JP2012182132A - Nonaqueous electrolyte secondary battery and nonaqueous electrolyte - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery excellent in long term durability and load characteristics.SOLUTION: A nonaqueous electrolyte secondary battery includes at least a positive electrode capable of absorbing/desorbing metal ions, a negative electrode capable of absorbing/desorbing metal ions, and a nonaqueous electrolyte containing a nonaqueous solvent and an electrolyte dissolved in the nonaqueous solvent. The negative electrode contains a carbonaceous material. The nonaqueous electrolyte contains, in addition to the electrolyte and the nonaqueous solvent, (A) a compound having at least two or more isocyanate groups in the molecule, and (B) monofluorophosphate or difluorophosphate.

Description

  The present invention relates to a non-aqueous electrolyte secondary battery, and more particularly to a non-aqueous electrolyte secondary battery containing a specific component.

  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 efforts to improve performance have been repeated until now.

  On the other hand, in recent years, with the background of global issues such as environmental problems and energy problems, 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, in general, it is indispensable to ensure the stability of such batteries against repeated charging and discharging over a long period of time, and further, they are expected to be used in an environment exposed to the outside air. The battery characteristics under a low temperature environment, particularly the low temperature discharge characteristics, is regarded as important.

Components constituting the lithium secondary battery are mainly classified into a positive electrode, a negative electrode, a separator, and an electrolytic solution. Among these, the electrolyte generally includes an electrolyte 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 to improve the long-term durability of lithium secondary batteries, by adding a specific compound to the above electrolyte, a passive film is formed on the negative electrode at the initial use of the battery, which is a major cause of deterioration. Efforts are being made to suppress side reactions such as reductive decomposition of solvents.

  Examples of such compounds include compounds containing an isocyanate group in the molecule. Patent Document 1, Patent Document 2 and Patent Document 3 disclose that cycle stability is improved by adding a low-molecular compound having an isocyanate group, a chain isocyanate compound or a diisocyanate compound to the electrolyte solution, respectively. Yes.

  Patent Document 4 proposes to use a specific sulfone compound and an isocyanate compound in combination as a compound to be added to the electrolytic solution for improving the cycle characteristics.

JP 2005-259641 A JP 2006-164759 A JP 2007-242411 A JP 2010-225522 A

As described above, attempts have been made to improve the long-term stability of the battery using a compound containing an isocyanate group in the molecule, but depending on the type of isocyanate compound, the type of additive combined therewith, or the blending amount thereof Does not have sufficient durability. Furthermore, further improvements are required to achieve sufficient battery characteristics including low temperature discharge characteristics.

  This invention is made | formed in view of this background art, and is providing the non-aqueous electrolyte secondary battery excellent in long-term durability and load characteristics.

As a result of intensive studies in view of the above problems, the present inventor contains a positive electrode capable of occluding and releasing metal ions, a negative electrode capable of occluding and releasing metal ions, a non-aqueous solvent and an electrolyte dissolved in the non-aqueous solvent. A non-aqueous electrolyte secondary battery comprising at least a non-aqueous electrolyte solution,
The negative electrode contains a carbonaceous material, and the non-aqueous electrolyte solution together with an electrolyte and a non-aqueous solvent,
(A) a compound having at least two isocyanate groups in the molecule, and (B) a monofluorophosphate or difluorophosphate,
The present inventors have found that cycle characteristics and low-temperature discharge characteristics superior to those of the prior art can be realized by using a non-aqueous electrolyte secondary battery characterized by containing a non-aqueous electrolyte solution.

  Moreover, this invention provides the non-aqueous electrolyte solution used for the said non-aqueous electrolyte secondary battery.

The excellent effect of the present invention is considered to be due to a synergistic effect in which the four actions described below are combined. The first action can be obtained by blending the compound (A) into the electrolytic solution. Thereby, the passive film induced | guided | derived from this compound is formed on the negative electrode surface, and suppresses reductive decomposition of a solvent effectively. However, the film produced by the compound (A) has a weak resistance that it becomes a high resistance component when metal ions are occluded / released, and the positive electrode resistance is increased by repeated charge / discharge or does not contribute to the suppression. Such properties lead to a significant decrease in low temperature discharge characteristics. On the other hand, a film | membrane produces | generates on a negative electrode also by mix | blending the compound of (B). This is the second action, and this film exhibits an action of suppressing the reductive decomposition of the solvent surpassing the compound (A) in the initial stage of repeated charge and discharge. Further, the resistance of the introduced film is extremely lower than that of the compound (A). This excellent property is due to the fact that the main component of the coating is a dense inorganic material. However, in repeated charge / discharge over a long period of time, the effect of increasing the durability as in the compound (A) cannot be obtained. This is probably because the film is rather rigid inorganic material and has low resistance to physical deformation due to expansion / contraction of the electrode accompanying charge / discharge. However, the compound (B) has another action not seen in the compound (A), which is an action of protecting the positive electrode by adsorption onto the positive electrode or film formation. As a result, the oxidation of the solvent and other secondary reactions are suppressed, and the deposition of an insulator that causes an increase in the positive electrode resistance is suppressed. This is the third action. The subsequent fourth action is attributed to the fact that the compound (A) contains an isocyanate group having a high reactivity of 2 or more. That is, when the compound (A) has a plurality of isocyanate groups, not only the above-mentioned film formation but also a part of the film is integrally formed with the film component made of the compound (B), and various bonds are formed in the electrode. Brings about the effect of a curing agent that increases the chemical and physical strength. In particular, when the negative electrode contains a carbonaceous material, since there are generally many active surface functional groups on the surface of such a carbonaceous material, the bond strength between the carbonaceous materials or between the carbonaceous material and the coating is further increased by the same action. Can be increased.
By the above four actions, the formation of a high-quality film and the stability of the entire electrode structure including the film are dramatically increased, so that the compounds (A) and (B) cannot be achieved by using each of them alone. Excellent durability and load characteristics can be achieved.

  According to the present invention, a passive film having a low resistance is formed on the electrode surface to improve the chemical stability of the substance in the battery, and to improve resistance to physical deformation such as expansion and contraction of the electrode accompanying charging and discharging. Therefore, it is possible to provide a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte having both excellent cycle characteristics and low-temperature discharge characteristics over a long period of time.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. However, the description of constituent elements described below is an example (representative example) of an embodiment of the present invention, and is not specified by these contents. Various modifications can be made within the scope of the gist.

<1-1. Electrolyte>
There is no limitation on the electrolyte used in the non-aqueous electrolyte secondary battery of the present invention, any known non-aqueous electrolyte secondary battery used as an electrolyte can be arbitrarily adopted and contained, The electrolyte is preferably a lithium salt.

Specific examples of the electrolyte include inorganic lithium salts such as LiClO ₄ , LiAsF ₆ , LiPF ₆ , Li ₂ CO ₃ , and 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 ( Fluorine-containing organic materials such as C ₂ F ₅ ), LiBF ₂ (CF ₃ ) ₂ , LiBF ₂ (C ₂ F ₅ ) ₂ , LiBF ₂ (CF ₃ SO ₂ ) ₂ , LiBF ₂ (C ₂ F ₅ SO ₂ ) ₂ Lithium salt;

  Dicarboxylic acid complex lithium salts such as lithium bis (oxalato) borate, lithium difluoro (oxalato) borate, lithium tris (oxalato) phosphate, lithium difluorobis (oxalato) phosphate, lithium tetrafluoro (oxalato) phosphate;

Sodium or potassium salt such as KPF ₆ , NaPF ₆ , NaBF ₄ , CF ₃ SO ₃ Na;
Etc.

Of these, LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ or lithium bis (oxalato) borate are preferable, and LiPF ₆ or LiBF ₄ is 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 an inorganic lithium salt and a fluorine-containing organic lithium salt are used in combination, gas generation during continuous charging is suppressed, or deterioration after high-temperature storage is suppressed. preferable.

  The final lithium salt concentration of the non-aqueous electrolyte in the present invention is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.5 mol / L or more, preferably 0.6 mol / L or more, more preferably. Is 0.8 mol / L or more, usually 3 mol / L or less, preferably 2 mol / L or less, more preferably 1.5 mol / L or less. If it is the said range, since there are not too few lithium which is a charged particle, and the viscosity of electrolyte solution is not too high, favorable electrical conductivity is securable.

<1-2. Non-aqueous solvent>
The non-aqueous solvent contained in the non-aqueous electrolyte in the present invention is not particularly limited as long as it does not adversely affect the battery characteristics when used as a battery, but the following solvents used for the non-aqueous electrolyte are not limited. 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.

  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 what is normally used, carbon number of the alkylene group which comprises cyclic carbonate has preferable 2-6, 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). Among these, ethylene carbonate or propylene carbonate is preferable in that various characteristics in the non-aqueous electrolyte secondary battery are good.

  The type of chain carboxylate 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-butyl, etc. Is mentioned. Among these, methyl acetate, ethyl acetate, methyl propionate or ethyl propionate are preferable in terms of industrial availability and various characteristics in the non-aqueous electrolyte secondary battery.

  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.

  The type of chain ether is not limited, but examples of commonly used ones 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.

  There are no particular restrictions on the type of phosphorus-containing organic solvent, but examples of commonly used organic solvents include phosphate esters such as trimethyl phosphate, triethyl phosphate, and triphenyl phosphate; trimethyl phosphite, phosphorous acid Phosphites such as triethyl and triphenyl phosphite; phosphine oxides such as trimethylphosphine oxide, triethylphosphine oxide and triphenylphosphine oxide; and the like.

  The type of sulfur-containing organic solvent is not particularly limited, but examples of commonly used solvents include ethylene sulfite, 1,3-propane sultone, 1,4-butane sultone, methyl methanesulfonate, busulfan, sulfolane, and sulfolene. Dimethylsulfone, diphenylsulfone, methylphenylsulfone, dibutyldisulfide, dicyclohexyldisulfide, tetramethylthiuram monosulfide, N, N-dimethylmethanesulfonamide, N, N-diethylmethanesulfonamide and the like.

  Among these, a chain and cyclic carbonate or a chain and cyclic carboxylic acid ester is 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 such as a cyclic carbonate in combination with a low viscosity solvent such as a chain carbonate or a chain ester. 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 whole 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 volume of cyclic carbonates with respect to the total of the carbonates is 5% or more, preferably 10% by volume or more, more preferably 15% or more, 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 combinations of ethylene carbonate and chain carbonates such as 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 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, especially 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 discharge load characteristics is good. Among these, the asymmetric chain carbonates are preferably ethyl methyl carbonate, 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 the discharge load characteristics of the battery. Examples of the chain esters include ethyl acetate and methyl propionate. Is particularly preferred. The volume 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 accounts for 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: 55, 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 discharge load characteristics is improved.

<1-3. (A) Compound having at least two isocyanate groups in the molecule>
The non-aqueous electrolyte in the present invention is characterized by containing a compound having at least two or more isocyanate groups in the molecule (hereinafter sometimes abbreviated as “compound (A)”). As long as the compound (A) according to the present invention has two or more isocyanate groups in the molecule, other structures are not particularly limited. For example, a linear or branched alkylene structure, a cycloalkylene structure, Examples thereof include an aromatic hydrocarbon structure, an ether structure (—O—), or a structure in which these are halogenated. In addition, a carbonyl group (—C (═O) —), a structure in which a carbonyl group and an alkylene group are linked, and the like can be given.

  Examples include diisocyanatomethane, 1,3-diisocyanatopropane, 1,4-diisocyanatobutane, 1,5-diisocyanatopentane, 1,6-diisocyanatohexane, 1,7-di- Isocyanatoheptane, 1,8-diisocyanatooctane, 1,12-diisocyanatododecane, 1,3-diisocyanato-2-fluoropropane, 1,4-diisocyanato-2-butene, 1,4-diisocyanato-2 -Fluorobutane, 1,4-diisocyanato-2,3-difluorobutane, 1,5-diisocyanato-2-pentene, 1,5-diisocyanato-2-methylpentane, 1,6-diisocyanato-2-hexene, 1, 6-diisocyanato-3-hexene, 1,6-diisocyanato-3-fluorohexane, 1,6-diisocyanato- , 4-difluorohexane, 1,3-bis (isocyanatomethyl) cyclohexane, dicyclohexylmethane diisocyanate, carbonyl diisocyanate, 1,4-diisocyanatobutane-1,4-dione, 1,5-diisocyanatopentane-1 , 5-dione, diisocyanatobenzene, toluene diisocyanate, xylene diisocyanate, ethyl diisocyanatobenzene, trimethyldiisocyanatobenzene, diisocyanatonaphthalene, diisocyanatobiphenyl, diphenylmethane diisocyanate, 2,2-bis (isocyanatophenyl) ) A compound such as hexafluoropropane.

Among these, a diisocyanate compound having a structure represented by the following general formula (1) is preferable because it can effectively increase resistance to physical deformation of expansion / contraction of the electrode accompanying charge / discharge. This is because chain-like methylene groups are incorporated into the film and / or electrode structure to impart appropriate elasticity to such a structure. Therefore, for this purpose, the length of the methylene group is important. In the general formula (1), x is preferably 4 to 12, more preferably 4 to 8, and particularly preferably 6.

一般式（２）中、Ｒは水素、又はイソシアネート基を有してもよい、水素原子、炭素原子、窒素原子、酸素原子、硫黄原子、リン原子、及びハロゲン原子からなる群より選ばれる原子で構成された炭素数１〜１２の有機基を表す。 Moreover, as a preferable example of the compound (A) according to the present invention, a compound having one or more partial structures represented by the following general formula (2) in the molecule can be given.

In general formula (2), R is an atom selected from the group consisting of a hydrogen atom, a carbon atom, a nitrogen atom, an oxygen atom, a sulfur atom, a phosphorus atom, and a halogen atom, which may have hydrogen or an isocyanate group. The comprised C1-C12 organic group is represented.

  In addition, the C1-C12 organic group comprised by the atom chosen from the group which consists of a hydrogen atom, a carbon atom, a nitrogen atom, an oxygen atom, a sulfur atom, a phosphorus atom, and a halogen atom is a carbon atom and a hydrogen atom The organic group which may contain the nitrogen atom, the oxygen atom, the sulfur atom, the phosphorus atom, or the halogen atom other than the organic group comprised from these is meant. An organic group which may contain a nitrogen atom, an oxygen atom, a sulfur atom, a phosphorus atom, or a halogen atom is an organic group in which a part of the carbon atoms of the skeleton is substituted with these atoms, or these atoms. It is meant to include an organic group having a configured substituent.

Moreover, the said C1-C12 comprised by the atom chosen from the group which consists of a hydrogen atom, a carbon atom, a nitrogen atom, an oxygen atom, a sulfur atom, a phosphorus atom, and a halogen atom which may have the said isocyanate group The organic group may have an isocyanate group, an alkyl group having 1 to 4 carbon atoms, an alkylene group having 1 to 12 carbon atoms, a cycloalkylene group having 4 to 12 carbon atoms, and an aromatic group having 6 to 12 carbon atoms. It is preferable that it is a C1-C12 organic group in which one or more elements of hydrocarbon or F, N, S, and O are contained.
In addition, from the viewpoint of stability as an organic substance, one of the ends of the structure of the general formula (2) is preferably bonded to a carbon atom, and the other is preferably bonded to a nitrogen atom or an oxygen atom. .

  From the viewpoint of ease of production, the compound (A) having one or more partial structures represented by the general formula (2) is one or more selected from uretdione, oxadiaditrione, biuret, urethane, allophanate and isocyanurate. Those having the skeleton are more preferred. Each skeleton may be contained in two or more in the molecule.

  The number of isocyanate groups in the compound (A) having one or more partial structures represented by the general formula (2) is not particularly limited as long as it is 2 or more, but is preferably 3 or more, and usually 15 or less, preferably 10 Below, more preferably 8 or less. When the number of isocyanate groups in the molecule is in the above range, the stability of the film can be increased, and the increase in charge transfer resistance of the positive electrode due to the increase in functional groups can be prevented.

  The molecular weight of the compound (A) having one or more partial structures represented by the general formula (2) is not particularly limited. However, since the higher molecular weight than a conventional isocyanate compound having a simple molecular structure and a low molecular weight appears, the number average The molecular weight is usually 200 or more, preferably 300 or more, and usually 10,000 or less, preferably 5000 or less, more preferably 3000 or less, and still more preferably 2000 or less. When the number average molecular weight is in the above range, the solubility in the electrolytic solution tends to be ensured. For the same reason as above, the average number of functional groups is 2 or more, preferably 3 or more, and usually 12 or less, preferably 10 or less, more preferably 8 or less.

  The isocyanate group at the end of the compound (A) having one or more partial structures represented by the general formula (2) is an alkylene group from the viewpoints of cost of raw materials, ease of production, durability of the bound film, and the like. It is preferable that it is couple | bonded with. The number of carbon atoms of the alkylene group to which the terminal isocyanate group is bonded is not particularly limited, but is preferably 4 or more, preferably 12 or less, more preferably 8 or less.

Specific examples of the compound (A) having one or more partial structures represented by the general formula (2) include compounds represented by the general formulas (2-1) to (2-4). These are, for example, a trimer compound derived from a diisocyanate compound represented by the general formula (1) or the like, or an aliphatic polyisocyanate obtained by adding a polyhydric alcohol thereto, each of which has a bifunctional or higher functional isocyanate group. Have. From the top, these are polyisocyanates of the type called (2-1) biuret, (2-2) isocyanurate, (2-3) adduct (urethane), and (2-4) adduct (urethane). The compounds represented by the general formulas (2-1) to (2-4) are commercially available, and examples thereof include Duranate ^™ TPA-100, Duranate ^™ D101, Duranate ^™ 24A-100 manufactured by Asahi Kasei Chemicals. In general formulas (2-1) to (2-4), R is derived from a diisocyanate compound as a raw material, and is preferably an alkylene group having 4 to 12 carbon atoms, and R ′ is It is derived from a polyhydric alcohol and is preferably an alkylene group having 2 to 12 carbon atoms, or a group represented by C _n H _{2n + 1} C (CH ₂ ) ₃ having 1 to 7 carbon atoms. .

  As the compound (A) having one or more partial structures represented by the general formula (2), one type may be used alone, or two or more types may be used in any combination and ratio. Moreover, the aliphatic unisocyanate etc. which are unreacted raw materials may be contained. Some of these monomer components are undesirable in terms of worker safety and health, and it is preferable to use them by removing them within a range that does not adversely affect the human body.

  For the purpose of accelerating the reaction based on the isocyanate compound and obtaining a higher effect, a metal catalyst such as dibutyltin dilaurate or an amine catalyst such as 1,8-diazabicyclo [5.4.0] undecene-7 is used. Use in combination is also preferred.

  The compound (A) demonstrated above may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio. The non-aqueous electrolyte solution of the present invention may contain a monoisocyanate compound. In particular, the addition of alkyl monoisocyanates has the effect of improving the low-temperature discharge characteristics.

  The concentration of the compound (A) in the nonaqueous electrolytic solution in the present invention is arbitrary as long as the effects of the present invention are not significantly impaired, but is usually 0.01% by mass or more, preferably 0.05% by mass or more, more preferably It is 0.1 mass% or more and less than 3 mass%, Preferably it is 2.5 mass% or less, More preferably, it is 1.5 mass% or less, More preferably, it is the range of 0.8 mass% or less. If it is the said range, while being able to fully improve the chemical and physical stability in a battery, the excessive increase in resistance by film formation can be suppressed.

<1-4. Compound (B) used in combination with Compound (A)>
In addition to the compound (compound (A)) having at least two or more isocyanate groups in the molecule, the non-aqueous electrolyte solution in the present invention further includes a monofluorophosphate or difluorophosphate (hereinafter referred to as “compound ( B) "may be abbreviated.)). These compounds are common in that they have the effect of directly or indirectly forming a low-resistance film on the positive and negative electrode surfaces (see the effect of compound (B) in paragraph [0013]). That is, it is a compound that reacts directly with the electrode surface to form a film, or reacts with other components to form a film with the generated components.

The counter cation of monofluorophosphate and difluorophosphate is not particularly limited. In addition to metal elements such as Li, Na, K, Mg, Ca, Fe and Cu, NR ⁵ R ⁶ R ⁷ R ⁸ ( In the formula, R ^{5 to} R ⁸ each independently represents a hydrogen atom or an organic group having 1 to 12 carbon atoms.
Here, the organic group having 1 to 12 carbon atoms of R ^{5 to} R ⁸ is not particularly limited. For example, the alkyl group may be substituted with a halogen element, or the cycloalkyl group may be substituted with a halogen atom. And an aryl group optionally substituted with a halogen atom, a nitrogen atom-containing heterocyclic group, and the like. Among these, as R ^{5 to} R ⁸ , a hydrogen atom, an alkyl group, a cycloalkyl group, a nitrogen atom-containing heterocyclic group, and the like are preferable. Among these counter cations, lithium, sodium, potassium, magnesium, calcium or NR ⁵ R ⁶ R ⁷ R ⁸ is preferable, and lithium is particularly preferable from the viewpoint of battery characteristics when used in a lithium secondary battery.

Specific examples of monofluorophosphate and difluorophosphate include
Lithium monofluorophosphate, sodium monofluorophosphate, potassium monofluorophosphate, lithium difluorophosphate, sodium difluorophosphate, potassium difluorophosphate and the like, lithium monofluorophosphate and lithium difluorophosphate are preferred, More preferred is lithium difluorophosphate.

Monofluorophosphate and difluorophosphate may be used singly or in combination of two or more in any combination and ratio. Moreover, the content of monofluorophosphate and difluorophosphate is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired. The content of monofluorophosphate and difluorophosphate is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, and still more preferably 0.1% in 100% by mass of the non-aqueous electrolyte. It is at least 5% by mass, preferably at most 5% by mass, more preferably at most 4% by mass, even more preferably at most 3% by mass.
Within this range, the non-aqueous electrolyte battery tends to exhibit a sufficient cycle characteristics improvement effect, and the high temperature storage characteristics deteriorate, the amount of gas generated increases, and the discharge capacity maintenance ratio decreases. Easy to avoid.

  The method of adding monofluorophosphate and difluorophosphate to the electrolytic solution is not particularly limited, but it is a method of adding monofluorophosphate and difluorophosphate synthesized by a known method directly to the electrolytic solution. Another method is to generate monofluorophosphate and difluorophosphate in the battery or in the electrolyte. Monofluorophosphate and difluorophosphate can be generated by adding compounds other than monofluorophosphate and difluorophosphate and oxidizing or hydrolyzing battery components such as electrolytes. The method of letting it be mentioned. Furthermore, a method of generating a battery by applying an electrical load such as charge / discharge is also mentioned.

  The content of monofluorophosphate and difluorophosphate in the nonaqueous electrolyte solution or nonaqueous electrolyte battery can be quantified by ion chromatography, F nuclear magnetic resonance spectroscopy, or the like.

  The mass ratio of the compound (A) to the compound (B) is usually in the range of 1: 500 to 300: 1, preferably 1:80 to 40: 1, more preferably 1:30 to 1.5: 1.

（一般式（３）中、ｌ及びｍは独立して０〜４の整数を表す。）
ここで、一般式（３）で表される化合物としては、より耐久性能に優れる皮膜が形成可能な点で、ｌ＝０及びｍ＝０、または、ｌ＝１及びｍ＝１であることが好ましい。 Moreover, you may make it contain in combination with the compound which has the same effect as a compound (B), for example, tetrafluoroborate, or the compound represented by following General formula (3).

(In general formula (3), l and m independently represent an integer of 0 to 4.)
Here, the compound represented by the general formula (3) is such that l = 0 and m = 0, or l = 1 and m = 1, in that a film having more excellent durability can be formed. preferable.

<1-5. Auxiliary>
In addition to the above-described electrolyte, non-aqueous solvent, compound (A) and compound (B), an auxiliary may be appropriately added to the non-aqueous electrolyte of the present invention depending on the purpose. Examples of the auxiliary agent include cyclic carbonates having an unsaturated bond shown below, cyclic carbonates having fluorine atoms, unsaturated cyclic carbonates having fluorine atoms, overcharge inhibitors, and other auxiliary agents.

(Cyclic carbonate having an unsaturated bond)
The cyclic carbonate having an unsaturated bond (hereinafter sometimes abbreviated as “unsaturated cyclic carbonate”) also has an effect of improving the battery life because a film is formed on the surface of the negative electrode.

  The unsaturated cyclic carbonate is not particularly limited as long as it is a cyclic carbonate having a carbon-carbon double bond and / or a carbon-carbon triple bond, and any unsaturated carbonate can be used. The cyclic carbonate having an aromatic ring is also included in the unsaturated cyclic carbonate.

  Examples of unsaturated cyclic carbonates include vinylene carbonates; ethylene carbonates substituted with an aromatic ring and a substituent having a carbon-carbon double bond or carbon-carbon triple bond; phenyl carbonates; vinyl carbonates; allyl carbonates; Catechol carbonates; ethynyl carbonates; propargyl carbonate and the like.

  As vinylene carbonates, vinylene carbonate, methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, phenyl vinylene carbonate, 4,5-diphenyl vinylene carbonate, vinyl vinylene carbonate, 4,5-vinyl vinylene carbonate, allyl vinylene carbonate, 4 , 5-diallyl vinylene carbonate and the like.

  Specific examples of the ethylene carbonate substituted with a substituent having an aromatic ring, a carbon-carbon double bond or a carbon-carbon triple bond include vinyl ethylene carbonate, 4,5-divinylethylene carbonate, 4-methyl-5- Vinylethylene carbonate, 4-allyl-5-vinylethylene carbonate, phenylethylene carbonate, 4,5-diphenylethylene carbonate, 4-phenyl-5-vinylethylene carbonate, 4-allyl-5-phenylethylene carbonate, allylethylene carbonate, Examples include 4,5-diallyl ethylene carbonate, 4-methyl-5-allyl ethylene carbonate, ethynyl ethylene carbonate, propargyl ethylene carbonate, and the like.

  Among these, preferable unsaturated cyclic carbonates for use in combination with the compound (A) and the compound (B) are vinylene carbonate, methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, vinyl vinylene carbonate, 4,5-vinyl. Vinylene carbonate, allyl vinylene carbonate, 4,5-diallyl vinylene carbonate, vinyl ethylene carbonate, 4,5-divinyl ethylene carbonate, 4-methyl-5-vinyl ethylene carbonate, allyl ethylene carbonate, 4,5-diallyl ethylene carbonate, 4 -Methyl-5-allylethylene carbonate and 4-allyl-5-vinylethylene carbonate are more preferably used because they form a stable interface protective film.

  The molecular weight of the unsaturated cyclic carbonate is not particularly limited and may be arbitrary as long as the effects of the present invention are not significantly impaired, but is usually 50 or more, preferably 80 or more, and usually 250 or less, preferably 150 or less. If it is in the said range, it will be easy to ensure the solubility of the unsaturated cyclic carbonate with respect to non-aqueous electrolyte solution, and the effect of this invention will fully be easy to be expressed. The production method of the unsaturated cyclic carbonate is not particularly limited, and can be produced by arbitrarily selecting a known method.

  An unsaturated cyclic carbonate may be used individually by 1 type, or may have 2 or more types by arbitrary combinations and ratios. Further, the content of unsaturated cyclic carbonate (the total content in the case of two or more types) is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired. The content of the unsaturated cyclic carbonate is 100% by mass of the non-aqueous electrolyte solution, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and further preferably 0.2% by mass or more. Moreover, Preferably it is 5 mass% or less, More preferably, it is 4 mass% or less, More preferably, it is 3 mass% or less. Within the above range, the cycle characteristics of the non-aqueous electrolyte secondary battery can be improved, and further, the decrease in the discharge capacity retention rate due to the decrease in the high temperature storage characteristics can be suppressed, while the resistance due to excessive film formation is reduced. Increase can be suppressed.

(Cyclic carbonate having a fluorine atom)
A cyclic carbonate having a fluorine atom (hereinafter sometimes abbreviated as “fluorinated cyclic carbonate”) also has an effect of improving the battery life because a film is formed on the surface of the negative electrode. The number of fluorine atoms contained in the fluorinated cyclic carbonate is not particularly limited as long as it is 1 or more. Among them, the fluorine atom is usually 6 or less, preferably 4 or less, and a fluorinated cyclic carbonate having 1 or 2 is most preferable.

  Specific examples of the fluorinated cyclic carbonate include fluoroethylene carbonate, 4,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4-fluoro-4-methylethylene carbonate, 4,5-difluoro-4-methylethylene. Carbonate, 4-fluoro-5-methylethylene carbonate, 4,4-difluoro-5-methylethylene carbonate, 4- (fluoromethyl) -ethylene carbonate, 4- (difluoromethyl) -ethylene carbonate, 4- (trifluoromethyl) ) -Ethylene carbonate, 4- (fluoromethyl) -4-fluoroethylene carbonate, 4- (fluoromethyl) -5-fluoroethylene carbonate, 4-fluoro-4,5-dimethylethylene carbonate, 4,5 Difluoro-4,5-dimethylethylene carbonate, 4,4-difluoro-5,5-dimethylethylene carbonate.

  Among these, preferred fluorinated cyclic carbonates for use in combination with the compound (A) and the compound (B) include fluoroethylene carbonate, 4- (fluoromethyl) -ethylene carbonate, 4,4-difluoroethylene carbonate, 4, Since 5-difluoroethylene carbonate forms an interface protective film, it is more preferably used.

  The molecular weight of the fluorinated cyclic carbonate is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired, but is usually 50 or more, preferably 100 or more, and usually 250 or less, preferably 200 or less. If it is the said range, it will be easy to ensure the solubility of the fluorinated cyclic carbonate with respect to a non-aqueous electrolyte solution, and the effect of this invention will be easy to be expressed. The production method of the fluorinated cyclic carbonate is not particularly limited, and any known method can be selected and produced.

  A fluorinated cyclic carbonate may be used individually by 1 type, and may have 2 or more types together by arbitrary combinations and ratios. Further, the content of the fluorinated cyclic carbonate is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired. The content of the fluorinated cyclic carbonate is usually in 100% by mass of the non-aqueous electrolyte solution, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and further preferably 0.2% by mass or more. In addition, it is preferably 5% by mass or less, more preferably 4% by mass or less, and further preferably 3% by mass or less. Within the above range, the cycle characteristics of the non-aqueous electrolyte secondary battery can be improved, and further, the decrease in the discharge capacity retention rate due to the decrease in the high temperature storage characteristics can be suppressed, while the excessive increase in resistance is suppressed. be able to.

(Fluorinated unsaturated cyclic carbonate)
As the fluorinated cyclic carbonate, a cyclic carbonate having an unsaturated bond and a fluorine atom (hereinafter sometimes abbreviated as “fluorinated unsaturated cyclic carbonate”) is also preferably used. The number of fluorine atoms in the fluorinated unsaturated cyclic carbonate is not particularly limited as long as it is 1 or more, but it is usually 6 or less, preferably 4 or less, and fluorinated unsaturated cyclic carbonate which is 1 or 2 is most preferable.

  Examples of the fluorinated unsaturated cyclic carbonate include fluorinated vinylene carbonate derivatives, fluorinated ethylene carbonate derivatives substituted with an aromatic ring or a substituent having a carbon-carbon double bond.

  Fluorinated vinylene carbonate derivatives include 4-fluoro vinylene carbonate, 4-fluoro-5-methyl vinylene carbonate, 4-fluoro-5-phenyl vinylene carbonate, 4-allyl-5-fluoro vinylene carbonate, 4-fluoro-5- And vinyl vinylene carbonate.

  Examples of the fluorinated ethylene carbonate derivative substituted with an aromatic ring or a substituent having a carbon-carbon double bond include 4-fluoro-4-vinylethylene carbonate, 4-fluoro-4-allylethylene carbonate, 4-fluoro-5. -Vinylethylene carbonate, 4-fluoro-5-allylethylene carbonate, 4,4-difluoro-4-vinylethylene carbonate, 4,4-difluoro-4-allylethylene carbonate, 4,5-difluoro-4-vinylethylene carbonate 4,5-difluoro-4-allylethylene carbonate, 4-fluoro-4,5-divinylethylene carbonate, 4-fluoro-4,5-diallylethylene carbonate, 4,5-difluoro-4,5-divinylethylene carbonate 4,5-diflu B-4,5-diallylethylene carbonate, 4-fluoro-4-phenylethylene carbonate, 4-fluoro-5-phenylethylene carbonate, 4,4-difluoro-5-phenylethylene carbonate, 4,5-difluoro-4- Examples thereof include phenylethylene carbonate.

  Among these, particularly preferred fluorinated unsaturated cyclic carbonates to be used in combination with the compound (A) and the compound (B) include 4-fluorovinylene carbonate, 4-fluoro-5-methylvinylene carbonate, 4-fluoro-5- Vinyl vinylene carbonate, 4-allyl-5-fluoro vinylene carbonate, 4-fluoro-4-vinyl ethylene carbonate, 4-fluoro-4-allyl ethylene carbonate, 4-fluoro-5-vinyl ethylene carbonate, 4-fluoro-5- Allylethylene carbonate, 4,4-difluoro-4-vinylethylene carbonate, 4,4-difluoro-4-allylethylene carbonate, 4,5-difluoro-4-vinylethylene carbonate, 4,5-difluoro-4-allylethylene Carbonet 4-fluoro-4,5-divinylethylene carbonate, 4-fluoro-4,5-diallylethylene carbonate, 4,5-difluoro-4,5-divinylethylene carbonate, 4,5-difluoro-4,5- Since diallyl ethylene carbonate forms a stable interface protective film, it is more preferably used.

  The molecular weight of the fluorinated unsaturated cyclic carbonate is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired, but usually 50 or more, preferably 100 or more, and usually 250 or less, preferably 200 or less. . If it is the said range, it will be easy to ensure the solubility of the fluorinated cyclic carbonate with respect to a non-aqueous electrolyte solution, and the effect of this invention will be easy to be expressed. The production method of the fluorinated unsaturated cyclic carbonate is not particularly limited, and can be produced by arbitrarily selecting a known method.

A fluorinated unsaturated cyclic carbonate may be used individually by 1 type, and may have 2 or more types by arbitrary combinations and ratios. Further, the content of the fluorinated unsaturated cyclic carbonate (the total content in the case of 2 or more types) is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired. The content of the fluorinated unsaturated cyclic carbonate is usually in 100% by mass of the non-aqueous electrolyte solution, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and further preferably 0.2% by mass. Further, it is preferably 5% by mass or less, more preferably 4% by mass or less, and further preferably 3% by mass or less. Within the above range, the cycle characteristics of the non-aqueous electrolyte secondary battery can be improved, and further, the decrease in the discharge capacity retention rate due to the decrease in the high temperature storage characteristics can be suppressed, while the resistance increase due to excessive film formation Can be suppressed.

(Overcharge prevention agent)
In the non-aqueous electrolyte solution of the present invention, an overcharge inhibitor can be used in order to effectively suppress battery explosion / ignition when the non-aqueous electrolyte secondary battery is in an overcharged state or the like. .

  As an overcharge inhibitor, aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, dibenzofuran; 2-fluorobiphenyl, Partially fluorinated products of the above aromatic compounds such as o-cyclohexylfluorobenzene and p-cyclohexylfluorobenzene; 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole, 3,5-difluoroanisole and the like And a fluorine-containing anisole compound. Among these, aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, and dibenzofuran are preferable. These may be used alone or in combination of two or more. When two or more kinds are used in combination, in particular, a combination of cyclohexylbenzene and t-butylbenzene or t-amylbenzene, biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, Using at least one selected from aromatic compounds not containing oxygen, such as t-amylbenzene, and at least one selected from oxygen-containing aromatic compounds such as diphenyl ether, dibenzofuran, and the like is an overcharge prevention property and a high temperature storage property. From the standpoint of balance.

  The content of the overcharge inhibitor is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired. The overcharge inhibitor is preferably 0.1% by mass or more and 5% by mass or less in 100% by mass of the non-aqueous electrolyte solution. Further, it is more preferably 0.2% by mass or more, further preferably 0.3% by mass or more, particularly preferably 0.5% by mass or more, more preferably 3% by mass or less, still more preferably 2% by mass or less. is there. If it is the said range, the overcharge prevention effect can fully be aimed at, On the other hand, battery characteristics, such as a high temperature storage characteristic, can be ensured.

<Other auxiliaries>
Other known auxiliary agents can be used in the non-aqueous electrolyte solution of the present invention. Other auxiliaries include carbonate compounds such as erythritan carbonate, spiro-bis-dimethylene carbonate, methoxyethyl-methyl carbonate; succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, anhydrous Carboxylic anhydrides such as itaconic acid, diglycolic anhydride, cyclohexanedicarboxylic anhydride, cyclopentanetetracarboxylic dianhydride and phenylsuccinic anhydride; 2,4,8,10-tetraoxaspiro [5.5 ] Spiro compounds such as undecane, 3,9-divinyl-2,4,8,10-tetraoxaspiro [5.5] undecane; ethylene sulfite, 1,3-propane sultone, 1-fluoro-1,3- Propane sultone, 2-fluoro-1,3-propane sultone, 3-ph Oro-1,3-propane sultone, 1-propene-1,3-sultone, 1-fluoro-1-propene-1,3-sultone, 2-fluoro-1-propene-1,3-sultone, 3-fluoro -1-propene-1,3-sultone, 1,4-butanesultone, 1-butene-1,4-sultone, 3-butene-1,4-sultone, methyl fluorosulfonate, ethyl fluorosulfonate, methanesulfonic acid Sulfur-containing compounds such as methyl, ethyl methanesulfonate, busulfan, sulfolene, diphenylsulfone, N, N-dimethylmethanesulfonamide, N, N-diethylmethanesulfonamide; 1-methyl-2-pyrrolidinone, 1-methyl-2 -Piperidone, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone and N-me Nitrogen-containing compounds such as succinimide, succinonitrile, adiponitrile, and pimelonitrile; hydrocarbon compounds such as heptane, octane, nonane, decane, and cycloheptane; fluorine-containing aromas such as fluorobenzene, difluorobenzene, hexafluorobenzene, and benzotrifluoride Group compounds and the like. These may be used alone or in combination of two or more. By adding these auxiliaries, capacity maintenance characteristics and cycle characteristics after high temperature storage can be improved.

  The content of other auxiliaries is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. The other auxiliary agent is preferably 0.01% by mass or more and 5% by mass or less in 100% by mass of the non-aqueous electrolyte solution. The content of other auxiliaries is more preferably 0.1% by mass or more, further preferably 0.2% by mass or more, more preferably 3% by mass or less, and further preferably 1% by mass or less. . If it is the said range, the bad influence to a battery can be suppressed, fully exhibiting the effect of an adjuvant.

  The non-aqueous electrolyte solution described above includes those existing inside the non-aqueous electrolyte secondary battery according to the present invention. Specifically, the components of the non-aqueous electrolyte solution such as lithium salt, solvent, and auxiliary agent are separately synthesized, and the non-aqueous electrolyte solution is prepared from what is substantially isolated by the method described below. In the case of a non-aqueous electrolyte solution in a non-aqueous electrolyte secondary battery obtained by pouring into a separately assembled battery, the components of the non-aqueous electrolyte solution of the present invention are individually placed in the battery, When the same composition as the non-aqueous electrolyte of the present invention is obtained by mixing in the battery, further, the compound constituting the non-aqueous electrolyte of the present invention is generated in the non-aqueous electrolyte secondary battery, The case where the same composition as the non-aqueous electrolyte solution of the present invention is obtained is also included.

[2. Non-aqueous electrolyte secondary battery]
The non-aqueous electrolyte secondary battery of the present invention includes a positive electrode capable of occluding and releasing metal ions, a negative electrode capable of occluding and releasing metal ions, a non-aqueous solvent and an electrolyte dissolved in the non-aqueous solvent. An aqueous electrolyte solution.

<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 non-aqueous electrolyte, and is usually impregnated with the non-aqueous electrolyte of the present invention. The positive electrode and the negative electrode are laminated via a 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 solution, the above-described non-aqueous electrolyte solution 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 in this invention.

<2-3. Negative electrode>
One feature of the non-aqueous electrolyte secondary battery of the present invention is that the negative electrode contains a carbonaceous material. By combining the above-described non-aqueous electrolyte and a negative electrode containing a carbonaceous material, the rate characteristics of the non-aqueous electrolyte secondary battery can be greatly improved. In addition, in this invention, a carbonaceous material shall mean what mainly exhibits the function as a negative electrode active material. The negative electrode in the present invention is not particularly limited as long as it contains a carbonaceous material. In addition to the carbonaceous material, the negative electrode contains a negative electrode active material such as an alloy-based material or a lithium-containing metal composite oxide material. It may be.

(Negative electrode active material)
As a carbonaceous material that functions as a negative electrode active material,
(1) natural graphite,
(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;
(3) a carbonaceous material in which the negative electrode active material layer is made of carbonaceous materials having at least two or more different crystallinities and / or has an interface in contact with the different crystalline carbonaceous materials,
(4) A carbonaceous material in which the negative electrode active material layer is made 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 (1) to (4) may be used alone or in combination of two or more in any combination and ratio.

  Examples of the artificial carbonaceous material and artificial graphite material of (2) above include natural graphite, coal-based coke, petroleum-based coke, coal-based pitch, petroleum-based pitch, those obtained by oxidizing these pitches, needle coke, pitch coke and Carbon materials that are partially graphitized, furnace black, acetylene black, organic pyrolysis products such as pitch-based carbon fibers, carbonizable organic materials and their carbides, or carbonizable organic materials are benzene, toluene, xylene, quinoline And a solution dissolved in a low-molecular organic solvent such as n-hexane, and carbides thereof.

  As an alloy material used together with the carbonaceous material, as long as lithium can be occluded / released, simple metals and alloys forming lithium alloys, or oxides, carbides, nitrides, silicides, sulfides or phosphides thereof Any of the above compounds may be used and is not particularly limited. The single metal and alloy forming the lithium alloy are preferably materials containing group 13 and group 14 metal / metalloid elements (that is, excluding carbon), more preferably aluminum, silicon and tin (hereinafter referred to as “ Simple metals) and alloys or compounds containing these atoms (sometimes abbreviated as “specific metal elements”). These may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

  As a negative electrode active material having at least one kind of atom selected from a specific metal element, a metal simple substance of any one specific metal element, an alloy composed of two or more specific metal elements, one type or two or more specific types Alloys comprising metal elements and one or more other metal elements, as well as compounds containing one or more specific metal elements, and oxides, carbides, nitrides and silicides of the compounds And composite compounds such as sulfides or phosphides. By using these simple metals, alloys or metal compounds as the negative electrode active material, the capacity of the battery can be increased.

  In addition, a compound in which these complex compounds are complexly bonded to several kinds of elements such as a simple metal, an alloy, or a nonmetallic element is also included. 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. 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 may be used. it can.

Among these negative electrode active materials, since the capacity per unit mass is large when a battery is formed, any one simple metal 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 mass and environmental load.

  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 a material containing titanium and lithium is preferable from the viewpoint of high current density charge / discharge characteristics, A lithium-containing composite metal oxide material containing titanium is more preferable, and a composite oxide of lithium and titanium (hereinafter sometimes abbreviated as “lithium titanium composite oxide”) is more 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 (A). In the general formula (A), 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.

LixTiyMzO ₄ (A)
[In the general formula (A), 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 (A),
(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 Li _4/3 Ti _5/3 O ₄ in (a), Li ₁ Ti ₂ O ₄ in (b), Li _4/5 Ti _11/5 O in (c). ₄ . As for the structure of Z ≠ 0, for example, Li _4/3 Ti _4/3 Al _1/3 O ₄ is preferable.

<Physical properties of carbonaceous materials>
When using a carbonaceous material as a negative electrode active material, it is desirable to have the following physical properties.
(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 preferably 0.335 nm or more, and is usually 0.360 nm or less. 350 nm or less is preferable, and 0.345 nm or less is more preferable. Further, the crystallite size (Lc) of the carbonaceous material obtained by X-ray diffraction by the Gakushin method is preferably 1.0 nm or more, and more preferably 1.5 nm or more.

(Volume-based average particle size)
The volume-based average particle diameter of the carbonaceous material is a volume-based average particle diameter (median diameter) obtained by a laser diffraction / scattering method, and is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and 7 μm. The above is particularly preferable, and is usually 100 μm or less, preferably 50 μm or less, more preferably 40 μm or less, further preferably 30 μm or less, and particularly preferably 25 μm or less.

When the volume-based average particle size is in the above range, the loss of the initial battery capacity due to the increase in irreversible capacity can be suppressed, and uniform electrode application is possible when the electrode preparation step by application is included.
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 can be performed 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.

(Raman R value, Raman half width)
The Raman R value of the carbonaceous material is a value measured using an argon ion laser Raman spectrum method, and is usually 0.01 or more, preferably 0.03 or more, more preferably 0.1 or more, and usually 1.5 or less, preferably 1.2 or less, more preferably 1 or less, and particularly preferably 0.5 or less.
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. Preferably, it is more preferably 60 cm ⁻¹ or less, particularly preferably 40 cm ⁻¹ or less.

  The Raman R value and the Raman half width are indices indicating the crystallinity of the surface of the carbonaceous material, but the carbonaceous material has appropriate crystallinity from the viewpoint of chemical stability, and Li enters through charge and discharge. The crystallinity is preferably such that the sites between the layers are not lost. In the case where the density of the negative electrode is increased by press after applying to the current collector, it is preferable to take account of this because crystals tend to be oriented in a direction parallel to the electrode plate.

  When the Raman R value or the Raman half-value width is in the above range, the reaction between the carbonaceous material and the nonaqueous electrolytic solution can be suppressed, and the deterioration of the load characteristics due to the disappearance of the site can be suppressed.

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. The resulting Raman spectrum, the intensity IA of a peak PA around 1580 cm ^-1, and measuring the intensity IB of the peak PB around 1360 cm ^-1, and calculates the intensity ratio R (R = IB / IA) . The Raman R value calculated by the measurement is defined as the Raman R value of the carbonaceous material of 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 of 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

(BET specific surface area)
BET specific surface area of the carbonaceous material is a value of the measured specific surface area using the BET method is usually 0.1 m ² · g ^-1 or more, 0.7 m ² · g ^-1 or more, 1. 0 m ² · g ^-1 or more, and particularly preferably 1.5 m ² · g ^-1 or more, generally not more than 100 m ² · g ^-1, preferably 25 m ² · g ^-1 or less, 15 m ² · More preferably, g ⁻¹ or less is 10 m ^2.
-G- ¹ or less is particularly preferable.

  When the value of the BET specific surface area is in the above range, precipitation of lithium on the electrode surface can be suppressed, while gas generation due to reaction with the non-aqueous electrolyte can be suppressed.

  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 of the present invention.

(Roundness)
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.

  The greater the degree of circularity of the carbonaceous material, the better the filling property and the resistance between particles, so that the high current density charge / discharge characteristics are improved. Therefore, it is preferable that the circularity is as high as the above range.

  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 determined by the measurement is defined as the circularity of the carbonaceous material of the present invention.

  The method for improving the circularity is not particularly limited, but a sphere-shaped 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 approaching a sphere by applying a shearing force and a compressive force, a mechanical / physical processing method of granulating a plurality of fine particles by the binder or the adhesive force of the particles themselves, etc. Is mentioned.

(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 1 g · cm ⁻³ or more. particularly preferred, and is preferably 2 g · cm ^-3 or less, more preferably 1.8 g · cm ^-3 or less, 1.6 g · cm ^-3 or less are particularly preferred. When the tap density is in the above range, battery capacity can be ensured and increase in resistance between particles can be suppressed.

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, manufactured by Seishin Enterprise Co., Ltd.). Using a tap 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 mass of the sample. The tap density calculated by the measurement is defined as the tap density of the carbonaceous material of the present invention.

(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 in the above range, excellent high-density charge / discharge characteristics can be ensured. 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 58.8 MN · 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 of 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 Light receiving slit = 0.15 mm
Scattering 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

(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. When the aspect ratio is in the above range, streaking at the time of forming an electrode plate is suppressed, and further uniform coating becomes possible, so that excellent high current density charge / discharge characteristics can be ensured. 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 particles when three-dimensional observation is performed by selecting arbitrary 50 graphite particles fixed to the end face of a metal having a thickness of 50 μm or less and rotating and tilting the stage on which the sample is fixed. The longest diameter A and the shortest diameter B orthogonal thereto 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 of the present invention.

(Mixed with secondary materials)
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, containing two or more carbonaceous materials having different Raman R values, And X-ray parameters are different.

  As an example of the effect of the admixture of secondary materials, carbonaceous material such as graphite (natural graphite, artificial graphite), carbon black such as acetylene black, and amorphous carbon such as needle coke is 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. When the mixing ratio is in the above range, the effect of reducing electric resistance can be secured and an increase in initial irreversible capacity can be suppressed.

<2-4. Structure of anode and fabrication method
Any known method can be used for producing the electrode as long as the effects of the present invention are not significantly impaired. 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.

  In the case of using an alloy-based material, a method of forming a thin film layer (negative electrode active material layer) containing the above-described negative electrode active material by a technique such as vapor deposition, sputtering, or plating is also used.

(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 aluminum, 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, 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.

  The thickness of the current collector is usually 1 μm or more, preferably 5 μm or more, and usually 100 μm or less, preferably 50 μm or less, from the viewpoint of securing battery capacity and handling properties.

(Thickness ratio between current collector and negative electrode active material layer)
The ratio of the thickness of the current collector to the negative electrode active material layer is not particularly limited, but the value of “(the thickness of the negative electrode active material layer on one side immediately before the nonaqueous electrolyte injection) / (thickness of the current collector)” However, 150 or less is preferable, 20 or less is more preferable, 10 or less is particularly preferable, 0.1 or more is preferable, 0.4 or more is more preferable, and 1 or more is particularly preferable. When the ratio of the thickness of the current collector to the negative electrode active material layer is in the above range, battery capacity can be secured and heat generation of the current collector during high current density charge / discharge can be suppressed.

(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, polyimide, cellulose, and nitrocellulose; SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluorine rubber, Rubber polymers such as NBR (acrylonitrile / butadiene rubber) and ethylene / propylene rubber; styrene / butadiene / styrene block copolymer or hydrogenated product thereof; EPDM (ethylene / propylene / diene terpolymer), styrene / Thermoplastic elastomeric polymers such as ethylene / butadiene / styrene copolymers, styrene / isoprene / styrene block copolymers or 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 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% by mass or less is further preferable, and 8% by 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 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. 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. It is preferably 15% by mass or less, preferably 10% by mass or less, and more preferably 8% by mass or less.

(Slurry forming solvent)
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 and alcohol. Examples of the organic solvent include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N, N- Examples include dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, diethyl ether, dimethylacetamide, hexamethylphosphalamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane, and the like.

  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.

(Thickener)
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 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 more preferable. When the ratio of the thickener to the negative electrode active material is within the above range, it is possible to suppress a decrease in battery capacity and an increase in resistance, and it is possible to ensure appropriate applicability.

(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 or more. but more preferably, particularly preferably 1.3 g · cm ^-3 or more, preferably 2.2 g · cm ^-3 or less, more preferably 2.1 g · cm ^-3 or less, 2.0 g · cm ^-3 or less Further preferred is 1.9 g · cm ⁻³ or less. When the density of the negative electrode active material existing on the current collector is in the above range, the negative electrode active material particles are prevented from being destroyed, and an increase in initial irreversible capacity or to the vicinity of the current collector / negative electrode active material interface. While the deterioration of the high current density charge / discharge characteristics due to the reduced permeability of the non-aqueous electrolyte solution can be suppressed, the decrease in battery capacity and the increase in resistance can be suppressed.

(Thickness of negative electrode plate)
The thickness of the negative electrode plate is designed according to the positive electrode plate to be used, and is not particularly limited. However, the thickness of the composite layer obtained by subtracting the thickness of the metal foil of the core is usually 15 μm or more, preferably 20 μm or more. More preferably, it is 30 μm or more, and usually 300 μm or less, preferably 280 μm or less, more preferably 250 μm or less.

(Surface coating of negative electrode plate)
Moreover, you may use what adhered the substance of the composition different from this to the surface of the said negative electrode plate. 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, calcium sulfate And sulfates such as aluminum sulfate and carbonates such as lithium carbonate, calcium carbonate and magnesium carbonate.

<2-5. Positive electrode>
(Positive electrode active material)
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.

The transition metal of the lithium transition metal composite oxide is preferably V, Ti, Cr, Mn, Fe, Co, Ni, Cu or the like, and specific examples include lithium / cobalt composite oxide such as LiCoO ₂ or LiNiO ₂ . Lithium / nickel composite oxides, LiMnO ₂ , LiMn ₂ O ₄ , Li ₂ MnO _{4 and} other lithium / manganese composite oxides, Al, Ti , V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, and those substituted with other metals such as Si. Specific examples of the substituted ones include, for example, LiNi _0.5 Mn _0.5 O ₂ , LiNi _0.85 Co _{0.1 0} Al _0.05 O ₂ , LiNi _0.33 Co _0.33 Mn _0.33 O ₂ , LiMn _1.8 Al _0.2 O ₄ , LiMn _1.5 Ni _0.5 O _4, etc. Is mentioned.

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, LiFePO ₄ , Li ₃ Fe ₂ (PO ₄ ). ₃ , iron phosphates such as LiFeP ₂ O ₇ , cobalt phosphates such as LiCoPO ₄ , and some of the 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, Cu, Zn, Mg, Ga, Zr, Nb, Si and the like substituted with other metals.

(Surface coating)
Moreover, you may use what the substance of the composition different from this adhered to the surface of the said positive electrode active material. 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, calcium sulfate And sulfates such as aluminum sulfate, carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate, and carbon.

  For example, these surface adhering substances are dissolved or suspended in a solvent, impregnated and added to the positive electrode active material, and dried. After the surface adhering substance precursor is dissolved or suspended in a solvent and impregnated and added to the positive electrode active material, 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. In addition, when making carbon adhere, the method of making carbonaceous adhere mechanically later in the form of activated carbon etc. can also be used, for example.

  The amount of the surface adhering substance is by mass with respect to the positive electrode active material, preferably 0.1 ppm or more, more preferably 1 ppm or more, still more preferably 10 ppm or more, and the upper limit, preferably 20% or less, more preferably, as the lower limit. Is used at 10% or less, more preferably 5% or less. The surface adhering substance can suppress the oxidation reaction of the electrolytic solution on the surface of the positive electrode active material, and can improve the battery life. Within the above range, an increase in resistance due to inhibition of the entry and exit of lithium ions can be suppressed, while the above effect can be sufficiently exhibited.

In the present invention, a material in which a material having a different composition is attached to the surface of the positive electrode active material is also referred to as “positive electrode active material”.
(shape)
Examples of the shape of the positive electrode active material particles include a lump shape, a polyhedron shape, a sphere shape, an oval sphere shape, a plate shape, a needle shape, and a column shape, which are conventionally used. It is preferable that the secondary particles have a spherical shape or an 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, it is preferable that the primary particles are aggregated to form secondary particles, rather than a single particle active material having only primary particles, in order to relieve expansion and contraction stress and prevent deterioration. In addition, spherical or oval spherical particles are less oriented during molding of the electrode than plate-like equiaxed particles, so that the electrode is less expanded and contracted during charge and discharge, and the electrode is produced. The mixing with the conductive material is also preferable because it is easy to mix uniformly.

(Tap density)
The tap density of the positive electrode active material is preferably 0.5 g / cm ³ or more, more preferably 1.0 g / cm ³ or more, further preferably 1.5 g / cm ³ or more, and most preferably 1.7 g / cm ³ or more. It is. When the tap density of the positive electrode active material is within the above range, the amount of the dispersion medium and the necessary amount of the conductive material and the binder necessary for forming the positive electrode active material layer can be suppressed. As a result, the filling rate of the positive electrode active material and the battery Capacity can be secured. By using a complex oxide powder having a high tap density, a high-density positive electrode active material layer can be formed. Tap density preferably as generally greater, particularly upper limit is not, preferably 2.7 g / cm ³ or less, more preferably 2.5 g / cm ³ or less. When it is within the above range, it is possible to suppress a decrease in load characteristics.

  In the present invention, the tap density is defined as the powder packing density (tap density) g / cc when 5 to 10 g of the positive electrode active material powder is put in a 10 ml glass measuring cylinder and tapped 200 times with a stroke of about 20 mm. Ask.

(Median diameter d50)
The median diameter d50 of the positive electrode active material particles (secondary particle diameter when primary particles are aggregated to form secondary particles) is preferably 0.3 μm or more, more preferably 1.2 μm or more, and even more preferably. Is 1.5 μm or more, most preferably 2 μm or more, and the upper limit is preferably 20 μm or less, more preferably 18 μm or less, still more preferably 16 μm or less, and most preferably 15 μm or less. Within the above range, a high tap density product can be obtained and the battery performance can be prevented from being lowered. On the other hand, when the positive electrode of the battery is produced, that is, when the active material and the conductive material or binder are slurried with a solvent and applied in a thin film form It is possible to prevent problems such as drawing streaks. Here, by mixing two or more kinds of the positive electrode active materials having different median diameters d50, the filling property at the time of producing the positive electrode can be further improved.

  In the present invention, the median diameter d50 is measured by a known laser diffraction / scattering particle size distribution measuring device. When LA-920 manufactured by HORIBA is used as a particle size distribution meter, a 0.1% by mass sodium hexametaphosphate aqueous solution is used as a dispersion medium for measurement, and a measurement refractive index of 1.24 is set after ultrasonic dispersion for 5 minutes. Measured.

(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 preferably 0.05 μm or more, more preferably 0.1 μm or more, and still more preferably 0.8 μm. The upper limit is preferably 2 μm or less, more preferably 1.6 μm or less, still more preferably 1.3 μm or less, and most preferably 1 μm or less. When it is in the above range, powder filling property and specific surface area can be secured and deterioration of battery performance can be suppressed, while reversibility of charge and discharge can be secured by obtaining appropriate crystallinity. .

  In the present invention, the 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.

(BET specific surface area)
The BET specific surface area of the positive electrode active material is preferably 0.4 m ² / g or more, more preferably 0.5 m ² / g or more, still more preferably 0.6 m ² / g or more, and the upper limit is 50 m ² / g or less. , Preferably 40 m ² / g or less, more preferably 30 m ² / g or less. When the BET specific surface area is in the above range, the battery performance can be secured and the applicability of the positive electrode active material can be kept good.

  In the present invention, the BET specific surface area is determined by using a surface area meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken), preliminarily drying the sample at 150 ° C. for 30 minutes under nitrogen flow, and then atmospheric pressure. This is defined as a value measured by a nitrogen adsorption BET one-point method using a gas flow method, using a nitrogen-helium mixed gas accurately adjusted so that the value of the relative pressure of nitrogen to 0.3 is 0.3.

(Method for producing positive electrode active material)
As a manufacturing method of the positive electrode active material, a general method is used as a manufacturing method of the inorganic compound. In particular, various methods are conceivable for producing a spherical or oval spherical active material. For example, a phosphorus raw material such as phosphoric acid and an M raw material in the composition formula (1) are dissolved in a solvent such as water. Or, pulverize and disperse, adjust the pH while stirring, produce and recover a spherical precursor, dry it as necessary, and then add a Li source such as LiOH, Li ₂ CO ₃ , LiNO _3, etc. Examples thereof include a method of obtaining an active material by baking at a high temperature.

For the production of the positive electrode, the positive electrode active material of the composition formula (1) and / or the positive electrode active material of the composition formula (1) coated with the surface adhesion material may be used alone, or one or more of different compositions And may be used in any combination or ratio. A preferred combination in this case is Li
Examples include a combination with Mn ₂ O ₄ or a part of this Mn substituted with another transition metal, or a combination with LiCoO ₂ or a part of this Co substituted with another transition metal or the like. . Here, the positive electrode active material of the composition formula (1) and / or the positive electrode active material of the composition formula (1) coated with the surface adhesion material is preferably 30% by mass or more of the whole positive electrode active material, More preferably, it is at least mass%. When the usage rate of the positive electrode active material of the composition formula (1) and / or the positive electrode active material of the composition formula (1) coated with the surface adhering material decreases, the battery capacity may be reduced. The “positive electrode active material of composition formula (1) and / or the positive electrode active material of composition formula (1) coated with the surface adhering material” and “the positive electrode active material of composition formula (1) and / or the surface adhering”. The “positive electrode active material other than the positive electrode active material of the composition formula (1) coated with the material” is collectively referred to as “positive electrode active material”.

<2-6. Structure and manufacturing method of positive electrode>
The structure of the positive electrode will be described below. In the present invention, the positive electrode can be produced by forming a positive electrode active material layer containing a positive electrode active material and a binder on a current collector. Manufacture of the positive electrode using a positive electrode active material can be performed by a conventional 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 into a sheet form are pressure-bonded to the 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 preferably 80% by mass or more, more preferably 82% by mass or more, and particularly preferably 84% by mass or more. Moreover, an upper limit becomes like this. Preferably it is 95 mass% or less, More preferably, it is 93 mass% or less. Within the above range, the electric capacity of the positive electrode active material in the positive electrode active material layer can be secured, and the strength of the positive electrode can be maintained.

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 1.5 g / cm ³ or more as a lower limit, more preferably 2 g / cm ³ , still more preferably 2.2 g / cm ³ or more, and the upper limit is preferably 3.5 g. / Cm ³ or less, more preferably 3 g / cm ³ or less, and even more preferably 2.8 g / cm ³ or less. If it exceeds this range, the permeability of the electrolyte solution to the vicinity of the current collector / active material interface decreases, and the charge / discharge characteristics particularly at a high current density decrease, and a high output may not be obtained. On the other hand, if it is lower, the conductivity between the active materials is lowered, the battery resistance is increased, and a high output may not be obtained.

(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 carbon 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 in the positive electrode active material layer, and the upper limit is usually 50% by mass or less, preferably It is used so as to contain 30% by mass or less, more preferably 15% by mass or less. Sufficient electrical conductivity and battery capacity can be ensured within the above range.

(Binder)
The binder used in the production of the positive electrode active material layer is not particularly limited, and in the case of the coating method, any material that can be dissolved or dispersed in the liquid medium used during electrode production may be used. , Polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, nitrocellulose, and other resin polymers; SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), fluororubber, isoprene rubber , Rubber polymers such as butadiene rubber and ethylene-propylene rubber; styrene / butadiene / styrene block copolymer or hydrogenated product thereof, EPDM (ethylene / propylene / diene terpolymer), styrene / ethylene / butadiene / Ethylene copolymer, styrene Thermoplastic elastomeric polymer such as isoprene / styrene block copolymer or hydrogenated product thereof; syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer Soft resinous polymers such as polymers; Fluoropolymers such as polyvinylidene fluoride (PVdF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymers; alkali metal ions (especially lithium ions) And a polymer composition having ion conductivity. 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 the upper limit is usually 80% by mass or less, preferably 60%. It is not more than mass%, more preferably not more than 40 mass%, most preferably not more than 10 mass%. Within the above range, the mechanical strength of the positive electrode can be ensured, and deterioration of battery performance such as cycle characteristics can be suppressed, while decrease in battery capacity and conductivity can be suppressed.

(Slurry forming solvent)
As the solvent for forming the slurry, the positive electrode active material, the conductive material, the binder, and a solvent capable of dissolving or dispersing the thickener used as necessary may be used. There is no restriction, 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 the organic medium 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, propylene oxide and tetrahydrofuran (THF); N-methylpyrrolidone (NMP) Amides such as dimethylformamide and dimethylacetamide; and aprotic polar solvents such as hexamethylphosphalamide and dimethylsulfoxide.

  In particular, when an aqueous medium is used, 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 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. When a thickener is further added, the ratio of the thickener to the active material is 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more. The upper limit is 5% by mass or less, preferably 3% by mass or less, more preferably 2% by mass or less. When it is in the above range, good coatability can be obtained, and a decrease in battery capacity and an increase in resistance can be suppressed.

(Current collector)
The material of the positive electrode current collector is not particularly limited, and a known material can be arbitrarily used. Specific examples include metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum; and carbon 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, and foam metal in the case of a metal material. A 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. Although the thickness of the thin film is arbitrary, from the viewpoint of strength and handleability as a current collector, it is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and the upper limit is usually 1 mm or less, preferably 100 μm or less. More preferably, it is 50 μm or less.

  Moreover, it is also preferable from the viewpoint of reducing the electronic contact resistance between the current collector and the positive electrode active material layer that a conductive additive is applied to the surface of the current collector. Examples of the conductive assistant include noble metals such as carbon, gold, platinum, and silver.

  The ratio of the thickness of the current collector to the positive electrode active material layer is not particularly limited, but the value of (thickness of the positive electrode active material layer on one side immediately before electrolyte injection) / (thickness of the current collector) is 20 The lower limit is preferably 15 or less, most preferably 10 or less, and the lower limit is preferably 0.5 or more, more preferably 0.8 or more, and most preferably 1 or more. Within the above range, heat generation of the current collector during high current density charge / discharge can be suppressed, and battery capacity can be secured.

(Electrode area)
When using the non-aqueous electrolyte of the present invention, it is preferable that the area of the positive electrode active material layer is larger than the outer surface area of the battery outer case from the viewpoint of increasing the stability at high output and high temperature. Specifically, the sum of the electrode areas of the positive electrode with respect to the surface area of the exterior of the secondary battery is preferably 15 times or more, and more preferably 40 times or more. The outer surface area of the outer case is the total area obtained by calculation from the vertical, horizontal, and thickness dimensions of the case part filled with the power generation element excluding the protruding part of the terminal in the case of a bottomed square shape. . In the case of a bottomed cylindrical shape, the geometric surface area approximates the case portion filled with the power generation element excluding the protruding portion of the terminal as a cylinder. The total electrode area of the positive electrode is the geometric surface area of the positive electrode mixture layer facing the mixture layer containing the negative electrode active material, and in the structure in which the positive electrode mixture layer is formed on both sides via the current collector foil. , The sum of the areas where each surface is calculated separately.

(Thickness of positive plate)
The thickness of the positive electrode plate is not particularly limited, but from the viewpoint of high capacity and high output, the thickness of the composite layer obtained by subtracting the metal foil thickness of the core material is preferably as a lower limit with respect to one side of the current collector. Is 10 μm or more, more preferably 20 μm or more, and the upper limit is preferably 500 μm or less, more preferably 450 μm or less.

(Positive electrode surface coating)
Moreover, you may use what adhered the substance of the composition different from this to the surface of the said positive electrode plate. 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, calcium sulfate And sulfates such as aluminum sulfate, carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate, and carbon.

<2-7. 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.

The material and shape of the separator are not particularly limited, and known ones can be arbitrarily adopted as long as the effects of the present invention are not significantly impaired. 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 glass fiber separator, for example, polyolefins such as polyethylene and polypropylene, aromatic polyamides, 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 8 μm or more, and usually 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less. Within the above range, insulation and mechanical strength can be secured, while battery performance such as rate characteristics and energy density can be secured.

  Furthermore, when using a porous material such as a porous sheet or nonwoven fabric 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, Further, it is usually 90% or less, preferably 85% or less, and more preferably 75% or less. When the porosity is in the above range, insulation and mechanical strength can be secured, while film resistance can be suppressed and good rate characteristics can be obtained.

  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. When the average pore diameter is in the above range, the film resistance can be suppressed and good rate characteristics can be obtained while preventing a short circuit. On the other hand, as inorganic materials, 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. 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 above-mentioned 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.

<2-8. Battery design>
(Electrode group)
The electrode group has a laminated structure in which the positive electrode plate and the negative electrode plate are interposed through the separator, and a structure in which the positive electrode plate and the negative electrode plate are wound in a spiral shape through the separator. Either is acceptable. 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 in the above range, the battery capacity can be secured and the deterioration of characteristics such as charge / discharge repetition performance and high temperature storage accompanying the increase in internal pressure can be suppressed, and further the operation of the gas release valve can be prevented Can do.

(Current collection structure)
The current collecting structure is not particularly limited, but in order to more effectively realize the high current density charge / discharge characteristics by the non-aqueous electrolyte solution of the present invention, a structure that reduces the resistance of the wiring part and the joint part is used. It is 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 above laminated structure, 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 provide a plurality of terminals in the electrode to reduce the resistance. 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 an exterior case using metals, the metal is welded together by laser welding, resistance welding, or ultrasonic welding to form a sealed sealed structure, or a caulking structure using the above metals via a resin gasket. Things. Examples of the outer case using the laminate film include a case where a resin-sealed structure is formed by heat-sealing resin layers. In order to improve 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)
Protective elements such as PTC (Positive Temperature Coefficient), thermal fuse, thermistor, whose resistance increases when abnormal heat generation or excessive current flows, cut off current flowing in the circuit due to sudden rise in battery internal pressure or internal temperature in abnormal heat generation A valve (current cutoff valve) or the like can be used. It is preferable to select a protective element that does not operate under normal use at a high current, and it is more preferable that the protective element is designed 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. This exterior body is not particularly limited, and any known one can be arbitrarily adopted as long as the effects of the present invention are not significantly impaired. 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 comparative example are given and this invention is demonstrated further more concretely, this invention is not limited to these Examples, unless the summary is exceeded.

<Example 1-1, Comparative Examples 1-1 to 1-2, Reference Examples 1-1 to 1-3>
[Example 1-1]
{Manufacture of non-aqueous electrolyte batteries}
(Preparation of non-aqueous electrolyte)
Under a dry argon atmosphere, a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) (volume ratio 30:70) was added to 1,6-diisocyanatohexane (HDI) 0. 5% by mass and 0.5% by mass of lithium difluorophosphate (LiPO ₂ F ₂ ) were mixed, and then sufficiently dried LiPF ₆ was dissolved at a rate of 1.0 mol / L to prepare an electrolytic solution. .

(Manufacture of positive electrode)
97% by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 1.5% by mass of acetylene black as a conductive material, and 1.5% by mass of polyvinylidene fluoride (PVdF) as a binder, N-methylpyrrolidone In a solvent, the mixture was slurried by mixing with a disperser. This was uniformly applied, dried and pressed on both sides of the aluminum foil. Thereafter, it was punched into a disk shape having a diameter of 12.5 mm to obtain a positive electrode for a non-aqueous electrolyte battery (coin type).

(Manufacture of negative electrode (carbon negative electrode))
94 parts by mass of graphite powder as a negative electrode active material and 6 parts by mass of PVdF were mixed, and N-methylpyrrolidone was added to form a slurry, which was applied, dried and pressed on one side of a current collector made of copper. Thereafter, it was punched into a disk shape having a diameter of 12.5 mm to obtain a negative electrode for a non-aqueous electrolyte battery (coin type). Hereinafter, this is referred to as a carbon negative electrode.

(Production of non-aqueous electrolyte battery (coin type))
Using the above positive electrode and negative electrode and the non-aqueous electrolyte prepared in each Example and Comparative Example, a coin-type cell was produced by the following procedure. That is, the negative electrode was placed via a polyethylene separator (thickness 25 μm) impregnated with an electrolytic solution on a positive electrode contained in a stainless steel can that also serves as a positive electrode conductor. The can body and a sealing plate serving also as a negative electrode conductor were caulked and sealed via an insulating gasket to produce a coin-type cell.

{Rate characteristics evaluation}
A non-aqueous electrolyte battery (coin type) was CCCV charged (0.05 C cut) to 4.1 V at a current corresponding to 0.2 C at 25 ° C., and then discharged to 3 V at a constant current of 0.2 C. Next, after CCCV charge (0.05 C cut) to 4.2 V at 0.2 C, the battery was discharged to 3 V at 0.2 C. Again, after CCCV charge (0.05C cut) to 4.2V at 0.2C, the battery was discharged to 3V at 0.2C to obtain a 0.2C capacity. Furthermore, after CCCV charge (0.05C cut) to 4.2V at 0.2C again, it discharged to 3V at 1C and calculated | required 1C capacity | capacitance. Then, the rate characteristic was obtained from the calculation formula of (1C capacity) ÷ (0.2C capacity) × 100. Furthermore, here, 1C represents a current value for discharging the reference capacity of the battery in one hour, and for example, 0.2C represents a current value of 1/5 thereof. Rate characteristics were evaluated using this non-aqueous electrolyte battery. The evaluation results are shown in Table 1.

[Comparative Example 1-1]
A non-aqueous electrolyte battery (coin type) was prepared in the same manner as in Example 1-1 except that the electrolyte solution of Example 1-1 used an electrolyte solution that did not contain LiPO ₂ F _2. Carried out. The evaluation results are shown in Table 1.

[Comparative Example 1-2]
A non-aqueous electrolyte battery (coin type) was produced in the same manner as in Example 1-1, except that the electrolyte solution of Example 1-1 used an electrolyte solution that did not contain HDI and LiPO ₂ F _2. Rate characteristics Evaluation was performed. The evaluation results are shown in Table 1.

[Reference Example 1-1]
(Manufacture of negative electrode (Si negative electrode))
A negative electrode active material, silicon powder, graphite powder, and a binder were mixed, and N-methylpyrrolidone was added to this to form a slurry, which was applied, dried, and pressed on one side of a current collector made of copper. Thereafter, it was punched into a disk shape having a diameter of 12.5 mm to obtain a negative electrode for a non-aqueous electrolyte battery (coin type). Hereinafter, this is referred to as a Si negative electrode.
In addition, manufacture of the nonaqueous electrolyte solution, the negative electrode, and the nonaqueous electrolyte battery (coin type) was produced by the same method as Example 1-1. Rate characteristics were evaluated using this non-aqueous electrolyte battery. The evaluation results are shown in Table 1.

[Reference Example 1-2]
A non-aqueous electrolyte battery (coin type) was prepared in the same manner as in Reference Example 1-1 except that the electrolyte solution of Reference Example 1-1 did not contain LiPO ₂ F ₂ , and rate characteristics were evaluated. Carried out. The evaluation results are shown in Table 1.

[Reference Example 1-3]
A non-aqueous electrolyte battery (coin type) was produced in the same manner as in Reference Example 1-1 except that the electrolyte solution of Reference Example 1-1 did not contain HDI and LiPO ₂ F ₂ , and rate characteristics were obtained. Evaluation was performed. The evaluation results are shown in Table 1.

  From Table 1, when the non-aqueous electrolyte battery of Example 1-1 containing both the compound (A) and the compound (B) does not contain the compound (A) and the compound (B) (Comparative Example 1-2). It can be seen that the rate characteristic is superior to Further, when the compound (A) is added alone (Comparative Example 1-1), the battery performance is insufficient because the rate characteristics are lowered. In addition, when Si is used as the negative electrode instead of carbon (Reference Examples 1-1 to 1-3), improvement in characteristics is observed by containing both the compound (A) and the compound (B). However, since the improvement rate is inferior to that when carbon is used for the negative electrode (Example 1-1 and Comparative Examples 1-1 to 1-2), the battery performance is insufficient. This factor is considered as follows. The difluorophosphate (compound (B)) usually has a property of forming a film with high Li affinity on the negative electrode, and the compound having two or more isocyanate groups (compound (A)) crosslinks the film. In addition to the effect, it has the property of reacting with the negative electrode surface functional group. When carbon is used for the negative electrode, the high affinity Li film formed by the compound (B) is cross-linked with the compound (A), whereby a high Li affinity film is formed on the entire surface of the negative electrode. As a result, the rate characteristics are greatly improved. On the other hand, when Si is used for the negative electrode, most of the compound (A) reacts with the surface functional groups of the Si active material and is consumed, so that the film crosslinking effect on the difluorophosphate is hardly exhibited. Therefore, the rate characteristic improvement effect becomes insufficient. Therefore, from the viewpoint of improving rate characteristics, when producing a non-aqueous electrolyte secondary battery using an electrolytic solution containing both the compound (A) and the compound (B), it is preferable to use carbon for the negative electrode.

<Examples 2-1 to 2-7, Comparative Examples 2-1 to 2-8>
[Example 2-1]
{Manufacture of non-aqueous electrolyte batteries}
(Preparation of non-aqueous electrolyte)
In a dry argon atmosphere, a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) (volume ratio 30:30:40) is added to the above formula (2) as the content in the non-aqueous electrolyte. -4) 0.5% by weight of Duranate ^™ D101 (manufactured by Asahi Kasei Chemicals Co., Ltd., hereinafter referred to as D101) and 0.5% by weight of LiPO ₂ F ₂ were mixed, and then fully dried LiPF ₆ Was dissolved at a rate of 1.0 mol / L to prepare an electrolytic solution.

(Manufacture of positive electrode)
Using 90 parts by mass of lithium nickel manganese cobaltate (LiNi _1/3 Mn _1/3 Co _1/3 O ₂ ) as the positive electrode active material, 7 parts by mass of carbon black as the conductive material, and 3 parts by mass of polyvinylidene fluoride as the binder N-methyl-2-pyrrolidone was added to form a slurry, which was uniformly coated on both sides of an aluminum foil having a thickness of 15 μm and dried, and then the density of the positive electrode active material layer was 2.6 g · cm ^−3. It was pressed to make a positive electrode.

(Manufacture of negative electrode)
Graphite Raman R value, defined as the ratio of the peak intensity of 1360 cm ^-1 to the peak intensity of 1580 cm ^-1 in the argon ion laser Raman spectroscopy is 0.33, an aqueous dispersion of sodium carboxymethyl cellulose as a thickening agent ( Sodium carboxymethylcellulose concentration 1% by mass) and an aqueous dispersion of styrene-butadiene rubber (concentration of styrene-butadiene rubber 50% by mass) as a binder were added and mixed to form a slurry. 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. In addition, in the negative electrode after drying, it created so that it might become mass ratio of graphite: sodium carboxymethylcellulose: styrene-butadiene rubber = 98: 1: 1.

(Preparation of non-aqueous electrolyte battery)
The positive electrode, the negative electrode, and a polyethylene separator (thickness 25 μm) were laminated in the order of the negative electrode, the separator, and the positive electrode to prepare a battery element. After inserting this battery element into a bag made of a laminate film in which both surfaces of aluminum (thickness 40 μm) are coated with a resin layer while projecting positive and negative terminals, a non-aqueous electrolyte solution is injected into the bag, Vacuum sealing was performed 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.

{Initial formation}
In a thermostatic bath at 25 ° C., the sheet-like non-aqueous electrolyte battery was CCCV charged to 4.1 V at 0.2 C and then discharged to 3.0 V at 0.2 C. This was repeated 5 times to form an initial formation. Here, 1C represents a current value for discharging the reference capacity of the battery in one hour, and for example, 0.2C represents a current value of 1/5 thereof.

{Cycle characteristics evaluation}
The process in which the non-aqueous electrolyte battery after the initial formation is placed in a constant temperature bath at 60 ° C. is charged with constant current to 4.1 V at 2 C and then discharged with constant current to 3.0 V at 2 C. Cycled. Then, the capacity maintenance rate at the 500th cycle was obtained from the formula of (discharge capacity at the 500th cycle) ÷ (discharge capacity at the first cycle) × 100.
Using this non-aqueous electrolyte battery, cycle characteristics were evaluated. The evaluation results are shown in Table 2.

[Example 2-2]
A non-aqueous electrolyte battery was produced in the same manner as in Example 2-1, except that 0.3% by mass of D101 was used instead of 0.5% by mass of D101 in the electrolyte solution of Example 2-1, and cycle characteristics were evaluated. Carried out. The evaluation results are shown in Table 2.

[Example 2-3]
A non-aqueous electrolyte battery was produced in the same manner as in Example 2-1, except that D101 1% by mass was used instead of D101 0.5% by mass in the electrolyte solution of Example 2-1, and cycle characteristics evaluation was performed. did. The evaluation results are shown in Table 2.

[Example 2-4]
Non-aqueous system similar to Example 2-1 except that Duranate ^™ TPA-100 (manufactured by Asahi Kasei Chemicals Co., Ltd., hereinafter sometimes referred to as TPA-100) was used instead of D101 in the electrolytic solution of Example 2-1. An electrolyte battery was produced and cycle characteristics were evaluated. The evaluation results are shown in Table 2.

[Example 2-5]
A non-aqueous electrolyte battery was produced in the same manner as in Example 2-1, except that tetramethylene diisocyanate (hereinafter sometimes referred to as TMI) was used in place of D101 in the electrolyte solution of Example 2-1, and the cycle was Characterization was performed. The evaluation results are shown in Table 2.

[Example 2-6]
A non-aqueous electrolyte battery was produced in the same manner as in Example 2-1, except that HDI was used in place of D101 in the electrolyte solution of Example 2-1, and cycle characteristics were evaluated. The evaluation results are shown in Table 2.

[Example 2-7]
A non-aqueous electrolyte battery was prepared in the same manner as in Example 2-1, except that dodecamemethylene diisocyanate (hereinafter sometimes referred to as DDMI) was used instead of D101 in the electrolyte solution of Example 2-1, and the cycle was Characterization was performed. The evaluation results are shown in Table 2.

[Comparative Example 2-1]
A non-aqueous electrolyte battery was produced in the same manner as in Example 2-1, except that an electrolyte containing neither D101 nor LiPO ₂ F ₂ was used in the electrolyte of Example 2-1, and cycle characteristics were evaluated. The evaluation results are shown in Table 2.

[Comparative Example 2-2]
A non-aqueous electrolyte battery was produced in the same manner as in Example 2-2 except that the electrolyte solution containing no LiPO ₂ F ₂ was used in the electrolyte solution of Example 2-2, and cycle characteristics were evaluated. The evaluation results are shown in Table 2.

[Comparative Example 2-3]
A non-aqueous electrolyte battery was produced in the same manner as in Example 2-1, except that an electrolyte containing no LiPO ₂ F ₂ was used in the electrolyte of Example 2-1, and cycle characteristics were evaluated. The evaluation results are shown in Table 11.

[Comparative Example 2-4]
A non-aqueous electrolyte battery was produced in the same manner as in Example 2-4 except that an electrolyte containing no LiPO ₂ F ₂ was used in the electrolyte of Example 2-4, and cycle characteristics were evaluated. The evaluation results are shown in Table 2.

[Comparative Example 2-5]
A non-aqueous electrolyte battery was produced in the same manner as in Example 2-5, except that an electrolyte solution containing no LiPO ₂ F ₂ was used in the electrolyte solution of Example 2-5, and cycle characteristics were evaluated. The evaluation results are shown in Table 2.

[Comparative Example 2-6]
A non-aqueous electrolyte battery was produced in the same manner as in Example 2-6 except that the electrolyte solution containing no LiPO ₂ F ₂ was used in the electrolyte solution of Example 2-6, and cycle characteristics were evaluated. The evaluation results are shown in Table 2.

[Comparative Example 2-7]
A non-aqueous electrolyte battery was produced in the same manner as in Example 2-7, except that an electrolyte solution containing no LiPO ₂ F ₂ was used in the electrolyte solution of Example 2-7, and cycle characteristics were evaluated. The evaluation results are shown in Table 2.

[Comparative Example 2-8]
A non-aqueous electrolyte battery was produced in the same manner as in Example 2-1, except that an electrolyte containing no D101 was used in the electrolyte of Example 2-1, and cycle characteristics were evaluated. The evaluation results are shown in Table 2.

  From Table 2, when the non-aqueous electrolyte battery of Examples 2-1 to 2-7 containing both the compound (A) and the compound (B) does not contain the compound (A) and the compound (B) (comparison) It can be seen that the capacity retention rate after 500 cycles is superior to Example 2-1). In addition, when the compound (A) or the compound (B) is added alone (Comparative Examples 2-2 to 2-8), although the improvement in the cycle capacity retention ratio is observed, the effect is insufficient. I know that there is.

  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 (13)

Non-aqueous electrolyte solution comprising at least a positive electrode capable of occluding and releasing metal ions, a negative electrode capable of occluding and releasing metal ions, and a non-aqueous electrolyte solution containing a non-aqueous solvent and an electrolyte dissolved in the non-aqueous solvent. A secondary battery,
The negative electrode contains a carbonaceous material, and the non-aqueous electrolyte solution together with an electrolyte and a non-aqueous solvent,
(A) a compound having at least two isocyanate groups in the molecule, and (B) a monofluorophosphate or difluorophosphate,
A non-aqueous electrolyte secondary battery comprising: 2. The nonaqueous electrolyte secondary battery according to claim 1, wherein lithium hexafluorophosphate (LiPF ₆ ) is contained as the electrolyte in a concentration of 0.5 to 3 mol / L in the entire nonaqueous electrolyte solution. The non-aqueous electrolyte secondary battery according to claim 1 or 2, which contains at least a diisocyanate compound having a structure represented by the following general formula (1) as (A).

(In general formula (1), x is 4 to 12)   The non-aqueous electrolyte secondary battery according to claim 3, which contains at least 1,6-diisocyanatohexane (HDI) as the (A). The said (A) contains at least the compound which has 1 or more of the partial structure represented by following General formula (2) in a molecule | numerator, and 2 or more of isocyanate groups in any one of Claims 1-4. Non-aqueous electrolyte secondary battery.

(In General Formula (2), R is an atom selected from the group consisting of a hydrogen atom, a carbon atom, a nitrogen atom, an oxygen atom, a sulfur atom, a phosphorus atom, and a halogen atom, which may have hydrogen or an isocyanate group. Represents an organic group having 1 to 12 carbon atoms composed of   One or more compounds selected from uretdione, oxadiaditrione, biuret, urethane, allophanate and isocyanurate are compounds having one or more partial structures represented by general formula (2) and two or more isocyanate groups in the molecule. The nonaqueous electrolyte secondary battery according to claim 5, which is a compound having a skeleton.   The non-aqueous system according to claim 5 or 6, wherein the compound having one or more partial structures represented by the general formula (2) and two or more isocyanate groups in the molecule is a compound having a number average molecular weight of 200 or more and 5000 or less. Electrolyte secondary battery. In addition to an electrolyte, a non-aqueous solvent, (A) and (B), at least a tetrafluoroborate salt and a compound represented by the following general formula (3) are contained. The non-aqueous electrolyte secondary battery according to Item 1.

(In general formula (3), l and m independently represent an integer of 0 to 4.)   The non-aqueous electrolyte secondary battery according to any one of claims 1 to 8, comprising (A) in an amount of 0.01% by mass to less than 3% by mass.   The non-aqueous electrolyte secondary battery according to claim 1, containing 0.01 to 5% by mass of (B).   In addition to the electrolyte, the non-aqueous solvent, (A) and (B), at least one selected from the group consisting of unsaturated cyclic carbonates and fluorinated cyclic carbonates is contained. The non-aqueous electrolyte secondary battery according to item. The carbonaceous material, the Raman R value, defined as the ratio of the peak intensity of 1360 cm ^-1 to the peak intensity of 1580 cm ^-1 in the argon ion laser Raman spectroscopy is 0.1 or more, of claims 1 to 11 The nonaqueous electrolyte secondary battery according to any one of the above.   The nonaqueous electrolyte solution used for the nonaqueous electrolyte secondary battery of any one of Claims 1-12.