JP2011044339A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery with improved battery characteristics at a high-temperature cycle through restraint of decomposition of a solvent and deformation of the battery. <P>SOLUTION: The nonaqueous electrolyte secondary battery is provided with a cathode, an anode, electrolyte and a separator. The cathode contains moisture by 1,000-50 ppm. The electrolyte contains a specific isocyanate compound and specific imide salt compounds. The isocyanate compound is contained by 0.01-5% by mass to the nonaqueous electrolyte. The imide salt compounds are lithium bis (trifluoromethane sulfonyl) imide, lithium bis (pentafluoroethane sulfonyl) imide, and perfluoro propane-1, 3-disulfonyl imide lithium. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a non-aqueous electrolyte secondary battery such as a lithium secondary battery.

  In recent years, portable electronic devices such as a camera-integrated VTR (Video Tape Recorder), a mobile phone, and a notebook personal computer are widely used, and there is a strong demand for miniaturization, weight reduction, and long life. Accordingly, as a power source, development of a battery, in particular, a secondary battery that is lightweight and capable of obtaining a high energy density is in progress.

Among them, secondary batteries (so-called lithium ion secondary batteries) that use lithium (Li) occlusion and release for charge and discharge reactions are highly expected because they can obtain higher energy density than lead batteries and nickel cadmium batteries. Yes. This lithium ion secondary battery includes an electrolyte together with a positive electrode and a negative electrode.
In order to improve various performances of the non-aqueous electrolyte secondary battery, intensive development is in progress.

  In particular, a laminated battery using an aluminum laminated film for the exterior has a high energy density because it is lightweight, but the laminated battery has a problem that the battery swells due to a gas generated by the decomposition of the electrolytic solution. As a method for solving this problem, there is a method of using a chain carbonate having a relatively large number of carbon atoms such as diethyl carbonate as the chain carbonate, but the viscosity and conductivity increase, and the discharge capacity is maintained during repeated charge and discharge. The rate will drop.

In order to solve the problem of battery swelling, for example, a lithium is composed of a carbonaceous material capable of absorbing and desorbing lithium (Li) ions, as exemplified by an intercalation reaction between graphite layers. For ion secondary batteries, propylene carbonate and gamma butyrolactone (γ-butyrolactone), which have a relatively high boiling point and high dielectric constant, are used in combination with ethylene carbonate and chain carbonate solvents as solvents that constitute the electrolyte. There is known a technique for suppressing the deterioration of battery characteristics due to (see Patent Document 1).
However, when a graphite-based material is used as the negative electrode active material, a reductive decomposition reaction occurs at the negative electrode, which not only deteriorates the characteristics as the battery is used, but also causes deformation of the battery due to decomposition and vaporization of the solvent. Has been a problem.

On the other hand, a solvent that forms a film called SEI (Solid Electrolyte Interface; solid electrolyte membrane) on the negative electrode during charge and discharge in the initial stage of use of the battery has an electrolyte configuration in which a solvent is added to the solvent in advance. A method for suppressing reductive decomposition and battery deformation has been proposed (see, for example, Patent Document 2).
However, in the case of the electrolyte configuration described in Patent Document 2, it is not possible to suppress deterioration of characteristics due to use, and gas generation and battery deformation occur during high-temperature storage.

In order to solve the same problem, a nonaqueous electrolyte and a battery including an aromatic compound having an isocyanate group with a structure represented by the following chemical formula have been proposed (see, for example, Patent Document 3).
O = C = N-Ar-N = C = O
(Ar in the formula represents an aryl group (aromatic carbon chain).)

In addition, in a lithium ion secondary battery, if moisture is contained in the positive electrode, negative electrode, separator, or nonaqueous electrolyte, the nonaqueous electrolyte component reacts with the moisture to decompose the nonaqueous electrolyte component, thereby Since the gas generation becomes remarkable, initial charge / discharge characteristics, charge / discharge cycle characteristics, storage characteristics, and the like are deteriorated.
Therefore, studies for reducing moisture contained in the electrode, the separator, and the non-aqueous electrolyte have been made. For example, the amount of water contained in the positive electrode mixture constituting the positive electrode is 260 ppm or less with respect to 1 g of the positive electrode mixture, and the amount of water contained in the negative electrode mixture constituting the negative electrode is 10 ppm or less with respect to 1 g of the negative electrode mixture. There has been proposed a technique for improving the initial charge / discharge characteristics and charge / discharge cycle characteristics of a lithium ion secondary battery by reducing the amount of water in the water electrolyte to 20 ppm or less with respect to the entire non-aqueous electrolyte (for example, Patent Documents). 4).

JP 09-92329 A JP 2003-151623 A JP 2002-8719 A JP 2001-297750 A

  However, in the non-aqueous electrolyte and battery described in Patent Document 3, by adopting an electrolyte configuration containing an additive represented by the above chemical formula, improvement in high-temperature storage characteristics is seen, but in the future In order to further increase the capacity, it is required to improve battery characteristics at high temperatures including gentle heat generation associated with charge / discharge, that is, to further suppress deformation and further improve cycle characteristics and capacity.

The present invention has been made in view of such problems of the prior art, and an object of the present invention is to provide a battery in which the decomposition of the solvent and the deformation of the battery are suppressed, and the battery characteristics during high-temperature cycle are improved. Is to provide.
In addition, the deformation of the battery exterior member, that is, the problem of the accompanying deterioration of the battery characteristics is not only in the configuration by the exterior member by the laminate film but also in the configuration by the exterior member by the metal can. It is considered useful in dealing with the thinning of the container.

  As a result of intensive studies to achieve the above object, the present inventor intentionally causes a specific amount of moisture to be present in the positive electrode, and causes the non-aqueous electrolyte to contain an isocyanate compound and an imide salt compound having a specific structure. Thus, the inventors have found that the above object can be achieved, and have completed the present invention.

That is, the nonaqueous electrolyte secondary battery of the present invention is a nonaqueous electrolyte battery comprising a positive electrode and a negative electrode, a nonaqueous electrolyte, and a separator,
The positive electrode contains 1000 ppm to 50 ppm of water,
The electrolyte has the following formulas (I) to (III)
X-R1-N = C = O (I)
O = C = N-R2-N = C = O (II)
O = C = N-R3-N = C = O (III)
(X in the formulas (I) to (III) represents a hydrogen atom or a halogen atom, and R1 and R2 have at least one heteroatom selected from the group consisting of halogen, phosphorus, silicon, oxygen and sulfur. C1 to C22 aliphatic hydrocarbon groups which may be present, and R3 may have the above heteroatoms C6 to C20 aromatic hydrocarbon groups and / or the above heteroatoms. An aliphatic hydrocarbon group containing 1 to 4 C6 to C20 alicyclic hydrocarbon groups and optionally having the above heteroatoms.), And
Formula (IV)-(V)
_{LiN (C m F 2m + 1} SO 2) (C n F 2n + 1 SO 2) ... (IV)
(M and n in the formula (IV) represent an integer of 1 or more.)

(R in the formula (V) contains at least one imide salt compound represented by a C2 to C4 linear or branched perfluoroalkylene group.)

  According to the present invention, a specific amount of moisture is intentionally present in the positive electrode, and the isocyanate compound and imide salt compound having a specific structure are included in the non-aqueous electrolyte. It is possible to provide a battery that is suppressed and has improved battery characteristics during a high-temperature cycle.

It is sectional drawing showing the structure of the 1st secondary battery using the nonaqueous electrolyte which concerns on one embodiment of this invention. It is sectional drawing which expands and represents a part of winding electrode body shown in FIG. It is a disassembled perspective view showing the structure of the 2nd secondary battery using the nonaqueous electrolyte which concerns on one embodiment of this invention. It is sectional drawing showing the structure along the IV-IV line of the wound electrode body shown in FIG.

Hereinafter, the nonaqueous electrolyte battery of the present invention will be described in detail.
As described above, in the nonaqueous electrolyte battery of the present invention, the positive electrode contains 1000 to 50 ppm of moisture.
That is, the water content in the positive electrode is in the range of 50 ppm to 1000 ppm and more preferably in the range of 100 ppm to 500 ppm with respect to 1 g of the material constituting the positive electrode active material-containing layer. Within this range, the desired effect of the present invention can be exhibited.

In the nonaqueous electrolyte battery of the present invention, the nonaqueous electrolyte contains a predetermined isocyanate compound and an imide salt compound.
First, the isocyanate compound will be described. Specifically, the nonaqueous electrolyte contains at least one of the isocyanate compounds represented by the above formulas (I) to (III).
That is, the nonaqueous electrolyte may contain only the compound represented by any one of the formulas (I), (II), or (III), or may contain a combination of two or more of these, Furthermore, in each case, one or more kinds can be used on the same general formula basis.

The content of the isocyanate compound in the nonaqueous electrolyte is preferably 0.01 to 5% by mass, and more preferably 0.1 to 1% by mass.
If it exceeds 5% by mass, the negative electrode film becomes thick and the film resistance may become too high. If it is less than 0.01% by mass, the desired effect may not be obtained.

In the present invention, the above-described isocyanate compound can appropriately substitute halogen, phosphorus, silicon, oxygen, sulfur and other elements on carbon for the purpose of imparting flame retardancy and conductivity.
These elements are preferably substituted as long as the reactivity of the isocyanate group is not impaired.

Specific examples of the isocyanate compound (formula (1) to formula (12)) will be given below, but usable isocyanate compounds are not limited to these.
H ₃ C— (CH ₂ ) ₄ —N═C═O (1)
H ₃ C— (CH ₂ ) ₅ —N═C═O (2)
H ₃ C— (CH ₂ ) ₇ —N═C═O (3)
H ₃ C— (CH ₂ ) ₁₁ —N═C═O (4)
H ₃ C— (CH ₂ ) ₁₇ —N═C═O (5)
_{O = C = N- (CH 2} ) 4 -N = C = O ... (6)
_{O = C = N- (CH 2} ) 6 -N = C = O ... (7)
_{O = C = N- (CH 2} ) 8 -N = C = O ... (8)
_{O = C = N- (CH 2} ) 12 -N = C = O ... (9)
_{O = C = N- (CH 2} ) 16 -N = C = O ... (10)

As the compounds of the formulas (1) to (12), those having 6 to 22 carbon atoms in the carbon chain are preferable. This is because it is easily available and a high effect can be obtained.
Furthermore, it is preferable that the carbon chain constituting the isocyanate compound is linear. Of these, compounds of formulas (4), (5), (7), (8), (9), (10), (11), and (12) are preferred, and formulas (5), (7), ( The compound of 11) is more preferable.

Next, the imide salt compound will be described. Examples of the imide salt compound include a chain compound represented by the following formula (IV).
_{LiN (C m F 2m + 1} SO 2) (C n F 2n + 1 SO 2) ... (IV)
Here, in formula (IV), m and n are integers of 1 or more.

Examples of the imide salt compound represented by the formula (IV) include lithium bis (trifluoromethanesulfonyl) imide [LiN (CF ₃ SO ₂ ) ₂ ], lithium bis (pentafluoroethanesulfonyl) imide [LiN (C ₂ F). ₅ SO ₂ ) ₂ ], lithium (trifluoromethanesulfonyl) (pentafluoroethanesulfonyl) imide [LiN (CF ₃ SO ₂ ) (C ₂ F ₅ SO ₂ )], lithium (trifluoromethanesulfonyl) (heptafluoropropanesulfonyl) Imido [LiN (CF ₃ SO ₂ ) (C ₃ F ₇ SO ₂ )], lithium (trifluoromethanesulfonyl) (nonafluorobutanesulfonyl) imide [LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ )], etc. Is mentioned.

  The content of the imide salt compound represented by the formula (IV) is preferably in the range of 0.1% by mass to 30% by mass with respect to the electrolyte, and is 0.3% by mass to 20% by mass. More preferably within the range. In this range, the desired effect can be exhibited.

  Furthermore, as another imide salt compound, the cyclic compound represented by following formula (V) is also mentioned.

  In said formula (V), R represents a C2-C4 (C2-C4) linear or branched perfluoroalkylene group.

  Examples of the compound represented by the formula (V) include perfluoropropane-1,3-disulfonylimide lithium.

  The content of the compound represented by the formula (V) is preferably in the range of 0.1% by mass to 30% by mass with respect to the electrolyte, and is in the range of 0.3% by mass to 20% by mass. More preferably, it is within. It can contribute in order to exhibit the effect of this invention in this range.

  In the present invention, these imide salt compounds represented by the formulas (IV) and (V) may be used alone or in combination of two or more.

In this embodiment, a specific amount of moisture is intentionally present in the positive electrode, and an isocyanate compound and an imide salt compound having a specific structure are contained in the nonaqueous electrolyte, thereby suppressing decomposition of the nonaqueous electrolyte at a high temperature. Thus, the battery characteristics during high-temperature cycle are improved.
The reason why such excellent characteristics can be obtained is not necessarily clear, but the non-aqueous electrolyte contains the chain isocyanate compounds represented by the above formulas (I) to (III), so that A stable SEI is formed on the negative electrode by the discharge, and it becomes possible to suppress the peeling of the carbonaceous material and the decomposition of the cyclic carbonate, and at the same time, reacts with the water present in the positive electrode, so It is considered that stable SEI can be formed.

Next, the solvent contained in the nonaqueous electrolyte will be described.
Examples of the solvent include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, γ-butyrolactone, γ-valerolactone, 1,2-dimethoxyethane. , Tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, methyl acetate, ethyl acetate, methyl propionate, propion Ethyl acetate, methyl butyrate, methyl isobutyrate, methyl trimethylacetate, ethyl trimethylacetate, acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, 3-methoxypropionitrile, N, N-dimethylformamide, N-methylpyrrolidi Non, N-methyloxazolidinone, N, N′-dimethylimidazolidinone, nitromethane, nitroethane, sulfolane, trimethyl phosphate, dimethyl sulfoxide, and the like can be used.
This is because, in an electrochemical device such as a battery provided with a nonaqueous electrolyte, excellent capacity, cycle characteristics and storage characteristics can be obtained. These may be used alone or in combination of two or more.

Among these, it is preferable to use a solvent containing at least one selected from the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. This is because a sufficient effect can be obtained.
In this case, in particular, ethylene carbonate or propylene carbonate having a high viscosity (high dielectric constant) solvent (for example, relative dielectric constant ε ≧ 30) and dimethyl carbonate having a low viscosity solvent (for example, viscosity ≦ 1 mPa · s). It is preferable to use a mixture containing diethyl carbonate or ethyl methyl carbonate. This is because the dissociation property of the electrolyte salt and the ion mobility are improved, so that a higher effect can be obtained.

  This solvent preferably contains at least one selected from the group consisting of cyclic carbonates having an unsaturated bond represented by the following chemical formulas 4 to 6. This is because the chemical stability of the nonaqueous electrolyte is further improved.

  Here, R4 and R5 in Chemical Formula 4 are each independently a hydrogen atom, a halogen atom, or an alkyl group that may contain a halogen atom having 1 to 12 carbon atoms.

  Here, R6 to R9 in Chemical Formula 5 are each independently a hydrogen atom, a halogen atom, a hydrocarbon group that may contain a halogen atom having 1 to 12 carbon atoms, or a carbon group having 2 to 12 carbon atoms. An alkenyl group, at least one of which is an alkenyl group having 2 to 12 carbon atoms.

  In addition, R10 in Chemical formula 6 is an alkylene group.

The cyclic ester carbonate having an unsaturated bond shown in Chemical Formula 4 is a vinylene carbonate compound.
Examples of the vinylene carbonate compound include vinylene carbonate (1,3-dioxol-2-one), methyl vinylene carbonate (4-methyl-1,3-dioxol-2-one), and ethyl vinylene carbonate (4-ethyl). -1,3-dioxol-2-one), 4,5-dimethyl-1,3-dioxol-2-one, 4,5-diethyl-1,3-dioxol-2-one, 4-fluoro-1, Examples include 3-dioxol-2-one and 4-trifluoromethyl-1,3-dioxol-2-one. These may be single and multiple types may be mixed. Among these, vinylene carbonate is preferable. This is because it is easily available and a high effect can be obtained.

The cyclic ester carbonate having an unsaturated bond shown in Chemical formula 5 is a vinyl ethylene carbonate compound.
Examples of the vinyl carbonate-based compound include vinyl ethylene carbonate (4-vinyl-1,3-dioxolan-2-one), 4-methyl-4-vinyl-1,3-dioxolan-2-one, and 4-ethyl. -4-vinyl-1,3-dioxolan-2-one, 4-n-propyl-4-vinyl-1,3-dioxolan-2-one, 5-methyl-4-vinyl-1,3-dioxolane-2 -One, 4,4-divinyl-1,3-dioxolan-2-one, 4,5-divinyl-1,3-dioxolan-2-one and the like. These may be single and multiple types may be mixed. Of these, vinyl ethylene carbonate is preferred. This is because it is easily available and a high effect can be obtained. Of course, as R6 to R9, all may be vinyl groups, all may be allyl groups, or vinyl groups and allyl groups may be mixed.

The cyclic ester carbonate having an unsaturated bond shown in Chemical formula 6 is a methylene ethylene carbonate compound.
Examples of the methylene ethylene carbonate compounds include 4-methylene-1,3-dioxolan-2-one, 4,4-dimethyl-5-methylene-1,3-dioxolan-2-one, and 4,4-diethyl-5. -Methylene-1,3-dioxolan-2-one and the like. These may be single and multiple types may be mixed. This methylene ethylene carbonate compound may have one methylene group (compound shown in Chemical Formula 6) or two methylene groups.
The cyclic carbonate having an unsaturated bond may be catechol carbonate having a benzene ring in addition to those shown in Chemical Formulas 4 to 6.

  Further, the solvent contains at least one of a chain carbonate ester having a halogen represented by Chemical Formula 7 as a constituent element and a cyclic carbonate ester having a halogen represented by Chemical Formula 8 as a constituent element. Is preferred. This is because the chemical stability of the nonaqueous electrolyte is further improved.

  Here, R11 to R16 are a hydrogen atom, a halogen atom, an alkyl group, or a halogenated alkyl group, and at least one of them is a halogen atom or a halogenated alkyl group.

  Here, R17 to R20 are a hydrogen atom, a halogen atom, an alkyl group or a halogenated alkyl group, and at least one of them is a halogen atom or a halogenated alkyl group.

In addition, R11 to R16 in Chemical Formula 7 may be the same or different. The same applies to R17 to R20 in Chemical Formula 8.
Although the kind of halogen is not specifically limited, For example, at least 1 sort (s) selected from the group which consists of a fluorine, chlorine, and a bromine is mentioned, Among these, a fluorine is preferable. This is because a high effect can be obtained. Of course, other halogens may be used.

The number of halogens is preferably two rather than one, and may be three or more. When used in electrochemical devices such as secondary batteries, the ability to form a protective film on the electrode surface is increased, and a stronger and more stable protective film is formed, so the decomposition reaction of the nonaqueous electrolyte is further suppressed. Because it is done.
Examples of the chain carbonate having a halogen shown in Chemical formula 7 include fluoromethyl methyl carbonate, bis (fluoromethyl) carbonate, difluoromethyl methyl carbonate, and the like. These may be single and multiple types may be mixed.

Examples of the cyclic carbonate having a halogen shown in Chemical formula 8 include 4-fluoro-1,3-dioxolan-2-one, 4-chloro-1,3-dioxolan-2-one, 4,5-difluoro- 1,3-dioxolan-2-one, tetrafluoro-1,3-dioxolan-2-one, 4-chloro-5-fluoro-1,3-dioxolan-2-one, 4,5-dichloro-1, 3-oxolan-2-one, tetrachloro-1,3-dioxolan-2-one, 4,5-bistrifluoromethyl-1,3-dioxolan-2-one, 4-trifluoromethyl-1,3-dioxolane -2-one, 4,5-difluoro-4,5-dimethyl-1,3-dioxolan-2-one, 4,4-difluoro-5-methyl-1,3-dioxolan-2-one, 4-e -5,5-difluoro-1,3-dioxolan-2-one, 4-fluoro-5-trifluoromethyl-1,3-dioxolan-2-one, 4-methyl-5-trifluoromethyl-1, 3-dioxolan-2-one, 4-fluoro-4,5-dimethyl-1,3-dioxolan-2-one, 5- (1,1-difluoroethyl) -4,4-difluoro-1,3-dioxolane 2-one, 4,5-dichloro-4,5-dimethyl-1,3-dioxolan-2-one, 4-ethyl-5-fluoro-1,3-dioxolan-2-one, 4-ethyl-4 , 5-Difluoro-1,3-dioxolan-2-one, 4-ethyl-4,5,5-trifluoro-1,3-dioxolan-2-one, 4-fluoro-4-methyl-1,3- Dioxolan-2-one etc. A. These may be single and multiple types may be mixed.
Of these, 4-fluoro-1,3-dioxolan-2-one and 4,5-difluoro-1,3-dioxolan-2-one are preferred, and 4,5-difluoro-1,3-dioxolan-2-one Is more preferable.
In particular, 4,5-difluoro-1,3-dioxolan-2-one is preferably a trans isomer rather than a cis isomer. This is because it is easily available and a high effect can be obtained.

In the present invention, the non-aqueous electrolyte comprises a chain carbonate ester, a saturated cyclic carbonate ester, and an unsaturated cyclic carbonate ester of 30 to 80% by mass, 10 to 50% by mass, and 0.01 to 5% by mass, respectively. It is preferable to include by a ratio.
If these esters deviate from the above range, the battery characteristics may be deteriorated due to a decrease in conductivity or the like.
Moreover, as a nonaqueous electrolyte, it is preferable to contain halogenated ethylene carbonate in the ratio of 0.1-40 mass%.
If the content of halogenated ethylene carbonate deviates from the above range, the ability to form a protective film on the electrode surface may not be sufficient, and the intended effect may not be obtained.

The electrolyte salt contains, for example, one or more light metal salts such as a lithium salt.
As this lithium salt, for example, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium tetraphenylborate (LiB (C ₆ H ₅ ) ₄ ), Lithium methanesulfonate (LiCH ₃ SO ₃ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), lithium tetrachloroaluminate (LiAlCl ₄ ), dilithium hexafluorosilicate (Li ₂ SiF ₆ ), lithium chloride ( LiCl) and lithium bromide (LiBr).
Among these, at least one selected from the group consisting of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium hexafluoroarsenate is preferable, and lithium hexafluorophosphate is more preferable. This is because the resistance of the non-aqueous electrolyte is lowered.
In particular, it is preferable to use lithium tetrafluoroborate together with lithium hexafluorophosphate. This is because a high effect can be obtained.

In the battery according to the present embodiment, the non-aqueous electrolyte includes, in a non-aqueous solvent (organic solvent), an isocyanate compound having a structure represented by the above-described formulas (I) to (III), and the formula (IV) or ( V) has a structure in which an imide salt compound having a structure represented by V) is dissolved.
This isocyanate compound has a structure having an aliphatic carbon chain R as the main chain as represented by the formulas (I) to (III), and has 6 carbon atoms in the main chain to which the isocyanate group is bonded. By selecting above, decomposition of the solvent and storage battery deformation during high temperature storage can be suppressed.
Furthermore, by simultaneously containing the imide salt compound represented by the formula (IV) or (V), it is possible to obtain a battery having improved battery characteristics during a high-temperature cycle.
Such a problem of deformation or expansion of the battery exterior member and the accompanying deterioration in battery characteristics is not only due to the configuration of the exterior member made of the laminate film but also the configuration of the exterior container made of a metal can. It is considered useful for dealing with thinning.

(First secondary battery)
1 and 2 show a cross-sectional configuration of a first nonaqueous electrolyte battery (secondary battery), and FIG. 2 shows an enlarged part of the spirally wound electrode body shown in FIG. . This battery is, for example, a lithium ion secondary battery in which the capacity of the negative electrode is expressed based on insertion and extraction of lithium as an electrode reactant.

The secondary battery mainly includes a wound electrode body 20 in which a positive electrode 21 and a negative electrode 22 are wound via a separator 23 inside a substantially hollow cylindrical battery can 11, and a pair of insulating plates 12 and 13. And are stored. The battery structure using the cylindrical battery can 11 is called a cylindrical type.
The battery can 11 has, for example, a hollow structure in which one end is closed and the other end is opened, and is made of a metal material such as iron, aluminum, or an alloy thereof.
In addition, when the battery can 11 is comprised with iron, plating, such as nickel, may be given, for example. The pair of insulating plates 12 and 13 are arranged so as to sandwich the wound electrode body 20 from above and below and to extend perpendicularly to the wound peripheral surface.

  A battery lid 14 and a safety valve mechanism 15 and a heat-sensitive resistance element (Positive Temperature Coefficient; PTC element) 16 provided inside thereof are caulked and attached to the open end of the battery can 11 via a gasket 17. The inside of the battery can 11 is sealed. The battery lid 14 is made of a metal material similar to that of the battery can 11, for example. The safety valve mechanism 15 is electrically connected to the battery lid 14 via the heat sensitive resistance element 16. In the safety valve mechanism 16, when the internal pressure becomes a certain level or more due to an internal short circuit or external heating, the disk plate 15A is reversed and the electrical connection between the battery lid 14 and the wound electrode body 20 is disconnected. It has come to be. The heat sensitive resistive element 16 limits the current by increasing the resistance according to the temperature rise, and prevents abnormal heat generation due to a large current. The gasket 17 is made of, for example, an insulating material, and asphalt is applied to the surface thereof.

  A center pin 24 may be inserted in the center of the wound electrode body 20. In this wound electrode body 20, a positive electrode lead 25 made of a metal material such as aluminum is connected to the positive electrode 21, and a negative electrode lead 26 made of a metal material such as nickel is connected to the negative electrode 22. . The positive electrode lead 25 is welded to the safety valve mechanism 15 and is electrically connected to the battery lid 14, and the negative electrode lead 26 is welded to and electrically connected to the battery can 11.

The positive electrode 21 is obtained, for example, by providing a positive electrode active material layer 21B on both surfaces of a positive electrode current collector 21A having a pair of opposed surfaces. However, the positive electrode active material layer 21B may be provided only on one surface of the positive electrode current collector 21A.
The positive electrode current collector 21 is made of, for example, a metal material such as aluminum, nickel, and stainless steel.
The positive electrode active material layer 21B includes one or more positive electrode materials capable of inserting and extracting lithium as a positive electrode active material, and a binder, a conductive agent, and the like as necessary. Other materials may be included.

As the positive electrode material capable of inserting and extracting lithium, for example, a lithium-containing compound is preferable. This is because a high energy density can be obtained. Examples of the lithium-containing compound include a composite oxide containing lithium and a transition metal element, and a phosphate compound containing lithium and a transition metal element.
Among these, those containing at least one selected from the group consisting of cobalt, nickel, manganese and iron as the transition metal element are preferable. This is because a higher voltage can be obtained. Its chemical formula is represented by, for example, LixM1O ₂ or LiyM ₂ PO _4. In the formula, M1 and M2 represent one or more transition metal elements. The values of x and y vary depending on the charge / discharge state, and are generally 0.05 ≦ x ≦ 1.10 and 0.05 ≦ y ≦ 1.10.

Examples of the composite oxide containing lithium and a transition metal element include lithium cobalt composite oxide (Li _x CoO ₂ ), lithium nickel composite oxide (Li _x NiO ₂ ), and lithium nickel cobalt composite oxide (Li _x Ni). _1-z Co _z O ₂ (z <1)), lithium nickel cobalt manganese composite oxide (Li _x Ni _(1-vw) Co _v Mn _w O ₂ (v + w <1)), or a spinel structure And a lithium manganese composite oxide (LiMn ₂ O ₄ ) or a lithium manganese nickel composite oxide (LiMn _2−t Ni _t O ₄ (t <2)). Among these, a complex oxide containing cobalt is preferable. This is because a high capacity can be obtained and excellent cycle characteristics can be obtained.
Examples of the phosphate compound containing lithium and a transition metal element include a lithium iron phosphate compound (LiFePO ₄ ) and a lithium iron manganese phosphate compound (LiFe _1-u MnuPO ₄ (u <1)). Can be mentioned.

  Furthermore, from the viewpoint that higher electrode filling properties and cycle characteristics can be obtained, the surface of the core particle composed of any of the lithium-containing compounds shown in the following [1] to [5] It may be a composite particle coated with fine particles made of the above.

Li _f Co _(1-g) M1 _g O ( _2-h) F _j ... [1]
Here, M1 in the formula is nickel (Ni), manganese (Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron It represents at least one selected from the group consisting of (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr) and tungsten (W). . f, g, h, and j are values in the range of 0.8 ≦ f ≦ 1.2, 0 ≦ g <0.5, −0.1 ≦ h ≦ 0.2, and 0 ≦ j ≦ 0.1. It is. Note that the composition of lithium varies depending on the state of charge and discharge, and the value of f represents a value in a fully discharged state.

_{Li k Mn (1-m-} n) Ni m M2 n O (2-p) F q ... [2]
Here, M2 in the formula is cobalt (Co), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper It represents at least one selected from the group consisting of (Cu), zinc (Zn), zirconium (Zr), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr) and tungsten (W). . k, m, n, p and q are 0.8 ≦ k ≦ 1.2, 0 <m <0.5, 0 ≦ n ≦ 0.5, m + n <1, −0.1 ≦ p ≦ 0. 2, 0 ≦ q ≦ 0.1. Note that the composition of lithium varies depending on the state of charge and discharge, and the value of k represents a value in a fully discharged state.

Li _r Ni _(1-s) M3 _s O _{(2-t) Fu} ... [3]
Here, M3 in the formula is cobalt (Co), manganese (Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron It represents at least one selected from the group consisting of (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr) and tungsten (W). . r, s, t and u are within the range of 0.8 ≦ r ≦ 1.2, 0.005 ≦ s ≦ 0.5, −0.1 ≦ t ≦ 0.2, 0 ≦ u ≦ 0.1 Is the value of Note that the composition of lithium varies depending on the state of charge and discharge, and the value of r represents a value in a complete discharge state.

_{Li v Mn 2-w M4 w} O x F y ... [4]
Here, M4 in the formula is cobalt (Co), nickel (Ni), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron It represents at least one selected from the group consisting of (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr) and tungsten (W). . v, w, x, and y are values within the range of 0.9 ≦ v ≦ 1.1, 0 ≦ w ≦ 0.6, 3.7 ≦ x ≦ 4.1, and 0 ≦ y ≦ 0.1. is there. Note that the composition of lithium varies depending on the state of charge and discharge, and the value of v represents a value in a fully discharged state.

Li _z M ₅ PO ₄ [5]
Here, M5 in the formula is cobalt (Co), manganese (Mn), iron (Fe), nickel (Ni), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium. (V), niobium (Nb), copper (Cu), zinc (Zn), molybdenum (Mo), calcium (Ca), strontium (Sr), tungsten (W) and zirconium (Zr) At least one species is represented. z is a value in the range of 0.9 ≦ z ≦ 1.1. Note that the composition of lithium varies depending on the state of charge and discharge, and the value of z represents a value in a fully discharged state.

In addition, examples of the positive electrode material capable of inserting and extracting lithium include oxides such as titanium oxide, vanadium oxide and manganese dioxide, disulfides such as titanium disulfide and molybdenum sulfide, and niobium selenide. And conductive polymers such as sulfur, polyaniline and polythiophene.
Of course, the positive electrode material capable of inserting and extracting lithium may be other than the above. Further, two or more kinds of the series of positive electrode materials described above may be mixed in any combination.

  Examples of the conductive agent include carbon materials such as graphite, carbon black, acetylene black, and ketjen black. These may be single and multiple types may be mixed. Note that the conductive agent may be a metal material or a conductive polymer as long as it is a conductive material.

  Examples of the binder include synthetic rubbers such as styrene butadiene rubber, fluorine rubber and ethylene propylene diene, and polymer materials such as polyvinylidene fluoride. These may be single and multiple types may be mixed.

In the negative electrode 22, for example, a negative electrode active material layer 22B is provided on both surfaces of a negative electrode current collector 22A having a pair of surfaces. However, the negative electrode active material layer 22B may be provided only on one surface of the negative electrode current collector 22A.
The negative electrode current collector 22A is made of, for example, a metal material such as copper, nickel, and stainless steel. The surface of the anode current collector 22A is preferably roughened. This is because the so-called anchor effect improves the adhesion between the negative electrode current collector 22A and the negative electrode active material layer 22B. In this case, the surface of the negative electrode current collector 22A only needs to be roughened at least in a region facing the negative electrode active material layer 22B. Examples of the roughening method include a method of forming fine particles by electrolytic treatment. This electrolytic treatment is a method of forming irregularities by forming fine particles on the surface of the negative electrode current collector by an electrolytic method in an electrolytic cell. The copper foil produced by the electrolytic method including the copper foil roughened by this electrolytic treatment is generally called “electrolytic copper foil”.

  The negative electrode active material layer 22B includes any one or more of negative electrode materials capable of inserting and extracting lithium as a negative electrode active material, and a binder, a conductive agent, and the like as necessary. Other materials may be included. Note that details regarding the binder and the conductive agent are the same as those described for the positive electrode, for example. Moreover, it is preferable that the charge capacity of the negative electrode material capable of inserting and extracting lithium is larger than the charge capacity of the positive electrode active material. This is because the possibility that lithium becomes a dendrite and precipitates on the negative electrode is reduced even at the time of full charge.

Examples of the negative electrode material capable of inserting and extracting lithium include a carbon material. Examples of the carbon material include graphitizable carbon, non-graphitizable carbon having a (002) plane spacing of 0.37 nm or more, and graphite having a (002) plane spacing of 0.34 nm or less. It is. More specifically, there are pyrolytic carbons, cokes, glassy carbon fibers, organic polymer compound fired bodies, activated carbon, and carbon blacks.
Of these, the cokes include pitch coke, needle coke, petroleum coke, and the like. The organic polymer compound fired body is obtained by firing and carbonizing a phenol resin, a furan resin, or the like at an appropriate temperature. The carbon material is preferable because the change in crystal structure associated with insertion and extraction of lithium is very small, so that a high energy density is obtained and excellent cycle characteristics are obtained, and the carbon material functions as a conductive agent. The shape of the carbon material may be any of a fibrous shape, a spherical shape, a granular shape, and a scale shape.

In addition to the above, as a negative electrode material capable of inserting and extracting lithium, for example, it can store and release lithium and has at least one of a metal element and a metalloid element as a constituent element Materials. This is because a high energy density can be obtained.
Such a negative electrode material may be a single element, an alloy or a compound of a metal element or a metalloid element, and may have one or two or more phases thereof at least in part. In addition, the “alloy” mentioned here includes an alloy containing one or more metal elements and one or more metalloid elements in addition to an alloy composed of two or more metal elements. Further, the “alloy” may contain a nonmetallic element. This structure includes solid solutions, eutectics (eutectic mixtures), intermetallic compounds, and those in which two or more of them coexist.

Examples of the metal element or metalloid element described above include a metal element or metalloid element capable of forming an alloy with lithium. Specifically, magnesium (Mg), boron (B), aluminum, gallium (Ga), indium (In), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), bismuth (Bi) ), Cadmium (Cd), silver (Ag), zinc (Zn), hafnium (Hf), zirconium (Zr), yttrium (Y), palladium (Pd) and platinum (Pt).
Examples of the material having at least one of these metal elements and metalloid elements as constituent elements include alloys and compounds of these metal elements and metalloid elements. Specifically, Ma _s Mb _t Li _u (values of s, t, and u are s> 0, t ≧ 0, u ≧ 0, respectively) and McMcqMdr (values of p, q, and r are p> 0, q> 0, r, respectively) ≧ 0)), and the like. However, Ma represents at least one of a metal element and a metalloid element capable of forming an alloy with lithium, and Mb represents at least one of a metal element and a metalloid element other than lithium and Ma. Mc represents at least one of non-metallic elements, and Md represents at least one of metallic elements and metalloid elements other than Ma. These materials may be crystalline or amorphous.

  As a negative electrode material composed of a metal element or a metalloid element capable of forming an alloy with lithium, at least one of a group 14 metal element and a metalloid element in the long-period periodic table is a constituent element. A material having at least one of silicon and tin as a constituent element is particularly preferable. This is because a high energy density can be obtained because of its large ability to occlude and release lithium.

Examples of the negative electrode material having at least one of silicon and tin include at least a part of silicon simple substance, alloy and compound, tin simple substance, alloy and compound, and one or more phases thereof. The material which has in is mentioned.
Examples of the silicon alloy include, as the second constituent element other than silicon, tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony (Sb), and chromium. The thing which has at least 1 sort (s) chosen from the group is mentioned.
Examples of the silicon compound include those having oxygen or carbon (C), and may have the above-described second constituent element in addition to silicon.
Examples of silicon alloys or compounds include SiB ₄ , SiB ₆ , Mg ₂ Si, Ni ₂ Si, TiSi ₂ , MoSi ₂ , CoSi ₂ , NiSi ₂ , CaSi ₂ , CrSi ₂ , Cu ₅ Si, FeSi ₂ , MnSi ₂ , NbSi ₂ , TaSi ₂ , VSi ₂ , WSi ₂ , ZnSi ₂ , SiC, Si ₃ N ₄ , Si ₂ N ₂ O, SiO _v (0 <v ≦ 2), LiSiO, and the like.

As the alloy of tin, for example, the second constituent element other than tin is selected from the group consisting of silicon, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony and chromium. And those having at least one selected from the above. Examples of the tin compound include those having oxygen or carbon, and may contain the above-described second constituent element in addition to tin. Examples of tin alloys or compounds include SnO _w (0 <w ≦ 2), SnSiO ₃ , LiSnO, and Mg ₂ Sn.
In particular, as the negative electrode material having at least one of silicon and tin, for example, a material having tin as the first constituent element and, in addition thereto, second and third constituent elements is preferable. The second constituent elements are cobalt, iron, magnesium, titanium, vanadium (V), chromium, manganese, nickel, copper, zinc, gallium, zirconium, niobium (Nb), molybdenum, silver, indium, cerium (Ce), It is at least one selected from the group consisting of hafnium, tantalum (Ta), tungsten (W), bismuth and silicon. The third constituent element is at least one selected from the group consisting of boron, carbon, aluminum, and phosphorus (P). This is because having the second and third constituent elements improves the cycle characteristics.

As a negative electrode material capable of inserting and extracting lithium, a simple substance of silicon, an alloy and a compound, a simple substance of tin, an alloy and a compound, and a material having at least a part of one or more phases thereof are used. The used negative electrode active material layer is formed by using, for example, a gas phase method, a liquid phase method, a thermal spraying method, a coating method or a baking method, or two or more of these methods.
In this case, the negative electrode current collector and the negative electrode active material layer are preferably alloyed at least at a part of the interface. Specifically, the constituent element of the negative electrode current collector may diffuse into the negative electrode active material layer at the interface between them, or the constituent element of the negative electrode active material layer may diffuse into the negative electrode current collector. These constituent elements may be diffused with each other. This is because breakage due to expansion and contraction of the negative electrode active material layer during charging and discharging is suppressed, and electronic conductivity between the negative electrode current collector and the negative electrode active material layer is improved.

As the vapor phase method, for example, physical deposition method or chemical deposition method, specifically, vacuum vapor deposition method, sputtering method, ion plating method, laser ablation method, thermal chemical vapor deposition (CVD). And plasma chemical vapor deposition.
As the liquid phase method, a known method such as electrolytic plating or electroless plating can be used. The application method is, for example, a method in which a particulate negative electrode active material is mixed with a binder and then dispersed in a solvent and applied. The baking method is, for example, a method in which a heat treatment is performed at a temperature higher than the melting point of a binder or the like after being applied by a coating method. Known methods can also be used for the firing method, and examples thereof include an atmospheric firing method, a reactive firing method, and a hot press firing method.

Further, examples of the negative electrode material capable of inserting and extracting lithium include metal oxides and polymer compounds capable of inserting and extracting lithium. Examples of the metal oxide include iron oxide, ruthenium oxide, and molybdenum oxide. Examples of the polymer compound include polyacetylene, polyaniline, and polypyrrole.
Of course, the negative electrode material capable of inserting and extracting lithium may be other than the above. Moreover, two or more kinds of the series of negative electrode materials described above may be mixed in any combination.

The separator 23 separates the positive electrode and the negative electrode, and allows lithium ions to pass through while preventing a short circuit of current due to contact between the two electrodes.
The separator may be, for example, a porous film having an average pore diameter of about 5 μm or less, and specifically, a porous film made of a synthetic resin such as polytetrafluoroethylene, polypropylene, and polyethylene, or a ceramic. Examples include a porous film and a laminate of two or more of these porous films. Among these, a porous film made of polyolefin is preferable because it is excellent in short-circuit preventing effect and can improve the safety of the secondary battery due to the shutdown effect. In particular, polyethylene is preferable because a shutdown effect can be obtained at 100 ° C. or higher and 160 ° C. or lower and the electrochemical stability is excellent. Polypropylene is also preferable, and other resins having chemical stability may be copolymerized with polyethylene or polypropylene, or blended.

Examples of the other materials include polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, aramid, polyimide, and polyacrylonitrile. One of these may be used alone, or two or more of these may be mixed or polymerized. Polyolefin porous membranes are preferable because they are excellent in short-circuit prevention effects and can improve battery safety due to shutdown effects.
In addition, although not particularly limited, it is typically preferable to use a polyethylene layer as an intermediate layer and a layer made of the above-mentioned other materials and having the same composition on one or both sides thereof.
The separator is impregnated with the above-described electrolytic solution as a liquid non-aqueous electrolyte. This is because the cycle characteristics are improved.

This secondary battery is manufactured, for example, by the following procedure.
First, a positive electrode is produced. First, a positive electrode active material, a binder, and a conductive agent are mixed to form a positive electrode mixture, and then dispersed in an organic solvent to obtain a paste-like positive electrode mixture slurry. Subsequently, the positive electrode mixture slurry is uniformly applied to both surfaces of the positive electrode current collector by a doctor blade, a bar coater or the like, and dried. Finally, the positive electrode active material layer is formed by compression molding the coating film with a roll press or the like while heating as necessary. In this case, compression molding may be repeated a plurality of times.
Next, a negative electrode is produced. First, after preparing a negative electrode current collector made of an electrolytic copper foil or the like, a negative electrode material is deposited on both surfaces of the negative electrode current collector by a vapor phase method such as a vapor deposition method to form a plurality of negative electrode active material particles. Finally, if necessary, an oxide-containing film is formed by a liquid phase method such as a liquid phase deposition method, or a metal material is formed by a liquid phase method such as an electrolytic plating method to form a negative electrode active material layer. .
Next, the positive electrode lead is attached to the positive electrode current collector by welding or the like, and the negative electrode lead is attached to the negative electrode current collector by welding or the like. To produce a wound electrode body.

The secondary battery is assembled as follows.
First, the center pin 24 is inserted into the winding center portion of the winding electrode body 20. Subsequently, the wound electrode body 20 is housed in the battery can 11 while being sandwiched between the pair of insulating plates 12 and 13, and the tip of the positive electrode lead 25 is welded to the safety valve mechanism 15, and the tip of the negative electrode lead 26 is attached. Weld to battery can 11. Subsequently, an electrolytic solution is injected into the battery can 11 and impregnated in the separator 23. Finally, the battery lid 14, the safety valve mechanism 15, and the heat sensitive resistance element 16 are fixed to the opening end of the battery can 11 by caulking through the gasket 17. Thereby, the secondary battery shown in FIGS. 1 and 2 is completed.

In this secondary battery, when charged, for example, lithium ions are released from the positive electrode and inserted in the negative electrode through the electrolyte solution impregnated in the separator. On the other hand, when discharging is performed, for example, lithium ions are released from the negative electrode and inserted into the positive electrode through the electrolytic solution impregnated in the separator.
According to this cylindrical secondary battery, when the capacity of the negative electrode is expressed based on insertion and extraction of lithium, since the above-described non-aqueous electrolyte is provided, even if charging and discharging are repeated, the electrolyte solution The decomposition reaction of is suppressed. Therefore, battery characteristics can be improved.
Other effects relating to the secondary battery are the same as those described for the nonaqueous electrolyte.

(Secondary secondary battery)
FIG. 3 illustrates an exploded perspective configuration of the second secondary battery. In this secondary battery, a wound electrode body 30 to which a positive electrode lead 31 and a negative electrode lead 32 are attached is mainly housed in a film-like exterior member 40. The battery structure using the film-shaped exterior member 40 is called a laminate film type.
For example, the positive electrode lead 31 and the negative electrode lead 32 are each led out in the same direction from the inside of the exterior member 40 toward the outside. The positive electrode lead 31 is made of, for example, a metal material such as aluminum. The negative electrode lead 32 is made of a metal material such as copper, nickel, and stainless steel, for example. Each metal material which comprises the positive electrode lead 31 and the negative electrode lead 32 is made into thin plate shape or mesh shape, for example.

The exterior member 40 is made of, for example, a rectangular aluminum laminated film in which a nylon film, an aluminum foil, and a polyethylene film are bonded together in this order. In this exterior member, for example, a polyethylene film is opposed to the wound electrode body, and each outer edge portion is in close contact with each other by fusion or an adhesive.
An adhesion film 41 is inserted between the exterior member 40 and the positive electrode lead 31 and the negative electrode lead 32 to prevent intrusion of outside air. The adhesion film 41 is made of a material having adhesion to the positive electrode lead 31 and the negative electrode lead 32, for example, a polyolefin resin such as polyethylene, polypropylene, modified polyethylene, and modified polypropylene.

The exterior member 40 may be constituted by a laminate film having another structure instead of the above-described three-layer aluminum laminate film, or may be constituted by a polymer film such as polypropylene or a metal film. It may be.
FIG. 4 shows a cross-sectional configuration along the line IV-IV of the spirally wound electrode body shown in FIG. The wound electrode body 40 is obtained by winding a positive electrode 33 and a negative electrode 34 after being laminated via a separator 35 and an electrolyte 36, and the outermost peripheral portion thereof is protected by a protective tape 37.

The positive electrode 33 is obtained by providing a positive electrode active material layer 33B on both surfaces of a positive electrode current collector 33A. The negative electrode 34 is provided with a negative electrode active material layer 34B on both surfaces of a negative electrode current collector 34A, and the negative electrode active material layer 34B is disposed so as to face the positive electrode active material layer 33B.
The configurations of the positive electrode current collector 33A, the positive electrode active material layer 33B, the negative electrode current collector 34A, the negative electrode active material layer 34B, and the separator 35 are respectively the positive electrode current collector, the positive electrode active material layer in the first secondary battery described above, The configurations of the negative electrode current collector, the negative electrode active material layer, and the separator are the same.

The electrolyte contains the above-described electrolytic solution and a polymer compound that holds the electrolyte, and is in a so-called gel form. A gel electrolyte is preferable because high ion conductivity (for example, 1 mS / cm or more at room temperature) is obtained and liquid leakage is prevented. Needless to say, an electrolyte that contains a small amount of polymer and forms a gel as a whole can also be used.
Examples of the polymer compound include polyacrylonitrile, polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and polyhexafluoropyrene, polytetrafluoroethylene, polyhexafluoropropylene, polyethylene oxide, polypropylene oxide, polyphosphazene, poly Examples include siloxane, polyvinyl acetate, polyvinyl alcohol, polymethyl methacrylate, polyacrylic acid, polymethacrylic acid, styrene-butadiene rubber, nitrile-butadiene rubber, polystyrene, and polycarbonate.
These may be used alone or in combination. In particular, from the viewpoint of electrochemical stability, it is preferable to use polyacrylonitrile, polyvinylidene fluoride, polyhexafluoropropylene, polyethylene oxide, and the like. The addition amount of the polymer compound in the electrolytic solution varies depending on the compatibility between the two, but is preferably 0.5% by mass or more and 50% by mass or less.

The composition of the electrolytic solution is the same as the composition of the electrolytic solution in the first battery described above. However, the term “solvent” as used herein is a broad concept including not only a liquid solvent but also one having ion conductivity capable of dissociating an electrolyte salt. Accordingly, when a polymer compound having ion conductivity is used, the polymer compound is also included in the solvent.
In place of the electrolyte in which the electrolytic solution is held by the polymer compound, the electrolytic solution may be used as it is. In this case, the separator is impregnated with the electrolytic solution.

This secondary battery is manufactured by the following three types of manufacturing methods, for example.
In the first manufacturing method, first, the positive electrode active material layer 33B is formed on both surfaces of the positive electrode current collector 33A by, for example, the same procedure as in the first battery manufacturing method, and the positive electrode 33 is manufactured. A negative electrode active material layer 34B is formed on both sides of the current collector 34A to produce a negative electrode 34.
Then, after preparing the precursor solution containing electrolyte solution, a high molecular compound, and a solvent and apply | coating to the positive electrode 33 and the negative electrode 34, the solvent is volatilized and the gel electrolyte 36 is formed. Subsequently, the positive electrode lead 31 and the negative electrode lead 32 are attached to the positive electrode current collector 33A and the negative electrode current collector 34A, respectively. Subsequently, the positive electrode 33 and the negative electrode 34 provided with the electrolyte 36 are laminated via a separator and then wound in the longitudinal direction, and a protective tape 37 is adhered to the outermost peripheral portion to form the wound electrode body 30. . Finally, for example, after the wound electrode body 30 is sandwiched between two film-shaped exterior members 40, the outer edge portions of the exterior member 40 are bonded to each other by heat fusion or the like, so that the wound electrode body 30 is Encapsulate. At that time, the adhesion film 41 is inserted between the positive electrode lead 31 and the negative electrode lead 32 and the exterior member 40. Thereby, the secondary battery shown in FIGS. 3 and 4 is completed.

  In the second manufacturing method, first, the positive electrode lead is attached to the positive electrode and the negative electrode lead is attached to the negative electrode, and then the positive electrode and the negative electrode are laminated and wound through the separator, and the protective tape is adhered to the outermost peripheral portion. Thus, a wound body that is a precursor of the wound electrode body is produced. Subsequently, after sandwiching the wound body between the two film-like exterior members, the remaining outer peripheral edge portion excluding the outer peripheral edge portion on one side is bonded by thermal fusion or the like, and the bag-like exterior member The wound body is housed inside. Subsequently, an electrolyte composition containing an electrolytic solution, a monomer that is a raw material of the polymer compound, a polymerization initiator, and other materials such as a polymerization inhibitor as necessary is prepared to form a bag-shaped exterior member. Then, the opening of the exterior member is sealed by heat sealing or the like. Finally, the monomer is thermally polymerized to obtain a polymer compound, thereby forming a gel electrolyte. Thereby, the secondary battery is completed.

In the third manufacturing method, first, a wound body is formed by forming a wound body in the same manner as in the second manufacturing method described above, except that a separator coated with a polymer compound on both sides is used. Store inside. Examples of the polymer compound applied to the separator include a polymer containing vinylidene fluoride as a component, that is, a homopolymer, a copolymer, a multi-component copolymer, and the like.
Specifically, polyvinylidene fluoride, a binary copolymer containing vinylidene fluoride and hexafluoropropylene as components, and a ternary copolymer containing vinylidene fluoride, hexafluoropropylene and chlorotrifluoroethylene as components. Such as coalescence. In addition, the high molecular compound may contain the other 1 type, or 2 or more types of high molecular compound with the polymer which uses the above-mentioned vinylidene fluoride as a component. Subsequently, after the electrolytic solution is prepared and injected into the exterior member, the opening of the exterior member is sealed by heat fusion or the like. Finally, the exterior member is heated while applying a load, and the separator is brought into close contact with the positive electrode and the negative electrode through the polymer compound. Thereby, the electrolytic solution is impregnated into the polymer compound, and the polymer compound is gelled to form an electrolyte, so that the secondary battery is completed.

In the third manufacturing method, the swollenness of the secondary battery is suppressed as compared with the first manufacturing method. Further, in the third production method, compared to the second production method, the monomer or solvent that is a raw material of the polymer compound hardly remains in the electrolyte, and the formation process of the polymer compound is well controlled. Therefore, sufficient adhesion is obtained between the positive electrode, the negative electrode, the separator, and the electrolyte.
According to the laminated film type secondary battery, since the above-described electrolyte solution is provided, the battery characteristics can be improved. The effects of the secondary battery other than those described above are the same as those of the first secondary battery.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited to these Examples.
The isocyanate compounds and imide salt compounds used in the following examples and the like are as follows.

In the isocyanate compound, chemical A is the above-described isocyanate compound (5), chemical B is the above-described isocyanate compound (4), chemical C is the above-described isocyanate compound (7), chemical compound D is the above-described isocyanate compound ( 6), Chemical E is the above-mentioned isocyanate compound (11).
In the imide salt compound, chemical F is lithium bis (trifluoromethanesulfonyl) imide, chemical G is lithium bis (pentafluoroethanesulfonyl) imide, and chemical H is perfluoropropane-1,3-disulfonylimide lithium. Each structural formula is as follows.

(Examples 1-1 to 1-4, Comparative Examples 1-1 to 1-5 (cylindrical battery))
First, 91 parts by mass of lithium cobaltate as a positive electrode active material, 6 parts by mass of graphite as a conductive agent, and 3 parts by mass of polyvinylidene fluoride as a binder are added, and N-methylpyrrolidone is added to mix the positive electrode mixture slurry. Got. Next, this positive electrode mixture slurry was uniformly applied to both surfaces on an aluminum foil having a thickness of 12 μm, dried, and then compression molded with a roll press to form a positive electrode active material layer. After that, an aluminum positive electrode lead was welded and attached to one end of the positive electrode current collector.

  The amount of moisture contained in the obtained positive electrode active material layer was determined by the following method. A part of the positive electrode active material layer vacuum-dried under the same conditions was collected as an analysis sample, and the water content in this sample was measured with a Karl Fischer moisture meter (manufactured by Hiranuma Sangyo Co., Ltd.). The moisture concentration in the positive electrode active material layer was adjusted to 50 ppm by adjusting the drying time.

  Further, 97 parts by mass of artificial graphite powder as a negative electrode active material and 3 parts by mass of polyvinylidene fluoride as a binder were mixed, and N-methylpyrrolidone was added to obtain a negative electrode mixture slurry. Next, this negative electrode mixture slurry was uniformly applied on both sides of a 15 μm thick copper foil serving as a negative electrode current collector, dried, and then compression molded with a roll press to form a negative electrode active material layer. . After that, a nickel negative electrode lead was attached to one end of the negative electrode current collector.

  As a non-aqueous electrolyte, a mixed solution in which 1% by mass of vinylene carbonate (VC) is added to ethylene carbonate (EC): dimethyl carbonate (DMC) = 3: 7 (mass ratio) is prepared, and phosphorus hexafluoride is used as an electrolyte salt. What dissolved lithium acid (LiPF6) so that it might become 1.2 mol / kg was used as Comparative Example 1-1, or as shown in Table 1, this isocyanate compound (A ) And / or an imide salt compound (F) was used.

  Subsequently, a positive electrode, a separator made of a microporous polypropylene film (thickness 25 μm), and a negative electrode are laminated in this order, and then wound many times in a spiral shape, and then the winding end portion is fixed with an adhesive tape. Thus, a wound electrode body was formed. Subsequently, after preparing a nickel-plated iron battery can, the wound electrode body was sandwiched between a pair of insulating plates, the negative electrode lead was welded to the battery can and the positive electrode lead was welded to the safety valve mechanism, The wound electrode body was housed inside the battery can. Subsequently, an electrolytic solution was injected into the battery can by a reduced pressure method.

(Examples 1-6 to 1-8 (cylindrical battery))
As shown in Table 1, each battery was produced in the same manner as described above except that the imide salt compound (G) was used instead of the imide salt compound (F), and the batteries were evaluated in the same manner.

(Examples 1-9 to 1-11 (cylindrical battery))
As shown in Table 1, each battery was prepared in the same manner as described above except that the imide salt compound (H) was used instead of the imide salt compound (F), and the batteries were evaluated in the same manner.

(Example 1-5, Comparative Examples 1-6, 1-7 (cylindrical battery))
As shown in Table 1, each battery was prepared in the same manner as described above except that the water concentration in the positive electrode active material layer was set to 1000 ppm, 1200 ppm, and 10 ppm, and evaluated in the same manner.

(Examples 2-1 to 2-15 (cylindrical battery))
As shown in Table 2, each battery was prepared in the same manner as above except that the types of the isocyanate compound and the imide salt compound were changed, and evaluated in the same manner. The results are shown in Table 2.

(Examples 3-1 to 3-15 (cylindrical battery))
Each battery was prepared and evaluated in the same manner as in Example 2 except that 4-fluoro-1,3-dioxolan-2-one (FEC) was used instead of vinylene carbonate (VC). . The results are shown in Table 3.

(Examples 4-1 to 4-4, Comparative Examples 4-1 to 4-5 (laminated film type batteries))
First, 94 parts by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 3 parts by mass of graphite as a conductive agent, and 3 parts by mass of polyvinylidene fluoride (PVdF) as a binder were uniformly mixed to form N-methyl. Pyrrolidone was added to obtain a positive electrode mixture slurry.

  Next, this positive electrode mixture slurry was uniformly applied to both surfaces of an aluminum foil having a thickness of 10 μm, dried and compression molded to form a positive electrode active material layer having a thickness of 30 μm on one surface. This was cut into a shape having a width of 50 mm and a length of 300 mm to obtain a positive electrode.

  The amount of moisture contained in the obtained positive electrode active material layer was determined by the same method as for the cylindrical battery. A part of the positive electrode active material layer vacuum-dried under the same conditions was collected as an analysis sample, and the water content in this sample was measured with a Karl Fischer moisture meter (manufactured by Hiranuma Sangyo Co., Ltd.). The moisture concentration in the positive electrode active material layer was adjusted to 50 ppm by adjusting the drying time.

  Further, 97 parts by mass of MCMB (mesocarbon microbeads) graphite as a negative electrode active material and 3 parts by mass of PVdF as a binder were mixed homogeneously, and N-methylpyrrolidone was added to obtain a negative electrode mixture slurry.

  Next, this negative electrode mixture slurry was uniformly applied on both sides of a 10 μm thick copper foil serving as a negative electrode current collector, dried and pressed to form a 30 μm negative electrode active material layer per side. This was cut into a shape having a width of 50 mm and a length of 300 mm to obtain a negative electrode.

As the separator, a 7 μm-thick microporous polyethylene film coated with 2 μm each of polyvinylidene fluoride was used.
As a non-aqueous electrolyte, a mixed solution in which 1% by mass of vinylene carbonate (VC) is added to ethylene carbonate (EC): diethyl carbonate (DEC) = 3: 7 (mass ratio) is prepared, and phosphorus hexafluoride is used as an electrolyte salt. or used after dissolving lithium acid (LiPF ₆₎ as a 1.0 mol / kg as a comparative example 4-1, in the Comparative examples 4-1, as described in Table 4, the isocyanate compound ( A) and / or imide salt compound (F) was dissolved and used.

  Example 4 After winding the positive electrode and the negative electrode through a separator and putting them in a bag-shaped exterior member made of an aluminum laminate film, 2 g of an electrolyte solution was injected, and then the bag was heat-sealed. A laminate film type battery was prepared.

(Examples 4-6 to 4-8 (laminate film type battery))
As shown in Table 4, each battery was prepared in the same manner as described above except that the imide salt compound (G) was used instead of the imide salt compound (F), and evaluated in the same manner.

(Examples 4-9 to 4-11 (laminated film type battery))
As shown in Table 4, each battery was prepared in the same manner as described above except that the imide salt compound (H) was used instead of the imide salt compound (F), and evaluated in the same manner.

(Example 1-5, Comparative Examples 4-6 and 4-7 (laminated film type battery))
As shown in Table 4, each battery was prepared in the same manner as described above except that the water concentration in the positive electrode active material layer was 1000 ppm, 1120 ppm, and 10 ppm, and evaluated in the same manner.

(Examples 5-1 to 5-15 (laminated film type battery))
As shown in Table 5, each battery was prepared in the same manner as above except that the types of isocyanate compound and imide salt compound were changed, and evaluated in the same manner. The results are shown in Table 5.

(Examples 6-1 to 6-15 (laminated film type battery))
Each battery was prepared in the same manner as in Example 5 except that 4-fluoro-1,3-dioxolan-2-one (FEC) was used in place of vinylene carbonate (VC), and evaluated in the same manner. . The results are shown in Table 6.

(Evaluation)
The high temperature cycle characteristics of the cylindrical batteries of Example 1-1 to Example 3-15 and Comparative Examples 1-1 to 1-5 were measured.
With respect to the laminated film type batteries of Example 4-1 to Example 6-15 and Comparative Examples 4-1 to 4-5, the swelling at high temperature cycle and the high temperature cycle characteristics were measured.

(Measurement of swelling during high-temperature cycle)
First, each battery was charged and discharged for 1 cycle at a current of 1 C in a 23 ° C. environment, and the thickness before evaluation was measured. When investigating the high-temperature cycle characteristics, charging and discharging were repeated in a 45 ° C. high-temperature tank, and the difference between the battery thickness before evaluation and the battery thickness after 300 cycles was determined as the swelling during the high-temperature cycle. As charging / discharging conditions, a constant current and a constant voltage were charged to a maximum voltage of 4.2 V with a current of 1 C, and then a constant current was discharged to a final voltage of 3.0 V with a current of 1 C. This “1C” is a current value at which the theoretical capacity can be discharged in one hour.

(Measurement of high temperature cycle characteristics)
Charging / discharging is repeated in a high temperature bath at 45 ° C., and the discharge capacity maintenance rate at 300 cycles with respect to the discharge capacity at the first cycle is determined as (discharge capacity at 300 cycles / discharge capacity at the first cycle) × 100 (%). It was. As charging / discharging conditions, a constant current and a constant voltage were charged to a maximum voltage of 4.2 V with a current of 1 C, and then a constant current was discharged to a final voltage of 3.0 V with a current of 1 C. This “1C” is a current value at which the theoretical capacity can be discharged in one hour.

From Table 1, it was found that the combined use of an isocyanate compound having a long-chain alkyl group and an imide salt compound provides sufficient high-temperature cycle characteristics as compared with the case where each is used alone.
When the water concentration in the positive electrode active material layer is 1000 ppm or more, the amount of water becomes excessive, and even if an isocyanate compound is added, sufficient charge / discharge cycle characteristics cannot be obtained. On the other hand, when the water concentration in the positive electrode active material layer is 50 ppm or less, the amount of water becomes insufficient, and the effect of the isocyanate compound becomes low.
As can be seen from Examples 1-1 to 1-3, there is an effect if the concentration of the isocyanate compound with respect to the electrolytic solution is in the range of 0.1 to 5% by mass. If it is 5% by mass, the high-temperature cycle characteristics deteriorate.

  From Table 2, it can be seen that the same effect can be obtained by using a monofunctional and bifunctional isocyanate compound and an imide salt compound in combination. At this time, the bifunctional diisocyanate compound tended to have a lower discharge capacity retention rate than the monofunctional isocyanate compound, but this was due to the relatively high concentration of isocyanate groups. Therefore, it is considered that SEI is excessively generated in the negative electrode and the surface resistance is increased. Therefore, in order to suppress a decrease in discharge capacity, it is considered preferable that the number of carbon atoms in the alkyl chain of the isocyanate compound is 6 or more. Further, when a diisocyanate compound having an aromatic ring in the main chain was used, sufficient cycle characteristics could not be obtained. This is presumably because the surface resistance of SEI increases in the negative electrode even when there is an aromatic ring in the main chain.

  From Table 3, it can be seen that the use of a cyclic carbonate having a halogen shown in Chemical Formula 8 as a solvent further improves the high-temperature cycle characteristics.

From Table 4, in the case of a laminate film type battery, the combined use of an isocyanate compound having a long-chain alkyl group and an imide salt compound is sufficient to prevent swelling during high-temperature storage compared to the case where each is used alone. It was found that high temperature cycle characteristics could be obtained.
When the imide salt compound is not added, the high-temperature cycle characteristics are deteriorated. When the isocyanate compound is not added, the swelling of the cell is increased and the high-temperature cycle characteristics are not sufficient. The same effect was observed with respect to the moisture concentration in the positive electrode active material. This is probably because the isocyanate compound generates SEI at the positive electrode and the negative electrode, and suppresses the decomposition of the solvent in the electrolyte as the cell is deformed.
As can be seen from Examples 1-1 to 1-3, there is an effect if the concentration of the isocyanate compound with respect to the electrolytic solution is in the range of 0.1 to 5% by mass. If it is 5% by mass, the high-temperature cycle characteristics deteriorate.

  From Table 5, it can be seen that the same effect can be obtained by using a bifunctional isocyanate compound and an imide salt compound in combination. In the case of a laminate film type battery, it is considered preferable that the alkyl chain has 6 or more carbon atoms from the viewpoint of the isocyanate group concentration.

  From Table 6, it can be seen that, when the cyclic carbonate having halogen shown in Chemical formula 8 is used as the solvent, the high-temperature cycle characteristics are further improved while suppressing the swelling of the laminate film type battery.

  The present invention is not limited to the above-described embodiment of the present invention, and various modifications and applications are possible without departing from the spirit of the present invention. For example, in the above-described embodiments and examples, a secondary battery having a winding structure has been described as a specific example, but the present invention includes a battery element in which a positive electrode and a negative electrode are stacked and folded in a zigzag manner, or The present invention can be similarly applied to a secondary battery having another stacked structure in which a positive electrode and a negative electrode are stacked.

  Moreover, although the above-mentioned embodiment and Example demonstrated the case where a film-shaped exterior member was used, you may use the exterior member of a can. In that case, the shape may be a cylindrical shape, a square shape, a coin shape, a button shape, or the like.

  Furthermore, in the above-described embodiments and examples, the case where lithium is used for the electrode reaction has been described. However, other alkali metals such as sodium (Na) and potassium (K), and alkaline earth metals such as magnesium and calcium (Ca). The present invention can also be applied to the case where other light metals such as metal or aluminum are used, and similar effects can be obtained. Further, lithium metal may be used as the negative electrode active material.

  As explained in the above embodiments and examples, in the nonaqueous electrolyte battery of the present invention, by using an isocyanate compound having an alkyl chain and an imide salt compound as an electrolyte additive serving as a SEI forming agent, The deformation of the battery can be suppressed while maintaining a high charge / discharge capacity during a high-temperature cycle.

DESCRIPTION OF SYMBOLS 11 ... Battery can, 12, 13 ... Insulation board, 14 ... Battery cover, 15 ... Safety valve mechanism, 15A ... Disc board, 16 ... Heat sensitive resistance element, 17 ... Gasket, 20, 30 ... Winding electrode body, 21, 33 ... Positive electrode, 21A, 33A ... Positive electrode current collector, 21B, 33B ... Positive electrode active material layer, 22, 34 ... Negative electrode, 22A, 34A ... Negative electrode current collector, 22B, 34B ... Negative electrode active material layer, 23, 35 ... Separator 24 ... Center pin, 25, 31 ... Positive electrode lead, 26, 32 ... Negative electrode lead, 36 ... Electrolyte, 37 ... Protective tape, 40 ... Exterior member, 41 ... Adhesion film

Claims (8)

A non-aqueous electrolyte battery including a positive electrode and a negative electrode, an electrolyte, and a separator,
The positive electrode contains 1000 ppm to 50 ppm of water,
The electrolyte has the following formulas (I) to (III)
X-R1-N = C = O (I)
O = C = N-R2-N = C = O (II)
O = C = N-R3-N = C = O (III)
(X in the formulas (I) to (III) represents a hydrogen atom or a halogen atom, and R1 and R2 have at least one heteroatom selected from the group consisting of halogen, phosphorus, silicon, oxygen and sulfur. C1 to C22 aliphatic hydrocarbon groups which may be present, and R3 may have the above heteroatoms C6 to C20 aromatic hydrocarbon groups and / or the above heteroatoms. An aliphatic hydrocarbon group containing 1 to 4 C6 to C20 alicyclic hydrocarbon groups and optionally having the above heteroatoms.), And
Formula (IV)-(V)
_{LiN (C m F 2m + 1} SO 2) (C n F 2n + 1 SO 2) ... (IV)
(M and n in the formula (IV) represent an integer of 1 or more.)

(R in Formula (V) represents a C2-C4 linear or branched perfluoroalkylene group), and a nonaqueous electrolyte battery containing at least one imide salt compound represented by:   The nonaqueous electrolyte battery according to claim 1, wherein the isocyanate compound is contained in an amount of 0.01 to 5 mass% with respect to the nonaqueous electrolyte.   The non-aqueous electrolyte battery according to claim 1, wherein the imide salt compound of the formula (IV) is lithium bis (trifluoromethanesulfonyl) imide or lithium bis (pentafluoroethanesulfonyl) imide.   The nonaqueous electrolyte battery according to claim 1, wherein the imide salt compound of the formula (V) is perfluoropropane-1,3-disulfonylimide lithium.   The non-aqueous electrolyte contains 30 to 80% by mass, 10 to 50% by mass, and 0.01 to 5% by mass of chain carbonate ester, saturated cyclic carbonate ester, and unsaturated cyclic carbonate ester, respectively. The nonaqueous electrolyte battery described.   The nonaqueous electrolyte battery according to claim 1, wherein the nonaqueous electrolyte contains 0.1 to 40 mass% of halogenated ethylene carbonate. The non-aqueous electrolyte is an electrolyte salt, such as lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium perchlorate (LiClO ₄ ), and lithium hexafluoroarsenate (LiAsF _6). The nonaqueous electrolyte battery according to claim 1, comprising at least one member selected from the group consisting of: The nonaqueous electrolyte battery is a lithium secondary battery, and the positive electrode active material is made of a lithium transition metal composite oxide material,
The negative electrode active material is (a) a carbonaceous material having a d value of 0.340 nm or less on the (002) plane in X-ray diffraction, and (b) at least one selected from the group consisting of Sn, Si and Al. (C) at least one metal selected from the group consisting of Sn, Si, and Al, or (a) a carbon material, (b) a metal oxide, and (c) at least one metal. The nonaqueous electrolyte battery according to claim 1, which is an alloy of lithium and an alloy of lithium.

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