbonate, 4-chloro-4-phenylethylene Carbonate, 4-chloro-5-phenylethylene carbonate, 4,4-dichloro-5-phenylethylene carbonate, 4,5-dichloro-4-phenylethylene carbonate, 4,5-difluoro-4,5-diphenylethylene carbonate, Examples include 4,5-dichloro-4,5-diphenylethylene carbonate.

  Specific examples of phenyl carbonates include fluoromethyl phenyl carbonate, 2-fluoroethyl phenyl carbonate, 2,2-difluoroethyl phenyl carbonate, 2,2,2-trifluoroethyl phenyl carbonate, chloromethyl phenyl carbonate, 2-chloro Examples include ethyl phenyl carbonate, 2,2-dichloroethyl phenyl carbonate, 2,2,2-trichloroethyl phenyl carbonate, and the like.

  Specific examples of vinyl carbonates include fluoromethyl vinyl carbonate, 2-fluoroethyl vinyl carbonate, 2,2-difluoroethyl vinyl carbonate, 2,2,2-trifluoroethyl vinyl carbonate, chloromethyl vinyl carbonate, 2-chloro Examples include ethyl vinyl carbonate, 2,2-dichloroethyl vinyl carbonate, 2,2,2-trichloroethyl vinyl carbonate, and the like.

Specific examples of allyl carbonates include fluoromethyl allyl carbonate, 2-fluoroethyl allyl carbonate, 2,2-difluoroethyl allyl carbonate, 2,2,2-trifluoroethyl allyl carbonate, chloromethyl allyl carbonate,
Examples include 2-chloroethyl allyl carbonate, 2,2-dichloroethyl allyl carbonate, 2,2,2-trichloroethyl allyl carbonate, and the like.
Among the examples of the halogenated unsaturated carbonates described above, the specific carbonate is highly effective when used alone, vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, 4,5-difluoroethylene carbonate, and derivatives thereof. It is particularly preferable to use one or more selected from the group consisting of:

<1-4-2. Other additives>
Hereinafter, additives other than the specific carbonate will be described. Examples of additives other than the specific carbonate include overcharge inhibitors, auxiliary agents for improving capacity maintenance characteristics and cycle characteristics after high-temperature storage, and the like.

<1-4-2-1. Overcharge prevention agent>
Specific examples of the overcharge inhibitor include toluene derivatives such as toluene and xylene; biphenyl derivatives unsubstituted or substituted with alkyl groups such as biphenyl, 2-methylbiphenyl and 3-methylbiphenyl 4-methylbiphenyl; o- A terphenyl derivative which is unsubstituted or substituted with an alkyl group, such as terphenyl, m-terphenyl and p-terphenyl;
Partially hydrogenated terphenyl derivatives unsubstituted or substituted with alkyl groups; cycloalkylbenzene derivatives such as cyclopentylbenzene and cyclohexylbenzene; directly bonded to benzene rings such as cumene, 1,3-diisopropylbenzene, 1,4-diisopropylbenzene Alkylbenzene derivatives having tertiary carbons; alkylbenzene derivatives having quaternary carbons directly bonded to the benzene ring such as t-butylbenzene, t-amylbenzene and t-hexylbenzene; having oxygen atoms such as diphenyl ether and dibenzofuran Aromatic compounds; and the like.

In addition, these overcharge inhibitors may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations. Moreover, when using together by arbitrary combinations, the compound of the same classification illustrated above may be used together, and you may use together by a compound of a different classification | category.
Specific examples of a combination of different classes of compounds include toluene derivatives and biphenyl derivatives; toluene derivatives and terphenyl derivatives; toluene derivatives and terphenyl derivatives partially hydrides; toluene derivatives and cycloalkylbenzene derivatives; Alkylbenzene derivatives having tertiary carbon directly bonded to benzene ring; Toluene derivatives and alkylbenzene derivatives having quaternary carbon directly bonded to benzene ring; Toluene derivatives and aromatic compounds having oxygen atom; Biphenyl derivatives and terphenyl derivatives Partial hydrides of biphenyl derivatives and terphenyl derivatives; biphenyl derivatives and cycloalkylbenzene derivatives; biphenyl derivatives and alkylbenzene derivatives having a tertiary carbon directly bonded to the benzene ring; biphenyl derivatives Benzene derivative and alkylbenzene derivative having quaternary carbon directly bonded to benzene ring; biphenyl derivative and aromatic compound having oxygen atom; terphenyl derivative and partial hydride of terphenyl derivative; terphenyl derivative and cycloalkylbenzene derivative; terphenyl derivative Benzene derivative having a tertiary carbon directly bonded to the benzene ring; a terphenyl derivative and an alkylbenzene derivative having a quaternary carbon directly bonded to the benzene ring; a terphenyl derivative and an aromatic compound having an oxygen atom; Partial hydride and cycloalkylbenzene derivative; Partial hydride of terphenyl derivative and alkylbenzene derivative having tertiary carbon directly bonded to benzene ring; Partial hydride of terphenyl derivative and directly bonded to benzene ring Aromatic compound having a partial hydride and oxygen atoms of terphenyl derivatives; alkylbenzene derivative having a quaternary carbon;

A cycloalkylbenzene derivative and an alkylbenzene derivative having a tertiary carbon directly bonded to the benzene ring; a cycloalkylbenzene derivative and an alkylbenzene derivative having a quaternary carbon directly bonded to the benzene ring; a cycloalkylbenzene derivative and an aromatic compound having an oxygen atom; An alkylbenzene derivative having a tertiary carbon directly bonded to the benzene ring and an alkylbenzene derivative having a quaternary carbon directly bonded to the benzene ring; an alkylbenzene derivative having a tertiary carbon directly bonded to the benzene ring and an aromatic having an oxygen atom Group compounds; alkylbenzene derivatives having a quaternary carbon directly bonded to the benzene ring, and aromatic compounds having an oxygen atom.

  Specific examples of these include a combination of biphenyl and o-terphenyl, a combination of biphenyl and m-terphenyl, a combination of biphenyl and a partial hydride of a terphenyl derivative, a combination of biphenyl and cumene, A combination of cyclopentylbenzene, a combination of biphenyl and cyclohexylbenzene, a combination of biphenyl and t-butylbenzene, a combination of biphenyl and t-amylbenzene, a combination of biphenyl and diphenyl ether, a combination of biphenyl and dibenzofuran, o- Combination of terphenyl and partial hydride of terphenyl derivative, combination of o-terphenyl and cumene, combination of o-terphenyl and cyclopentylbenzene, combination of o-terphenyl and cyclohexylbenzene, o-terphenyl Combination of t-butylbenzene, combination of o-terphenyl and t-amylbenzene, combination of o-terphenyl and diphenyl ether, combination of o-terphenyl and dibenzofuran, m-terphenyl and terphenyl derivatives Combination with partial hydride, combination of m-terphenyl and cumene, combination of m-terphenyl and cyclopentylbenzene, combination of m-terphenyl and cyclohexylbenzene, combination of m-terphenyl and t-butylbenzene Combinations, combinations of m-terphenyl and t-amylbenzene, combinations of m-terphenyl and diphenyl ether, combinations of m-terphenyl and dibenzofuran, combinations of partial hydrides of terphenyl derivatives and cumene, terphenyl Partial hydrides of derivatives and cyclopentylben Combinations of terphenyl derivatives, partial hydrides and cyclohexylbenzene, terphenyl derivatives, partial hydrides and t-butylbenzene, terphenyl derivatives, partial hydrides and t-amylbenzene , A combination of a partial hydride of a terphenyl derivative and diphenyl ether, a combination of a partial hydride of a terphenyl derivative and dibenzofuran, a combination of cumene and cyclopentylbenzene, a combination of cumene and cyclohexylbenzene, a cumene and t-butylbenzene A combination of cumene and t-amylbenzene, a combination of cumene and diphenyl ether, a combination of cumene and dibenzofuran, a combination of cyclohexylbenzene and t-butylbenzene, and a combination of cyclohexylbenzene and t-amylbenzene. Combinations, combinations of cyclohexylbenzene and diphenyl ether, combinations of cyclohexylbenzene and dibenzofuran, combinations of t-butylbenzene and t-amylbenzene, combinations of t-butylbenzene and diphenylether, combinations of t-butylbenzene and dibenzofuran , A combination of t-amylbenzene and diphenyl ether, a combination of t-amylbenzene and dibenzofuran, a combination of diphenyl ether and dibenzofuran, and the like.

When the non-aqueous electrolyte solution of the present invention contains an overcharge inhibitor, the concentration thereof is arbitrary as long as the effects of the present invention are not significantly impaired. 5
It is desirable to make it into the range below mass%.
If the non-aqueous electrolyte of the present invention contains an overcharge inhibitor within a range that does not significantly impair the effects of the present invention, the overcharge protection circuit such as an incorrect usage or an abnormality of the charging device should operate normally. Even if the battery is overcharged due to the situation, it is preferable because the safety of the non-aqueous electrolyte secondary battery is improved.

<1-4-2-2. Auxiliary>
As a specific example of an auxiliary agent for improving capacity maintenance characteristics and cycle characteristics after high temperature storage,
Dicarboxylic acid anhydrides such as succinic acid, maleic acid and phthalic acid;
Carbonate compounds other than those corresponding to specific carbonates such as erythritan carbonate and spirobisdimethylene carbonate;
Ethylene sulfite, 1,3-propane sultone, 1,4-butane sultone, methyl methanesulfonate, busulfan, sulfolane, sulfolene, dimethyl sulfone, diphenyl sulfone, methylphenyl sulfone, dibutyl disulfide, dicyclohexyl disulfide, tetramethylthiuram monosulfide Sulfur-containing compounds such as id, N, N-dimethylmethanesulfonamide, N, N-diethylmethanesulfonamide;
Nitrogen-containing compounds such as 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone, N-methylsuccinimide;
Hydrocarbon compounds such as heptane, octane, cycloheptane;
Etc.

[2. Non-aqueous electrolyte secondary battery]
The non-aqueous electrolyte secondary battery of the present invention comprises a negative electrode and a positive electrode capable of occluding and releasing ions, and the non-aqueous electrolyte of the present invention.
<2-1. Battery configuration>
The non-aqueous electrolyte secondary battery of the present invention is the same as the conventionally known non-aqueous electrolyte secondary battery except for the negative electrode and the non-aqueous electrolyte, and usually the non-aqueous electrolyte of the present invention is A positive electrode and a negative electrode are laminated via an impregnated porous film (separator), and these are housed in a case (exterior body). Therefore, the shape of the non-aqueous electrolyte secondary battery of the present invention is not particularly limited, and may be any of a cylindrical shape, a square shape, a laminate shape, a coin shape, a large size, and the like.

<2-2. Non-aqueous electrolyte>
As the non-aqueous electrolyte, the above-described non-aqueous electrolyte of the present invention is used. In addition, in the range which does not deviate from the meaning of this invention, it is also possible to mix | blend and use other nonaqueous electrolyte solutions with respect to the nonaqueous electrolyte solution of this invention.
<2-3. Negative electrode>
The negative electrode active material used for the negative electrode is described below.
The negative electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions. Specific examples thereof include carbonaceous materials, alloy-based materials, lithium-containing metal composite oxide materials, and the like.

<2-3-1. Carbonaceous material>
As a carbonaceous material used as a negative electrode active material,
(2-3-1-1) natural graphite,
(2-3-1-2) a carbonaceous material obtained by heat-treating an artificial carbonaceous material and an artificial graphite material at least once in the range of 400 to 3200 ° C.,
(2-3-1-3) a carbonaceous material in which the negative electrode active material layer is composed of at least two types of carbonaceous materials having different crystallinity and / or has an interface in contact with the different crystalline carbonaceous materials,
(2-3-1-4) a carbonaceous material in which the negative electrode active material layer is composed of carbonaceous materials having at least two or more different orientations and / or has an interface in contact with the carbonaceous materials having different orientations,
Is preferably a good balance between initial irreversible capacity and high current density charge / discharge characteristics.
Moreover, the carbonaceous materials (2-3-1-1) to (2-3-1-4) may be used alone or in combination of two or more in any combination and ratio. Good.

  Specific examples of the artificial carbonaceous material and the artificial graphite material of (2-3-1-2) include natural graphite, coal-based coke, petroleum-based coke, coal-based pitch, petroleum-based pitch, or these pitches. Oxidized, needle coke, pitch coke and carbon materials partially graphitized from these, pyrolytic products of organic materials such as furnace black, acetylene black, pitch-based carbon fibers, carbonizable organic materials, and carbides thereof, Alternatively, a solution in which an organic substance that can be carbonized is dissolved in a low molecular organic solvent such as benzene, toluene, xylene, quinoline, n-hexane, and these carbides can be used.

  Specific examples of the above carbonizable organic substances include coal tar pitch from soft pitch to hard pitch, or heavy coal-based oil such as dry distillation liquefied oil, normal pressure residual oil, reduced pressure residual DC. Heavy oils such as ethylene tar produced as a by-product during pyrolysis of heavy oils such as heavy oil, crude oil, naphtha, etc., and aromatic hydrocarbons such as acenaphthylene, decacyclene, anthracene, phenanthrene, and nitrogen atom-containing complexes such as phenazine and acridine Cyclic compounds, heterocyclic compounds containing sulfur atoms such as thiophene and bithiophene, polyphenylenes such as biphenyl and terphenyl, polyvinyl chloride, polyvinyl alcohol, polyvinyl butyral, insolubilized products of these, nitrogen-containing polyacrylonitrile Organic polymers such as polypyrrole, organic polymers such as sulfur-containing polythiophene and polystyrene Natural polymers such as polysaccharides such as saccharose, cellulose, lignin, mannan, polygalacturonic acid, chitosan, saccharose, thermoplastic resins such as polyphenylene sulfide and polyphenylene oxide, furfuryl alcohol resin, phenol-formaldehyde resin, imide Examples thereof include thermosetting resins such as resins.

<2-3-2. Configuration, physical properties, preparation method of carbonaceous negative electrode>
Regarding the properties of the carbonaceous material, the negative electrode containing the carbonaceous material, the electrode-forming method, the current collector, and the non-aqueous electrolyte secondary battery, (2-3-2-1) to (2- It is desirable that one or more of 3-2-18) is satisfied at the same time.

(2-3-2-1) X-ray parameters
The d value (interlayer distance) of the lattice plane (002 plane) determined by X-ray diffraction by the Gakushin method of carbonaceous materials is usually 0.335 to 0.340 nm, particularly 0.335 to 0.338 nm, especially What is 0.335-0.337 nm is preferable. The crystallite size (Lc) determined by X-ray diffraction by the Gakushin method is usually 1.0 nm or more, preferably 1.5 nm or more, and particularly preferably 2 nm or more.

  The graphite surface coated with amorphous carbon is preferably graphite having a d-value of 0.335 to 0.338 nm on the lattice plane (002 plane) in X-ray diffraction as a core material. A carbonaceous material having a larger d-value on the lattice plane (002 plane) in X-ray diffraction than the core material is attached, and the d-value on the lattice plane (002 plane) in X-ray diffraction is greater than that of the core material and the core material. The ratio with respect to the carbonaceous material having a large is 99/1 to 80/20 by weight. When this is used, a negative electrode having a high capacity and hardly reacting with the electrolytic solution can be produced.

(2-3-2-2) Ash
The ash contained in the carbonaceous material is preferably 1% by mass or less, more preferably 0.5% by mass or less, particularly preferably 0.1% by mass or less, and the lower limit is 1 ppm or more with respect to the total mass of the carbonaceous material. It is preferable. When the weight ratio of ash exceeds the above range, deterioration of battery performance due to reaction with the non-aqueous electrolyte during charge / discharge may not be negligible. On the other hand, if it falls below the above range, the production requires a lot of time, energy and equipment for preventing contamination, which may increase the cost.
1.

(2-3-2-2-3) Volume-based average particle diameter
The volume-based average particle diameter of the carbonaceous material is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and further preferably 7 μm or more. Is usually 100 μm or less, preferably 50 μm or less, more preferably 40 μm or less, still more preferably 30 μm or less, and particularly preferably 25 μm or less. If the volume-based average particle size is below the above range, the irreversible capacity may increase, leading to loss of initial battery capacity. On the other hand, when the above range is exceeded, when an electrode is produced by coating, an uneven coating surface tends to be formed, which may be undesirable in the battery production process.

  The volume-based average particle size is measured by dispersing carbon powder in a 0.2% by weight aqueous solution (about 10 mL) of polyoxyethylene (20) sorbitan monolaurate, which is a surfactant, and laser diffraction / scattering particle size distribution. This is carried out using a meter (LA-700 manufactured by Horiba, Ltd.). The median diameter determined by the measurement is defined as the volume-based average particle diameter of the carbonaceous material of the present invention.

(2-3-2-2-4) Raman R value, Raman half width
As for the Raman R value of the carbonaceous material, a value measured by using an argon ion laser Raman spectrum method is usually 0.01 or more, preferably 0.03 or more, more preferably 0.1 or more, and usually 1 0.5 or less, preferably 1.2 or less, more preferably 1 or less, and particularly preferably 0.5 or less.

  When the Raman R value is below the above range, the crystallinity of the particle surface becomes too high, and there are cases where the number of sites where Li enters between layers decreases with charge / discharge. That is, charge acceptance may be reduced. In addition, when the negative electrode is densified by applying it to the current collector and then pressing it, the crystals are likely to be oriented in a direction parallel to the electrode plate, which may lead to a decrease in load characteristics. On the other hand, if it exceeds the above range, the crystallinity of the particle surface is lowered, the reactivity with the non-aqueous electrolyte is increased, and the efficiency may be lowered and the gas generation may be increased.

Further, the Raman half-width in the vicinity of 1580 cm −1 of the carbonaceous material is not particularly limited, but is usually 10 cm −1 or more, preferably 15 cm −1 or more, and usually 100 cm −1 or less, and 80 cm −1 or less. 60 cm-1 or less is more preferable, and 40 cm-1 or less is particularly preferable.
If the Raman half width is less than the above range, the crystallinity of the particle surface becomes too high, and there are cases where the number of sites where Li enters between layers decreases with charge and discharge. That is, charge acceptance may be reduced. In addition, when the negative electrode is densified by applying it to the current collector and then pressing it, the crystals are likely to be oriented in a direction parallel to the electrode plate, which may lead to a decrease in load characteristics. On the other hand, when the above range is exceeded, the crystallinity of the particle surface is lowered, the reactivity with the non-aqueous electrolyte is increased, and the efficiency may be reduced and the gas generation may be increased.

The measurement of the Raman spectrum, using a Raman spectrometer (manufactured by JASCO Corporation Raman spectrometer), the sample is naturally dropped into the measurement cell and filled, and while irradiating the sample surface in the cell with argon ion laser light, This is done by rotating the cell in a plane perpendicular to the laser beam. For the obtained Raman spectrum, the intensity IA of the peak PA near 1580 cm −1 and 1
The intensity IB of the peak PB near 360 cm −1 is measured, and the intensity ratio R (R = IB / IA) is calculated. The Raman R value calculated by the measurement is defined as the Raman R value of the carbonaceous material in the present invention. Further, the half width of the peak PA near 1580 cm −1 of the obtained Raman spectrum is measured, and this is defined as the Raman half width of the carbonaceous material in the present invention.

Moreover, said Raman measurement conditions are as follows.
Argon ion laser wavelength: 514.5nm
・ Laser power on the sample: 15-25mW
・ Resolution: 10-20cm-1
Measurement range: 1100 cm-1 to 1730 cm-1
・ Raman R value, Raman half width analysis: Background processing
-Smoothing processing: Simple average, 5 points of convolution

(2-3-2-5) BET specific surface area
As for the BET specific surface area of the carbonaceous material, the specific surface area value measured using the BET method is usually 0.1 m 2 · g −1 or more, preferably 0.7 m 2 · g −1 or more, and 1.0 m 2 · g. -1 or more is more preferable, 1.5 m2 · g-1 or more is particularly preferable, usually 100 m2 · g-1 or less, preferably 25 m2 · g-1 or less, more preferably 15 m2 · g-1 or less, 10 m 2 · g −1 or less is particularly preferable.

  When the value of the BET specific surface area is less than this range, the acceptability of lithium is likely to deteriorate during charging when used as a negative electrode material, lithium is likely to precipitate on the electrode surface, and stability may be reduced. On the other hand, if it exceeds this range, when used as a negative electrode material, the reactivity with the non-aqueous electrolyte increases, gas generation tends to increase, and a preferable battery may be difficult to obtain.

  The specific surface area was measured by the BET method using a surface area meter (a fully automated surface area measuring device manufactured by Okura Riken), preliminarily drying the sample at 350 ° C. for 15 minutes under nitrogen flow, Using a nitrogen helium mixed gas accurately adjusted so that the value of the relative pressure becomes 0.3, the nitrogen adsorption BET one-point method by the gas flow method is used. The specific surface area determined by the measurement is defined as the BET specific surface area of the carbonaceous material in the present invention.

(2-3-2-6) Pore size distribution
The pore size distribution of the carbonaceous material is calculated by measuring the mercury intrusion amount. By using mercury porosimetry (mercury intrusion method), fine pores with a diameter of 0.01 μm or more and 1 μm or less with voids in particles of carbonaceous material, irregularities caused by steps on the particle surface, and contact surfaces between particles, etc. The carbonaceous material measured to correspond to pores is usually 0.01 cm 3 · g −1 or more, preferably 0.05 cm 3 · g −1 or more, more preferably 0.1 cm 3 · g −1 or more, and usually 0. It is desirable to have a pore size distribution of 6 cm3 · g-1 or less, preferably 0.4 cm3 · g-1 or less, more preferably 0.3 cm3 · g-1 or less.

If the pore size distribution exceeds the above range, a large amount of binder may be required when forming an electrode plate. On the other hand, if it falls below the above range, the high current density charge / discharge characteristics may be deteriorated, and the effect of relaxing the expansion and contraction of the electrode during charge / discharge may not be obtained.
Further, the total pore volume, which is obtained by mercury porosimetry (mercury intrusion method) and corresponds to pores having a diameter of 0.01 μm or more and 100 μm or less, is usually 0.1 cm 3 · g −1 or more and 0.25 cm 3・ G-1 or more is preferable, 0.4 cm3 · g-1 or more is more preferable, and usually 10 cm3 · g-1 or less, preferably 5 cm3 · g-1 or less, more preferably 2 cm3 · g-1 or less. . If the total pore volume exceeds the above range, a large amount of binder may be required when forming an electrode plate. On the other hand, if the amount is below the above range, the effect of dispersing the thickener or the binder may not be obtained when forming the electrode plate.

  The average pore diameter is usually 0.05 μm or more, preferably 0.1 μm or more, more preferably 0.5 μm or more, and usually 50 μm or less, preferably 20 μm or less, more preferably 10 μm or less. If the average pore diameter exceeds the above range, a large amount of binder may be required. Moreover, when it is less than the above range, the high current density charge / discharge characteristics may deteriorate.

  The mercury intrusion is measured using a mercury porosimeter (Autopore 9520: manufactured by Micromeritex Corporation) as an apparatus for mercury porosimetry. As a pretreatment, about 0.2 g of a sample is sealed in a powder cell and deaerated for 10 minutes at room temperature under vacuum (50 μmHg or less). Subsequently, the pressure is reduced to 4 psia (about 28 kPa), mercury is introduced, the pressure is increased stepwise from 4 psia (about 28 kPa) to 40000 psia (about 280 MPa), and then the pressure is reduced to 25 psia (about 170 kPa). The number of steps at the time of pressure increase is 80 points or more, and the mercury intrusion amount is measured after an equilibration time of 10 seconds in each step.

  The pore size distribution is calculated from the mercury intrusion curve thus obtained using the Washburn equation. The surface tension (γ) of mercury is 485 dyne · cm −1 (1 dyne = 10 μN) and the contact angle (ψ) is 140 °. As the average pore diameter, the pore diameter when the cumulative pore volume is 50% is used.

(2-3-2-7) Circularity
When the circularity is measured as the degree of the sphere of the carbonaceous material, it is preferably within the following range. The circularity is defined as “circularity = (peripheral length of an equivalent circle having the same area as the particle projection shape) / (actual perimeter of the particle projection shape)”. Become a true sphere.
The degree of circularity of the particles having a carbonaceous material particle size in the range of 3 to 40 μm is desirably as close to 1, and is preferably 0.1 or more, more preferably 0.5 or more, and more preferably 0.8 or more, 0.85 or more is more preferable, and 0.9 or more is particularly preferable.
High current density charge / discharge characteristics improve as the degree of circularity increases. Therefore, when the circularity is less than the above range, the filling property of the negative electrode active material is lowered, the resistance between particles is increased, and the high current density charge / discharge characteristics may be lowered for a short time.

  The circularity is measured using a flow type particle image analyzer (FPIA manufactured by Sysmex Corporation). About 0.2 g of a sample was dispersed in a 0.2% by mass aqueous solution (about 50 mL) of polyoxyethylene (20) sorbitan monolaurate as a surfactant, and irradiated with 28 kHz ultrasonic waves at an output of 60 W for 1 minute. The detection range is specified as 0.6 to 400 μm, and the particle size is measured in the range of 3 to 40 μm. The circularity obtained by the measurement is defined as the circularity of the carbonaceous material in the present invention.

  The method for improving the degree of circularity is not particularly limited, but a spheroidized sphere is preferable because the shape of the interparticle void when the electrode body is formed is preferable. Examples of spheroidizing treatment include a method of mechanically approximating a sphere by applying a shearing force and a compressive force, a mechanical / physical processing method of granulating a plurality of fine particles by an adhesive force possessed by a binder or particles, etc. Is mentioned.

(2-3-2-8) True density
The true density of the carbonaceous material is usually 1.4 g · cm −3 or more, preferably 1.6 g · cm −3 or more, more preferably 1.8 g · cm −3 or more, and 2.0 g · cm −3. The above is particularly preferable, and usually 2.26 g · cm −3 or less. When the true density is below the above range, the crystallinity of carbon is too low, and the initial irreversible capacity may increase. The upper limit of the above range is
This is the theoretical upper limit of the true density of graphite.
The true density of the carbonaceous material is measured by a liquid phase substitution method (pycnometer method) using butanol. The value obtained by the measurement is defined as the true density of the carbonaceous material in the present invention.

(2-3-2-9) Tap density
The tap density of the carbonaceous material is usually 0.1 g · cm −3 or more, preferably 0.5 g · cm −3 or more, more preferably 0.7 g · cm −3 or more, and 0.9 g · cm −3. The above is particularly preferable, 2 g · cm −3 or less is preferable, 1.8 g · cm −3 or less is more preferable, and 1.6 g · cm −3 or less is particularly preferable.
When the tap density is below the above range, the packing density is difficult to increase when used as a negative electrode, and a high-capacity battery may not be obtained. On the other hand, when the above range is exceeded, there are too few voids between the particles in the electrode, it is difficult to ensure conductivity between the particles, and it may be difficult to obtain preferable battery characteristics.

  The tap density is measured by passing a sieve having a mesh opening of 300 μm, dropping the sample onto a 20 cm 3 tapping cell and filling the sample to the upper end surface of the cell, and then measuring a powder density measuring instrument (for example, a tap manufactured by Seishin Enterprise Co., Ltd.). Using a denser, tapping with a stroke length of 10 mm is performed 1000 times, and the tap density is calculated from the volume at that time and the weight of the sample. The tap density calculated by the measurement is defined as the tap density of the carbonaceous material in the present invention.

(2-3-2-10) Orientation ratio
The orientation ratio of the carbonaceous material is usually 0.005 or more, preferably 0.01 or more, more preferably 0.015 or more, and usually 0.67 or less. When the orientation ratio is below the above range, the high-density charge / discharge characteristics may deteriorate. The upper limit of the above range is the theoretical upper limit value of the orientation ratio of the carbonaceous material.

  The orientation ratio is measured by X-ray diffraction after pressure-molding the sample. Set the molded body obtained by filling 0.47 g of the sample into a molding machine with a diameter of 17 mm and compressing it with 58.8MN · m-2 so that it is flush with the surface of the sample holder for measurement. X-ray diffraction is measured. From the (110) diffraction and (004) diffraction peak intensities of the obtained carbon, a ratio represented by (110) diffraction peak intensity / (004) diffraction peak intensity is calculated. The orientation ratio calculated by the measurement is defined as the orientation ratio of the carbonaceous material in the present invention.

The X-ray diffraction measurement conditions are as follows. “2θ” indicates a diffraction angle.
・ Target: Cu (Kα ray) graphite monochromator
・ Slit:
Divergence slit = 0.5 degree
Receiving slit = 0.15mm
Scatter slit = 0.5 degree
・ Measurement range and step angle / measurement time:
(110) plane: 75 degrees ≦ 2θ ≦ 80 degrees 1 degree / 60 seconds
(004) plane: 52 degrees ≦ 2θ ≦ 57 degrees 1 degree / 60 seconds

(2-3-2-1-11) Aspect ratio (powder)
The aspect ratio of the carbonaceous material is usually 1 or more and usually 10 or less, preferably 8 or less, and more preferably 5 or less. If the aspect ratio exceeds the above range, streaking or a uniform coated surface cannot be obtained when forming an electrode plate, and the high current density charge / discharge characteristics may deteriorate. The lower limit of the above range is the theoretical lower limit value of the aspect ratio of the carbonaceous material.

The aspect ratio is measured by magnifying and observing the carbonaceous material particles with a scanning electron microscope. Carbonaceous material when three-dimensional observation is performed by selecting arbitrary 50 graphite particles fixed to the end surface of a metal having a thickness of 50 microns or less and rotating and tilting the stage on which the sample is fixed. The longest diameter A of the particles and the shortest diameter B orthogonal to the same are measured, and the average value of A / B is obtained. The aspect ratio (A / B) obtained by the measurement is defined as the aspect ratio of the carbonaceous material in the present invention.

(2-3-2-12) Secondary material mixing
The sub-material mixing means that two or more types of carbonaceous materials having different properties are contained in the negative electrode and / or the negative electrode active material. The properties referred to here are selected from the group consisting of X-ray diffraction parameters, median diameter, aspect ratio, BET specific surface area, orientation ratio, Raman R value, tap density, true density, pore distribution, circularity, and ash content. Shows more than one characteristic.

As a particularly preferred example of mixing these secondary materials, the volume-based particle size distribution is not symmetrical when centered on the median diameter, and contains two or more carbonaceous materials having different Raman R values, And X-ray parameters are different.
As an example of the effect of the auxiliary material mixing, carbonaceous materials such as graphite (natural graphite, artificial graphite and the like), carbon black such as acetylene black, and amorphous carbon such as needle coke are contained as a conductive material. Reducing electrical resistance.

  When mixing a conductive material as a secondary material mixture, one type may be mixed alone, or two or more types may be mixed in any combination and ratio. The mixing ratio of the conductive material to the carbonaceous material is usually 0.1% by mass or more and 0.5% by mass or more, more preferably 0.6% by mass or more, and usually 45% by mass or less. Yes, 40 mass% or less is preferable. If the mixing ratio is less than the above range, it may be difficult to obtain the effect of improving conductivity. On the other hand, exceeding the above range may increase the initial irreversible capacity.

(2-3-2-13) Electrode production
Any known method can be used to manufacture the electrode as long as the effects of the present invention are not significantly limited. For example, it is formed by adding a binder, a solvent, and, if necessary, a thickener, a conductive material, a filler, etc. to a negative electrode active material to form a slurry, which is applied to a current collector, dried and then pressed. Can do.

  The thickness of the negative electrode active material layer per side in the stage immediately before the non-aqueous electrolyte injection process of the battery is usually 15 μm or more, preferably 20 μm or more, more preferably 30 μm or more, and usually 150 μm or less. 20 μm or less is preferable, and 100 μm or less is more preferable. This is because if the thickness of the negative electrode active material exceeds this range, the non-aqueous electrolyte solution hardly penetrates to the vicinity of the current collector interface, and thus the high current density charge / discharge characteristics may be deteriorated. Further, if the ratio is below this range, the volume ratio of the current collector to the negative electrode active material increases, and the battery capacity may decrease. Further, the negative electrode active material may be roll-formed to form a sheet electrode, or may be formed into a pellet electrode by compression molding.

(2-3-2-14) Current collector
As the current collector for holding the negative electrode active material, a known material can be arbitrarily used. Examples of the current collector for the negative electrode include metal materials such as copper, nickel, stainless steel, and nickel-plated steel. Copper is particularly preferable from the viewpoint of ease of processing and cost.
In addition, the shape of the current collector may be, for example, a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, an expanded metal, a punch metal, a foam metal, or the like when the current collector is a metal material. Among them, a metal thin film is preferable, and a copper foil is more preferable, and a rolled copper foil by a rolling method and an electrolytic copper foil by an electrolytic method are more preferable, and both can be used as a current collector.

In addition, when the thickness of the copper foil is less than 25 μm, a copper alloy (phosphor bronze, titanium copper, Corson alloy, Cu—Cr—Zr alloy, etc.) having higher strength than pure copper can be used.
A current collector made of a copper foil produced by a rolling method is suitable for use in a small cylindrical battery because the copper crystals are arranged in the rolling direction so that the negative electrode is hard to crack even if it is rounded sharply or rounded at an acute angle. be able to.

  Electrolytic copper foil, for example, immerses a metal drum in a non-aqueous electrolyte solution in which copper ions are dissolved, and causes the copper to precipitate on the surface of the drum by flowing current while rotating it. Is obtained. Copper may be deposited on the surface of the rolled copper foil by an electrolytic method. One side or both sides of the copper foil may be subjected to a roughening treatment or a surface treatment (for example, a chromate treatment having a thickness of about several nm to 1 μm, a base treatment such as Ti).

The following physical properties are desired for the current collector substrate.
(2-3-2-14-1) Average surface roughness (Ra)
The average surface roughness (Ra) of the negative electrode active material thin film forming surface of the current collector substrate defined by the method described in JIS B0601-1994 is not particularly limited, but is usually 0.05 μm or more and 0.1 μm or more. Preferably, it is more preferably 0.15 μm or more, and is usually 1.5 μm or less, preferably 1.3 μm or less, and more preferably 1.0 μm or less. This is because when the average surface roughness (Ra) of the current collector substrate is within the above range, good charge / discharge cycle characteristics can be expected. Further, the area of the interface with the negative electrode active material thin film is increased, and the adhesion with the negative electrode active material thin film is improved. The upper limit value of the average surface roughness (Ra) is not particularly limited, but those having an average surface roughness (Ra) exceeding 1.5 μm are generally available as foils having a practical thickness as a battery. Since it is difficult, those of 1.5 μm or less are usually used.

(2-3-2-14-2) Tensile strength
The tensile strength is obtained by dividing the maximum tensile force required until the test piece breaks by the cross-sectional area of the test piece. The tensile strength in the present invention is measured by the same apparatus and method as described in JISZ2241 (metal material tensile test method).
The tensile strength of the current collector substrate is not particularly limited, but is usually 100 N · mm −2 or more, preferably 250 N · mm −2 or more, more preferably 400 N · mm −2 or more, and 500 N · mm −2 or more. Particularly preferred. The tensile strength is preferably as high as possible, but is usually 1000 N · mm −2 or less from the viewpoint of industrial availability. If the current collector substrate has a high tensile strength, cracking of the current collector substrate due to expansion / contraction of the negative electrode active material thin film accompanying charging / discharging can be suppressed, and good cycle characteristics can be obtained.

(2-3-2-14-3) 0.2% yield strength
The 0.2% proof stress is the magnitude of the load necessary to give a plastic (permanent) strain of 0.2%. It means that The 0.2% yield strength is measured with the same equipment and method as the tensile strength.
The 0.2% proof stress of the current collector substrate is not particularly limited, but is usually 30 N · mm −2 or more, preferably 150 N · mm −2 or more, particularly preferably 300 N · mm −2 or more. The 0.2% resistance value is preferably as high as possible, but 900 N · mm −2 or less is usually desirable from the viewpoint of industrial availability. If the current collector substrate has a high 0.2% proof stress, plastic deformation of the current collector substrate due to expansion / contraction of the negative electrode active material thin film accompanying charging / discharging can be suppressed, and good cycle characteristics can be obtained. Can do.

(2-3-2-14-4) Thickness of current collector
The thickness of the current collector is arbitrary, but is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and usually 1 mm or less, preferably 100 μm or less, 50 μm
m or less is more preferable. If the thickness of the metal film is less than 1 μm, the strength may be reduced, making application difficult. Moreover, when it becomes thicker than 100 micrometers, the shape of electrodes, such as winding, may be changed. The current collector may be mesh.

(2-3-2-15) Ratio of thickness of current collector and negative electrode active material layer
The thickness ratio between the current collector and the negative electrode active material layer is not particularly limited, but “(Negative electrode active material layer thickness just before non-aqueous electrolyte injection) / (current collector thickness)” The value is preferably 150 or less, more preferably 20 or less, particularly preferably 10 or less, more preferably 0.1 or more, still more preferably 0.4 or more, and particularly preferably 1 or more.
When the ratio of the thickness of the current collector to the negative electrode active material layer exceeds the above range, the current collector may generate heat due to Joule heat during high current density charge / discharge. On the other hand, below the above range, the volume ratio of the current collector to the negative electrode active material increases, and the battery capacity may decrease.

(2-3-2-16) Electrode density
The electrode structure when the negative electrode active material is converted into an electrode is not particularly limited, but the density of the negative electrode active material present on the current collector is preferably 1 g · cm −3 or more, and 1.2 g · cm −3. The above is more preferable, 1.3 g · cm −3 or more is particularly preferable, 2 g · cm −3 or less is preferable, 1.9 g · cm −3 or less is more preferable, and 1.8 g · cm −3 or less is further more preferable. It is preferably 1.7 g · cm −3 or less. When the density of the negative electrode active material existing on the current collector exceeds the above range, the negative electrode active material particles are destroyed, and the initial irreversible capacity increases or non-aqueous system near the current collector / negative electrode active material interface. There is a case where high current density charge / discharge characteristics are deteriorated due to a decrease in permeability of the electrolytic solution. On the other hand, if the amount is less than the above range, the conductivity between the negative electrode active materials decreases, the battery resistance increases, and the capacity per unit volume may decrease.

(2-3-2-17) Binder
The binder for binding the negative electrode active material is not particularly limited as long as it is a material that is stable with respect to the non-aqueous electrolyte solution and the solvent used in manufacturing the electrode.
Specific examples include resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, and nitrocellulose; SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluorine rubber, NBR ( Acrylonitrile / butadiene rubber), rubbery polymers such as ethylene / propylene rubber; styrene / butadiene / styrene block copolymers or hydrogenated products thereof; EPDM (ethylene / propylene / diene terpolymer), styrene / ethylene / Thermoplastic elastomeric polymer such as butadiene / styrene copolymer, styrene / isoprene / styrene block copolymer or hydrogenated product thereof; syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene Soft resinous polymers such as vinyl acetate copolymer and propylene / α-olefin copolymer; Fluorine-based polymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene / ethylene copolymer Polymers: Polymer compositions having ionic conductivity of alkali metal ions (particularly lithium ions), and the like. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios.

The solvent for forming the slurry is not particularly limited as long as it is a solvent capable of dissolving or dispersing the negative electrode active material, the binder, and the thickener and conductive material used as necessary. Alternatively, either an aqueous solvent or an organic solvent may be used.
Examples of the aqueous solvent include water, alcohol and the like, and examples of the organic solvent include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N , N-dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, diethyl ether, dimethylacetamide, hexamethylphosphamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane, etc. .

In particular, when an aqueous solvent is used, it is preferable to add a dispersant or the like in addition to the thickener and slurry it using a latex such as SBR. In addition, these solvents may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio.
The ratio of the binder to the negative electrode active material is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, particularly preferably 0.6% by mass or more, and preferably 20% by mass or less, 15% by mass. The following is more preferable, 10 mass% or less is still more preferable, and 8 mass% or less is especially preferable. When the ratio of the binder with respect to a negative electrode active material exceeds the said range, the binder ratio from which the amount of binders does not contribute to battery capacity may increase, and the fall of battery capacity may be caused. On the other hand, below the above range, the strength of the negative electrode may be reduced.

In particular, when a rubbery polymer typified by SBR is contained as a main component, the ratio of the binder to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, and 0 .6% by mass or more is more preferable, and is usually 5% by mass or less, preferably 3% by mass or less, and more preferably 2% by mass or less.
Moreover, when the main component contains a fluorine-based polymer typified by polyvinylidene fluoride, the ratio to the negative electrode active material is usually 1% by mass or more, preferably 2% by mass or more, and more preferably 3% by mass or more. Preferably, it is usually 15% by mass or less, preferably 10% by mass or less, and more preferably 8% by mass or less.

  A thickener is usually used to adjust the viscosity of the slurry. The thickener is not particularly limited, and specific examples include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios.

  Furthermore, when using a thickener, the ratio of the thickener to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, Moreover, it is 5 mass% or less normally, 3 mass% or less is preferable, and 2 mass% or less is still more preferable. When the ratio of the thickener to the negative electrode active material is less than the above range, applicability may be significantly reduced. Moreover, when it exceeds the said range, the ratio of the negative electrode active material which occupies for a negative electrode active material layer will fall, and the problem that the capacity | capacitance of a battery falls and the resistance between negative electrode active materials may increase.

(2-3-2-18) Polar plate orientation ratio
The electrode plate orientation ratio is usually 0.001 or more, preferably 0.005 or more, more preferably 0.01 or more, and usually 0.67 or less. When the electrode plate orientation ratio is below the above range, the high-density charge / discharge characteristics may be deteriorated. The upper limit of the above range is the theoretical upper limit of the electrode plate orientation ratio of the carbonaceous material.

The electrode plate orientation ratio is measured by measuring the orientation ratio of the negative electrode active material of the electrode by X-ray diffraction for the negative electrode after being pressed to the target density. The specific method is not particularly limited, but as a standard method, peak separation is performed by fitting the peaks of (110) and (004) diffraction of carbon by X-ray diffraction using asymmetric Pearson VII as a profile function. The integrated intensities of the peaks of (110) diffraction and (004) diffraction are calculated. From the obtained integrated intensity, a ratio represented by (110) diffraction integrated intensity / (004) diffraction integrated intensity is calculated. The electrode negative electrode active material orientation ratio calculated by this measurement is defined as the electrode plate orientation ratio of the carbonaceous material in the present invention.

The X-ray diffraction measurement conditions are as follows. “2θ” indicates a diffraction angle.
・ Target: Cu (Kα ray) graphite monochromator
・ Slit: Diverging slit = 1 degree, Receiving slit = 0.1 mm, Scattering slit = 1 degree ・ Measurement range and step angle / measurement time:
(110) plane: 76.5 degrees ≦ 2θ ≦ 78.5 degrees 0.01 degrees / 3 seconds
(004) plane: 53.5 degrees ≦ 2θ ≦ 56.0 degrees 0.01 degrees / 3 seconds
・ Sample preparation: Electrode fixed to glass plate with double-sided tape of 0.1mm thickness

<2-3-3. Structure, physical properties, preparation method of negative electrode using metal compound material and metal compound material>
As the metal compound material used as the negative electrode active material, if lithium can be occluded / released, a single metal or alloy that forms a lithium alloy, or oxides, carbides, nitrides, silicides, sulfides thereof, Any compound such as phosphide is not particularly limited. Examples of such metal compounds include compounds containing metals such as Ag, Al, Ba, Bi, Cu, Ga, Ge, In, Ni, P, Pb, Sb, Si, Sn, Sr, and Zn. Among these, a single metal or an alloy that forms a lithium alloy is preferable, and a material containing a group 13 or group 14 metal / metalloid element (that is, excluding carbon) is more preferable. Further, silicon (Si ), Tin (Sn) or lead (Pb) (hereinafter, these three elements may be referred to as “specific metal elements”), simple metals, alloys containing these atoms, or their metals (specific metal elements) It is preferable that it is a compound of these. These may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  Examples of the negative electrode active material having at least one kind of atom selected from the specific metal element include a single metal of any one specific metal element, an alloy composed of two or more specific metal elements, one type, or two or more types Alloys composed of the specified metal element and one or more other metal elements, and compounds containing one or more specified metal elements, or oxides, carbides and nitrides of the compounds -Complex compounds such as silicides, sulfides, and phosphides are listed. By using these simple metals, alloys or metal compounds as the negative electrode active material, the capacity of the battery can be increased.

  Moreover, the compound which these complex compounds combined with several elements, such as a metal simple substance, an alloy, or a nonmetallic element, can also be mentioned as an example. More specifically, for example, in silicon and tin, an alloy of these elements and a metal that does not operate as a negative electrode can be used. In addition, for example, in the case of tin, a complex compound containing 5 to 6 kinds of elements in combination with a metal that acts as a negative electrode other than tin and silicon, a metal that does not operate as a negative electrode, and a nonmetallic element can also be used. .

Among these negative electrode active materials, since the capacity per unit weight is large when a battery is formed, any one metal element of a specific metal element, an alloy of two or more specific metal elements, oxidation of a specific metal element In particular, silicon and / or tin metal simple substance, alloy, oxide, carbide, nitride and the like are preferable from the viewpoint of capacity per unit weight and environmental load. In addition, although the capacity per unit weight is inferior to that of a single metal or an alloy, the following compounds containing silicon and / or tin are also preferable because of excellent cycle characteristics.
The element ratio of silicon and / or tin to oxygen is usually 0.5 or more, preferably 0.7 or more, more preferably 0.9 or more, and usually 1.5 or less, preferably 1. “Oxides of silicon and / or tin” of 3 or less, more preferably 1.1 or less.
-Element ratio of silicon and / or tin and nitrogen is usually 0.5 or more, preferably 0.7 or more, more preferably 0.9 or more, and usually 1.5 or less, preferably 1. “Silicon and / or tin nitride” of 3 or less, more preferably 1.1 or less.
The elemental ratio of silicon and / or tin to carbon is usually 0.5 or more, preferably 0.7 or more, more preferably 0.9 or more, and usually 1.5 or less, preferably 1. 3 or less
More preferably 1.1 or less “silicon carbide and / or tin carbide”.

In addition, any one of the above-described negative electrode active materials may be used alone, or two or more thereof may be used in any combination and ratio.
The negative electrode in the non-aqueous electrolyte secondary battery of the present invention can be manufactured using any known method. Specifically, as a manufacturing method of the negative electrode, for example, a method in which a negative electrode active material added with a binder or a conductive material is roll-formed as it is to form a sheet electrode, or a compression-molded pellet electrode and The above negative electrode is usually applied to a negative electrode current collector (hereinafter also referred to as “negative electrode current collector”) by a method such as a coating method, a vapor deposition method, a sputtering method, or a plating method. A method of forming a thin film layer (negative electrode active material layer) containing an active material is used. In this case, by adding a binder, a thickener, a conductive material, a solvent, etc. to the above-mentioned negative electrode active material to form a slurry, applying this to the negative electrode current collector, drying, and pressing to increase the density A negative electrode active material layer is formed on the negative electrode current collector.

Examples of the material of the negative electrode current collector include steel, copper alloy, nickel, nickel alloy, and stainless steel. Of these, copper foil is preferred from the viewpoint of easy processing into a thin film and cost.
The thickness of the negative electrode current collector is usually 1 μm or more, preferably 5 μm or more, and is usually 100 μm or less, preferably 50 μm or less. This is because if the thickness of the negative electrode current collector is too thick, the capacity of the entire battery may be too low, and conversely if it is too thin, handling may be difficult.

  In addition, in order to improve the binding effect with the negative electrode active material layer formed on the surface, the surface of these negative electrode current collectors is preferably subjected to a roughening treatment in advance. Surface roughening methods include blasting, rolling with a rough surface roll, abrasive cloth paper with abrasive particles fixed, grinding wheel, emery buff, machine that polishes the current collector surface with a wire brush equipped with steel wire, etc. Examples thereof include a mechanical polishing method, an electrolytic polishing method, and a chemical polishing method.

  Further, in order to reduce the weight of the negative electrode current collector and improve the energy density per weight of the battery, a perforated negative electrode current collector such as an expanded metal or a punching metal can be used. In this type of negative electrode current collector, the weight can be changed to white by changing the aperture ratio. Further, when a negative electrode active material layer is formed on both surfaces of this type of negative electrode current collector, the negative electrode active material layer is further less likely to peel due to the rivet effect through the hole. However, when the aperture ratio becomes too high, the contact area between the negative electrode active material layer and the negative electrode current collector becomes small, and thus the adhesive strength may be lowered.

The slurry for forming the negative electrode active material layer is usually prepared by adding a binder, a thickener and the like to the negative electrode material. In addition, the “negative electrode material” in this specification refers to a material in which a negative electrode active material and a conductive material are combined.
The content of the negative electrode active material in the negative electrode material is usually 70% by mass or more, particularly 75% by mass or more, and usually 97% by mass or less, particularly preferably 95% by mass or less. If the content of the negative electrode active material is too small, the capacity of the secondary battery using the obtained negative electrode tends to be insufficient. This is because the strength of the negative electrode tends to be insufficient. When two or more negative electrode active materials are used in combination, the total amount of the negative electrode active materials may be set to satisfy the above range.

Examples of the conductive material used for the negative electrode include metal materials such as copper and nickel; carbon materials such as graphite and carbon black. These may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio. In particular, it is preferable to use a carbon material as the conductive material because the carbon material acts as an active material. The content of the conductive material in the negative electrode material is usually 3
It is preferably at least 5% by mass, particularly at least 5% by mass, usually at most 30% by mass, particularly at most 25% by mass. When the content of the conductive material is too small, the conductivity tends to be insufficient. When the content is too large, the content of the negative electrode active material or the like is relatively insufficient, which tends to decrease the battery capacity and strength. . Note that when two or more conductive materials are used in combination, the total amount of the conductive materials may satisfy the above range.

  As the binder used for the negative electrode, any material can be used as long as it is a material safe with respect to the solvent and the electrolytic solution used at the time of producing the electrode. Examples thereof include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, styrene / butadiene rubber / isoprene rubber, butadiene rubber, ethylene-acrylic acid copolymer, and ethylene / methacrylic acid copolymer. These may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio. The content of the binder is usually 0.5 parts by weight or more, particularly 1 part by weight or more, and usually 10 parts by weight or less, particularly 8 parts by weight or less, with respect to 100 parts by weight of the negative electrode material. When the content of the binder is too small, the strength of the obtained negative electrode tends to be insufficient. When the content is too large, the content of the negative electrode active material and the like is relatively insufficient, and thus the battery capacity and conductivity tend to be insufficient. It is because it becomes. In addition, when using two or more binders together, what is necessary is just to make it the total amount of a binder satisfy | fill the said range.

  Examples of the thickener used for the negative electrode include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, and casein. These may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio. The thickener may be used as necessary, but when used, the thickener content in the negative electrode active material layer is usually in the range of 0.5% by mass or more and 5% by mass or less. Is preferred.

  The slurry for forming the negative electrode active material layer is prepared by mixing the negative electrode active material with a conductive material, a binder, or a thickener as necessary, and using an aqueous solvent or an organic solvent as a dispersion medium. . As the aqueous solvent, water is usually used, but a solvent other than water such as alcohols such as ethanol or cyclic amides such as N-methylpyrrolidone is used in combination at a ratio of about 30% by mass or less with respect to water. You can also. As the organic solvent, usually, cyclic amides such as N-methylpyrrolidone, linear amides such as N, N-dimethylformamide and N, N-dimethylacetamide, and aromatic carbonization such as anisole, toluene and xylene Examples thereof include alcohols such as hydrogens, butanol and cyclohexanol, among which cyclic amides such as N-methylpyrrolidone, linear amides such as N, N-dimethylformamide and N, N-dimethylacetamide are preferable. . Any one of these may be used alone, or two or more may be used in any combination and ratio.

The viscosity of the slurry is not particularly limited as long as it is a viscosity that can be applied onto the current collector. What is necessary is just to prepare suitably by changing the usage-amount of a solvent etc. at the time of preparation of a slurry so that it may become the viscosity which can be apply | coated.
The obtained slurry is applied onto the above-described negative electrode current collector, dried, and then pressed to form a negative electrode active material layer. The method of application is not particularly limited, and a method known per se can be used. The drying method is not particularly limited, and a known method such as natural drying, heat drying, or reduced pressure drying can be used.

  The electrode structure when the negative electrode active material is made into an electrode by the above method is not particularly limited, but the density of the active material present on the current collector is preferably 1 g · cm −3 or more, and 1.2 g · cm −3 or more is more preferable, 1.3 g · cm −3 or more is particularly preferable, 2 g · cm −3 or less is preferable, 1.9 g · cm −3 or less is more preferable, and 1.8 g · cm −3 or less is preferable. Is more preferable, and 1.7 g · cm −3 or less is particularly preferable.

If the density of the active material present on the current collector exceeds the above range, the active material particles are destroyed, the initial irreversible capacity increases, and the non-aqueous electrolyte solution near the current collector / active material interface There is a case where high current density charge / discharge characteristics are deteriorated due to a decrease in permeability. On the other hand, below the above range, the conductivity between the active materials may be reduced, the battery resistance may be increased, and the capacity per unit volume may be reduced.
<2-3-4. Lithium-containing metal composite oxide material, and negative electrode configuration, physical properties, and preparation method using lithium-containing metal composite oxide material>
The lithium-containing metal composite oxide material used as the negative electrode active material is not particularly limited as long as it can occlude and release lithium, but lithium-containing composite metal oxide materials containing titanium are preferable, and lithium and titanium composite oxidation (Hereinafter abbreviated as “lithium titanium composite oxide”) is particularly preferable. That is, it is particularly preferable to use a lithium titanium composite oxide having a spinel structure in a negative electrode active material for a non-aqueous electrolyte secondary battery because the output resistance is greatly reduced.

In addition, lithium or titanium of the lithium titanium composite oxide is at least selected from the group consisting of other metal elements such as Na, K, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, and Nb. Those substituted with one element are also preferred.
The metal oxide is a lithium titanium composite oxide represented by the general formula (3). In the general formula (3), 0.7 ≦ x ≦ 1.5, 1.5 ≦ y ≦ 2.3, It is preferable that 0 ≦ z ≦ 1.6 because the structure upon doping and dedoping of lithium ions is stable.

LixTiyMzO4 (3)
[In General Formula (3), M represents at least one element selected from the group consisting of Na, K, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, and Nb. ]
Among the compositions represented by the general formula (3),
(A) 1.2 ≦ x ≦ 1.4, 1.5 ≦ y ≦ 1.7, z = 0
(B) 0.9 ≦ x ≦ 1.1, 1.9 ≦ y ≦ 2.1, z = 0
(C) 0.7 ≦ x ≦ 0.9, 2.1 ≦ y ≦ 2.3, z = 0
This structure is particularly preferable because the battery performance is well balanced.

Particularly preferred representative compositions of the above compounds are Li4 / 3Ti5 / 3O4 in (a), Li1Ti2O4 in (b), and Li4 / 5Ti11 / 5O4 in (c). As for the structure of Z ≠ 0, for example, Li4 / 3Ti4 / 3Al1 / 3O4 is preferable.
In addition to the above-described requirements, the lithium titanium composite oxide as the negative electrode active material in the present invention further has the physical properties and the following (2-3-4-1) to (2-3-4-13) It is preferable to satisfy at least one of the features such as the shape, and it is particularly preferable to satisfy two or more at the same time.

(2-3-4-1) BET specific surface area
As for the BET specific surface area of the lithium titanium composite oxide used as the negative electrode active material, the value of the specific surface area measured using the BET method is preferably 0.5 m 2 · g −1 or more, more preferably 0.7 m 2 · g −1 or more. More preferably, 1.0 m2 · g-1 or more is further preferable, 1.5 m2 · g-1 or more is particularly preferable, 200 m2 · g-1 or less is preferable, 100 m2 · g-1 or less is more preferable, and 50 m2 · g-1 or less is further preferable, and 25 m2 · g-1 or less is particularly preferable.

When the BET specific surface area is less than the above range, the reaction area in contact with the non-aqueous electrolyte when used as the negative electrode material may decrease, and the output resistance may increase. On the other hand, if it exceeds the above range, the surface of the metal oxide crystal containing titanium and the portion of the end face increase, and due to this, crystal distortion also occurs, irreversible capacity cannot be ignored, which is preferable It may be difficult to obtain a battery.

  The specific surface area was measured by the BET method using a surface area meter (a fully automated surface area measuring device manufactured by Okura Riken), preliminarily drying the sample at 350 ° C. for 15 minutes under nitrogen flow, Using a nitrogen helium mixed gas accurately adjusted so that the value of the relative pressure becomes 0.3, the nitrogen adsorption BET one-point method by the gas flow method is used. The specific surface area determined by the measurement is defined as the BET specific surface area of the lithium titanium composite oxide in the present invention.

(2-3-4-2) Volume-based average particle diameter
The volume-based average particle diameter of lithium-titanium composite oxide (secondary particle diameter when primary particles are aggregated to form secondary particles) is the volume-based average particle diameter determined by the laser diffraction / scattering method. (Median diameter).
The volume-based average particle size of the lithium titanium composite oxide is usually 0.1 μm or more, preferably 0.5 μm or more, more preferably 0.7 μm or more, and usually 50 μm or less, preferably 40 μm or less, 30 μm. The following is more preferable, and 25 μm or less is particularly preferable.

The volume-based average particle size is measured by dispersing a carbon powder in a 0.2% by mass aqueous solution (10 mL) of polyoxyethylene (20) sorbitan monolaurate, which is a surfactant, and a laser diffraction / scattering particle size distribution analyzer. (LA-700 manufactured by Horiba Ltd.) is used. The median diameter determined by the measurement is defined as the volume-based average particle diameter of the carbonaceous material in the present invention.
When the volume average particle size of the lithium titanium composite oxide is below the above range, a large amount of binder is required at the time of producing the electrode, and as a result, the battery capacity may be reduced. On the other hand, if it exceeds the above range, an uneven coating surface tends to be formed when forming an electrode plate, which may be undesirable in the battery manufacturing process.

(2-3-4-3) Average primary particle size
In the case where primary particles are aggregated to form secondary particles, the average primary particle diameter of the lithium titanium composite oxide is usually 0.01 μm or more, preferably 0.05 μm or more, and preferably 0.1 μm or more. More preferably, it is particularly preferably 0.2 μm or more, and is usually 2 μm or less, preferably 1.6 μm or less, more preferably 1.3 μm or less, and particularly preferably 1 μm or less. If the volume-based average primary particle diameter exceeds the above range, it is difficult to form spherical secondary particles, which adversely affects the powder packing property and the specific surface area greatly decreases. There is a possibility that performance is likely to deteriorate. On the other hand, below the above range, there are cases where the performance of the secondary battery is lowered, for example, reversibility of charge / discharge is inferior because crystals are underdeveloped.

  The primary particle diameter is measured by observation using a scanning electron microscope (SEM). Specifically, in a photograph at a magnification at which particles can be confirmed, for example, a magnification of 10,000 to 100,000 times, the longest value of the intercept by the left and right boundary lines of the primary particles with respect to the horizontal straight line is determined for any 50 primary particles. Obtained and obtained by taking an average value.

(2-3-4-4) Shape
As for the shape of the lithium titanium composite oxide particles, a lump shape, a polyhedron shape, a sphere shape, an oval sphere shape, a plate shape, a needle shape, a column shape, etc., which are conventionally used, are used. It is preferably formed by forming particles, and the shape of the secondary particles is spherical or elliptical.
In general, an electrochemical element expands and contracts as the active material in the electrode expands and contracts as it is charged and discharged. Therefore, the active material is easily damaged due to the stress or the conductive path is broken. Therefore, the primary particles are aggregated to form secondary particles rather than a single particle active material composed of only primary particles, so that the expansion and contraction stress is relieved and deterioration is prevented.
In addition, spherical or oval spherical particles are less oriented during molding of the electrode than plate-like equiaxed particles, so there is less expansion and contraction of the electrode during charge and discharge, and an electrode is produced. The mixing with the conductive material is also preferable because it can be easily mixed uniformly.

(2-3-4-5) Tap density
The tap density of the lithium titanium composite oxide is preferably 0.05 g · cm −3 or more, more preferably 0.1 g · cm −3 or more, still more preferably 0.2 g · cm −3 or more, and 0.4 g · cm. -3 or more is particularly preferable, 2.8 g · cm −3 or less is preferable, 2.4 g · cm −3 or less is further preferable, and 2 g · cm −3 or less is particularly preferable. When the tap density is less than the above range, the packing density is difficult to increase when used as a negative electrode, and the contact area between particles decreases, so that the resistance between particles increases and the output resistance may increase. On the other hand, if the above range is exceeded, the voids between the particles in the electrode may become too small, and the output resistance may increase due to a decrease in the flow path of the non-aqueous electrolyte solution.

  The tap density is measured by passing a sieve having a mesh opening of 300 μm, dropping the sample onto a 20 cm 3 tapping cell and filling the sample to the upper end surface of the cell, and then measuring a powder density measuring instrument (for example, a tap manufactured by Seishin Enterprise Co., Ltd.). Density) is used to perform tapping with a stroke length of 10 mm 1000 times, and the density is calculated from the volume at that time and the weight of the sample. The tap density calculated by the measurement is defined as the tap density of the lithium titanium composite oxide in the present invention.

(2-3-4-6) Circularity
When the circularity of the lithium titanium composite oxide is measured as a sphere, it is preferably within the following range. The circularity is defined as “circularity = (peripheral length of an equivalent circle having the same area as the particle projection shape) / (actual perimeter of the particle projection shape)”. It becomes.

  The circularity of the lithium-titanium composite oxide is preferably as close to 1, and is usually 0.10 or more, preferably 0.80 or more, more preferably 0.85 or more, and particularly preferably 0.90 or more. High current density charge / discharge characteristics improve as the circularity increases. Therefore, when the circularity is less than the above range, the filling property of the negative electrode active material is lowered, the resistance between particles is increased, and the high current density charge / discharge characteristics may be lowered for a short time.

  The circularity is measured using a flow type particle image analyzer (FPIA manufactured by Sysmex Corporation). About 0.2 g of a sample was dispersed in a 0.2% by mass aqueous solution (about 50 mL) of polyoxyethylene (20) sorbitan monolaurate as a surfactant, and irradiated with 28 kHz ultrasonic waves at an output of 60 W for 1 minute. The detection range is specified as 0.6 to 400 μm, and the particle size is measured in the range of 3 to 40 μm. The circularity obtained by the measurement is defined as the circularity of the lithium titanium composite oxide in the present invention.

(2-3-4-7) Aspect ratio
The aspect ratio of the lithium titanium composite oxide is usually 1 or more and usually 5 or less, preferably 4 or less, more preferably 3 or less, and particularly preferably 2 or less. If the aspect ratio exceeds the above range, streaking or a uniform coated surface cannot be obtained when forming an electrode plate, and high current density charge / discharge characteristics may be deteriorated for a short time. The lower limit of the above range is the theoretical lower limit value of the aspect ratio of the lithium titanium composite oxide.

The aspect ratio is measured by magnifying and observing lithium titanium composite oxide particles with a scanning electron microscope. Arbitrary 50 particles fixed to the end face of a metal having a thickness of 50 μm or less are selected, and the stage on which the sample is fixed is rotated and tilted for each, and the maximum particle size is obtained when three-dimensionally observed. The diameter A and the shortest diameter B perpendicular to it are measured, and the average value of A / B is obtained. The aspect ratio (A / B) determined by the measurement is defined as the aspect ratio of the lithium titanium composite oxide in the present invention.

(2-3-4-8) Production method of negative electrode active material
Although it does not restrict | limit especially as a manufacturing method of lithium titanium complex oxide in the range which does not exceed the summary of this invention, Several methods are mentioned, A general method is used as a manufacturing method of an inorganic compound.
For example, a titanium raw material such as titanium oxide and a raw material of another element and a Li source such as LiOH, Li 2 CO 3, or LiNO 3 as necessary are uniformly mixed and fired at a high temperature to obtain an active material.

  In particular, various methods are conceivable for producing a spherical or elliptical active material. As an example, a titanium precursor material such as titanium oxide and, if necessary, a raw material material of another element are dissolved or pulverized and dispersed in a solvent such as water, and the pH is adjusted while stirring to create a spherical precursor. There is a method in which the active material is obtained by recovering and drying it as necessary, and then adding a Li source such as LiOH, Li2CO3, LiNO3 and the like and baking at a high temperature.

As another example, a titanium raw material such as titanium oxide and, if necessary, a raw material of another element are dissolved or pulverized and dispersed in a solvent such as water. Alternatively, a method of obtaining an active material by forming an elliptical precursor, adding a Li source such as LiOH, Li 2 CO 3, LiNO 3, etc. to the precursor and baking it at a high temperature may be mentioned.
Further, as another method, a titanium raw material such as titanium oxide, a Li source such as LiOH, Li2CO3, and LiNO3, and a raw material material of another element as necessary are dissolved or pulverized and dispersed in a solvent such as water. There is a method in which it is dried and molded with a spray dryer or the like to obtain a spherical or elliptical precursor, which is fired at a high temperature to obtain an active material.

  Also, during these steps, elements other than Ti, such as Al, Mn, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, C, Si, Sn , Ag may be present in the metal oxide structure containing titanium and / or in contact with the oxide containing titanium. By containing these elements, the operating voltage and capacity of the battery can be controlled.

(2-3-4-9) Electrode preparation
Any known method can be used to manufacture the electrode. For example, it is formed by adding a binder, a solvent, and, if necessary, a thickener, a conductive material, a filler, etc. to a negative electrode active material to form a slurry, which is applied to a current collector, dried and then pressed. Can do.
The thickness of the negative electrode active material layer per side in the stage immediately before the non-aqueous electrolyte injection process of the battery is usually 15 μm or more, preferably 20 μm or more, more preferably 30 μm or more, and the upper limit is 150 μm or less, preferably 120 μm. Below, more preferably 100 μm or less.

If it exceeds this range, the non-aqueous electrolyte solution hardly penetrates to the vicinity of the current collector interface, and thus the high current density charge / discharge characteristics may deteriorate. On the other hand, below this range, the volume ratio of the current collector to the negative electrode active material increases, and the battery capacity may decrease. Further, the negative electrode active material may be roll-formed to form a sheet electrode, or may be formed into a pellet electrode by compression molding.
(2-3-4-10) Current collector
As the current collector for holding the negative electrode active material, a known material can be arbitrarily used. Examples of the current collector for the negative electrode include metal materials such as copper, nickel, stainless steel, and nickel-plated steel. Of these, copper is particularly preferable from the viewpoint of ease of processing and cost.

The shape of the current collector includes, for example, a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, an expanded metal, a punch metal, and a foam metal when the current collector is a metal material. Among them, a metal foil film containing copper (Cu) and / or aluminum (Al) is preferable, copper foil and aluminum foil are more preferable, rolled copper foil by a rolling method, and electrolytic copper by an electrolytic method are more preferable. There are foils, both of which can be used as current collectors.

In addition, when the thickness of the copper foil is less than 25 μm, a copper alloy (phosphor bronze, titanium copper, Corson alloy, Cu—Cr—Zr alloy, etc.) having higher strength than pure copper can be used. Moreover, since the specific gravity of aluminum foil is light, when it is used as a current collector, the weight of the battery can be reduced and can be preferably used.
A current collector made of a copper foil produced by a rolling method is suitable for use in a small cylindrical battery because the copper crystals are arranged in the rolling direction so that the negative electrode is hard to crack even if it is rounded sharply or rounded at an acute angle. be able to.

  Electrolytic copper foil, for example, immerses a metal drum in a non-aqueous electrolyte solution in which copper ions are dissolved, and causes the copper to precipitate on the surface of the drum by flowing current while rotating it. Is obtained. Copper may be deposited on the surface of the rolled copper foil by an electrolytic method. One side or both sides of the copper foil may be subjected to a roughening treatment or a surface treatment (for example, a chromate treatment having a thickness of about several nm to 1 μm, a base treatment such as Ti).

Further, the following physical properties are desired for the current collector substrate.
(2-3-4-10-1) Average surface roughness (Ra)
The average surface roughness (Ra) of the active material thin film forming surface of the current collector substrate defined by the method described in JIS B0601-1994 is not particularly limited, but is usually 0.01 μm or more, preferably 0.03 μm or more. Further, it is usually 1.5 μm or less, preferably 1.3 μm or less, and more preferably 1.0 μm or less.

  This is because when the average surface roughness (Ra) of the current collector substrate is within the above range, good charge / discharge cycle characteristics can be expected. In addition, the area of the interface with the active material thin film is increased, and the adhesion with the negative electrode active material thin film is improved. The upper limit value of the average surface roughness (Ra) is not particularly limited, but those having an average surface roughness (Ra) exceeding 1.5 μm are generally available as foils having a practical thickness as a battery. Since it is difficult, those of 1.5 μm or less are usually used.

(2-3-4-10-2) Tensile strength
The tensile strength is obtained by dividing the maximum tensile force required until the test piece breaks by the cross-sectional area of the test piece. The tensile strength in the present invention is measured by the same apparatus and method as described in JISZ2241 (metal material tensile test method).
The tensile strength of the current collector substrate is not particularly limited, but is usually 50 N · mm −2 or more, preferably 100 N · mm −2 or more, and more preferably 150 N · mm −2 or more. The tensile strength is preferably as high as possible, but usually 1000 N · mm−2 or less is desirable from the viewpoint of industrial availability.

If the current collector substrate has a high tensile strength, cracking of the current collector substrate due to expansion / contraction of the active material thin film accompanying charging / discharging can be suppressed, and good cycle characteristics can be obtained.
(2-3-4-10-3) 0.2% yield strength
The 0.2% proof stress is the magnitude of the load necessary to give a plastic (permanent) strain of 0.2%. It means that The 0.2% yield strength is measured by the same apparatus and method as the tensile strength.

The 0.2% yield strength of the current collector substrate is not particularly limited, but is usually 30 N · mm −2 or more, preferably 100 N · mm −2 or more, and particularly preferably 150 N · mm −2 or more. The 0.2% proof stress is preferably as high as possible, but usually 900 N · mm −2 or less is desirable from the viewpoint of industrial availability.
If the current collector substrate has a high 0.2% proof stress, plastic deformation of the current collector substrate due to expansion / contraction of the active material thin film accompanying charging / discharging can be suppressed, and good cycle characteristics can be obtained. This is because it can.

(2-3-4-10-4) Current collector thickness
The thickness of the current collector is arbitrary, but is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and usually 1 mm or less, preferably 100 μm or less, more preferably 50 μm or less.
If the thickness of the metal film is less than 1 μm, the strength may be reduced, making application difficult. Moreover, when it becomes thicker than 100 micrometers, the shape of electrodes, such as winding, may be changed. The metal thin film may be mesh.

(2-3-4-11) Ratio of current collector to active material layer thickness
The ratio of the thickness of the current collector to the active material layer is not particularly limited, but the value of “(thickness of active material layer on one side immediately before non-aqueous electrolyte injection) / (thickness of current collector)” However, it is usually 150 or less, preferably 20 or less, more preferably 10 or less, and usually 0.1 or more, preferably 0.4 or more, and more preferably 1 or more.

  When the ratio of the thickness of the current collector to the negative electrode active material layer exceeds the above range, the current collector may generate heat due to Joule heat during high current density charge / discharge. On the other hand, below the above range, the volume ratio of the current collector to the negative electrode active material increases, and the battery capacity may decrease.

(2-3-4-12) Electrode density
The electrode structure when the negative electrode active material is converted into an electrode is not particularly limited, but the density of the active material present on the current collector is preferably 1 g · cm −3 or more, and 1.2 g · cm −3 or more. Is more preferably 1.3 g · cm −3 or more, particularly preferably 1.5 g · cm −3 or more, more preferably 3 g · cm −3 or less, and even more preferably 2.5 g · cm −3 or less. 2.2 g · cm −3 or less is more preferable, and 2 g · cm −3 or less is particularly preferable.
When the density of the active material present on the current collector exceeds the above range, the binding between the current collector and the negative electrode active material becomes weak, and the electrode and the active material may be separated. On the other hand, below the above range, the conductivity between the negative electrode active materials may decrease, and the battery resistance may increase.

(2-3-4-13) Binder
The binder for binding the negative electrode active material is not particularly limited as long as it is a material that is stable with respect to the non-aqueous electrolyte solution and the solvent used in manufacturing the electrode.
Specific examples include resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, nitrocellulose; SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluororubber, Rubber polymers such as NBR (acrylonitrile / butadiene rubber) and ethylene / propylene rubber; styrene / butadiene / styrene block copolymer and hydrogenated products thereof; EPDM (ethylene / propylene / diene terpolymer), styrene / Thermoplastic elastomeric polymers such as ethylene / butadiene / styrene copolymers, styrene / isoprene / styrene block copolymers and hydrogenated products thereof; syndiotactic-1,2-polybutadiene, polyvinyl acetate , Soft resinous polymers such as ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer; polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymer, etc. And a polymer composition having ion conductivity of alkali metal ions (particularly lithium ions). These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios.

The solvent for forming the slurry is not particularly limited as long as it is a solvent that can dissolve or disperse the negative electrode active material, binder, thickener and conductive material used as necessary. Alternatively, either an aqueous solvent or an organic solvent may be used.
Examples of the aqueous solvent include water, alcohol and the like, and examples of the organic solvent include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N , N-dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, dimethyl ether, dimethylacetamide, hexameryl phosphalamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane and the like. In particular, when an aqueous solvent is used, a dispersant or the like is added in addition to the above-described thickener, and a slurry is formed using a latex such as SBR. In addition, these may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio.

The ratio of the binder to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, and usually 20% by mass or less, 15% by mass. % Or less is preferable, 10 mass% or less is more preferable, and 8 mass% or less is particularly preferable.
When the ratio of the binder with respect to a negative electrode active material exceeds the said range, the binder ratio in which the amount of binders does not contribute to battery capacity may increase, and battery capacity may fall. On the other hand, if it is below the above range, the strength of the negative electrode is lowered, which may be undesirable in the battery production process.

In particular, when a rubbery polymer represented by SBR is contained as a main component, the ratio of the binder to the active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, and 6 mass% or more is still more preferable, and it is 5 mass% or less normally, 3 mass% or less is preferable, and 2 mass% or less is still more preferable.
Further, when the main component contains a fluorine polymer represented by polyvinylidene fluoride, the ratio to the active material is 1% by mass or more, preferably 2% by mass or more, more preferably 3% by mass or more, Usually, it is 15 mass% or less, 10 mass% or less is preferable, and 8 mass% or less is still more preferable.

  A thickener is usually used to adjust the viscosity of the slurry. The thickener is not particularly limited, and specific examples include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios.

  Further, when a thickener is used, the ratio of the thickener to the negative electrode active material is 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, Usually, it is 5 mass% or less, 3 mass% or less is preferable, and 2 mass% or less is still more preferable. When the ratio of the thickener to the negative electrode active material is less than the above range, applicability may be significantly reduced. Moreover, when it exceeds the said range, the ratio of the active material which occupies for a negative electrode active material layer will fall, the problem that the capacity | capacitance of a battery falls, and the resistance between negative electrode active materials may increase.

<2-4 positive electrode>
The positive electrode used for the non-aqueous electrolyte secondary battery of the present invention will be described below.
<2-4-1 positive electrode active material>
The positive electrode active material used for the positive electrode will be described below.
(2-4-1-1) Composition
The positive electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions. For example, a material containing lithium and at least one transition metal is preferable. Specific examples include lithium transition metal composite oxides and lithium-containing transition metal phosphate compounds.

  V, Ti, Cr, Mn, Fe, Co, Ni, Cu and the like are preferable as the transition metal of the lithium transition metal composite oxide. Specific examples include lithium-cobalt composite oxides such as LiCoO2 and lithium- Nickel composite oxides, lithium manganese composite oxides such as LiMnO2, LiMn2O4, Li2MnO4, and some of transition metal atoms that are the main components of these lithium transition metal composite oxides are Al, Ti, V, Cr, Mn, Fe, Examples include those substituted with other metals such as Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, and Si.

Specific examples of the substituted ones include, for example, LiNi0.5Mn0.5O2, LiNi0.85Co0.10Al0.05O2, LiNi0.33Co0.33Mn0.33O2, LiMn1.8Al0.2O4, LiMn1.5Ni0.5O4, and the like.
As the transition metal of the lithium-containing transition metal phosphate compound, V, Ti, Cr, Mn, Fe, Co, Ni, Cu and the like are preferable, and specific examples include, for example, LiFePO4, Li3Fe2 (PO4) 3, LiFeP2O7, and the like. Iron phosphates, cobalt phosphates such as LiCoPO4, and some of transition metal atoms that are the main components of these lithium transition metal phosphate compounds are Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Examples include those substituted with other metals such as Cu, Zn, Mg, Ga, Zr, Nb, and Si.

(2-4-1-2) Surface coating
A material having a composition different from that of the main constituent of the positive electrode active material (hereinafter referred to as “surface adhering material” as appropriate) may be used on the surface of the positive electrode active material. Examples of surface adhering substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, Examples thereof include sulfates such as calcium sulfate and aluminum sulfate, and carbonates such as lithium carbonate, calcium carbonate and magnesium carbonate.

These surface adhering substances are, for example, a method in which they are dissolved or suspended in a solvent and impregnated and added to the positive electrode active material and then dried, or a surface adhering substance precursor is dissolved or suspended in a solvent and impregnated and added to the positive electrode active material. Then, it can be made to adhere to the surface of the positive electrode active material by a method of reacting by heating or the like, a method of adding to the positive electrode active material precursor and firing simultaneously.
The mass of the surface adhering material adhering to the surface of the positive electrode active material is usually 0.1 ppm or more, preferably 1 ppm or more, more preferably 10 ppm or more, and usually 20% with respect to the mass of the positive electrode active material. Or less, preferably 10% or less, more preferably 5% or less.

The surface adhering substance can suppress the oxidation reaction of the non-aqueous electrolyte on the surface of the positive electrode active material, and can improve the battery life. However, when the adhesion amount is less than the above range, the effect is not sufficiently exhibited. When the adhesion amount is more than the above range, the resistance may increase in order to inhibit the entry / exit of lithium ions, so the above range is preferable.
(2-4-1-3) Shape
As the shape of the positive electrode active material particles, a lump shape, a polyhedron shape, a sphere shape, an oval sphere shape, a plate shape, a needle shape, a column shape, etc., which are conventionally used, are used, and the primary particles are aggregated to form secondary particles. It is preferable that the secondary particles have a spherical or elliptical shape.

In general, an electrochemical element expands and contracts as the active material in the electrode expands and contracts as it is charged and discharged. Therefore, the active material is easily damaged due to the stress or the conductive path is broken. Therefore, the primary particles are aggregated to form secondary particles rather than a single particle active material having only primary particles, so that the stress of expansion and contraction is relieved and deterioration is prevented.
In addition, spherical or oval spherical particles are less oriented at the time of forming the electrode than the plate-like equiaxially oriented particles, so there is less expansion and contraction of the electrode during charge and discharge, and when creating the electrode Also in the mixing with the conductive material, it is preferable because it is easily mixed uniformly.

(2-4-1-4) Tap density
The tap density of the positive electrode active material is usually 1.3 g · cm −3 or more, preferably 1.5 g · cm −3 or more, more preferably 1.6 g · cm −3 or more, and 1.7 g · cm −3. The above is particularly preferable, and is usually 2.5 g · cm −3 or less, and preferably 2.4 g · cm −3 or less.

  By using a metal composite oxide powder having a high tap density, a high-density positive electrode active material layer can be formed. Therefore, when the tap density of the positive electrode active material is lower than the above range, the amount of the dispersion medium necessary for forming the positive electrode active material layer increases, and the necessary amount of the conductive material and the binder increases. The filling rate of the positive electrode active material is limited, and the battery capacity may be limited. In general, the tap density is preferably as large as possible, but there is no particular upper limit. However, if the tap density is less than the above range, diffusion of lithium ions in the positive electrode active material layer using the non-aqueous electrolyte solution as a medium becomes rate-determining, and load characteristics are likely to deteriorate. There is a case.

  The tap density is measured by passing a sieve having an opening of 300 μm, dropping the sample onto a 20 cm 3 tapping cell to fill the cell volume, and then using a powder density measuring device (eg, tap denser manufactured by Seishin Enterprise Co., Ltd.). Then, tapping with a stroke length of 10 mm is performed 1000 times, and the density is calculated from the volume at that time and the weight of the sample. The tap density calculated by the measurement is defined as the tap density of the positive electrode active material in the present invention.

(2-4-1-5) Median diameter d50
The median diameter d50 (secondary particle diameter when primary particles are aggregated to form secondary particles) of the positive electrode active material particles should also be measured using a laser diffraction / scattering particle size distribution analyzer. Can do.
The median diameter d50 is usually 0.1 μm or more, preferably 0.5 μm or more, more preferably 1 μm or more, particularly preferably 3 μm or more, and usually 20 μm or less, preferably 18 μm or less, more preferably 16 μm or less. 15 μm or less is particularly preferable. If the median diameter d50 is below the above range, a high bulk density product may not be obtained. If the median diameter d50 is above the above range, it takes time to diffuse lithium in the particles. That is, when an active material, a conductive material, a binder, or the like is slurried with a solvent and applied in a thin film shape, streaks may occur.

In addition, the filling property at the time of positive electrode preparation can be further improved by mixing two or more types of positive electrode active materials having different median diameters d50 at an arbitrary ratio.
The median diameter d50 is measured using a 0.1 mass% sodium hexametaphosphate aqueous solution as a dispersion medium, and using LA-920 manufactured by Horiba, Ltd. as a particle size distribution meter, the measured refractive index is 1.24 after ultrasonic dispersion for 5 minutes. Set and measure.

(2-4-1-6) Average primary particle size
When primary particles are aggregated to form secondary particles, the average primary particle diameter of the positive electrode active material is usually 0.01 μm or more, preferably 0.05 μm or more, more preferably 0.08 μm or more, 0 0.1 μm or more is particularly preferable, usually 3 μm or less, preferably 2 μm or less, more preferably 1 μm or less, and particularly preferably 0.6 μm or less. If the above range is exceeded, it may be difficult to form spherical secondary particles, which may adversely affect the powder filling property, or the specific surface area will be greatly reduced, which may increase the possibility that the battery performance such as output characteristics will deteriorate. is there. On the other hand, below the above range, the performance of the secondary battery may be lowered, for example, the reversibility of charge / discharge is inferior because the crystals are not developed.

The average primary particle diameter is measured by observation using a scanning electron microscope (SEM). Specifically, in a photograph at a magnification of 10000 times, the longest value of the intercept by the left and right boundary lines of the primary particles with respect to the horizontal straight line is obtained for any 50 primary particles and obtained by taking the average value. It is done.
(2-4-1-7) BET specific surface area
As for the BET specific surface area of the positive electrode active material, the value of the specific surface area measured using the BET method is usually 0.2 m 2 · g −1 or more, preferably 0.3 m 2 · g −1 or more, and 0.4 m 2 · g. −1 or more is more preferable, and is usually 4.0 m 2 · g −1 or less, preferably 2.5 m 2 · g −1 or less, and more preferably 1.5 m 2 · g −1 or less. When the value of the BET specific surface area is below the above range, the battery performance tends to be lowered. Moreover, when it exceeds the said range, a tap density becomes difficult to raise and the applicability | paintability at the time of positive electrode active material formation may fall.

  The BET specific surface area is measured using a surface area meter (a fully automatic surface area measuring device manufactured by Okura Riken). The sample was preliminarily dried at 150 ° C. for 30 minutes under a nitrogen flow, and then a nitrogen helium mixed gas that was accurately adjusted so that the relative pressure of nitrogen with respect to atmospheric pressure was 0.3 was used. It is measured by the nitrogen adsorption BET one-point method by the flow method. The specific surface area determined by the measurement is defined as the BET specific surface area of the anode active material in the present invention.

(2-4-1-8) Method for producing positive electrode active material
Although it does not restrict | limit especially as a manufacturing method of a positive electrode active material in the range which does not exceed the summary of this invention, Several methods are mentioned, A general method is used as a manufacturing method of an inorganic compound.
In particular, various methods are conceivable for producing a spherical or elliptical active material. For example, transition metal source materials such as transition metal nitrates and sulfates, and other element source materials as required. Is dissolved or pulverized and dispersed in a solvent such as water, and the pH is adjusted while stirring to produce and recover a spherical precursor, which is dried as necessary, and then LiOH such as LiOH, Li2CO3, and LiNO3. A method of obtaining an active material by adding a source and baking at a high temperature can be mentioned.

  In addition, as an example of another method, transition metal raw materials such as transition metal nitrates, sulfates, hydroxides, oxides and the like, and if necessary, raw materials of other elements are dissolved or pulverized and dispersed in a solvent such as water. Then, it may be dry-molded with a spray drier or the like to obtain a spherical or elliptical precursor, and a Li source such as LiOH, Li2CO3, LiNO3 or the like is added thereto and baked at a high temperature to obtain an active material.

  Examples of other methods include transition metal source materials such as transition metal nitrates, sulfates, hydroxides and oxides, Li sources such as LiOH, Li2CO3 and LiNO3, and source materials of other elements as necessary. Is dissolved or pulverized and dispersed in a solvent such as water, and then dried and molded with a spray dryer or the like to obtain a spherical or elliptical precursor, which is fired at a high temperature to obtain an active material.

<2-4-2 Electrode structure and fabrication method>
Below, the structure of the positive electrode used for this invention and its preparation method are demonstrated.
(2-4-2-1) Method for producing positive electrode
The positive electrode is produced by forming a positive electrode active material layer containing positive electrode active material particles and a binder on a current collector. The production of the positive electrode using the positive electrode active material can be produced by any known method. That is, a positive electrode active material and a binder, and if necessary, a conductive material and a thickener mixed in a dry form are pressure-bonded to a positive electrode current collector, or these materials are liquid media A positive electrode can be obtained by forming a positive electrode active material layer on the current collector by applying it to a positive electrode current collector and drying it as a slurry by dissolving or dispersing in a slurry.

  The content of the positive electrode active material in the positive electrode active material layer is usually 10% by mass or more, preferably 30% by mass or more, particularly preferably 50% by mass or more, and usually 99.9% by mass or less, preferably 99% by mass. It is as follows. This is because if the content of the positive electrode active material in the positive electrode active material layer is less than the above range, the electric capacity may be insufficient. Moreover, it is because the intensity | strength of a positive electrode may be insufficient when it exceeds the said range. In addition, the positive electrode active material powder in this invention may be used individually by 1 type, and may use together 2 or more types of a different composition or different powder physical properties by arbitrary combinations and ratios.

(2-4-2-2) Conductive material
A known conductive material can be arbitrarily used as the conductive material. Specific examples include metal materials such as copper and nickel; graphite such as natural graphite and artificial graphite (graphite); carbon black such as acetylene black; and carbonaceous materials such as amorphous carbon such as needle coke. In addition, these may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

  The conductive material is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 1% by mass or more, and usually 50% by mass or less, preferably 30% by mass or less in the positive electrode active material layer. More preferably, it is used so as to contain 15% by mass or less. If the content is lower than the above range, the conductivity may be insufficient. Moreover, when it exceeds the said range, battery capacity may fall.

(2-4-2-3) Binder
The binder used for manufacturing the positive electrode active material layer is not particularly limited as long as it is a material that is stable with respect to the non-aqueous electrolyte solution and the solvent used during electrode manufacturing.
In the case of the coating method, any material can be used as long as it is dissolved or dispersed in the liquid medium used during electrode production. Specific examples include polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, nitro Resin polymers such as cellulose; Rubber polymers such as SBR (styrene butadiene rubber), NBR (acrylonitrile butadiene rubber), fluoro rubber, isoprene rubber, butadiene rubber, ethylene propylene rubber; styrene butadiene styrene block Copolymer or its hydrogenated product, EPDM (ethylene / propylene / diene terpolymer), styrene / ethylene / butadiene / ethylene copolymer, styrene / isoprene / styrene block copolymer or its hydrogenated product, etc. Thermoplastic Stoma-like polymers; soft resin-like polymers such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer; polyvinylidene fluoride (PVdF), Examples include fluorine-based polymers such as polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene / ethylene copolymers; polymer compositions having ion conductivity of alkali metal ions (particularly lithium ions). In addition, these substances may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

The ratio of the binder in the positive electrode active material layer is usually 0.1% by mass or more, preferably 1% by mass or more, more preferably 3% by mass or more, and usually 80% by mass or less, and 60% by mass. % Or less is preferable, 40% by mass or less is more preferable, and 10% by mass or less is particularly preferable. When the ratio of the binder is below the above range, the positive electrode active material cannot be sufficiently retained, the positive electrode has insufficient mechanical strength, and battery performance such as cycle characteristics may be deteriorated. Moreover, when it exceeds the said range, it may lead to a battery capacity or electroconductivity fall.

(2-4-2-4) Liquid medium
The liquid medium for forming the slurry may be any type of solvent that can dissolve or disperse the positive electrode active material, the conductive material, the binder, and the thickener used as necessary. There is no particular limitation, and either an aqueous solvent or an organic solvent may be used.
Examples of the aqueous medium include water, a mixed medium of alcohol and water, and the like. Examples of organic media include aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, and methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; ketones such as acetone, methyl ethyl ketone, and cyclohexanone. Esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N, N-dimethylaminopropylamine; ethers such as diethyl ether and tetrahydrofuran (THF); N-methylpyrrolidone (NMP) and dimethylformamide And amides such as dimethylacetamide; aprotic polar solvents such as hexamethylphosphalamide and dimethyl sulfoxide. In addition, these may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

(2-4-2-5) Thickener
When an aqueous medium is used as the liquid medium for forming the slurry, it is preferable to make a slurry using a thickener and a latex such as styrene butadiene rubber (SBR). A thickener is usually used to adjust the viscosity of the slurry.
The thickener is not limited as long as the effect of the present invention is not significantly limited. Specifically, carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein and salts thereof Etc. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios.

  Further, when using a thickener, the ratio of the thickener to the active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, Usually, it is 5% by mass or less, preferably 3% by mass or less, more preferably 2% by mass or less. If it falls below the above range, applicability may be remarkably reduced, and if it exceeds the above range, the ratio of the active material in the positive electrode active material layer is lowered, the battery capacity is reduced, and the resistance between the positive electrode active materials. May increase.

(2-4-2-6) Consolidation
The positive electrode active material layer obtained by coating and drying is preferably consolidated by a hand press, a roller press or the like in order to increase the packing density of the positive electrode active material. The density of the positive electrode active material layer is preferably 1 g · cm −3 or more, more preferably 1.5 g · cm −3 or more, particularly preferably 2 g · cm −3 or more, and preferably 4 g · cm −3 or less. 3.5 g · cm −3 or less is more preferable, and 3 g · cm −3 or less is particularly preferable.

If the density of the positive electrode active material layer exceeds the above range, the permeability of the non-aqueous electrolyte solution to the vicinity of the current collector / active material interface may decrease, and the charge / discharge characteristics at a high current density may decrease. Moreover, when less than the said range, the electroconductivity between active materials may fall and battery resistance may increase.
(2-4-2-7) Current collector
There is no restriction | limiting in particular as a material of a positive electrode electrical power collector, A well-known thing can be used arbitrarily. Specific examples include metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum; and carbonaceous materials such as carbon cloth and carbon paper. Of these, metal materials, particularly aluminum, are preferred.

Examples of the shape of the current collector include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punch metal, foam metal, etc. A carbon thin film, a carbon cylinder, etc. are mentioned. Of these, metal thin films are preferred. In addition, you may form a thin film suitably in mesh shape.
The thickness of the current collector is arbitrary, but is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and usually 1 mm or less, preferably 100 μm or less, more preferably 50 μm or less. If the thin film is thinner than the above range, the strength required for the current collector may be insufficient. Moreover, when a thin film is thicker than the said range, a handleability may be impaired.

<2-5. Separator>
Usually, a separator is interposed between the positive electrode and the negative electrode in order to prevent a short circuit. In this case, the nonaqueous electrolytic solution of the present invention is usually used by impregnating the separator.
There is no restriction | limiting in particular about the material and shape of a separator, As long as the effect of this invention is not impaired remarkably, a well-known thing can be employ | adopted arbitrarily. Among them, a resin, glass fiber, inorganic material, etc. formed of a material that is stable with respect to the non-aqueous electrolyte solution of the present invention is used, and a porous sheet or a nonwoven fabric-like material having excellent liquid retention properties is used. Is preferred.

  As materials for the resin and the glass fiber separator, for example, polyolefins such as polyethylene and polypropylene, polytetrafluoroethylene, polyethersulfone, glass filters and the like can be used. Of these, glass filters and polyolefins are preferred, and polyolefins are more preferred. These materials may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  The thickness of the separator is arbitrary, but is usually 1 μm or more, preferably 5 μm or more, more preferably 10 μm or more, and usually 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less. If the separator is too thin than the above range, the insulating properties and mechanical strength may decrease. On the other hand, if it is thicker than the above range, not only the battery performance such as the rate characteristic may be lowered, but also the energy density of the whole non-aqueous electrolyte secondary battery may be lowered.

  Furthermore, when a porous material such as a porous sheet or nonwoven fabric is used as the separator, the porosity of the separator is arbitrary, but is usually 20% or more, preferably 35% or more, more preferably 45% or more, Moreover, it is 90% or less normally, 85% or less is preferable and 75% or less is still more preferable. If the porosity is too smaller than the above range, the membrane resistance tends to increase and the rate characteristics tend to deteriorate. Moreover, when larger than the said range, it exists in the tendency for the mechanical strength of a separator to fall and for insulation to fall.

Moreover, although the average pore diameter of a separator is also arbitrary, it is 0.5 micrometer or less normally, 0.2 micrometer or less is preferable, and it is 0.05 micrometer or more normally. If the average pore diameter exceeds the above range, a short circuit tends to occur. On the other hand, below the above range, the film resistance may increase and the rate characteristics may deteriorate.
On the other hand, as the inorganic material, for example, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate are used. Things are used.

As the form, a thin film shape such as a non-woven fabric, a woven fabric, or a microporous film is used. In the thin film shape, those having a pore diameter of 0.01 to 1 μm and a thickness of 5 to 50 μm are preferably used. In addition to the independent thin film shape, a separator formed by forming a composite porous layer containing the inorganic particles on the surface layer of the positive electrode and / or the negative electrode using a resin binder can be used. For example, a porous layer may be formed by using alumina particles having a 90% particle size of less than 1 μm on both surfaces of the positive electrode and using a fluororesin as a binder.

<2-6. Battery design>
[Electrode group]
The electrode group has a laminated structure in which the positive electrode plate and the negative electrode plate are interposed via the separator, and a structure in which the positive electrode plate and the negative electrode plate are wound in a spiral shape via the separator. Either may be used. The ratio of the volume of the electrode group to the internal volume of the battery (hereinafter referred to as the electrode group occupation ratio) is usually 40% or more, preferably 50% or more, and usually 90% or less, preferably 80% or less. . When the electrode group occupancy is below the above range, the battery capacity decreases. Also, if the above range is exceeded, the void space is small, the battery expands, and the member expands or the vapor pressure of the electrolyte liquid component increases and the internal pressure rises. In some cases, a gas release valve that lowers various characteristics such as storage at high temperature and the like, or releases the internal pressure to the outside is activated.

[Current collection structure]
The current collecting structure is not particularly limited, but in order to more effectively realize the improvement of the discharge characteristics by the non-aqueous electrolyte solution of the present invention, it is necessary to make the structure to reduce the resistance of the wiring part and the joint part. preferable. Thus, when internal resistance is reduced, the effect of using the non-aqueous electrolyte solution of this invention is exhibited especially favorable.

  In the case where the electrode group has the laminated structure described above, a structure formed by bundling the metal core portions of the electrode layers and welding them to the terminals is preferably used. When the area of one electrode increases, the internal resistance increases. Therefore, it is also preferable to reduce the resistance by providing a plurality of terminals in the electrode. When the electrode group has the winding structure described above, the internal resistance can be lowered by providing a plurality of lead structures for the positive electrode and the negative electrode, respectively, and bundling the terminals.

[Exterior case]
The material of the outer case is not particularly limited as long as it is a substance that is stable with respect to the non-aqueous electrolyte used. Specifically, a nickel-plated steel plate, stainless steel, aluminum, an aluminum alloy, a metal such as a magnesium alloy, or a laminated film (laminate film) of a resin and an aluminum foil is used. From the viewpoint of weight reduction, an aluminum or aluminum alloy metal or a laminate film is preferably used.

  In the exterior case using the above metals, a laser-sealed, resistance-welded, ultrasonic welding is used to weld the metals together to form a sealed sealed structure, or a caulking structure using the above-mentioned metals via a resin gasket To do. Examples of the outer case using the laminate film include those having a sealed and sealed structure by heat-sealing resin layers. In order to improve the sealing performance, a resin different from the resin used for the laminate film may be interposed between the resin layers. In particular, when a resin layer is heat-sealed through a current collecting terminal to form a sealed structure, a metal and a resin are joined, so that a resin having a polar group or a modified group having a polar group introduced as an intervening resin is used. Resins are preferably used.

[Protective element]
PTC (Positive Temperature Coefficient), thermal fuse, thermistor, which increases resistance when abnormal heat is generated or excessive current flows, the current flowing through the circuit due to a sudden rise in battery internal pressure or internal temperature during abnormal heat generation For example, a valve (current cutoff valve) that shuts off the current can be used. It is preferable to select a protective element that does not operate under normal use at a high current. From the viewpoint of high output, it is more preferable to design the protective element so as not to cause abnormal heat generation or thermal runaway even without the protective element.

[Exterior body]
The non-aqueous electrolyte secondary battery of the present invention is usually configured by housing the non-aqueous electrolyte, the negative electrode, the positive electrode, the separator, and the like in an exterior body. There is no restriction | limiting in this exterior body, As long as the effect of this invention is not impaired remarkably, a well-known thing can be employ | adopted arbitrarily.
Specifically, the material of the exterior body is arbitrary, but usually, for example, nickel-plated iron, stainless steel, aluminum or an alloy thereof, nickel, titanium, or the like is used.

  The shape of the exterior body is also arbitrary, and may be any of a cylindrical shape, a square shape, a laminate shape, a coin shape, a large size, and the like.

EXAMPLES Hereinafter, although an Example and a reference example are given and this invention is demonstrated further more concretely, this invention is not limited to these Examples, unless the summary is exceeded.
[Production of secondary battery]
<Preparation of positive electrode>
Lithium nickel manganese cobaltate (LiNi1 / 3Mn1 / 3Co1 / 3) as positive electrode active material
O2) Using 90 parts by mass, 7 parts by mass of carbon black and 3 parts by mass of polyvinylidene fluoride were mixed, and N-methyl-2-pyrrolidone was added to form a slurry, which was uniformly applied to both sides of an aluminum foil having a thickness of 15 μm. After drying, the positive electrode active material layer was pressed so as to have a density of 2.6 g · cm −3 to obtain a positive electrode.

<Production of negative electrode>
To graphite, an aqueous dispersion of sodium carboxymethylcellulose (concentration of 1% by mass of sodium carboxymethylcellulose) as a thickener and an aqueous dispersion of styrene-butadiene rubber (concentration of styrene-butadiene rubber of 50% by mass) as a binder are added. The slurry was mixed with a disperser. The obtained slurry was uniformly applied to one side of a 12 μm thick copper foil and dried, and then pressed so that the density of the negative electrode active material layer was 1.4 g · cm ⁻³ to obtain a negative electrode. The graphite used has a d50 value of 10.9 μm, a specific surface area of 3.41 m ² / g, and a tap density of 0.985 g / cm ³ . Further, the slurry was prepared so that the weight ratio of graphite: sodium carboxymethylcellulose: styrene-butadiene rubber = 98: 1: 1 was obtained in the negative electrode after drying.

<Manufacture of non-aqueous electrolyte secondary battery>
The positive electrode, the negative electrode, and the polyethylene separator were laminated in the order of the negative electrode, the separator, and the positive electrode. The battery element thus obtained was wrapped in a cylindrical aluminum laminate film, injected with an electrolyte described later, and then vacuum sealed to produce a sheet-like non-aqueous electrolyte secondary battery. Furthermore, in order to increase the adhesion between the electrodes, the sheet battery was sandwiched between glass plates and pressed.

[Battery evaluation]
<Initial charge / discharge test>
In a constant temperature bath at 25 ° C., the sheet-like non-aqueous electrolyte secondary battery was charged at 0.05 C for 10 hours, rested for 6 hours, and then charged at constant current at 0.2 C to 4.1 V. Further, after resting for 6 hours, constant current-constant voltage charging was performed at 0.2 C up to 4.1 V, and then constant current discharging was performed up to 3.0 V at 1/3 C. After that, two charging / discharging cycles were carried out, in which 1 / 3C constant current-constant voltage charging up to 4.1V and subsequent 1 / 3C constant current discharging up to 3.0V were taken as one cycle. Furthermore, after charging at a constant current-constant voltage at 1/3 C to 4.1 V, the battery was stored at 60 ° C. for 12 hours to stabilize the battery. After that, the charge / discharge cycle of 1 / 3C constant current-constant voltage charge up to 4.1V at 25 ° C. and 1 / 3C constant current discharge up to 3.0V following this was repeated.
Cycled. The last discharge capacity at this time was defined as the initial capacity. In addition, 1C is a current value when discharging the entire capacity of the battery in one hour.

<Low-temperature discharge characteristic evaluation test>
For a battery charged by an amount of electricity corresponding to 50% of the initial capacity (hereinafter, the battery in this state may be referred to as SOC 50%), in an environment of −30 ° C., 0.3 C, 0.5 C, Each of the batteries was discharged at 1.0 C, 1.5 C, 2.0 C, and 2.5 C, and the voltage after 2 seconds was measured. In the current-voltage curve thus obtained, the current value at 3V was calculated, and the product of this current value and 3V was used as the initial low temperature discharge characteristic.

[Example 1]
Under a dry argon atmosphere, fully dried LiPF ₆ was dissolved in a mixture of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate (volume ratio 3: 3: 4) so that the total amount of the non-aqueous electrolyte was 1 mol / L. (This electrolyte solution may be referred to as “reference electrolyte solution”). A non-aqueous electrolyte solution was prepared by adding 0.5 mass of (a) and Chemical Formula 2 to the reference electrolyte solution. A battery was prepared by the above-described method using this electrolytic solution, and the low-temperature discharge characteristics were measured. The ratio of the results thus obtained to Reference Example 6 is shown in Table 1.

[Example 2]
An electrolytic solution was prepared in the same manner as in Example 1 except that 2.0% by mass of Chemical 3 was added to the electrolytic solution instead of Chemical 2, and the battery was prepared and the low-temperature discharge characteristics were evaluated in the same manner as in Example 1. Went. The ratio of the results thus obtained to Reference Example 6 is shown in Table 1.

[Example 3]
An electrolytic solution was prepared in the same manner as in Example 1 except that 0.5% by mass of Chemical 4 was added to the electrolytic solution instead of Chemical 2. Preparation of a battery and evaluation of low-temperature discharge characteristics were performed in the same manner as in Example 1. Went. The ratio of the results thus obtained to Reference Example 6 is shown in Table 1.
[Example 4]
An electrolyte solution was prepared in the same manner as in Example 1 except that 1.0% by mass of (j) was added to the electrolyte solution instead of (a), and battery preparation and low-temperature discharge characteristics were performed in the same manner as in Example 1. Was evaluated. The ratio of the results thus obtained to Reference Example 6 is shown in Table 1.

[Example 5]
An electrolytic solution was prepared in the same manner as in Example 4 except that 0.5% by mass of Chemical 4 was added to the electrolytic solution instead of Chemical 2, and the battery was prepared and the low-temperature discharge characteristics were evaluated in the same manner as in Example 1. Went. The ratio of the results thus obtained to Reference Example 6 is shown in Table 1.
[Reference Example 1]
An electrolyte solution was prepared in the same manner as in Example 1 except that Chemical Formula 2 was not added to the electrolyte solution, and a battery was prepared and low-temperature discharge characteristics were evaluated in the same manner as in Example 1. The ratio of the results thus obtained to Reference Example 6 is shown in Table 1.

[Reference Example 2]
An electrolyte solution was prepared in the same manner as in Example 4 except that Chemical Formula 2 was not added to the electrolyte solution, and a battery was prepared and low-temperature discharge characteristics were evaluated in the same manner as in Example 1. The ratio of the results thus obtained to Reference Example 6 is shown in Table 1.
[Reference Example 3]
An electrolyte solution was prepared in the same manner as in Example 1 except that (a) was not added to the electrolyte solution, and a battery was prepared and low-temperature discharge characteristics were evaluated in the same manner as in Example 1. The ratio of the results thus obtained to Reference Example 6 is shown in Table 1.

[Reference Example 4]
An electrolyte solution was prepared in the same manner as in Example 2 except that (a) was not added to the electrolyte solution, and a battery was prepared and low-temperature discharge characteristics were evaluated in the same manner as in Example 1. The ratio of the results thus obtained to Reference Example 6 is shown in Table 1.
[Reference Example 5]
An electrolyte solution was prepared in the same manner as in Example 3 except that (a) was not added to the electrolyte solution, and a battery was prepared and low-temperature discharge characteristics were evaluated in the same manner as in Example 1. The ratio of the results thus obtained to Reference Example 6 is shown in Table 1.

[Reference Example 6]
Using the reference electrolyte, the battery was prepared and the low-temperature discharge characteristics were evaluated in the same manner as in Example 1. The low temperature discharge characteristics thus obtained are shown in Table 1 as 1.00.

  From Reference Example 1 to Reference Example 5 in Table 1, “specific Si compound” in the present invention represented by (a) and (j) and “specific salt” in the present invention represented by Chemical Formulas 2 to 4 It was found that the low temperature discharge characteristics were improved by adding. And in Example 1-Example 5, it turned out that the low temperature discharge characteristic is improving by the specific synergistic effect instead of the mere sum of these both effects.

[Reference Example 7]
An electrolyte solution was prepared in the same manner as in Example 1 except that 1.0% by mass of 1,2-divinyltetramethyldisilane was added to the electrolyte solution instead of (a), and a battery was prepared in the same manner as in Example 1. In addition, the low-temperature discharge characteristics were evaluated. Table 2 shows the ratio of the results thus obtained to Reference Example 6.

[Reference Example 8]
An electrolyte solution was prepared in the same manner as in Reference Example 7 except that Chemical Formula 2 was not added to the electrolyte solution, and a battery was prepared and low-temperature discharge characteristics were evaluated in the same manner as in Example 1. Table 2 shows the ratio of the results thus obtained to Reference Example 6.

From Table 2, when 1,2-divinyltetramethyldisilane, which is an Si compound other than the “specific Si compound” in the present invention, is added, when used together with the “specific salt” in the present invention, the low temperature discharge characteristics Tended to decrease.
As a cause of this, Si-Si compounds having an aliphatic substituent having an unsaturated bond represented by 1,2-divinyltetramethyldisilane have a high self-polymerization of the aliphatic substituent having an unsaturated bond. It is presumed that since the film tends to progress, a film more than necessary was formed, and the film became more resistant.

According to the non-aqueous electrolyte solution of the present invention, a non-aqueous electrolyte secondary battery excellent in low-temperature discharge characteristics can be produced, and thus suitable for all fields such as electronic devices in which the non-aqueous electrolyte secondary battery is used. Available to:
The application of the non-aqueous electrolyte solution or the non-aqueous electrolyte secondary battery of the present invention is not particularly limited, and can be used for various known applications. Specific examples include notebook computers, pen input computers, mobile computers, electronic book players, mobile phones, mobile faxes, mobile copy, mobile printers, headphone stereos, video movies, LCD TVs, handy cleaners, portable CDs, minidiscs, and transceivers. , Electronic notebook, calculator, memory card, portable tape recorder, radio, backup power supply, motor, automobile, motorcycle, motorbike, bicycle, lighting equipment, toy, game equipment, clock, electric tool, strobe, camera, etc. Can do.

Claims (6)

A non-aqueous electrolyte used in a non-aqueous electrolyte secondary battery comprising a negative electrode and a positive electrode capable of occluding and releasing metal ions, and a non-aqueous electrolyte, wherein the non-aqueous electrolyte comprises the following (A) and A non-aqueous electrolyte containing (B).
(A) Compound having Si-Si bond having no aliphatic substituent having unsaturated bond (B) Selected from the group consisting of monofluorophosphate, difluorophosphate, fluorosulfonate, and imide salt At least one compound At least one compound selected from the group consisting of the monofluorophosphate, difluorophosphate, fluorosulfonate, and imide salt is lithium monofluorophosphate, lithium difluorophosphate, lithium fluorosulfonate, LiN _2. The compound according to claim 1, wherein the compound is at least one compound selected from the group consisting of (FSO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , and LiN (C ₂ F ₅ SO ₂ ) ₂ . Non-aqueous electrolyte. The non-aqueous system according to claim 1 or 2, wherein the compound having an Si-Si bond having no unsaturated substituent having an unsaturated bond is a compound represented by the following general formula (1). Electrolytic solution.

(A ^{1 to} A ⁶ may be the same or different, and may be a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 10 carbon atoms that may have a hetero atom, or silicon that may have a substituent. Represents a silicic acid group of 1 to 10, and A ^{1 to} A ⁶ may be bonded to each other to form a ring, provided that A ^{1 to} A ⁶ are all aliphatic substituents having an unsaturated bond. Absent.)   Compounds having an Si—Si bond having no unsaturated substituent having an unsaturated bond are hexamethyldisilane, hexaethyldisilane, 1,2-diphenyltetramethyldisilane, and 1,1,2,2-tetra. The non-aqueous electrolyte solution according to any one of claims 1 to 3, wherein the non-aqueous electrolyte solution is at least one selected from the group consisting of phenyldisilane.   5. The composition according to claim 1, further comprising 0.01% by mass or more and 10% by mass or less of a compound having an Si—Si bond having no unsaturated substituent having an unsaturated bond. The non-aqueous electrolyte described. It is a non-aqueous electrolyte secondary battery provided with the carbon-type negative electrode and positive electrode which can occlude and discharge | release metal ion, and a non-aqueous electrolyte, Comprising: This non-aqueous electrolyte is any one of Claims 1-5. A nonaqueous electrolyte secondary battery, characterized by being a nonaqueous electrolyte solution.