JP5391944B2 - Non-aqueous electrolyte and battery using the same - Google Patents

Description

  The present invention relates to a non-aqueous electrolyte and a non-aqueous electrolyte battery using the same.

Non-aqueous electrolyte batteries, especially lithium secondary batteries, have the advantages of high energy density and are less likely to cause self-discharge. Therefore, in recent years, it has been widely used as a power source for consumer mobile devices such as mobile phones, notebook computers, and PDAs.
Usually, the electrolyte for a non-aqueous electrolyte battery such as a lithium secondary battery is mainly composed of a supporting electrolyte and a non-aqueous organic solvent. The non-aqueous organic solvent used here has various properties such as having a high dielectric constant for dissociating the lithium salt, exhibiting high ionic conductivity in a wide temperature range, and being stable in the battery. Is required. Since it is difficult to achieve these requirements with a single solvent, usually a combination of a high boiling point solvent typified by propylene carbonate, ethylene carbonate and the like and a low boiling point solvent such as dimethyl carbonate, diethyl carbonate, Used as a non-aqueous solvent.

Non-aqueous electrolyte batteries are required to satisfy various characteristics such as initial capacity, rate characteristics, cycle characteristics, high temperature storage characteristics, low temperature characteristics, continuous charge characteristics, self-discharge characteristics, and overcharge prevention characteristics. In order to improve the above, many methods have been reported so far in which various auxiliary agents are contained in the electrolytic solution in small amounts. For example, it has been proposed to contain an acid anhydride as an auxiliary agent.
Patent Document 1 discloses that the decomposition of the electrolytic solution at the negative electrode can be suppressed by using an electrolytic solution containing carboxylic anhydride having a carbon-carbon unsaturated bond and / or an aromatic ring in a molecule such as maleic anhydride. Has been. Patent Document 2 discloses that the storage characteristics are improved by using an electrolytic solution containing one or more cyclic carbonates and acid anhydrides each having a π bond.

Patent Document 3 discloses that the discharge capacity retention rate is improved in cycle characteristics by using a negative electrode using an alloy such as Si and using an electrolytic solution containing an acid anhydride and a halogen-containing carbonate. .
Patent Document 4 discloses that cycle characteristics are improved by using an electrolytic solution containing a halogen-containing acid anhydride such as trifluoromethylmaleic anhydride.

JP 2001-57236 A JP 2004-22174 A JP 2007-299541 A JP 2007-317647 A

  In recent years, the demand for higher performance of non-aqueous electrolyte batteries such as lithium secondary batteries has increased, and various characteristics such as high capacity, cycle characteristics, high temperature storage characteristics, continuous charge characteristics, overcharge characteristics, etc. Therefore, it is required to achieve both at a high dimension, and a higher level of characteristics is desired than the techniques disclosed in Patent Documents 1 to 4. In particular, in a battery using a positive electrode active material containing a lithium nickel-containing transition metal oxide, improvement in cycle characteristics has been strongly demanded. As shown in the comparative example, according to the study by the present inventors, when maleic anhydride described in Patent Document 1 was added, the negative electrode resistance was increased, resulting in a significant decrease in the initial capacity, and further the cycle. No improvement in properties was observed.

  The present invention was devised in view of the above problems, and an object thereof is to provide a non-aqueous electrolyte having improved characteristics such as cycle characteristics and storage characteristics, particularly cycle characteristics, and a battery using the electrolyte. And

  As a result of intensive studies to solve the above problems, the inventors of the present invention have achieved cycle characteristics and storage by using a non-aqueous electrolyte containing a specific amount of an unsaturated cyclic acid anhydride having a specific structure. The inventors have found that various characteristics such as characteristics, especially cycle characteristics, are improved, and the present invention has been completed.

That is, the gist of the present invention is as shown in the following (1) to ( 6 ).
(1) A nonaqueous electrolytic solution containing an electrolyte and a nonaqueous organic solvent, and at least selected from the group of compounds represented by the following general formulas (1) to (4) with respect to the weight of the nonaqueous electrolytic solution the one unsaturated cyclic anhydrides 0. A non-aqueous electrolyte containing 0001 to 10% by weight and 0.01 to 5 % by weight of succinonitrile.

(In the formula, R ₁ and R ₂ are each independently a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms, and R ₁ and R ₂ are bonded to each other and have 7 to 26 carbon atoms. An aliphatic ring may be formed, except when both R ₁ and R ₂ are hydrogen atoms, and when _one of R ₁ and R ₂ is a hydrogen atom and the other is a methyl group .)

(In the formula, R ₃ and R ₄ are each independently a hydrogen atom, a fluorine atom or a C 1-12 optionally substituted hydrocarbon group, and R ₃ and R ₄ are a bond. Z may be a fluorine-substituted divalent hydrocarbon group having 1 to 12 carbon atoms, provided that when Z is a methylene group, R ₃ and R ₄ Neither of them is a hydrogen atom at the same time.)

(In the formula, R _{5 to} R ₈ are each independently a hydrogen atom, a fluorine atom, or a fluorine-substituted hydrocarbon group having 1 to 12 carbon atoms, but all of R _{5 to} R ₈ are simultaneously selected. It is not a hydrogen atom.)

(In the formula, R _{9 to} R ₁₄ are each independently a hydrogen atom, a fluorine atom, or a fluorine-substituted hydrocarbon group having 1 to 12 carbon atoms, but all of R _{9 to} R ₁₄ are simultaneously selected. It is not a hydrogen atom.)

(2) The non-aqueous organic solvent contains ethylene carbonate, fluorine-substituted cyclic carbonate, and methyl carbonate in a proportion of x wt%, y wt%, and z wt % , respectively, with respect to the entire non-aqueous organic solvent (however, 0 ≦ x ≦ 39, 0 ≦ y ≦ 39, and 0 ≦ z <100, which satisfy the following [1] or [2]: [1] 5 ≦ x + 1.1 y ≦ 39, [2] 10 ≦ z < 100) The nonaqueous electrolytic solution according to (1) above, wherein
(3) The unsaturated cyclic acid anhydride is at least one compound selected from the compound group represented by the general formula (1), as described in (1) or (2) above Non-aqueous electrolyte.
( 4 ) A nonaqueous electrolyte battery comprising a positive electrode, a negative electrode, and the nonaqueous electrolyte solution according to any one of (1) to ( 3 ) above.
( 5 ) The nonaqueous electrolyte battery according to ( 4 ) above, wherein a negative electrode active material containing a carbonaceous material is used for the negative electrode.
( 6 ) The nonaqueous electrolyte battery according to ( 4 ) or ( 5 ) above, wherein a positive electrode active material containing a lithium nickel-containing transition metal oxide is used for the positive electrode.

  According to the present invention, in an electrolyte for a non-aqueous electrolyte battery, various characteristics such as cycle characteristics and storage characteristics, in particular, cycle characteristics can be greatly improved.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments, and can be arbitrarily modified without departing from the gist of the present invention. For example, the battery will be described centering on a lithium secondary battery, but can be applied to other batteries as long as it is a non-aqueous electrolyte battery.
When the non-aqueous electrolyte solution of the present invention is used for a battery, the battery includes a non-aqueous electrolyte solution, a positive electrode, and a negative electrode. Moreover, the non-aqueous electrolyte battery of the present invention may include other components.

[I. Non-aqueous electrolyte]
The non-aqueous electrolyte solution of the present invention is a non-aqueous electrolyte solution in which an electrolyte such as a lithium salt is dissolved in a non-aqueous organic solvent (hereinafter referred to as “non-aqueous organic solvent in the present invention” as appropriate). At least one or more kinds of unsaturated cyclic acid anhydrides having a structure (hereinafter, appropriately referred to as “unsaturated cyclic acid anhydrides in the present invention”) are contained in an amount of 0.0001 to 10% by weight based on the weight of the non-aqueous electrolyte solution. This is a non-aqueous electrolyte solution.

[1. Unsaturated cyclic acid anhydride]
[1-1. type]
The non-aqueous electrolyte solution in the present invention contains at least one cyclic acid anhydride (carboxylic acid anhydride) having a carbon-carbon unsaturated bond represented by the following general formulas (1) to (4).

In the general formula (1), R ₁ and R ₂ are each independently a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms. R ₁ and R ₂ may form an aliphatic ring having 7 to 26 carbon atoms. However, both R ₁ and R ₂ are not hydrogen atoms at the same time, and when _one of R ₁ and R ₂ is a hydrogen atom, the other is not a methyl group.
Preferred hydrocarbon groups include alkyl groups, alkenyl groups, aryl groups, aralkyl groups and the like. Of these, an alkyl group and an aryl group are more preferable.

  Carbon number of the said alkyl group is 1-12, Preferably it is 1-8, More preferably, it is 1-4. Specific examples of preferred alkyl groups include methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, decyl and the like. Among these, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, and an octyl group are preferable, and a methyl group, an ethyl group, a propyl group, and a butyl group are more preferable.

Carbon number of the said alkenyl group is 2-12 normally, Preferably it is 2-8, More preferably, it is 2-4. Specific examples of preferred alkenyl groups include vinyl, isopropenyl, 1-propenyl, and allyl groups. Among these, a vinyl group and an allyl group are more preferable.
The aryl group usually has 6 to 12 carbon atoms. Specific examples of the aryl group include phenyl group, tolyl group, ethylphenyl group, dimethylphenyl group, isopropyl group, t-butylphenyl group, t-amylphenyl group, cyclohexylphenyl group, α-naphthyl group, β-naphthyl group and the like. Is mentioned. Among these, a phenyl group, a t-butylphenyl group, and a t-amylphenyl group are more preferable.

The carbon number of the aralkyl group is usually 7-12. Specific examples of the aralkyl group include benzyl group, α-phenethyl group, β-phenethyl group and the like. Among these, a benzyl group is more preferable.
R ₁ and R ₂ may combine to form an aliphatic ring. The constituent carbon number of the aliphatic ring is usually 7 to 26, preferably 7 to 18, and more preferably 7 to 12. More preferred specific examples include 3-methylcyclohexene ring, 4-methylcyclohexene ring, 4,4-dimethylcyclopentene ring, 4,5-dimethylcyclohexene ring, 4-vinylcyclohexene ring, cycloheptene ring, cyclooctene ring, 1, Monocyclic rings such as 3-cyclooctadiene ring, 1,5-cyclooctadiene ring, cyclododecene ring; 1,4,5,6,9,10-hexahydronaphthalene ring, 1,2,3,4,5, Examples include condensed rings such as 6,9,10-octahydronaphthalene ring; and bicyclo rings such as norbornylene ring and bicyclo [2.2.2] oct-2-ene ring.

In the general formula (2), R ₃ and R ₄ are each independently a hydrogen atom, a fluorine atom, or an optionally substituted fluorine group having 1 to 12 carbon atoms, and R ₃ and R ₄ May combine to form a ring. Z is a divalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with fluorine. However, when Z is a methylene group, R ₃ and R ₄ are not simultaneously hydrogen atoms.

Preferred hydrocarbon groups for R ₃ and R ₄ include alkyl groups, alkenyl groups, aryl groups, aralkyl groups, and the like. Of these, an alkyl group and an aryl group are more preferable.
When R ₃ and / or R ₄ is an alkyl group, the carbon number of the alkyl group is usually 1 to 12, preferably 1 to 8, more preferably 1-4. Specific examples of preferred alkyl groups include methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, decyl and the like. Among these, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, and an octyl group are preferable, and a methyl group, an ethyl group, a propyl group, and a butyl group are more preferable.

When R ₃ and / or R ₄ is an alkenyl group, the alkenyl group usually has 2 to 12 carbon atoms, preferably 2 to 8 carbon atoms, more preferably 2 to 4 carbon atoms. Specific examples of preferred alkenyl groups include vinyl, isopropenyl, 1-propenyl, and allyl groups. Among these, a vinyl group and an allyl group are more preferable.
When R ₃ and / or R ₄ is an aryl group, the aryl group usually has 6 to 12 carbon atoms. Specific examples include phenyl group, tolyl group, ethylphenyl group, dimethylphenyl group, isopropyl group, t-butylphenyl group, t-amylphenyl group, cyclohexylphenyl group, α-naphthyl group, β-naphthyl group and the like. . Among these, a phenyl group, a t-butylphenyl group, and a t-amylphenyl group are more preferable.

When R ₃ and / or R ₄ is an aralkyl group, the aralkyl group usually has 7 to 12 carbon atoms. Specific examples include benzyl group, α-phenethyl group, β-phenethyl group and the like. Among these, a benzyl group is more preferable.
R ₃ and R ₄ may be bonded to form a ring. In this case, the ring may be either an aliphatic ring or an aromatic ring, but more preferably an aromatic ring. Specific examples of the aliphatic ring include cyclobutene ring, cyclopentene ring, cyclohexene ring, methylcyclohexene ring, 4-methylcyclohexene ring, 4,4-dimethylcyclopentene ring, 4,5-dimethylcyclohexene ring, 4-vinylcyclohexene ring, Monocycles such as cycloheptene ring, cyclooctene ring, 1,3-cyclooctadiene ring, 1,5-cyclooctadiene ring, cyclododecene ring; 1,4,5,6,9,10-hexahydronaphthalene ring, 1 , 2,3,4,5,6,9,10-octahydronaphthalene ring; bicyclo rings such as norbornylene ring and bicyclo [2.2.2] oct-2-ene ring. Specific examples of the aromatic ring include benzene ring, methylbenzene ring, dimethylbenzene ring, 1,2-dihydronaphthalene ring, 1,4-dihydronaphthalene ring, naphthalene ring and the like.

In the case where R ₃ and / or R ₄ is a fluorine-substituted hydrocarbon group, the degree of fluorine substitution is not limited, and some or all of the hydrogen atoms constituting the hydrocarbon group described above are fluorine atoms. It may be replaced.
Z is a divalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with fluorine. Specific examples include a methylene group, an ethylene group, a propylene group, a butylene group, a phenylene group, and a neftylene group, with a methylene group and a phenylene group being preferred. Some or all of the hydrogen atoms constituting the divalent hydrocarbon group described above may be substituted with fluorine atoms.

In the general formula (3), R _{5 to} R ₈ are each independently a hydrogen atom, a fluorine atom, or an optionally substituted fluorine group having 1 to 12 carbon atoms, but R _{5 to} R 8 Not all ₈ are hydrogen atoms at the same time. Preferred hydrocarbon groups for R _{5 to} R ₈ include alkyl groups, alkenyl groups, aryl groups, aralkyl groups, and the like. Of these, an alkyl group and an aryl group are more preferable.

When R < ₅ > -R < ₈ > is an alkyl group, carbon number of the alkyl group is 1-12 normally, Preferably it is 1-8, More preferably, it is 1-4. Specific examples of preferred alkyl groups include methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, decyl and the like. Among these, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, and an octyl group are preferable, and a methyl group, an ethyl group, a propyl group, and a butyl group are more preferable.

When R < ₅ > -R < ₈ > is an alkenyl group, carbon number of the alkenyl group is 2-12 normally, Preferably it is 2-8, More preferably, it is 2-4. Specific examples of preferred alkenyl groups include vinyl, isopropenyl, and allyl groups. Among these, a vinyl group and an allyl group are more preferable.
When R _{5 to} R ₈ are aryl groups, the aryl group usually has 6 to 12 carbon atoms. Specific examples include phenyl group, tolyl group, ethylphenyl group, dimethylphenyl group, isopropyl group, t-butylphenyl group, t-amylphenyl group, cyclohexylphenyl group, α-naphthyl group, β-naphthyl group and the like. . Among these, a phenyl group, a t-butylphenyl group, and a t-amylphenyl group are more preferable.

When R < ₅ > -R < ₈ > is an aralkyl group, the carbon number of the aralkyl group is usually 7-12. Specific examples include benzyl group, α-phenethyl group, β-phenethyl group and the like. Among these, a benzyl group is more preferable.
Further, in the case R ₅ to R ₈ is a fluorine-substituted hydrocarbon group, limiting the degree of fluorine substitution is not, some or all of the hydrogen atoms constituting the hydrocarbon group described above is substituted with a fluorine atom May be.

In the general formula (4), R _{9 to} R ₁₄ are each independently a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 12 carbon atoms, or a hydrocarbon group having 1 to 12 carbon atoms substituted with fluorine. However, not all of R _{9 to} R ₁₄ are hydrogen atoms at the same time.
Preferred hydrocarbon groups for R _{9 to} R ₁₄ include alkyl groups, alkenyl groups, aryl groups, aralkyl groups, and the like. Of these, an alkyl group and an aryl group are more preferable.

When R < ₉ > -R < ₁₄ > is an alkyl group, carbon number of the alkyl group is 1-12 normally, Preferably it is 1-8, More preferably, it is 1-4. Specific examples of preferred alkyl groups include methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, decyl and the like. Among these, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, and an octyl group are preferable, and a methyl group, an ethyl group, a propyl group, and a butyl group are more preferable.

When R _{9 to} R ₁₄ are alkenyl groups, the alkenyl group has usually 2 to 12 carbon atoms, preferably 2 to 8 carbon atoms, and more preferably 2 to 4 carbon atoms. Specific examples of preferred alkenyl groups include vinyl, isopropenyl, and allyl groups. Among these, a vinyl group and an allyl group are more preferable.
When R _{9 to} R ₁₄ are aryl groups, the aryl group usually has 6 to 12 carbon atoms. Specific examples include phenyl group, tolyl group, ethylphenyl group, dimethylphenyl group, isopropyl group, t-butylphenyl group, t-amylphenyl group, cyclohexylphenyl group, α-naphthyl group, β-naphthyl group and the like. . Among these, a phenyl group, a t-butylphenyl group, and a t-amylphenyl group are more preferable.

When R _{9 to} R ₁₄ are an aralkyl group, the carbon number of the aralkyl group is usually 7 to 12. Specific examples include benzyl group, α-phenethyl group, β-phenethyl group and the like. Among these, a benzyl group is more preferable.
When R _{9 to} R ₁₄ are fluorine-substituted hydrocarbon groups, the degree of fluorine substitution is not limited, and some or all of the hydrogen atoms constituting the above-described hydrocarbon group are substituted with fluorine atoms. May be.

Further, the unsaturated acid anhydride in the present invention has a molecular weight of usually 120 or more, usually 400 or less, preferably 320 or less, more preferably 260 or less. If the upper limit of this range is exceeded, the compatibility or solubility of the unsaturated acid anhydride with respect to the non-aqueous electrolyte solution is lowered, and the characteristics of the battery using the non-aqueous electrolyte solution may be insufficient.
Hereinafter, although the specific example of the unsaturated acid anhydride in this invention is given, the unsaturated acid anhydride in this invention is not limited to the following illustrations.

  Examples of the compound represented by the general formula (1) include the following compounds.

  Examples of the compound represented by the general formula (2) include the following compounds.

  Examples of the compound represented by the general formula (3) include the following compounds.

  Examples of the compound represented by the general formula (4) include the following compounds.

Among these, preferred as the unsaturated acid anhydride in the present invention is
Compound represented by general formula (1) (1): ethyl maleic anhydride (2): isopropyl maleic anhydride (3): normal propyl maleic anhydride (4): butyl maleic anhydride (7) : Phenylmaleic anhydride (8): benzylmaleic anhydride (10): vinylmaleic anhydride (12): allylmaleic anhydride (13): 2,3-dimethylmaleic anhydride (14): 2-ethyl-3-methylmaleic anhydride (15): 2,3-diethylmaleic anhydride (17): 2-methyl-3-phenylmaleic anhydride (18): 2,3-diphenylmaleic acid Anhydride (19): 2,3-Dibenzylmaleic anhydride (20): 2-Methyl-3-vinylmaleic anhydride (21): 2,3-divinylmaleic Anhydride (26): Bicyclo [2.2.2] oct-2-ene-2,3-dicarboxylic anhydride Compound represented by the general formula (2) (1): 4-methyl-2H-pyran- 2,6 (3H) -dione (2): 3-methyl-2H-pyran-2,6 (3H) -dione (8): 5-methyl-1H-2-benzopyran-1,3 (4H) -dione (9): 7-Methyl-1H-2-benzopyran-1,3 (4H) -dione (10): 8-Methyl-1H-2-benzopyran-1,3 (4H) -dione (11): Diphenic acid Compound represented by general formula (3) of anhydride (1): Dihydro-3-ethylidene-2,5-furandion (2): Dihydro-3- (1-methylethylidene) -2,5-furandion ( 3): Dihydro-3-propylidene-2,5-flangio (9): 2-methyl-3-methylene succinic anhydride (11): dimethylene succinic anhydride (12): 2-methylene-3-phenyl succinic anhydride compound represented by general formula (4) (1): Dihydro-3- (1-propylene-1-yl) -2,5-furandion (2): Dihydro-3- (2-methyl-1-propylene-1-yl) -2,5-furandion (7 ): Dihydro-3- (2-phenylethenyl) -2,5-furandione (8): 2-methyl-3-vinyl succinic anhydride (9): 2,3-divinyl succinic anhydride.
Particularly preferably, as the compound represented by the general formula (1),
(1): Ethyl maleic anhydride (2): Isopropyl maleic anhydride (7): Phenyl maleic anhydride (10): Vinyl maleic anhydride (13): 2,3-dimethyl maleic anhydride ( 18): 2,3-diphenylmaleic anhydride (21): 2,3-divinylmaleic anhydride (26): bicyclo [2.2.2] oct-2-ene-2,3-dicarboxylic anhydride The compounds represented by the general formula (2) include: (1): 4-methyl-2H-pyran-2,6 (3H) -dione (8): 5-methyl-1H-2-benzopyran -1,3 (4H) -dione (9): 7-methyl-1H-2-benzopyran-1,3 (4H) -dione (11): diphenic anhydride, which is represented by the general formula (3) As a compound to be (1) Dihydro-3-ethylidene-2,5-furandione (9): 2-methyl-3-methylene succinic anhydride (11): Examples include dimethylene succinic anhydride, and the compound represented by the general formula (4) (1): Dihydro-3- (1-propylene-1-yl) -2,5-furandione (8): 2-methyl-3-vinyl succinic anhydride (9): 2,3-divinyl succinic anhydride It is.
Most preferably, among the compounds represented by the general formula (1): (7): phenylmaleic anhydride (10): vinylmaleic anhydride (13): 2,3-dimethylmaleic anhydride (18 ): 2,3-diphenylmaleic anhydride (21): 2,3-divinylmaleic anhydride (26): bicyclo [2.2.2] oct-2-ene-2,3-dicarboxylic anhydride It is.

  Moreover, the unsaturated cyclic acid anhydride in this invention mentioned above may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

[1-2. composition]
The content of the unsaturated cyclic acid anhydride in the present invention is 0.0001% by weight or more, preferably 0.001% by weight or more, more preferably 0.01% by weight or more, based on the weight of the non-aqueous electrolyte. More preferably 0.05% by weight or more, most preferably 0.1% by weight or more, and usually 10% by volume or less, preferably 5% by weight or less, more preferably 3% by weight or less, still more preferably 2% by weight or less, Most preferably, it is 1 weight% or less. If the amount added is too large, the film resistance of the negative electrode increases and the capacity tends to decrease. If the concentration is too small, the effects of the present invention may not be sufficiently exhibited.

[2. Non-aqueous organic solvent]
[2-1. type]
There is no restriction | limiting in particular about the non-aqueous organic solvent used by this invention, A well-known non-aqueous organic solvent can be used arbitrarily. Examples of these include chain carbonates, cyclic carbonates, chain esters, cyclic esters (lactone compounds), chain ethers, cyclic ethers, sulfur-containing organic solvents, and the like. In particular, as a solvent that exhibits high lithium ion conductivity, chain carbonates, cyclic carbonates, chain esters, cyclic esters, chain ethers, and cyclic ethers are usually preferable.

  Specific examples of the chain carbonates include carbonates such as dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, dipropyl carbonate, methyl phenyl carbonate, ethyl phenyl carbonate, diphenyl carbonate; Examples include halogen-substituted carbonates such as (trifluoromethyl) carbonate, methyl trifluoromethyl carbonate, bis (monofluoroethyl) carbonate, methyl monofluoroethyl carbonate, bis (trifluoroethyl) carbonate, and methyl trifluoroethyl carbonate. Among these, methyl carbonate such as dimethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, methyl phenyl carbonate, methyl trifluoromethyl carbonate, methyl monofluoroethyl carbonate, methyl difluoroethyl carbonate, methyl trifluoroethyl carbonate, methyl pentafluoroethyl carbonate, etc. Are preferred.

  Specific examples of cyclic carbonates include ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl ethylene carbonate, diethyl ethylene carbonate, monopropyl ethylene carbonate, dipropyl ethylene carbonate, phenyl ethylene carbonate, diphenyl ethylene carbonate, catechol carbonate, etc. Carbonates; fluorine-substituted carbonates such as monofluoroethylene carbonate, difluoroethylene carbonate, trifluoroethylene carbonate, tetrafluoroethylene carbonate, monofluoromethylethylene carbonate, trifluoromethylethylene carbonate, and the like. Among these, ethylene carbonate, propylene carbonate, monofluoroethylene carbonate, difluoroethylene carbonate, and trifluoromethylethylene carbonate are preferable.

Specific examples of the chain esters include methyl esters such as methyl formate, methyl acetate, methyl propionate and methyl butyrate; ethyl esters such as ethyl formate, ethyl acetate, ethyl propionate and ethyl butyrate.
Specific examples of cyclic esters include γ-butyrolactone, γ-valerolactone, δ-valerolactone, α-methyl-γ-butyrolactone, and the like.

Specific examples of the chain ethers include 1,2-dimethoxyethane, 1,2-diethoxyethane, diethyl ether and the like.
Specific examples of cyclic ethers include tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane and the like.
The molecular weight of the organic solvent used as the non-aqueous organic solvent is usually 50 or more, preferably 80 or more, and usually 250 or less, preferably 150 or less. If the molecular weight is too large, the viscosity increases, and the discharge capacity particularly at a high current tends to decrease. On the other hand, if the molecular weight is too small, the volatility is increased, which causes an increase in the internal pressure of the battery, which is not preferable.

Further, the non-aqueous organic solvent may be used alone or in combination of two or more in any combination and ratio, but in order to satisfy various properties in a well-balanced manner, two or more non-aqueous organic solvents are used. It is preferable to use a mixture of organic solvents.
In particular, the combined use of cyclic carbonates and chain carbonates is preferable, and among them, the combination of ethylene carbonate and / or fluorine-substituted cyclic carbonate as the cyclic carbonate and methyl carbonate as the chain carbonate is particularly preferable. Examples of the fluorine-substituted cyclic carbonate in this combination include fluoroethylene carbonate, difluoroethylene carbonate, trifluoroethylene carbonate, tetrafluoroethylene carbonate, monofluoromethylethylene carbonate, and trifluoromethylethylene carbonate. Among these, fluoroethylene carbonate and difluoroethylene carbonate are preferable. Examples of methyl carbonates include dimethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, methyl phenyl carbonate, methyl trifluoromethyl carbonate, methyl monofluoroethyl carbonate, methyl difluoroethyl carbonate, methyl trifluoroethyl carbonate, and methyl pentafluoroethyl carbonate. Can be mentioned. Among these, dimethyl carbonate, ethyl methyl carbonate, and methyl trifluoromethyl carbonate are preferable.

[2-3. Composition ratio]
When two or more kinds of non-aqueous organic solvents are used, the composition ratio is not limited as described above, but preferably the content ratio of ethylene carbonate, fluorine-substituted cyclic carbonate, and methyl carbonate to the whole non-aqueous organic solvent is x. In the case of weight%, y weight%, and z weight % , x, y, and z satisfy 0 ≦ x ≦ 39, 0 ≦ y ≦ 39, 0 ≦ z <100, and further, the following formula [1] or [ [2] It is preferable to satisfy the formula.
[1] 5 ≦ x + 1.1y ≦ 39, [2] 10 ≦ z <100
That is, when z is 10 or more and less than 100, there is no particular limitation as long as x and y are 39 or less, but when z is less than 10, both x and y are 39 or less and “x + 1.1y Must be between 5 and 39.

A more preferred embodiment will be further described. X is more preferably 35 or less, further preferably 32 or less, particularly preferably 28 or less, and most preferably 25 or less. Further, y is more preferably 35 or less, further preferably 32 or less, particularly preferably 28 or less, and most preferably 25 or less.
In the formula [1], “x + 1.1y” is more preferably 8 or more, further preferably 12 or more, particularly preferably 16 or more, most preferably 20 or more, and more preferably 37 or less, still more preferably 35 or less, Especially preferably, it is 33 or less, Most preferably, it is 31 or less.

In the formula [2], z is more preferably 20 or more, further preferably 30 or more, particularly preferably 40 or more, and most preferably 50 or more.
When z satisfies the above formula [2], x + 1.1y is not limited, but is usually 5 or more, preferably 8 or more, more preferably 10 or more, still more preferably 12 or more, particularly preferably 15 or more, and usually 60 Hereinafter, it is preferably 50 or less, more preferably 45 or less, still more preferably 39 or less, and particularly preferably 33 or less.

In addition, when the non-aqueous organic solvent from which the value of x, y, and x remove | deviated from the conditions mentioned previously is used, the negative electrode film formed from the unsaturated cyclic acid anhydride of this invention melt | dissolves in a non-aqueous organic solvent. As a result, various characteristics such as cycle characteristics tend to deteriorate.
[3. Lithium salt]
As the electrolyte, a lithium salt is usually used. There is no restriction | limiting in particular in lithium salt, Either inorganic lithium salt and organic lithium salt may be used.

Examples of inorganic lithium salts include inorganic fluoride salts such as LiPF ₆ , LiAsF ₆ , LiBF ₄ and LiSbF ₆ ; inorganic chloride salts such as LiAlCl ₄ ; perhalogenates such as LiClO ₄ , LiBrO ₄ and LiIO _4. Etc.
Examples of organic lithium salts include perfluoroalkane sulfonates such as CF ₃ SO ₃ Li and C ₄ F ₉ SO ₃ Li; perfluoroalkane carboxylates such as CF ₃ COOLi; (CF ₃ CO) ₂ Perfluoroalkanecarbonimide salt such as NLi; (CF ₃ SO ₂ ) ₂
Examples thereof include fluorine-containing organic lithium salts such as perfluoroalkanesulfonimide salts such as NLi and (C ₂ F ₅ SO ₂ ) ₂ NLi.

Among these, LiPF ₆ , LiBF ₄ , CF ₃ SO ₃ Li, (CF ₃ SO ₂ ) ₂ NLi, and the like are preferable because they are easily soluble in non-aqueous organic solvents and exhibit a high degree of dissociation.
In addition, lithium salt may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
In particular, the combined use of LiPF ₆ and LiBF ₄ or the combined use of LiPF ₆ and (CF ₃ SO ₂ ) ₂ NLi is preferable because it has an effect of improving the continuous charge characteristics.

  Furthermore, the concentration of the lithium salt in the non-aqueous electrolyte solution is arbitrary as long as the effects of the present invention are not significantly impaired, but usually 0.5 mol / L or more, preferably 0.75 mol / L with respect to the non-aqueous electrolyte solution. L or more, and usually 2 mol / L or less, preferably 1.75 mol / L or less. If the concentration of the electrolyte is too low, the electric conductivity of the non-aqueous electrolyte may be insufficient. On the other hand, if the concentration of the electrolyte is too high, the electrical conductivity is lowered due to an increase in viscosity, and precipitation at a low temperature is likely to occur, and the performance of the lithium secondary battery tends to be lowered.

[4. Film-forming agent]
The nonaqueous electrolytic solution according to the present invention further comprises a cyclic carbonate having a carbon-carbon unsaturated bond, a monofluorophosphate, and a difluorophosphate for the purpose of forming a film on the negative electrode and improving battery characteristics. It is preferable to contain 1 type.
The cyclic carbonate having a carbon-carbon unsaturated bond is not particularly limited as long as it is a cyclic carbonate having a carbon-carbon unsaturated bond, and any one can be used. Specifically, vinylene carbonate, methyl vinylene carbonate, 1,2-dimethyl vinylene carbonate, phenyl vinylene carbonate, 1,2-diphenyl vinylene carbonate, fluoro vinylene carbonate, 1,2-difluoro vinylene carbonate, 1-fluoro-2- Vinylene carbonate derivatives such as methyl vinylene carbonate and 1-fluoro-2-phenyl vinylene carbonate; vinyl ethylene carbonate, 1,1-divinyl ethylene carbonate, 1,2-divinyl ethylene carbonate, 1-methyl-2-vinyl ethylene carbonate, Examples thereof include vinylethylene carbonate derivatives such as 1-phenyl-2-vinylethylene carbonate and 1-fluoro-2-vinylethylene carbonate.

Among these, vinylene carbonate derivatives such as vinylene carbonate, methyl vinylene carbonate and 1,2-dimethyl vinylene carbonate; vinyl ethylene carbonate derivatives such as vinyl ethylene carbonate and 1,2-divinyl ethylene carbonate are preferable. In particular, vinylene carbonate and vinyl ethylene carbonate are more preferable.
In addition, the cyclic carbonate which has a carbon-carbon unsaturated bond may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  The carbon number of the cyclic carbonate having a carbon-carbon unsaturated bond is usually 3 or more, and usually 20 or less, preferably 15 or less. If the upper limit of the above range is exceeded, the solubility in the electrolytic solution tends to deteriorate. Furthermore, the molecular weight of the cyclic carbonate having a carbon-carbon unsaturated bond is usually 80 or more, and usually 250 or less, preferably 150 or less. If the molecular weight is too large, the solubility in the electrolytic solution is deteriorated, and there is a possibility that the effect of the present invention of improving high-temperature storage characteristics cannot be sufficiently exhibited.

  The concentration of the cyclic carbonate having a carbon-carbon unsaturated bond is usually 0.01% by weight or more, preferably 0.1% by weight or more, more preferably 0.3% by weight or more, based on the whole electrolyte solution. Usually, it is 10 weight% or less, Preferably it is 7 weight% or less, More preferably, it is 5 weight% or less, More preferably, it is 3 weight% or less. If the concentration of the cyclic carbonate having a carbon-carbon unsaturated bond is too large, the high-temperature storage characteristics tend to be deteriorated, and further, the amount of gas generated increases when the battery is used, and the capacity retention rate may be reduced. On the other hand, if the concentration is too small, the effects of the present invention may not be sufficiently exhibited. In addition, when using together 2 or more types of cyclic carbonate which has a carbon-carbon unsaturated bond, it is made for the sum total of a density | concentration to be in the said range.

  The monofluorophosphate and difluorophosphate are preferably sodium monofluorophosphate, lithium monofluorophosphate, potassium monofluorophosphate, sodium difluorophosphate, lithium difluorophosphate, and potassium difluorophosphate. Is particularly preferably lithium monofluorophosphate or lithium difluorophosphate. The concentration of monofluorophosphate and difluorophosphate is usually 0.01% by weight or more, preferably 0.1% by weight or more, more preferably 0.2% by weight or more, and usually 10% by weight based on the entire electrolyte. % By weight or less, preferably 3% by weight or less, more preferably 2% by weight or less, and further preferably 1% by weight or less. If the concentrations of monofluorophosphate and difluorophosphate are too high, the reaction resistance of the negative electrode tends to increase and the capacity tends to decrease. On the other hand, if the concentration is too small, the effects of the present invention may not be sufficiently exhibited.

[5. Other auxiliaries]
The non-aqueous electrolyte in the present invention may contain other auxiliary agents for the purpose of improving the wettability, overcharge characteristics, etc. of the non-aqueous electrolyte in a range that does not significantly impair the effects of the present invention.
Examples of auxiliaries include carboxylic acid esters such as vinyl acetate, divinyl adipate, and allyl acetate; diphenyl disulfide, 1,3-propane sultone, 1,3-propene sultone, 1,4-butane sultone, dimethyl sulfone, and divinyl sulfone. , Sulfur-containing compounds such as dimethyl sulfite, ethylene sulfite, 1,4-butanediol dimethanesulfonate, methyl methanesulfonate, and 2-propynyl methanesulfonate; t-butylbenzene, t-amylbenzene, biphenyl, o -Aromatics such as terphenyl, 4-fluorobiphenyl, fluorobenzene, 2,4-difluorobenzene, cyclohexylbenzene, diphenyl ether, 2,4-difluoroanisole, 3,5-difluoroanisole, trifluoromethylbenzene Like compounds and those of the aromatic compound substituted with a fluorine atom. Moreover, 1 type may be used independently for an adjuvant, and 2 or more types may be used together by arbitrary combinations and a ratio.

  The concentration of the auxiliary agent in the nonaqueous electrolytic solution is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.01% by weight or more, preferably 0.05% by weight or more, and usually 5% by weight or less. It is preferably 3% by weight or less. In addition, when using 2 or more types of adjuvants together, it is made for the sum total of these density | concentrations to be settled in the said range.

[6. Non-aqueous electrolyte state]
The non-aqueous electrolyte is usually present in a liquid state when used in the non-aqueous electrolyte battery of the present invention. For example, it may be gelled with a polymer to form a semi-solid electrolyte. The polymer used for the gelation is arbitrary, and examples thereof include polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and hexafluoropropylene, polyethylene oxide, polyacrylate, and polymethacrylate. In addition, the polymer | macromolecule used for gelatinization may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  When the non-aqueous electrolyte is used as a semisolid electrolyte, the ratio of the non-aqueous electrolyte in the semisolid electrolyte is arbitrary as long as the effects of the present invention are not significantly impaired. As a suitable range, the ratio of the non-aqueous electrolyte to the total amount of the semisolid electrolyte is usually 30% by weight or more, preferably 50% by weight or more, more preferably 75% by weight or more, and usually 99.95. % By weight or less, preferably 99% by weight or less, more preferably 98% by weight or less. If the ratio of the non-aqueous electrolyte is too large, it may be difficult to hold the electrolyte and the liquid may easily leak. Conversely, if it is too small, the charge / discharge efficiency and the capacity may be insufficient.

[7. Method for producing non-aqueous electrolyte]
The production method of the non-aqueous electrolyte solution in the present invention is not particularly limited. For example, a lithium salt is added to the non-aqueous organic solvent, and the unsaturated cyclic acid anhydride in the present invention is added to 0.0001 to 10% with respect to the weight of the non-aqueous electrolyte solution. It can prepare by adding weight%.
When preparing the non-aqueous electrolyte, each raw material of the non-aqueous electrolyte, that is, the lithium salt, the non-aqueous organic solvent, the unsaturated cyclic acid anhydride in the present invention, and other auxiliary agents should be dehydrated in advance. Is preferred. As the degree of dehydration, it is desirable to dehydrate until the water content is usually 50 ppm or less, preferably 30 ppm or less. In the present specification, ppm means a ratio based on weight.

If water is present in the non-aqueous electrolyte, electrolysis of water, reaction between water and lithium metal, hydrolysis of lithium salt, and the like may occur, which is not preferable.
The dehydration means is not particularly limited. For example, when the object to be dehydrated is a liquid such as a non-aqueous solvent, a molecular sieve or the like may be used. When the object to be dehydrated is a solid such as an electrolyte, it may be dried at a temperature lower than the temperature at which decomposition occurs.

[8. mechanism]
The mechanism by which the effect of the present invention can be obtained is not clear, but is considered as follows.
A part of the unsaturated cyclic acid anhydride of the present invention is reduced during the initial charging of battery production, and a protective film is formed on the negative electrode. Since this protective film has low resistance and high Li ion permeability, the capacity of the battery is improved, and further, cycle characteristics are improved. Here, the lowering of the resistance of the protective coating is related to the structure of the unsaturated cyclic acid anhydride of the present invention. That is, since the unsaturated cyclic acid anhydride of the present invention has a relatively large substituent, it becomes a steric hindrance and does not form a dense film with high resistance. In addition, the participation of an unsaturated cyclic acid anhydride remaining in the electrolyte without being decomposed during initial charging is also conceivable. The unsaturated cyclic acid anhydride of the present invention captures metal ions such as cobalt, nickel, manganese and the like eluted from the positive electrode active material into the electrolyte as the cycle deteriorates, and these metals are reduced at the negative electrode to form a high resistance coating. Prevent forming. It is assumed that nickel works particularly effectively among metals.

That is, the unsaturated cyclic acid anhydride of the present invention improves the battery characteristics such as cycle characteristics, such as that the film derived from the unsaturated acid anhydride has low resistance, and the unsaturated acid anhydride captures metal ions. Thus, there are two points of suppressing the increase in film resistance.
The non-aqueous electrolyte of the present invention is suitable for use as a secondary battery among non-aqueous electrolyte batteries, that is, as an electrolyte for a non-aqueous electrolyte secondary battery, for example, a lithium secondary battery. Hereinafter, a non-aqueous secondary battery using the electrolytic solution of the present invention will be described focusing on a lithium secondary battery.

[II. Non-aqueous electrolyte battery]
The non-aqueous electrolyte battery of the present invention comprises the above-described non-aqueous electrolyte of the present invention, and a positive electrode and a negative electrode capable of inserting and extracting lithium ions. In the case of a lithium secondary battery, the battery may have other configurations. For example, a lithium secondary battery usually includes a spacer.

[1. Positive electrode]
As long as the positive electrode can occlude and release lithium, any positive electrode can be used as long as the effects of the present invention are not significantly impaired.
Usually, a positive electrode having a positive electrode active material layer provided on a current collector is used. Note that the positive electrode may include other layers as appropriate.

[1-1. Positive electrode active material layer]
The positive electrode active material layer includes a positive electrode active material. The positive electrode active material is not limited as long as it can occlude and release lithium ions. Examples include oxides of transition metals such as Fe, Co, Ni, and Mn, composite oxides of transition metals and lithium, and sulfides of transition metals.

Specific examples of transition metal oxides include MnO, V ₂ O ₅ , V ₆ O ₁₃ , and TiO ₂ . Specific examples of the composite oxide of transition metal and lithium include a lithium nickel composite oxide whose basic composition is LiNiO ₂ ; a lithium cobalt composite oxide whose basic composition is LiCoO ₂ ; a basic composition of LiMnO ₂ and LiMnO. _And lithium manganese composite oxide such as ₄ . Further, specific examples of the transition metal sulfide include TiS ₂ and FeS.

Among these, a composite oxide of lithium and a transition metal is preferable because it can achieve both high capacity and high cycle characteristics of a lithium secondary battery. In the present invention, lithium nickel-containing transition metal oxides are particularly preferable, and examples thereof include LiNiO ₂ , LiNi _x MyO ₂ (M is Al, B, Ti, Zr, V, Cr, Mn, Fe, Co, Cu, Zn, And at least one selected from Mg, Ca, and Ga, and x and y represent arbitrary numbers). As M, Co, Mn, Fe, Al, Mg, and Ti are particularly preferable. In particular, Mn alone and a combination of Co—Mn, Co—Al, and Co—Al—Mg are effective for improving thermal stability. .

Specifically, _{LiNi 1-ab Mn a Co b} O 2 (a, b represents less than one digit 0 or _{more), LiNi 1-cd Co a} Al d Mg e O 2 (c, d, e is 0 or more less represents a number) is preferably 1, furthermore _{LiNi 1-ab Mn a Co b} O 2 (0 ≦ a <0.4,0 ≦ b <0.4), LiNi 1-cd Co a Al d Mg e O ₂ (0 ≦ c <0.3, 0 ≦ d <0.1, 0 ≦ e <0.05) is preferable, especially LiNi _1/3 Mn _1/3 Co _1/3 O ₂ , LiNi _0.5 Mn _0.3 Co _0.2 O ₂ , LiNi _0.5 Mn _0.5 O ₂ , LiNi _0.85 Co _0.10 Al _0.05 O ₂ , LiNi _0.85 Co _0.10 Al _0.03 Mg _0.02 O ₂ are preferred.

Furthermore, the surface of the composite oxide of transition metal and lithium described above is oxidized with metals such as Al, B, Ti, Zr, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mg, Ca, and Ga. It is preferable to coat with an object because the oxidation reaction of the solvent at a high voltage is suppressed. Of these, Al ₂ O ₃ , TiO ₂ , ZrO ₂ , and MgO are particularly preferable because they have high strength and exhibit a stable coating effect.

In addition, any one of these positive electrode active materials may be used alone, or two or more thereof may be used in any combination and ratio.
The specific surface area of the positive electrode active material is arbitrary as long as the effect of the present invention is not significantly impaired,
Usually 0.1 m ² / g or more, preferably 0.2 m ² / g or more, and usually 10 m ² / g or less, preferably 5.0 m ² / g or less, more preferably 3.0 m ² / g or less. It is. If the specific surface area is too small, the rate characteristics and capacity may be reduced. If the specific surface area is too large, the positive electrode active material may cause an undesirable reaction with the non-aqueous electrolyte and the like, and the cycle characteristics may be deteriorated.

  Further, the average secondary particle size of the positive electrode active material is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.2 μm or more, preferably 0.3 μm or more, and usually 20 μm or less, preferably 10 μm or less. It is. If the average secondary particle size is too small, the cycle deterioration of the lithium secondary battery may be increased and handling may be difficult. If the average secondary particle size is too large, the internal resistance of the battery may be increased and output may be difficult to output.

  The thickness of the positive electrode active material layer is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 1 μm or more, preferably 10 μm or more, more preferably 20 μm or more, and most preferably 40 μm or more. Usually, it is 200 micrometers or less, Preferably it is 150 micrometers or less, More preferably, it is 100 micrometers or less. If it is too thin, it becomes difficult to apply the coating and it is difficult to ensure uniformity, and the capacity of the lithium secondary battery of the present invention may be small. On the other hand, if it is too thick, there is a risk that the rate characteristics will deteriorate.

The positive electrode active material layer is formed by, for example, slurrying the above-described positive electrode active material, a binder (binder), and various auxiliary agents as necessary with a solvent to form a coating liquid, and collecting the coating liquid. It can be manufactured by applying to the body and drying. Further, for example, the positive electrode active material described above may be roll-formed to form a sheet electrode, or compression-molded to form a pellet electrode.
Hereinafter, a case where the slurry is applied to the positive electrode current collector and dried will be described.

  The binder is not particularly limited as long as it is a material that is stable with respect to the non-aqueous solvent used in the non-aqueous electrolyte solution or the solvent used during electrode production, but weather resistance, chemical resistance, heat resistance, difficulty It is preferable to select in consideration of flammability and the like. Specific examples include inorganic compounds such as silicate and water glass, alkane polymers such as polyethylene, polypropylene and poly-1,1-dimethylethylene; unsaturated polymers such as polybutadiene and polyisoprene; polystyrene and polymethylstyrene. , Polymers having rings such as polyvinyl pyridine, poly-N-vinyl pyrrolidone; polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, polymethyl acrylate, polyethyl acrylate, polyacrylic acid, polymethacrylic acid, Acrylic derivative polymers such as polyacrylamide; Fluorine resins such as polyvinyl fluoride, polyvinylidene fluoride, and polytetrafluoroethylene; CN group-containing polymers such as polyacrylonitrile and polyvinylidene cyanide; Polyvinyl chloride, halogen-containing polymers of polyvinylidene chloride; polyvinyl alcohol polymers such as polyvinyl alcohol such as a conductive polymer such as polyaniline can be used.

In addition, mixtures such as the above polymers, modified products, derivatives, random copolymers, alternating copolymers, graft copolymers, block copolymers, and the like can also be used.
Among these, preferred binders are a fluororesin and a CN group-containing polymer.
In addition, a binder may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

  When a resin is used as the binder, the weight average molecular weight of the resin is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 10,000 or more, preferably 100,000 or more, and usually 300. 10,000 or less, preferably 1,000,000 or less. If the molecular weight is too low, the strength of the electrode tends to decrease. On the other hand, if the molecular weight is too high, the viscosity becomes high and it may be difficult to form an electrode.

  Furthermore, the amount of the binder used is arbitrary as long as the effects of the present invention are not significantly impaired. However, the positive electrode active material (in the case of use in the negative electrode, the negative electrode active material. Hereinafter, the positive electrode active material and the negative electrode active material are distinguished. Without being referred to, simply referred to as “active material”) is usually 0.1 parts by weight or more, preferably 1 part by weight or more, and usually 30 parts by weight or less, preferably 20 parts by weight. It is as follows. If the amount of the binder is too small, the strength of the electrode tends to decrease, and if the amount of the binder is too large, the ionic conductivity tends to decrease.

The electrode may contain various auxiliaries as described above. Examples of the auxiliary agent include a conductive material that increases the conductivity of the electrode, and a reinforcing material that improves the mechanical strength of the electrode.
Specific examples of the conductive material are not particularly limited as long as an appropriate amount can be mixed with the active material to impart conductivity. However, carbon powders such as acetylene black, carbon black, and graphite, and various metals are usually used. Examples include fibers and foils.

As specific examples of the reinforcing material, various inorganic, organic spherical, fibrous fillers and the like can be used.
In addition, these adjuvants etc. may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.
The solvent for forming the slurry is not particularly limited in type as long as it is a solvent capable of dissolving or dispersing the active material, the binder, and auxiliary agents used as necessary. Either an aqueous solvent or an organic solvent may be used.

  Examples of the aqueous solvent include water and alcohol. On the other hand, examples of organic solvents include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, NN-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran ( THF), toluene, acetone, dimethyl ether, dimethylacetamide, hexamethylphosphalamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane and the like.

In addition, these solvents may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
The active material layer obtained by coating and drying is preferably consolidated by a roller press or the like in order to increase the packing density of the positive electrode active material.

[1-2. Current collector]
As a material for the current collector, a known material can be arbitrarily used, but usually a metal or an alloy is used. Specifically, examples of the current collector for the positive electrode include aluminum, nickel, and SUS (stainless steel). Among these, aluminum is preferable as the positive electrode current collector. In addition, these may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and ratios.

  Furthermore, in order to improve the binding effect between the current collector and the active material layer formed on the surface, it is preferable that the surface of these current collectors is roughened in advance. The surface roughening method includes blasting or rolling with a rough roll, and the surface of the current collector with a wire brush equipped with abrasive cloth paper, grindstone, emery buff, steel wire, etc. to which abrasive particles are fixed. Examples thereof include a mechanical polishing method, an electrolytic polishing method, and a chemical polishing method.

  Further, the shape of the current collector is arbitrary. For example, in order to reduce the weight of the battery, that is, to improve the energy density per weight, a perforated type current collector such as an expanded metal or a punching metal can be used. In this case, the weight can be freely changed by changing the aperture ratio. In addition, when a coating layer is formed on both surfaces of such a perforated current collector, the coating layer tends to be more difficult to peel due to the rivet effect of the coating layer through the hole, but the aperture ratio is too high. When it becomes high, the contact area between the coating layer and the current collector becomes small, so the adhesive strength is rather low.

  When a thin film is used as the positive electrode current collector, its thickness is arbitrary as long as the effects of the present invention are not significantly impaired, but it is usually 1 μm or more, preferably 5 μm or more, and usually 100 μm or less, preferably 50 μm or less. . If it is too thick, the capacity of the entire battery will be reduced. Conversely, if it is too thin, handling will be difficult.

[2. Negative electrode]
Any negative electrode can be used as long as it can occlude and release lithium as long as the effects of the present invention are not significantly impaired.
Usually, as in the case of the positive electrode, a negative electrode having a negative electrode active material layer provided on a current collector is used. Note that, similarly to the positive electrode, the negative electrode may include other layers as appropriate.

[2-1. Negative electrode active material]
The negative electrode active material is not particularly limited as long as it is a material capable of occluding and releasing lithium ions, and a known negative electrode active material can be arbitrarily used. For example, carbonaceous materials such as coke, acetylene black, mesophase microbeads, and graphite; lithium metal; lithium alloys such as lithium-silicon and lithium-tin, and lithium titanate are preferably used. Among these, it is most preferable to use a carbonaceous material in terms of good cycle characteristics and safety and excellent continuous charge characteristics. In addition, a negative electrode active material may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

Further, the particle size of the negative electrode active material is arbitrary as long as the effects of the present invention are not significantly impaired, but is usually 1 μm or more, preferably 15 μm in terms of excellent battery characteristics such as initial efficiency, rate characteristics, and cycle characteristics. These are usually 50 μm or less, preferably about 30 μm or less.
In addition, for example, those obtained by coating the above carbonaceous material with an organic substance such as pitch and then firing, those obtained by forming amorphous carbon on the surface using the CVD method, etc. It can be suitably used as a quality material. Here, organic substances used for coating include coal tar pitch from soft pitch to hard pitch; coal heavy oil such as dry distillation liquefied oil; straight heavy oil such as atmospheric residual oil and vacuum residual oil; crude oil And petroleum heavy oils such as cracked heavy oil (for example, ethylene heavy end) produced as a by-product during thermal decomposition of naphtha and the like. Moreover, what grind | pulverized the solid residue obtained by distilling these heavy oils at 200-400 degreeC to 1-100 micrometers can also be used. Furthermore, a vinyl chloride resin, a phenol resin, an imide resin, etc. can also be used.

  For example, the negative electrode active material layer can be formed into a sheet electrode by roll molding the negative electrode active material described above, or a pellet electrode by compression molding. Usually, as in the case of the positive electrode active material layer, The negative electrode active material, the binder, and, if necessary, various auxiliary agents and the like can be produced by applying a coating solution obtained by slurrying with a solvent onto a current collector and drying it. it can. As the solvent, binder, auxiliary agent and the like for forming the slurry, the same materials as those described above for the positive electrode active material can be used.

[2-2. Current collector]
As a material for the current collector of the negative electrode, a known material can be arbitrarily used. For example, a metal material such as copper, nickel, or SUS is used. Among these, copper is particularly preferable from the viewpoint of ease of processing and cost.
The negative electrode current collector is also preferably subjected to a roughening treatment in advance, as with the positive electrode current collector.
Further, like the positive electrode, the shape of the current collector is also arbitrary, and a perforated current collector such as expanded metal or punching metal can also be used. Moreover, the preferable thickness when using a thin film as a current collector is the same as that of the positive electrode.

[3. Spacer]
In order to prevent a short circuit, a spacer is usually interposed between the positive electrode and the negative electrode. The material and shape of the spacer are not particularly limited, but those that are stable with respect to the non-aqueous electrolyte described above, have excellent liquid retention properties, and can reliably prevent short-circuiting between electrodes are preferable.
As a material for the spacer, for example, polyolefin such as polyethylene and polypropylene, polytetrafluoroethylene, polyethersulfone and the like can be used, and polyolefin is preferable.
The spacer is preferably porous. In this case, the non-aqueous electrolyte is used by impregnating a porous spacer.

  The thickness of the spacer is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 1 μm or more, preferably 5 μm or more, more preferably 10 μm or more, and usually 50 μm or less, preferably 40 μm or less, more preferably. Is 30 μm or less. If the spacer is too thin, the insulation and mechanical strength may be deteriorated. If the spacer is too thick, not only the battery performance such as rate characteristics may be deteriorated, but also the energy density of the entire battery may be reduced. .

  Further, when a porous film is used as the spacer, the porosity of the spacer is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 20% or more, preferably 35% or more, more preferably 45% or more. It is usually 90% or less, preferably 85% or less, and more preferably 75% or less. If the porosity is too small, the membrane resistance increases and the rate characteristics tend to deteriorate. On the other hand, if it is too large, the mechanical strength of the film tends to decrease and the insulating property tends to decrease.

  Further, when a porous film is used as the spacer, the average pore diameter of the spacer is arbitrary as long as the effect of the present invention is not significantly impaired, but it is usually 0.5 μm or less, preferably 0.2 μm or less, and usually 0.8. It is 05 μm or more. If it is too large, a short circuit is likely to occur, and if it is too small, the film resistance increases and the rate characteristics may deteriorate.

[4. Assembly of secondary battery]
The non-aqueous electrolyte battery of the present invention is manufactured by assembling the above-described non-aqueous electrolyte of the present invention, a positive electrode, a negative electrode, and a spacer used as necessary into an appropriate shape. Furthermore, other components such as an outer case can be used as necessary. Further, the shape of the battery of the present invention is not particularly limited, and can be appropriately selected from various shapes generally employed according to the application. For example, a coin-type battery, a cylindrical battery, a square battery, etc. are raised. The method for assembling the battery is not particularly limited, and can be appropriately selected from various commonly used methods according to the shape of the target battery. The battery operating voltage can be used in the range of 2.5 V to 5 V, but the positive electrode potential upon completion of charging is preferably 4.0 V or higher, more preferably 4.2 V or higher. More preferably, it is 4.3 V or more, and most preferably 4.4 V or more.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to these examples and comparative examples, and may be arbitrarily set without departing from the gist of the present invention. It can be implemented with deformation.
<Explanation of test operation>
[Production of positive electrode]
94 parts by weight of lithium nickel cobalt manganese composite oxide (LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ) which is a positive electrode active material, ₃ parts by weight of polyvinylidene fluoride (hereinafter referred to as “PVdF” as appropriate) and acetylene black 3 parts by weight was mixed, and N-methylpyrrolidone added to form a slurry was applied to both sides of a current collector made of aluminum and dried to obtain a positive electrode.

[Manufacture of negative electrode]
A negative electrode was obtained by mixing 94 parts by weight of graphite powder, which is a negative electrode active material, and 6 parts by weight of PVdF, adding N-methylpyrrolidone into a slurry, and coating and drying on one side of a current collector made of copper. .
[Manufacture of lithium secondary batteries]
The positive electrode, the negative electrode, and the polyethylene separator were laminated in the order of the negative electrode, the separator, the positive electrode, the separator, and the negative electrode. The battery element thus obtained was wrapped in a cylindrical aluminum laminate film, injected with an electrolyte described later, and then vacuum sealed to produce a sheet-like non-aqueous electrolyte secondary battery. Furthermore, in order to improve the adhesion between the electrodes, the sheet-like battery was sandwiched between glass plates and pressurized.

[Initial conditioning]
In a constant temperature bath at 25 ° C., the battery was constant current-constant voltage charged (hereinafter referred to as “CCCV charge” as appropriate) to 4.1 V with a current corresponding to 0.2 C, and then discharged to 3 V at 0.2 C. This was repeated three times to form a negative electrode film. Next, CCCV charge to 4.4 V (positive electrode potential is 4.5 V) at 0.2 C and then discharge to 3 V at 0.2 C were repeated twice to obtain initial conditioning. The cut current during charging was set to 0.05C.
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 characteristic evaluation test]
The battery after initial conditioning is placed in a 45 ° C. thermostatic chamber, charged at 0.5C to 4.4V (positive electrode potential is 4.5V), and charged / discharged at a constant current of 0.5C to 3V. Repeated 100 times. The discharge capacity retention rate at the 100th cycle was determined from the following formula.

[Equation 1]
100th cycle capacity recovery rate (%) = [100th discharge capacity (mAh / g) / first discharge capacity (mAh / g)] × 100
Further, the discharge capacity (relative value) of the first cycle was obtained from the following formula. This is an index indicating the magnitude of the initial discharge capacity when compared with Example 1.

[Equation 2]
First cycle capacity recovery rate (%) = [First discharge capacity (mAh / g) / First discharge capacity (mAh / g) in Example 1] × 100

<Example 1>
In a mixed solvent (weight ratio 13: 13: 64: 10) with ethylene carbonate (EC), fluoroethylene carbonate (FEC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC), 1 mol / liter of LiPF ₆ as an electrolyte was added. L was dissolved at a ratio of L, and phenylmaleic anhydride was further added to 0.3 wt% with respect to the total weight of the electrolytic solution to obtain a non-aqueous electrolytic solution.
Using the obtained nonaqueous electrolytic solution, a lithium secondary battery was produced according to the above-described method, and an initial conditioning and a cycle characteristic evaluation test were performed. The results are shown in Table 1.

<Example 2>
A secondary battery was fabricated and evaluated using the same electrolytic solution as in Example 1 except that diphenylmaleic anhydride was added instead of phenylmaleic anhydride. The results are shown in Table 1.
<Example 3>
A secondary battery was fabricated and evaluated using the same electrolytic solution as in Example 1 except that dimethylmaleic anhydride was added instead of phenylmaleic anhydride. The results are shown in Table 1.

<Example 4>
A secondary battery was prepared using the same electrolytic solution as in Example 1 except that bicyclo [2.2.2] oct-2-ene-2,3-dicarboxylic anhydride was added instead of phenylmaleic anhydride. Fabricated and evaluated. The results are shown in Table 1.
<Example 5>
A secondary battery was fabricated and evaluated using the same electrolytic solution as in Example 1 except that diphenic anhydride was added instead of phenylmaleic anhydride. The results are shown in Table 1.

<Example 6>
In addition to phenylmaleic anhydride, an electrolytic solution similar to that of Example 1 was used except that 1,3-propane sultone (PS) was further added so as to be 1% by weight based on the total weight of the electrolytic solution. A secondary battery was fabricated and evaluated. The results are shown in Table 1.
<Example 7>
In addition to phenylmaleic anhydride, a secondary battery using the same electrolyte as in Example 1 except that succinonitrile (SN) was further added to 1% by weight with respect to the total weight of the electrolyte. Were prepared and evaluated. The results are shown in Table 1.

<Example 8>
The mixed solvent ratio (weight ratio) of ethylene carbonate (EC), fluoroethylene carbonate (FEC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) was changed to 30:13:50 instead of 13: 13: 64: 10. : A secondary battery was prepared and evaluated using the same electrolytic solution as in Example 1 except that it was set to 7. The results are shown in Table 1.
<Example 9>
Example 1 except that a mixed solvent (weight ratio 20: 18: 32: 30) with ethylene carbonate (EC), fluoroethylene carbonate (FEC), dimethyl carbonate (DMC) and diethyl carbonate (DEC) was used as the solvent. A secondary battery was fabricated using the same electrolytic solution as in Example 1, and evaluated. The results are shown in Table 1.

<Example 10>
Example 1 except that a mixed solvent (weight ratio 20: 18: 8: 54) with ethylene carbonate (EC), fluoroethylene carbonate (FEC), dimethyl carbonate (DMC) and diethyl carbonate (DEC) was used as the solvent. A secondary battery was fabricated using the same electrolytic solution as in Example 1, and evaluated. The results are shown in Table 1.

<Example 11>
In a mixed solvent (weight ratio 11: 25: 54: 10) with ethylene carbonate (EC), fluoroethylene carbonate (FEC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC), 1 mol / liter of LiPF ₆ as an electrolyte was added. A secondary battery was prepared in the same manner as in Example 1 except that an electrolytic solution in which diphenylmaleic anhydride was added at a rate of 1.0% by weight with respect to the total weight of the electrolytic solution was used. Fabricated and evaluated. The results are shown in Table 1.

<Example 12>
In a mixed solvent (weight ratio 11: 25: 54: 10) with ethylene carbonate (EC), fluoroethylene carbonate (FEC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC), 1 mol / liter of LiPF ₆ as an electrolyte was added. A secondary battery was prepared in the same manner as in Example 1 except that an electrolytic solution in which diphenylmaleic anhydride was added at a rate of 2.0% by weight with respect to the total weight of the electrolytic solution was used. Fabricated and evaluated. The results are shown in Table 1.

<Comparative Example 1>
A secondary battery was prepared and evaluated using the same electrolytic solution as in Example 1 except that phenylmaleic anhydride was not added. The results are shown in Table 1.
<Comparative example 2>
A secondary battery was prepared and evaluated using the same electrolytic solution as in Example 1 except that maleic anhydride was added instead of phenylmaleic anhydride. The results are shown in Table 1.

  From Table 1, when the non-aqueous electrolyte solution of Examples 1-12 concerning this invention is used, when the cyclic acid anhydride is not added (comparative example 1), it corresponds to the unsaturated cyclic acid anhydride of this invention. It can be seen that the capacity retention rate after 100 cycles is significantly improved as compared with the case where maleic anhydride is not added (Comparative Example 2). Particularly, in Comparative Example 2, the discharge capacity at the first cycle is greatly reduced, and a sufficient capacity is not obtained at the initial stage, which is a serious problem in practical use.

  The application of the nonaqueous electrolyte 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 CD players, and mini disc players. , Walkie-talkies, electronic notebooks, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, lighting equipment, toys, game machines, watches, strobes, cameras, etc.

Claims (6)

A non-aqueous electrolyte containing an electrolyte and a non-aqueous organic solvent, wherein at least one selected from the group of compounds represented by the following general formulas (1) to (4) with respect to the weight of the non-aqueous electrolyte Unsaturated cyclic acid anhydrides of 0 . A non-aqueous electrolyte containing 0001 to 10% by weight and 0.01 to 5 % by weight of succinonitrile.

(In the formula, R ₁ and R ₂ are each independently a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms, and R ₁ and R ₂ are bonded to each other to form 7 to 26 carbon atoms. An aliphatic ring may be formed, except when both R ₁ and R ₂ are hydrogen atoms, and when _one of R ₁ and R ₂ is a hydrogen atom and the other is a methyl group .)

(In the formula, R ₃ and R ₄ are each independently a hydrogen atom, a fluorine atom, or an optionally substituted hydrocarbon group having 1 to 12 carbon atoms, and R ₃ and R ₄ are a bond. Z may be a fluorine-substituted divalent hydrocarbon group having 1 to 12 carbon atoms, provided that when Z is a methylene group, R ₃ and R ₄ Neither of them is a hydrogen atom at the same time.)

(In the formula, R _{5 to} R ₈ are each independently a hydrogen atom, a fluorine atom, or an optionally substituted fluorine group having 1 to 12 carbon atoms, but all of R _{5 to} R ₈ are simultaneously selected. It is not a hydrogen atom.)

(In the formula, R _{9 to} R ₁₄ are each independently a hydrogen atom, a fluorine atom, or a fluorine-substituted hydrocarbon group having 1 to 12 carbon atoms, but all of R _{9 to} R ₁₄ are simultaneously formed. It is not a hydrogen atom.) The non-aqueous organic solvent contains ethylene carbonate, fluorine-substituted cyclic carbonate and methyl carbonate in a proportion of x wt%, y wt% and z wt % , respectively, with respect to the total non-aqueous organic solvent (where 0 ≦ x ≤39, 0≤y≤39, 0≤z <100, and satisfies the following [1] or [2]: [1] 5≤x + 1.1y≤39, [2] 10≤z <100) The non-aqueous electrolyte solution according to claim 1, wherein The non-aqueous electrolyte solution according to claim 1 or 2, wherein the unsaturated cyclic acid anhydride is at least one compound selected from the group of compounds represented by the general formula (1). A positive electrode and the negative electrode, a nonaqueous electrolyte battery which comprises a non-aqueous electrolyte solution according to any one of claims 1-3. The non-aqueous electrolyte battery according to claim 4 , wherein a negative electrode active material containing a carbonaceous material is used for the negative electrode. Nonaqueous electrolyte battery according to claim 4 or 5, characterized by using a cathode active material containing lithium nickel-containing transition metal oxide positive electrode.