Nonaqueous electrolyte solution for secondary battery, and secondary battery

Abstract

Disclosed is a nonaqueous electrolyte solution for a secondary battery, the nonaqueous electrolyte solution containing a hexafluorophosphate, a compound represented by formula (1), and a nonaqueous solvent.　(1): FSO2NHR1 [In formula (1), R1 represents a hydrogen atom or an optionally substituted hydrocarbon group having 1 to 18 carbon atoms.]

Description

Non-aqueous electrolyte for secondary batteries and secondary batteries

[0001] The present disclosure relates to a nonaqueous electrolyte for a secondary battery and a secondary battery.

[0002] Secondary batteries are used as power sources for electronic devices such as smartphones and personal computers, as well as for automobiles, etc. Research into batteries used in these applications has been extensively conducted with the aim of improving various properties such as higher output, higher energy density, cycle characteristics, and rate characteristics.

[0003] For example, Patent Document 1 discloses a 2.4 mol / L (FSO ２ ) ２ NLi and 1 mass% of FSO ２ NH ２ and a mixed solvent of dimethyl carbonate and ethyl methyl carbonate in a molar ratio of 9:1.

[0004] Japanese Patent Application Laid-Open No. 2020-87825

[0005] In the positive electrode of a secondary battery, a positive electrode current collector such as an aluminum foil is used, and corrosion of the positive electrode current collector due to elution of aluminum, etc., can be a problem. Corrosion of the positive electrode current collector can accelerate deterioration of the secondary battery and shorten its lifespan.

[0006] Furthermore, since secondary batteries are likely to be stored under high-temperature conditions in various devices, a secondary battery that is less likely to self-discharge even when stored under high-temperature conditions can be useful and suitable for use in such devices. The present inventors have found that there is room for improvement in the self-discharge during high-temperature storage in the nonaqueous electrolyte solution described in Patent Document 1.

[0007] An object of the present disclosure is to provide a nonaqueous electrolyte for a secondary battery, which suppresses corrosion of a positive electrode current collector in the secondary battery and suppresses self-discharge during high-temperature storage, and a secondary battery.

[0008] The present disclosure relates to, for example, the following [1] to [9]. [1] A non-aqueous electrolyte solution for a secondary battery, comprising a hexafluorophosphate salt, a compound represented by the following formula (1), and a non-aqueous solvent: FSO２ NHR １ ...(1) [In formula (1), R １ represents a hydrogen atom or an optionally substituted hydrocarbon group having 1 to 18 carbon atoms.] [2] The nonaqueous electrolyte solution according to [1], wherein the content of the compound represented by the formula (1) is 0.001 mass % or more and 0.8 mass % or less in the total amount of the nonaqueous electrolyte solution. [3] The nonaqueous electrolyte solution according to [1] or [2], further containing a salt containing an anion represented by the following formula (2): N － (R ２ SO ２ ) (R ３ SO ２ )...(2) [In formula (2), R ２ and R ３ and each independently represent a fluorine atom or an alkyl group having 1 to 6 carbon atoms which may be substituted with a fluorine atom.] [4] The non-aqueous electrolyte solution according to any one of [1] to [3], further containing at least one additive selected from the group consisting of unsaturated cyclic carbonates, cyclic sulfonate esters, nitrile compounds, ester compounds, and fluorine-containing alkali metal salts. [5] The non-aqueous electrolyte solution according to any one of [1] to [4], wherein the secondary battery is a lithium ion secondary battery, and the hexafluorophosphate salt is lithium hexafluorophosphate. [6] A secondary battery comprising the non-aqueous electrolyte solution according to any one of [1] to [5], a positive electrode having a positive electrode mixture layer and a positive electrode current collector, and a negative electrode having a negative electrode mixture layer and a negative electrode current collector, wherein the positive electrode mixture layer contains at least one positive electrode active material selected from the group consisting of a positive electrode active material represented by the following formula (3), a positive electrode active material represented by the following formula (4), and a positive electrode active material represented by the following formula (5): ３ ｖ Ni ｘ Co ｙ Mn ｚ O （２＋ｗ） ...(3) [In formula (3), M ３ represents an alkali metal atom, and v, x, y, z, and w are real numbers indicating the number of moles, where 0.2≦v≦1.2, 0.3≦x≦0.9, 0<y≦0.3, 0<z≦0.4, x+y+z=1, and −0.2≦w≦0.2.] M １ M２ P.O. ４ ...(4) [In formula (4), M １ represents an alkali metal atom, M ２ represents Ni, Mn, Co or Fe.] Li （１＋ｘ） Mn （１－ｙ－ｚ） Fe ｙ A ｚ P.O. ４ ... (5) [In formula (5), x, y, and z are real numbers indicating the number of moles, -0.1<x<0.1, 0<y<1.0, 0≦z<0.1, 0<1-y-z, and A represents at least one atom selected from the group consisting of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Ni, Co, Ga, Sn, Sb, Nb, and Ge.] [7] The secondary battery according to [6], wherein the positive electrode mixture layer contains at least one positive electrode active material selected from the group consisting of a positive electrode active material represented by the following formula (4-1) and a positive electrode active material represented by the following formula (5-1): M １ M ２ P.O. ４ ...(4-1) [In formula (4-1), M １ represents an alkali metal atom, M ２ represents Ni, Mn, or Fe.] Li （１＋ｘ） Mn （１－ｙ－ｚ） Fe ｙ A ｚ P.O. ４ ... (5-1) [In formula (5-1), x, y, and z are real numbers indicating the number of moles, -0.1<x<0.1, 0<y<1.0, 0≦z<0.1, 0<1-y-z, and A represents at least one atom selected from the group consisting of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Ni, Ga, Sn, Sb, Nb, and Ge.] [8] The secondary battery according to [6] or [7], wherein the positive electrode current collector is aluminum. [9] The secondary battery according to any one of [6] to [8], which is a lithium ion secondary battery.

[0009] The present disclosure provides a nonaqueous electrolyte for a secondary battery, which inhibits corrosion of a positive electrode current collector in the secondary battery and inhibits self-discharge during high-temperature storage, and a secondary battery.

[0010] Modes for carrying out the invention included in this disclosure will be described below, but the invention included in this disclosure is not limited to the following embodiments. Note that when a numerical range is indicated as X to Y, it means X or more and Y or less. Furthermore, unless otherwise specified, the materials, components, or methods exemplified in this specification can be used alone or in combination of two or more.

[0011] <Non-aqueous Electrolyte> One embodiment of the present invention is a non-aqueous electrolyte for a secondary battery, which contains a hexafluorophosphate salt, a compound represented by formula (1) described below, and a non-aqueous solvent.

[0012] <Hexafluorophosphate> Hexafluorophosphate is a salt composed of a hexafluorophosphate ion and a counter cation. That is, one embodiment of the present invention can be said to be a non-aqueous electrolyte solution for a secondary battery containing a hexafluorophosphate ion, a counter cation, a compound represented by formula (1) described below, and a non-aqueous solvent. The hexafluorophosphate ion is a PF ６ － It is an ion (anion) represented by the chemical formula:

[0013] The counter cation in the hexafluorophosphate is not particularly limited as long as it can form a salt with the hexafluorophosphate ion, but may be a monovalent cation. Furthermore, the counter cation in the hexafluorophosphate may be an alkali metal ion, a lithium ion, a sodium ion, or even a lithium ion. In other words, the hexafluorophosphate according to this embodiment may be an alkali metal salt of hexafluorophosphate, lithium hexafluorophosphate, sodium hexafluorophosphate, or lithium hexafluorophosphate. For example, when the nonaqueous electrolyte for a secondary battery according to this embodiment is a nonaqueous electrolyte for a lithium-ion secondary battery, the hexafluorophosphate may be lithium hexafluorophosphate.

[0014] The content of hexafluorophosphate in the non-aqueous electrolyte may be, for example, 0.01 mol / L to 10.0 mol / L, 0.05 mol / L to 4.00 mol / L, 0.10 mol / L to 2.00 mol / L, 0.15 mol / L to 1.20 mol / L, 0.20 mol / L to 1.00 mol / L, or 0.40 mol / L to 0.80 mol / L. When the molar concentration of hexafluorophosphate is within the above range, self-discharge during high-temperature storage is more unlikely to occur. An example of a molar concentration of hexafluorophosphate that further reduces self-discharge during high-temperature storage is 0.40 mol / L to 0.80 mol / L.

[0015] <Compound Represented by Formula (1)> The nonaqueous electrolyte solution for a secondary battery according to this embodiment contains a compound represented by the following formula (1). Hereinafter, the compound represented by the following formula (1) will also be referred to as the "compound of formula (1)". FSO ２ NHR １ ...(1)

[0016] In the above formula (1), R １ represents a hydrogen atom or an optionally substituted hydrocarbon group having 1 to 18 carbon atoms. The hydrocarbon group may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group, or may be an aliphatic hydrocarbon group. The hydrocarbon group may be a chain or cyclic hydrocarbon group, or may be a chain hydrocarbon group, or may be a chain aliphatic hydrocarbon group. The chain hydrocarbon group may be a linear or branched hydrocarbon group, or may be a linear hydrocarbon group, or may be a linear aliphatic hydrocarbon group. The hydrocarbon group may be a saturated hydrocarbon group or an unsaturated hydrocarbon group, or may be a saturated hydrocarbon group. The number of carbon atoms in the hydrocarbon group may be, for example, 1 to 18, 1 to 8, 1 to 5, 1 to 4, 1 to 3, 1 to 2, or 1.

[0017] In the above formula (1), R １ The number of substituents on the hydrocarbon group in may be, for example, 1 to 18, 1 to 6, 1 to 4, 1 to 3, 1 to 2, or 1.

[0018] In the above formula (1), R １The substituents of the hydrocarbon group in may each independently be, for example, a group selected from the group consisting of a halogen atom, a hydroxy group, a nitro group, a cyano group, an aryl group, an alkoxy group, an acyl group, an alkoxycarbonyl group, and a carbamoyl group.

[0019] R １ may be a hydrogen atom or a hydrocarbon group having 1 to 18 carbon atoms (i.e., a hydrocarbon group having no substituent). １ may be a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, or an alkenyl group having 2 to 18 carbon atoms. １ may be a hydrogen atom or an alkyl group having 1 to 18, 1 to 8, 1 to 5, 1 to 4, 1 to 3, 1 to 2, or 1 carbon atom. １ may be a hydrogen atom, methyl, ethyl, propyl, isopropyl, cyclopropyl, vinyl or allyl, may be a hydrogen atom, methyl or ethyl, or may be a hydrogen atom or methyl. １ is a hydrogen atom, the compound of formula (1) has the chemical formula FSO ２ NH ２ It is expressed as: R １ The compound of formula (1) where is methyl has the chemical formula FSO ２ NHCH ３ That is, the compound of formula (1) is represented by FSO ２ NH ２ or FSO ２ NHCH ３ The compound of formula (1) containing one or two hydrogen atoms as substituents on the nitrogen atom may be able to suppress self-discharge during high-temperature storage in a secondary battery to a greater extent than a compound that does not contain a hydrogen atom as a substituent on the nitrogen atom.

[0020] The content of the formula (1) compound in the total amount of the non-aqueous electrolyte may be, for example, 0.0005% by mass to 1.0% by mass, 0.001% by mass to 0.8% by mass, 0.001% by mass to 0.5% by mass, 0.001% by mass to 0.1% by mass, 0.005% by mass to 0.1% by mass, or 0.01% by mass to 0.1% by mass. When the content of the formula (1) compound is within the above range, self-discharge during high-temperature storage in the secondary battery is more unlikely to occur. An example of the content of the formula (1) compound that further reduces self-discharge during high-temperature storage is 0.001% by mass to 0.1% by mass.

[0021] The content of the compound of formula (1) in the non-aqueous electrolyte relative to 100 parts by mass of hexafluorophosphate may be, for example, 0.001 parts by mass to 100 parts by mass, 0.003 parts by mass to 50 parts by mass, 0.1 parts by mass to 30 parts by mass, 0.3 parts by mass to 25 parts by mass, or 0.5 parts by mass to 20 parts by mass. When the content of the compound of formula (1) relative to hexafluorophosphate is within the above range, self-discharge during high-temperature storage in the secondary battery becomes less likely to occur.

[0022] <Non-aqueous solvent> The non-aqueous solvent is an organic solvent that is not water. A non-aqueous solvent that is commonly used by those skilled in the art as a solvent for electrolytes in secondary batteries can be used. The non-aqueous solvent may contain at least one solvent selected from the group consisting of, for example, ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), fluoroethylene carbonate (FEC), dimethyl carbonate, diethyl carbonate, methyl propionate, ethyl propionate, butyl propionate, isopropyl propionate, propyl propionate, ethyl acetate, methyl acetate, propyl acetate, and isopropyl acetate, in a proportion of 90% by volume or more of the total amount of non-aqueous solvent contained in the non-aqueous electrolyte. When these solvents are contained in a proportion of 90% by volume or more, storage stability at high temperatures is improved. From the viewpoint of further improving storage stability at high temperatures, these solvents may be contained in a proportion of 95% by volume or more, or even 100% by volume.

[0023] Furthermore, from the viewpoint of further improving storage stability at high temperatures, the nonaqueous solvent may contain at least one solvent selected from the group consisting of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, fluoroethylene carbonate, methyl propionate, and dimethyl carbonate in a proportion of 90% by volume or more, 95% by volume or more, or 100% by volume of the total amount of nonaqueous solvent contained in the nonaqueous electrolyte solution.

[0024] The solvent contained in the non-aqueous electrolyte may contain other organic solvents. Specific examples thereof include saturated cyclic carbonate (carbonate ester) solvents such as 2,3-dimethylethylene carbonate, 1,2-butylene carbonate, and erythritan carbonate; chain carbonate (carbonate ester) solvents such as diphenyl carbonate and methyl phenyl carbonate; ether solvents such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, 2,6-dimethyltetrahydrofuran, tetrahydropyran, crown ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,4-dioxane, and 1,3-dioxolane; cyclic carbonate (carbonate ester) solvents having an unsaturated bond such as vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, 2-vinyl ethylene carbonate, and phenyl ethylene carbonate; fluorine-containing cyclic carbonate (carbonate ester) solvents such as fluoroethylene carbonate, 4,5-difluoroethylene carbonate, and trifluoropropylene carbonate; methyl benzoate, ethyl benzoate, and the like. aromatic carboxylic acid ester solvents such as butyl; lactone solvents such as γ-butyrolactone, γ-valerolactone, δ-valerolactone; phosphate ester solvents such as trimethyl phosphate, ethyl dimethyl phosphate, diethyl methyl phosphate, triethyl phosphate; nitrile solvents such as acetonitrile, propionitrile, methoxypropionitrile, glutaronitrile, adiponitrile, 2-methylglutaronitrile, valeronitrile, butyronitrile, isobutyronitrile; dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone Examples of suitable solvents include sulfur compound solvents such as benzene, sulfolane, 3-methylsulfolane, and 2,4-dimethylsulfolane; aromatic nitrile solvents such as benzonitrile and tolunitrile; aromatic solvents such as toluene, amylbenzene, cyclohexylbenzene, fluorobenzene, anisole, 2,4-difluoroanisole, and trifluoromethoxybenzene; nitromethane, 1,3-dimethyl-2-imidazolidinone, 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone, and 3-methyl-2-oxazolidinone. The solvent in the nonaqueous electrolyte does not need to contain water.

[0025] <Salt containing anion represented by formula (2)> The nonaqueous electrolyte solution according to this embodiment may further contain a salt containing an anion represented by the following formula (2). Hereinafter, the salt containing an anion represented by the following formula (2) will also be referred to as "salt containing anion of formula (2)". － (R ２ SO ２ ) (R ３ SO ２ ) ... (2)

[0026] In formula (2), R ２ and R ３ each independently represents a fluorine atom or an alkyl group having 1 to 6 carbon atoms which may be substituted with a fluorine atom. The number of carbon atoms in the alkyl group may be 1 to 6, 1 to 5, 1 to 4, 1 to 3, 1 to 2, or 1. The number of fluorine atoms substituted in the alkyl group may be, for example, 1 to 13, 1 to 9, 1 to 8, 1 to 5, 1 to 3, 1 to 2, or 1. The alkyl group having 1 to 6 carbon atoms which may be substituted with a fluorine atom may be a perfluoroalkyl group having 1 to 6 carbon atoms.

[0027] For example, in formula (2), R ２ and R ３ may each independently represent a fluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms, may each independently represent a fluorine atom, trifluoromethyl, or pentafluoroethyl, may each independently represent a fluorine atom or trifluoromethyl, or may each independently represent a fluorine atom.

[0028] The anion-containing salt of formula (2) contains a counter cation in addition to the anion represented by formula (2). The anion-containing salt of formula (2) may be a salt consisting of the anion represented by formula (2) and a counter cation. The counter cation is not particularly limited as long as it can form a salt with the anion represented by formula (2), and may be, for example, a monovalent cation. The counter cation in the anion-containing salt of formula (2) may be an alkali metal ion, a lithium ion, a sodium ion, or a lithium ion. R in formula (2) ２ and R３ The compound in which R is a fluorine atom and the counter cation is a lithium ion is lithium bis(fluorosulfonyl)imide, also known as LiFSI. ２ and R ３ is trifluoromethyl and the counter cation is lithium ion, the compound is lithium bis(trifluoromethylsulfonyl)imide. The salt containing the anion of formula (2) preferably contains lithium bis(fluorosulfonyl)imide or lithium bis(trifluoromethylsulfonyl)imide, more preferably lithium bis(fluorosulfonyl)imide.

[0029] The content of the anion-containing salt of formula (2) in the non-aqueous electrolyte may be, for example, 0 mol / L to 10.0 mol / L, 0.05 mol / L to 4.00 mol / L, 0.10 mol / L to 2.00 mol / L, 0.15 mol / L to 1.20 mol / L, 0.20 mol / L to 1.00 mol / L, or 0.40 mol / L to 0.80 mol / L. When the molar concentration of the anion-containing salt of formula (2) is within the above range, self-discharge during high-temperature storage in the secondary battery is more unlikely to occur. An example of a molar concentration of the anion-containing salt of formula (2) that further reduces self-discharge during high-temperature storage is a concentration of 0.40 mol / L to 0.80 mol / L.

[0030] The content of the anion-containing salt of formula (2) in the non-aqueous electrolyte may be 0 to 1,000 molar parts, 5 to 700 molar parts, 9 to 600 molar parts, 20 to 500 molar parts, 40 to 300 molar parts, or 50 to 200 molar parts relative to 100 molar parts of hexafluorophosphate. When the above conditions are satisfied, self-discharge during high-temperature storage in the secondary battery is more unlikely to occur. Examples of the content of the anion-containing salt of formula (2) that further reduces self-discharge during high-temperature storage include 20 to 500 molar parts and 50 to 200 molar parts relative to 100 molar parts of hexafluorophosphate, and 100 molar parts is an example.

[0031] <Other Additives> The nonaqueous electrolyte may further contain other additives in addition to the components described above. For example, the nonaqueous electrolyte may further contain at least one additive selected from the group consisting of unsaturated cyclic carbonates, cyclic sulfonic acid esters, nitrile compounds, ester compounds, and fluorine-containing alkali metal salts.

[0032] The unsaturated cyclic carbonate may be, for example, at least one selected from the group consisting of vinylene carbonate (VC), methylvinylene carbonate, ethylvinylene carbonate, 2-vinylethylene carbonate, and phenylethylene carbonate. For example, the unsaturated cyclic carbonate may be vinylene carbonate.

[0033] The cyclic sulfonate ester may be, for example, a cyclic sulfonate ester containing a 5- to 10-membered ring, a 5- to 8-membered ring, or a 5- to 6-membered ring, or may be at least one selected from the group consisting of 1,3-propane sultone, 1,4-butane sultone, and 1-propene 1,3-sultone. For example, the cyclic sulfonate ester may be 1,3-propane sultone.

[0034] A nitrile compound is a compound having a cyano group in its molecule. The nitrile compound according to the present invention may be, for example, a compound having one cyano group in its molecule (mononitrile compound), a compound having two cyano groups in its molecule (dinitrile compound), or a compound having three or more cyano groups in its molecule. The nitrile compound according to the present invention is preferably a compound having two or more cyano groups in its molecule. The compound having two or more cyano groups in its molecule may be a dinitrile compound or a compound having three or more cyano groups in its molecule.

[0035] Examples of dinitrile compounds include succinonitrile, malononitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, azelanitrile, sebaconitrile, undecanedinitrile, dodecanedinitrile, methylmalononitrile, ethylmalononitrile, isopropylmalononitrile, tert-butylmalononitrile, methylsuccinonitrile, 2,2-dimethylsuccinonitrile, and 2,3-dimethylsuccinonitrile. , 2,3,3-trimethylsuccinonitrile, 2,2,3,3-tetramethylsuccinonitrile, 2,3-diethyl-2,3-dimethylsuccinonitrile, 2,2-diethyl-3,3-dimethylsuccinonitrile, bicyclohexyl-1,1-dicarbonitrile, bicyclohexyl-2,2-dicarbonitrile, bicyclohexyl-3,3-dicarbonitrile, 2,5-dimethyl-2,5-hexanedicarbonitrile, 2,3-diisobutyl-2,3-dimethylsuccinonitrile succinonitrile, 2,2-diisobutyl-3,3-dimethylsuccinonitrile, 2-methylglutaronitrile, 2,3-dimethylglutaronitrile, 2,4-dimethylglutaronitrile, 2,2,3,3-tetramethylglutaronitrile, 2,2,4,4-tetramethylglutaronitrile, 2,2,3,4-tetramethylglutaronitrile, 2,3,3,4-tetramethylglutaronitrile, maleonitrile, fumaronitrile, 1,4-dicyanopentane, 2,6 The dinitrile compound may be at least one selected from the group consisting of 1,3-dicyanoheptane, 2,7-dicyanooctane, 2,8-dicyanononane, 1,6-dicyanodecane, 1,2-dicyanobenzene, 1,3-dicyanobenzene, 1,4-dicyanobenzene, 3,3'-(ethylenedioxy)dipropionitrile, 3,3'-(ethylenedithio)dipropionitrile, and 3,9-bis(2-cyanoethyl)-2,4,8,10-tetraoxaspiro[5,5]undecane. The dinitrile compound may be at least one selected from the group consisting of succinonitrile, malononitrile, glutaronitrile, adiponitrile, pimelonitrile, and suberonitrile. For example, the dinitrile compound may be succinonitrile.

[0036] The compound having three or more cyano groups in the molecule may be at least one selected from the group consisting of, for example, 1,2,3-propanetricarbonitrile, 1,3,5-pentanetricarbonitrile, 1,3,6-hexanetricarbonitrile, 1,2,3-tris(2-cyanoethoxy)propane, tris(2-cyanoethyl)amine, 1,3,5-cyclohexanetricarbonitrile, 1,3,5-cyclohexanetricyanobenzene, tris(2-cyanoethyl)amine, tris(2-cyanoethyl)phosphine, 7,7,8,8-tetracyanoquinodimethane, 2,5-dimethyl-7,7,7,8-tetracyanoquinodimethane, 2,5-difluoro-7,7,8,8-tetracyanoquinodimethane, and 1,2,3,4-butanetetracarbonitrile.

[0037] The mononitrile compound may be at least one selected from the group consisting of, for example, acetonitrile, propionitrile, butyronitrile, pentanenitrile, hexanenitrile, heptanenitrile, octanenitrile, pelargononitrile, decanenitrile, undecanenitrile, dodecanenitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, acrylonitrile, methacrylonitrile, crotononitrile, 3-methylcrotononitrile, 2-methyl-2-butenenitrile, 2-pentenenitrile, 2-methyl-2-pentenenitrile, 3-methyl-2-pentenenitrile, and 2-hexenenitrile.

[0038] The ester compound is a compound having an ester bond in the molecule. The ester compound may be a carbonate ester compound. The carbonate ester compound is a compound having a divalent group represented by -O-C(=O)-O- in the molecule. The carbonate ester compound according to this embodiment may be a compound having two divalent groups represented by -O-C(=O)-O- in the molecule. For example, the ester compound may be a compound represented by the following formula (A): [In formula (A), R ４ and R ５ R each independently represents an alkyl group having 1 to 6 carbon atoms which may have a substituent, an alkenyl group having 2 to 6 carbon atoms which may have a substituent, or an alkynyl group having 2 to 6 carbon atoms which may have a substituent.６ represents an alkylene group having 1 to 6 carbon atoms which may have a substituent, an alkenylene group having 2 to 6 carbon atoms which may have a substituent, an alkynylene group having 2 to 6 carbon atoms which may have a substituent, or a bridged ring which may have a substituent. The substituent represents a halogen atom or an alkyl group.] For example, the ester compound may be dimethyl 2,5-dioxahexanedioate.

[0039] The fluorine-containing alkali metal salt is a salt composed of an anion having a fluorine atom and an alkali metal ion. The fluorine-containing alkali metal salt may be a fluorine-containing alkali metal salt that can be used as an electrolyte. The alkali metal ion may be a lithium ion or a sodium ion, or may be a lithium ion. In other words, the fluorine-containing alkali metal salt may be a fluorine-containing lithium salt or a fluorine-containing sodium salt, or may be a fluorine-containing lithium salt. The anion having a fluorine atom is, for example, BF ４ － , P.O. ２ F ２ － , FSO ３ － , B.F. ２ (C ２ O ４ ) － , P.F. ２ (C ２ O ４ ) － , (SO ２ CF ２ CF ２ SO ２ ) N － , (SO ２ CF ２ CF ２ CF ２ SO ２ ) N － , FSO ２ (CH ３ SO ２ ) N － , FSO ２ (C ２ F ５ SO ２ ) N － , FSO ２ (C２ H ５ SO ２ ) N － , and AsF ６ － and BF ４ － , P.O. ２ F ２ － , FSO ３ － , B.F. ２ (C ２ O ４ ) － , P.F. ４ (C ２ O ４ ) and PF ２ (C ２ O ４ ) ２ － It may be at least one selected from the group consisting of (SO ２ CF ２ CF ２ SO ２ ) N － and (SO ２ CF ２ CF ２ CF ２ SO ２ ) N － is the anion of a cyclic sulfonimide. The fluorine-containing alkali metal salt is LiBF ４ , LiPO ２ F ２ , FSO ３ Li, lithium difluorooxalatoborate (LiBF ２ (C ２ O ４ ), LiDFOB) and lithium difluorobis(oxalato)phosphate (LiPF ２ (C ２ O ４ ) ２ , LiDFOP).

[0040] As described above, the non-aqueous electrolyte contains vinylene carbonate, 1,3-propane sultone, succinonitrile, dimethyl 2,5-dioxahexanedioate, and LiBF ４, LiPO ２ F ２ , FSO ３ Li, LiBF ２ (C ２ O ４ ) and LiPF ２ (C ２ O ４ ) ２ The non-aqueous electrolyte may further contain at least one additive selected from the group consisting of: In addition, the non-aqueous electrolyte may further contain additives other than those described above. Examples of such additives include carboxylic acid anhydrides such as succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, diglycolic anhydride, cyclohexanedicarboxylic anhydride, cyclopentanetetracarboxylic dianhydride, and phenylsuccinic anhydride; sulfur-containing compounds such as ethylene sulfite, methyl methanesulfonate, busulfan, sulfolene, tetramethylthiuram monosulfide, and trimethylene glycol sulfate; nitrogen-containing compounds such as 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, and N-methylsuccinimide; saturated hydrocarbon compounds such as heptane, octane, and cycloheptane; sulfamic acid (amidosulfuric acid, H ３ NSO ３ ); sulfamates (e.g., alkali metal salts such as lithium salts, sodium salts, potassium salts, etc.; alkaline earth metal salts such as calcium salts, strontium salts, barium salts, etc.; other metal salts such as manganese salts, copper salts, zinc salts, iron salts, cobalt salts, nickel salts, etc.; ammonium salts; guanidine salts, etc.); sodium fluorosulfonate (NaFSO ３ ), potassium fluorosulfonate (KFSO ３ ), magnesium fluorosulfonate (Mg(FSO ３ ) ２ fluorosulfonic acid compounds such as borates (e.g., B(C ２ O ４ ) ２ － ) etc.

[0041] When the non-aqueous electrolyte contains at least one additive selected from the group consisting of unsaturated cyclic carbonates, cyclic sulfonate esters, nitrile compounds, ester compounds, and fluorine-containing alkali metal salts, the total content of these additives may be 0.1% by mass or more and 10% by mass or less, or 0.3% by mass or more and 5% by mass or less. When the content of these additives is 0.1% by mass or more, the effects derived from the additives tend to be easily obtained, and when the content of these additives is 10% by mass or less, an increase in the viscosity of the non-aqueous electrolyte tends to be suppressed.

[0042] The non-aqueous electrolyte contains carbon dioxide (CO ２ ), carbon monoxide (CO), bicarbonate ion (HCO ３ － ) and carbonate ions (CO ３ ２－ ) may be dissolved in the solution.

[0043] The non-aqueous electrolyte solution is added with carbon dioxide (CO ２ ), carbon monoxide (CO), bicarbonate ion (HCO ３ － ) and carbonate ions (CO ３ ２－ When at least one selected from the group consisting of carbon dioxide (CO ２ ), carbon monoxide (CO), bicarbonate ion (HCO ３ － ) and carbonate ions (CO ３ ２－ The total dissolved amount of at least one selected from the group consisting of may be 20 ppm by mass or more, 100 ppm by mass or more, or 250 ppm by mass or more, and may be the saturated dissolved amount at 25°C or less.

[0044] <Applications> The nonaqueous electrolyte solution described above can be used as a nonaqueous electrolyte solution for a secondary battery. The nonaqueous electrolyte solution for a secondary battery according to this embodiment may be a nonaqueous electrolyte solution for an alkali metal ion secondary battery, a nonaqueous electrolyte solution for a lithium ion secondary battery or a sodium ion secondary battery, or a nonaqueous electrolyte solution for a lithium ion secondary battery.

[0045] When used as an electrolyte for a secondary battery (e.g., an alkali metal ion secondary battery), the nonaqueous electrolyte according to this embodiment can suppress self-discharge during high-temperature storage in the secondary battery. The ability to suppress self-discharge during high-temperature storage in a secondary battery may mean, for example, that the decrease in the open circuit voltage (OCV) of the cell after high-temperature storage is suppressed by 4% or more, 6% or more, 8% or more, 10% or more, 15% or more, 20% or more, 25% or more, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, or 80% or more, compared to a battery using an electrolyte that does not satisfy the requirements of the present invention. In this case, the high-temperature storage temperature may be, for example, 50°C to 120°C, 60°C to 110°C, 65°C to 105°C, or 70°C to 100°C, and 85°C is an example. The high-temperature storage period may be, for example, 10 days.

[0046] When used as an electrolyte for a secondary battery (e.g., an alkali metal ion secondary battery), the nonaqueous electrolyte according to this embodiment can suppress corrosion of a positive electrode current collector (e.g., aluminum foil) in the secondary battery. Suppression of corrosion of the positive electrode current collector in the secondary battery may mean, for example, that ions (e.g., aluminum ions) eluted due to corrosion are not detected in the electrolyte of the battery after charge / discharge, or the amount of ions detected is reduced. Detection of ions eluted due to corrosion may be performed, for example, by ICP.

[0047] <Battery> Another aspect of the present invention is a secondary battery including the nonaqueous electrolyte solution according to one embodiment of the present invention, a positive electrode having a positive electrode mixture layer and a positive electrode current collector, and a negative electrode having a negative electrode mixture layer and a negative electrode current collector. The secondary battery may be, for example, an alkali metal ion secondary battery, a lithium ion secondary battery, a sodium ion secondary battery, or a lithium ion secondary battery.

[0048] <Positive Electrode> The positive electrode of the secondary battery according to this embodiment has a positive electrode mixture layer and a positive electrode current collector. The positive electrode mixture layer is formed on the positive electrode current collector.

[0049] The positive electrode mixture layer of the secondary battery according to one embodiment contains at least one positive electrode active material selected from the group consisting of a positive electrode active material represented by the following formula (3), a positive electrode active material represented by the following formula (4), and a positive electrode active material represented by the following formula (5). ３ ｖ Ni ｘ Co ｙ Mn ｚ O （２＋ｗ） ... (3) M １ M ２ P.O. ４ ... (4) Li （１＋ｘ） Mn （１－ｙ－ｚ） Fe ｙ A ｚ P.O. ４ ...(5)

[0050] In formula (3), M ３ represents an alkali metal atom, and may be, for example, Li or Na, or may be Li.

[0051] In formula (3), v, x, y, z, and w are real numbers indicating the number of moles, and 0.2≦v≦1.2, 0.3≦x≦0.9, 0<y≦0.3, 0<z≦0.4, x+y+z=1, and −0.2≦w≦0.2.

[0052] In formula (3), v is preferably 0.5 or more and 1.2 or less, more preferably 0.8 or more and 1.1 or less, and further preferably 1.

[0053] In formula (3), w is preferably −0.1 or more and 0.1 or less, and more preferably 0.

[0054] The positive electrode active material represented by formula (3) is LiNi １／３ Co １／３ Mn １／３ O ２ , LiNi ０．８ Co ０．１ Mn ０．１ O ２ , LiNi ０．６ Co ０．２ Mn ０．２ O ２ , or LiNi ０．７ Co ０．２ Mn ０．１ O ２is preferred, and LiNi １／３ Co １／３ Mn １／３ O ２ , LiNi ０．８ Co ０．１ Mn ０．１ O ２ , or LiNi ０．６ Co ０．２ Mn ０．２ O ２ is more preferred.

[0055] In formula (4), M １ represents an alkali metal atom. １ may be Li or Na, or may be Li.

[0056] In formula (4), M ２ represents Ni, Mn, Co, or Fe. In other words, in formula (4), M ２ is a transition metal, the transition metal being selected from the group consisting of Ni (nickel), Mn (manganese), Co (cobalt), and Fe (iron).

[0057] The positive electrode active material represented by formula (4) is LiFePO ４ , LiNiPO ４ , LiMnPO ４ or LiCoPO ４ It may be: M １ M ２ P.O. ４ The positive electrode active material represented by ４ may be.

[0058] In formula (5), x, y, and z are real numbers indicating the number of moles, and −0.1<x<0.1, 0<y<1.0, 0≦z<0.1, and 0<1−y−z.

[0059] In formula (5), A represents at least one atom selected from the group consisting of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Ni, Co, Ga, Sn, Sb, Nb, and Ge. When A represents two or more atoms, 0≦z<0.1 means that the sum of the real numbers representing the mole numbers of the respective atoms is 0≦z<0.1. For example, when A is Zn and Al, the positive electrode active material represented by formula (5) is Li （１＋ｘ）Mn(1-y-z1-z2)Fe ｙ Zn ｚ１ Al ｚ２ P.O. ４ where x, y, z1, and z2 are real numbers indicating the number of moles, and are -0.1<x<0.1, 0<y<1.0, 0≦z1, 0≦z2, 0≦z1+z2<0.1, and 0<1-y-z1-z2.

[0060] The positive electrode active material represented by formula (5) is LiMn ０．００５ Fe ０．９９５ P.O. ４ , LiMn ０．１ Fe ０．９ P.O. ４ , LiMn ０．３ Fe ０．７ P.O. ４ , LiMn ０．７ Fe ０．３ P.O. ４ or LiMn ０．８５ Fe ０．１５ P.O. ４ Li （１＋ｘ） Mn （１－ｙ－ｚ） Fe ｙ A ｚ P.O. ４ The positive electrode active material represented by ０．７ Fe ０．３ P.O. ４ may be.

[0061] The positive electrode mixture layer preferably contains at least one positive electrode active material selected from the group consisting of a positive electrode active material represented by the following formula (4-1) and a positive electrode active material represented by the following formula (5-1): M １ M ２ P.O. ４ ...(4-1) [In formula (4-1), M １ represents an alkali metal atom, M ２ represents Ni, Mn, or Fe.] Li （１＋ｘ） Mn （１－ｙ－ｚ） Fe ｙ A ｚ P.O. ４...(5-1) [In formula (5-1), x, y, and z are real numbers indicating the number of moles, -0.1<x<0.1, 0<y<1.0, 0≦z<0.1, and 0<1-y-z, and A represents at least one atom selected from the group consisting of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Ni, Ga, Sn, Sb, Nb, and Ge.]

[0062] From the viewpoint of improving the output characteristics and electrical characteristics of the secondary battery according to this embodiment, the content of the positive electrode active material in the positive electrode composite layer is preferably 75% by mass or more and 99% by mass or less, and more preferably 85% by mass or more and 95% by mass or less.

[0063] The positive electrode mixture layer may further contain a conductive additive such as carbon black (e.g., ketjen black or acetylene black), carbon fiber, or graphite, with acetylene black and graphite being preferred.

[0064] From the viewpoint of improving the output characteristics and electrical characteristics of the secondary battery according to this embodiment, the content of the conductive additive in the positive electrode mixture layer is preferably 0.5% by mass or more and 20% by mass or less, and more preferably 1% by mass or more and 5% by mass or less.

[0065] The positive electrode mixture layer may further contain a binder. Examples of the binder include fluorine-based resins such as polyvinylidene fluoride, polyvinylidene fluoride, and polytetrafluoroethylene; synthetic rubbers such as styrene-butadiene rubber and nitrile butadiene rubber; polyamide-based resins such as polyamideimide; polyolefin-based resins such as polyethylene and polypropylene; poly(meth)acrylic resins; polyacrylic acid; and cellulose-based resins such as carboxymethyl cellulose, with polyvinylidene fluoride being preferred.

[0066] The content of the binder in the positive electrode mixture layer is preferably 0.5% by mass or more and 20% by mass or less, and more preferably 1% by mass or more and 5% by mass or less.

[0067] The positive electrode mixture layer may further contain other components as necessary. Examples of other components include polymers such as non-fluorinated polymers such as (meth)acrylic polymers, nitrile polymers, and diene polymers, and fluorinated polymers such as polytetrafluoroethylene; emulsifiers such as anionic emulsifiers, nonionic emulsifiers, and cationic emulsifiers; dispersants such as polymer dispersants such as styrene-maleic acid copolymers and polyvinylpyrrolidone; thickeners such as carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, polyacrylic acid (salts), and alkali-soluble (meth)acrylic acid-(meth)acrylic acid ester copolymers; and preservatives.

[0068] The content of the other components in the positive electrode mixture layer may be 0% by mass or more and 15% by mass or less, or may be 0% by mass or more and 10% by mass or less.

[0069] Examples of the positive electrode current collector include iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, and platinum, with aluminum being preferred.

[0070] The positive electrode is not particularly limited and can be produced by a known method. For example, the positive electrode may be produced by dispersing a positive electrode active material, a conductive additive, and a binder in a solvent to form a slurry, applying the slurry to a positive electrode current collector, drying the slurry, and then performing roll pressing.

[0071] Examples of the solvent include N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methyl ethyl ketone, tetrahydrofuran, acetonitrile, acetone, ethanol, ethyl acetate, and water, with N-methylpyrrolidone being preferred.

[0072] <Negative Electrode> The negative electrode of the secondary battery according to this embodiment has a negative electrode mixture layer and a negative electrode current collector. The negative electrode mixture layer is formed on the negative electrode current collector.

[0073] The negative electrode mixture layer may contain, as a negative electrode active material, graphite such as artificial graphite or natural graphite, a mesophase fired body made from coal or petroleum pitch, a carbon material such as non-graphitizable carbon, Si-based negative electrode materials such as Si, Si alloys, and SiO, Sn-based negative electrode materials such as Sn alloys, lithium metal, lithium alloys such as lithium-aluminum alloys, and the like, and preferably contains graphite.

[0074] The content of the negative electrode active material in the negative electrode mixture layer is preferably 80% by mass or more and 99% by mass or less, and more preferably 90% by mass or more and 98% by mass or less.

[0075] The negative electrode mixture layer may further contain a conductive additive. The conductive additive may be the same as that in the positive electrode mixture layer, and is preferably carbon fiber. The content of the conductive additive in the negative electrode mixture layer is preferably 0.1% by mass or more and 10% by mass or less, and more preferably 1% by mass or more and 5% by mass or less.

[0076] The negative electrode mixture layer may further contain a binder. The binder may be the same as that in the positive electrode mixture layer, and is preferably styrene-butadiene rubber or carboxymethyl cellulose. The content of the binder in the negative electrode mixture layer is preferably 0.1% by mass or more and 10% by mass or less, and more preferably 1% by mass or more and 5% by mass or less.

[0077] The negative electrode mixture layer may further contain other components as necessary. The other components may be the same as those in the positive electrode mixture layer. The content of the other components in the negative electrode mixture layer may be the same as that in the positive electrode mixture layer.

[0078] The negative electrode current collector may be the same as the positive electrode current collector, and is preferably made of copper.

[0079] The negative electrode can be produced by any known method without any particular limitation, for example, it may be produced in the same manner as the positive electrode, and in this case, the solvent is preferably water.

[0080] <Separator> The secondary battery according to this embodiment may include a separator. The separator is disposed to separate the positive electrode from the negative electrode. Examples of the separator include a porous sheet made of a polymer capable of absorbing and retaining a non-aqueous electrolyte (e.g., a polyolefin-based microporous separator, a cellulose-based separator, etc.), a nonwoven fabric separator, a porous metal body, etc. Examples of materials for the porous sheet include polyethylene, polypropylene, and a laminate having a three-layer structure of polypropylene / polyethylene / polypropylene. Examples of materials for the nonwoven fabric separator include cotton, rayon, acetate, nylon, polyester, polypropylene, polyethylene, polyimide, aramid, glass, etc. A porous sheet made of polyethylene is preferred as the separator.

[0081] <Battery Exterior Material> The secondary battery according to this embodiment may be housed in a battery exterior material. The material of the battery exterior material is not particularly limited, and any conventionally known exterior material may be used. If necessary, the battery exterior material may contain an expanded metal, a fuse, an overcurrent prevention element such as a PTC element, a lead plate, or the like, to prevent pressure buildup inside the battery and overcharging and discharging.

[0082] The shape of the secondary battery according to this embodiment is not particularly limited, and may be any known shape, such as a cylindrical shape, a square shape, a laminated shape, a coin shape, or a large shape.

[0083] The rated charging voltage of the secondary battery according to this embodiment is not particularly limited, but from the viewpoint of increasing the energy density, it may be 3.6 V or more, or 4.2 V or more. From the viewpoint of increasing safety, the rated charging voltage may be 4.6 V or less.

[0084] <Method for suppressing self-discharge of secondary battery during high-temperature storage> Another aspect of the present invention is a method for suppressing self-discharge of a secondary battery including a non-aqueous electrolyte solution containing a hexafluorophosphate during high-temperature storage, the method comprising further containing a compound of formula (1) in the non-aqueous electrolyte solution.

[0085] In the method according to this embodiment, the non-aqueous electrolyte solution further containing the compound of formula (1) may be the same as the non-aqueous electrolyte solution according to one embodiment with respect to components other than the compound of formula (1). The compound of formula (1) may be further contained by, for example, further adding the compound of formula (1) to a non-aqueous electrolyte solution containing a hexafluorophosphate salt. Furthermore, the compound of formula (1) may be further contained by, for example, adding the hexafluorophosphate salt and other components to a non-aqueous solvent in which the compound of formula (1) has been dissolved in advance.

[0086] In the method according to the present embodiment, the non-aqueous electrolyte containing hexafluorophosphate may further contain a salt containing an anion of formula (2). When the non-aqueous electrolyte contains hexafluorophosphate and a salt containing an anion of formula (2), the addition of the compound of formula (1) can more effectively suppress self-discharge during high-temperature storage. When the non-aqueous electrolyte contains hexafluorophosphate and a salt containing an anion of formula (2), the content of the salt containing an anion of formula (2) may be the same as that of the non-aqueous electrolyte according to an embodiment. When the non-aqueous electrolyte contains hexafluorophosphate and a salt containing an anion of formula (2), the content ratio of the two may be the same as that of the non-aqueous electrolyte according to an embodiment.

[0087] In the method according to this embodiment, the type of the formula (1) compound further contained in the non-aqueous electrolyte is the same as the formula (1) compound according to the non-aqueous electrolyte according to one embodiment. The amount of the formula (1) compound further contained in the non-aqueous electrolyte may be, for example, such that the content of the formula (1) compound is 0.0005% by mass to 1.0% by mass, 0.001% by mass to 0.8% by mass, 0.003% by mass to 0.5% by mass, 0.005% by mass to 0.1% by mass, or 0.01% by mass to 0.1% by mass, based on the total amount of the non-aqueous electrolyte. When the content of the formula (1) compound is within the above range, self-discharge during high-temperature storage in the secondary battery is more unlikely to occur. An example of the content of the formula (1) compound that is more unlikely to cause self-discharge during high-temperature storage is 0.001% by mass to 0.1% by mass. The amount of the compound of formula (1) further contained in the non-aqueous electrolyte solution may be 0.001 to 100 parts by mass, 0.002 to 50 parts by mass, 0.1 to 30 parts by mass, 0.3 to 25 parts by mass, or 0.5 to 20 parts by mass, relative to 100 parts by mass of the hexafluorophosphate. When the amount of the compound of formula (1) contained relative to the hexafluorophosphate is within the above range, the secondary battery is less likely to self-discharge during high-temperature storage.

[0088] In the method according to this embodiment, the secondary battery may be the same as the secondary battery according to one embodiment of the present invention, for example, the secondary battery may be a lithium ion battery.

[0089] The method according to this embodiment may be a method for suppressing self-discharge during high-temperature storage while suppressing corrosion of the positive electrode current collector in a secondary battery including a nonaqueous electrolyte solution containing hexafluorophosphate.

[0090] The method according to the present embodiment may suppress self-discharge during high-temperature storage, as described above for the secondary battery using the nonaqueous electrolyte according to the embodiment. The method according to the present embodiment may suppress corrosion of the positive electrode current collector, as described above for the secondary battery using the nonaqueous electrolyte according to the embodiment.

[0091] The present invention will be described in more detail below using examples, but the present invention is not limited to the following examples.

[0092] Test Example 1: Fabrication and Evaluation of Lithium-ion Secondary Battery Including NCM111 Positive Electrode / Gr Negative Electrode Cell In Test Example 1, a lithium-ion secondary battery including a cell made from a positive electrode (NCM111 positive electrode) containing nickel, cobalt, and manganese in a molar ratio of 1:1:1 and a negative electrode (Gr negative electrode) based on graphite was fabricated and evaluated.

[0093] (Fabrication of Positive Electrode) LiNi, a ternary positive electrode active material １／３ Co １／３ Mn １／３ O ２ (manufactured by Umicore), acetylene black (AB, manufactured by Denka Co., Ltd., product name: Denka Black (registered trademark)), graphite (manufactured by Nippon Graphite Industries Co., Ltd., product number: SP270), and polyvinylidene fluoride (PVdF, manufactured by Kureha Corporation, product number: KF1120) were dispersed in N-methyl-2-pyrrolidone (NMP) to prepare a positive electrode mixture slurry (positive electrode active material: AB: graphite: PVdF = 93:3:3:3 (solid content mass ratio)). Subsequently, the obtained positive electrode mixture slurry was applied to an aluminum foil (positive electrode current collector, manufactured by Nippon Foil Co., Ltd., thickness 15 μm) so that the coating weight after drying was 19.4 mg / cm ２ The mixture was coated on one side with an applicator so that the density was 3.1 g / cm 3 and dried on a hot plate at 110° C. for 10 minutes. The mixture was further dried in a vacuum drying oven at 110° C. for 12 hours. Thereafter, the density was adjusted to 3.1 g / cm 3 using a roll press. ３ The mixture was pressed and molded until a sheet-like positive electrode was obtained.

[0094] (Preparation of Negative Electrode) First, lump natural graphite (manufactured by Hitachi Chemical Co., Ltd., product name: "SMG") and flake artificial graphite (manufactured by TIMCAL, product name: "SFG-15") were mixed in a mass ratio of 85:15 to obtain mixed graphite. An aqueous slurry having a composition (mass ratio) of mixed graphite:carbon fiber (VGCF):styrene butadiene rubber (SBR):carboxymethyl cellulose (CMC) = 100:2:1.5:1.5 was prepared. The obtained aqueous slurry was applied to a substrate having a coating weight of 10.8 mg / cm after drying. ２After drying, the density was 1.4 g / cm ３ The mixture was roll-pressed by pressure molding until the temperature reached 100°C, thereby preparing a negative electrode.

[0095] (Preparation of Electrolyte) The electrolyte was prepared by dissolving LiFSI (manufactured by Nippon Shokubai Co., Ltd.), LiPF in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 3:7 (EC / EMC=3 / 7 (vol / vol) mixed solvent, referred to as "EC / EMC" in the table) or a mixed solvent of ethylene carbonate (EC) and propyl propionate (PP) at a volume ratio of 3:7 (EC / PP=3 / 7 (vol / vol) mixed solvent, referred to as "EC / PP" in the table) to give the salt concentrations shown in Tables 1 and 2. ６ (Kishida Chemical Co., Ltd.), FSO ２ NH ２ (Nippon Shokubai Co., Ltd.) and FSO ２ NHCH ３ In the batteries described in Table 1 (Examples 1-1 to 1-36 and Comparative Example 1-3), the electrolyte solution contained FSO 4 as the compound of formula (1). ２ NH ２ In addition, in the batteries shown in Table 2 (Comparative Examples 2-1 to 2-36 and Comparative Example 2-3), the electrolyte solution contains FSO as the compound of formula (1). ２ NHCH ３ Includes.

[0096] (Fabrication of Battery) The fabricated positive electrode was placed in a battery with an effective area of ​​12 cm ２ The negative electrode was cut at 13.44 cm², and a polarity lead was welded to the cut positive electrode using an ultrasonic welder. ２The battery was cut into pieces, and a polarity lead was welded to the ultrasonically cut negative electrode. The positive and negative electrodes were placed opposite each other with a 25 μm thick polyethylene separator interposed between them, and the three sides were sealed with a laminate exterior. 700 μL of electrolyte solution with the salt concentration shown in Tables 1 and 2 was added to the unsealed side. After the electrolyte was injected, the battery was pre-charged at 0.2 C (6 mA) for 2 hours in an unsealed state. It was then vacuum sealed and left at room temperature for 3 days. It was then charged at 0.5 C (15 mA) and 4.2 V for 5 hours, and then discharged at 0.2 C (6 mA) to a final voltage of 2.75 V. One piece of the battery laminate was opened and vacuum sealed again to degas the battery. After degassing, the battery was charged and discharged under the following conditions to condition the cell. <Conditioning conditions> 1st cycle: Charge: 3mA, 4.2V constant current / constant voltage charge, terminated at 0.3mA ⇒ Discharge: 6mA discharge, terminated at 2.75V 2nd cycle: Charge: 6mA, 4.2V constant current / constant voltage charge, terminated at 0.6mA ⇒ Discharge: 6mA discharge, terminated at 2.75V 3rd cycle: Charge: 6mA, 4.2V constant current / constant voltage charge, terminated at 0.6mA ⇒ Discharge: 30mA discharge, terminated at 2.75V

[0097] (OCV Measurement After High-Temperature Storage) The conditioned cell was charged at room temperature with a constant current and constant voltage of 1 C (30 mA) and a termination of 0.02 C (0.6 mA) at 4.2 V, fully charged, and then stored at 85° C. for 10 days. The open circuit voltage (OCV) of the cell was measured before and after storage. The results are shown in Tables 1 and 2.

[0098] (Confirmation of Aluminum Dissolution) After measuring the OCV, the batteries were subjected to constant current discharge at 25°C at 0.6 mA (0.02 C) with a cutoff voltage of 2.75 V. After discharge, the cells were disassembled in a glove box, and the negative electrodes were washed with MEC and dried. The negative electrodes from which the copper foil had been removed were immersed in nitric acid for 24 hours to dissolve them. Each of the resulting nitric acid solutions was filtered and diluted with ultrapure water, and the diluted solutions were analyzed by ICP to determine whether aluminum was detected. The results are shown in Tables 1 and 2.

[0099]

[0100]

[0101] According to the results in Tables 1 and 2, the non-aqueous electrolyte solution is LiPF ６ In the lithium ion secondary batteries according to Examples 1-1 to 1-36 and 2-1 to 2-36 containing the compound of formula (1), the decrease in OCV from 4.2 V after high-temperature storage was significantly suppressed, and self-discharge during high-temperature storage was significantly suppressed, compared to the lithium ion secondary batteries according to Comparative Examples 1-1, 1-2, 2-1 and 2-2 in which the non-aqueous electrolyte solution did not contain the compound of formula (1).

[0102] Furthermore, according to the results in Tables 1 and 2, the non-aqueous electrolyte is LiPF ６ In the lithium ion secondary batteries according to Examples 1-1 to 1-36 and 2-1 to 2-36 containing the compound of formula (1), no aluminum elution was observed in the positive electrode current collector. ６ In the lithium ion secondary batteries according to Examples 1-1 to 1-36 and 2-1 to 2-36 containing the compound of formula (1), the decrease in OCV from 4.2 V was significantly suppressed, and self-discharge during high-temperature storage was significantly suppressed, compared to the lithium ion secondary batteries according to Comparative Examples 1-2, 1-3, 2-2 and 2-3 in which the nonaqueous electrolyte solution contained LiFSI alone as the electrolyte.

[0103] Test Example 2: Preparation and evaluation of lithium ion secondary battery including NCM811 positive electrode / SiO&Gr mixed negative electrode cell In Test Example 2, a lithium ion secondary battery including a cell made from a positive electrode (NCM811 positive electrode) containing nickel, cobalt, and manganese in a molar ratio of 8:1:1 and a negative electrode (SiO&Gr mixed negative electrode) based on silicon oxide and graphite was prepared and evaluated.

[0104] (Fabrication of Positive Electrode) LiNi, a ternary positive electrode active material ０．８ Co ０．１ Mn ０．１ O ２(Beijing Dangsheng), acetylene black (AB, Denka Co., Ltd., product name: Denka Black (registered trademark)), graphite (Nippon Graphite Industries Co., Ltd., product number: SP270), and polyvinylidene fluoride (PVdF, Kureha Corporation, product number: KF1120) were dispersed in N-methyl-2-pyrrolidone (NMP) to prepare a positive electrode mixture slurry (positive electrode active material: AB: graphite: PVdF = 93:3:3:3 (solid content mass ratio)). Subsequently, the obtained positive electrode mixture slurry was applied to an aluminum foil (positive electrode current collector, Nippon Foil Co., Ltd., thickness 15 μm) so that the coating weight after drying was 19.4 mg / cm ２ The mixture was coated on one side with an applicator so that the density was 3.1 g / cm 3 and dried on a hot plate at 110° C. for 10 minutes. The mixture was further dried in a vacuum drying oven at 110° C. for 12 hours. Thereafter, the density was adjusted to 3.1 g / cm 3 using a roll press. ３ The mixture was pressed and molded until a sheet-like positive electrode was obtained.

[0105] (Preparation of negative electrode) As a negative electrode active material, silicon oxide (SiO 2 ) / graphite composite material (manufactured by BTR, product number: BSO-600), conductive additive (manufactured by Showa Denko K.K., product number: VGCF-H (registered trademark) and manufactured by Imerys, product number: Super-P (registered trademark)), styrene-butadiene rubber (SBR, binder) and carboxymethyl cellulose (CMC, binder) were dispersed in ultrapure water to prepare a negative electrode mixture slurry (negative electrode active material: VGCF: Super-P: SBR: CMC = 90: 2: 3: 3: 2 (solid content mass ratio)). Subsequently, the obtained negative electrode mixture slurry was applied to a copper foil (negative electrode current collector, manufactured by Fukuda Metal Foil and Powder Co., Ltd., thickness 15 μm) so that the coating weight after drying was 6.8 mg / cm ２ The mixture was coated on one side with an applicator so that the density was 1.3 g / cm 3 and dried on a hot plate at 80°C for 10 minutes. The mixture was then dried in a vacuum drying oven at 100°C for 12 hours. Thereafter, the density was adjusted to 1.3 g / cm 3 using a roll press. ３ The mixture was pressed and molded until a sheet-like negative electrode was obtained.

[0106] (Preparation of Electrolyte) The electrolyte was prepared by dissolving LiFSI (manufactured by Nippon Shokubai Co., Ltd.), LiPF in an EC / fluoroethylene carbonate (FEC) / EMC = 2 / 1 / 7 (vol / vol) mixed solvent (referred to as "EC / FEC / EMC" in the tables) or an EC / PP = 3 / 7 (vol / vol) mixed solvent (referred to as "EC / PP" in the tables) to give the salt concentrations shown in Tables 3 and 4. ６ (Kishida Chemical Co., Ltd.) and FSO ２ NH ２ The solution was prepared by dissolving vinylene carbonate (VC, manufactured by Kishida Chemical Co., Ltd.), 1,3-propane sultone (manufactured by Aldrich Chemical Co., Ltd.), dimethyl 2,5-dioxahexanedioate (manufactured by Tokyo Chemical Industry Co., Ltd.), lithium tetrafluoroborate (LiBF ４ , manufactured by Kishida Chemical Co., Ltd.), lithium difluoro(oxalate)borate (LiBF ２ Ox, manufactured by Kishida Chemical Co., Ltd.), lithium difluorophosphate (LiPO ２ F ２ , manufactured by Kishida Chemical Co., Ltd.), lithium difluorobis(oxalate)phosphate (LiPF ２ (Ox) ２ ) or lithium fluorosulfonate (FSO ３ Li, manufactured by Nippon Shokubai Co., Ltd.) was used.

[0107] (Preparation of battery) The positive and negative electrodes were placed in a 13.44 cm ２The battery was cut into pieces, and the polarity leads were ultrasonically welded. Then, a 20 μm polyethylene (PE) separator was placed between the two pieces, and the three sides were sealed with a laminate exterior. 700 μL of electrolyte solution with the salt concentration shown in Tables 3 and 4 was added to one of the unsealed sides. After the electrolyte was added, the battery was precharged at 0.2 C (6 mA) for 2 hours in an unsealed state. It was then vacuum-sealed and left at room temperature for 3 days. It was then charged at 0.5 C (15 mA) for 5 hours at 4.2 V, and then discharged at 0.2 C (6 mA) until the end of the discharge, at 2.75 V. One piece of the battery laminate was cleaved and vacuum-sealed again to allow for degassing. The degassed battery was charged and discharged under the following conditions to condition the cell. <Conditioning conditions> 1st cycle: Charge: 3mA, 4.2V constant current / constant voltage charge, terminated at 0.3mA ⇒ Discharge: 6mA discharge, terminated at 2.75V 2nd cycle: Charge: 6mA, 4.2V constant current / constant voltage charge, terminated at 0.6mA ⇒ Discharge: 6mA discharge, terminated at 2.75V 3rd cycle: Charge: 6mA, 4.2V constant current / constant voltage charge, terminated at 0.6mA ⇒ Discharge: 30mA discharge, terminated at 2.75V

[0108] (OCV Measurement After High-Temperature Storage) The conditioned cells were charged at room temperature with a constant current and constant voltage of 1 C (30 mA) and a termination current of 0.02 C (0.6 mA) at 4.2 V, fully charged, and stored at 85° C. for 10 days. The open circuit voltage (OCV) of the cells was measured before and after storage. The results are shown in Tables 3 and 4.

[0109] (Confirmation of Aluminum Dissolution) After measuring the OCV, the batteries were subjected to constant current discharge at 25°C at 0.6 mA (0.02 C) with a cutoff voltage of 2.75 V. After discharge, the cells were disassembled in a glove box, and the negative electrodes were washed with MEC and dried. The negative electrodes from which the copper foil had been removed were immersed in nitric acid for 24 hours to dissolve them. Each of the resulting nitric acid solutions was filtered and diluted with ultrapure water, and the diluted solutions were analyzed by ICP to determine whether aluminum was detected. The results are shown in Tables 3 and 4.

[0110]

[0111]

[0112] According to the results in Table 3, the non-aqueous electrolyte is LiPF ６ In the lithium ion secondary batteries according to Examples 3-1 to 3-36 containing the compound of formula (1), the decrease in OCV from 4.2 V after high-temperature storage was significantly suppressed, and self-discharge during high-temperature storage was significantly suppressed, compared to the lithium ion secondary batteries according to Comparative Examples 3-1 and 3-2 in which the non-aqueous electrolyte solution did not contain the compound of formula (1).

[0113] Furthermore, according to the results in Table 3, the non-aqueous electrolyte is LiPF ６ In the lithium ion secondary batteries according to Examples 3-1 to 3-36 containing the compound of formula (1), no aluminum elution was observed in the positive electrode current collector. ６ In the lithium ion secondary batteries according to Examples 3-1 to 3-36 containing the compound of formula (1), the decrease in OCV from 4.2 V was significantly suppressed, and self-discharge during high-temperature storage was significantly suppressed, compared to the lithium ion secondary batteries according to Comparative Examples 3-2 and 3-3 in which the nonaqueous electrolyte solution contained LiFSI alone as the electrolyte.

[0114] Furthermore, according to the results of Table 4, the lithium ion secondary batteries according to Examples 4-1 to 4-18, in which the nonaqueous electrolyte solution further contained various additives, exhibited suppressed self-discharge during high-temperature storage to the same extent as the lithium ion secondary batteries according to Examples 3-15 and 3-19, in which the nonaqueous electrolyte solution had the same composition except that it did not contain the various additives, and no elution of aluminum was observed in the positive electrode current collector.

[0115] Test Example 3: Fabrication and evaluation of lithium ion secondary battery including LFP positive electrode / Gr negative electrode cell In Test Example 3, a lithium ion secondary battery including a cell made from a positive electrode containing lithium iron phosphate (LFP positive electrode) and a negative electrode based on graphite (Gr negative electrode) was fabricated and evaluated.

[0116] (Preparation of Positive Electrode) Commercially available LiFePO as a positive electrode active material ４, acetylene black (HS-100), and PVdF (Kureha #L7208) were weighed in a composition ratio (mass ratio) of 100:9:6 and dispersed in NMP to prepare a slurry. The obtained slurry was coated on one side of an aluminum foil (coating weight 20.20 mg / cm). ２ ), dried, and roll-pressed to prepare a positive electrode.

[0117] (Preparation of Negative Electrode) First, agglomerated natural graphite (manufactured by Hitachi Chemical Co., Ltd., product name: "SMG") and flake artificial graphite (manufactured by TIMCAL, product name: "SFG-15") were mixed in a mass ratio of 85:15 to obtain a mixed graphite. An aqueous slurry having a composition (mass ratio) of mixed graphite:VGCF:SBR:CMC=100:2:1.5:1.5 was prepared, and the slurry was applied to a copper foil at a coating weight of 8.8 mg / cm. ２ The mixture was coated with the solvent, dried, and roll-pressed to prepare a negative electrode.

[0118] (Preparation of Electrolyte) The electrolyte was prepared by dissolving LiFSI, LiPF in an EC / EMC=3 / 7 (vol / vol) mixed solvent (referred to as "EC / EMC" in the table) or an EC / PP=3 / 7 (vol / vol) mixed solvent (referred to as "EC / PP" in the table) to give the salt concentrations shown in Table 5. ６ and FSO ２ NH ２ was prepared by dissolving

[0119] (Fabrication of Battery) The fabricated positive electrode was placed in a battery with an effective area of ​​12 cm ２ The negative electrode was cut at 13.44 cm², and a polarity lead was welded to the cut positive electrode using an ultrasonic welder. ２The battery was then cut into 1 / 4" pieces, and a polarity lead was welded to the ultrasonically cut negative electrode. The positive and negative electrodes were placed opposite each other with a 25 μm thick polyethylene separator interposed between them, and the three sides were sealed with a laminate exterior. 700 μL of electrolyte solution with the salt concentration shown in Table 5 was added to the unsealed side. After the battery was charged at a constant current of 5 mA for 3 hours, one piece was cleaved and resealed in a vacuum to degas the battery. After degassing, the cell was stored at 25°C for 48 hours and then charged and discharged under the following conditioning conditions to complete the evaluation battery. <Conditioning conditions> 1st cycle: Charge: 2.5mA, 3.6V constant current / constant voltage charge, terminated at 0.25mA ⇒ Discharge: 5mA discharge, terminated at 2.0V 2nd cycle: Charge: 2.5mA, 3.6V constant current / constant voltage charge, terminated at 0.5mA ⇒ Discharge: 5mA discharge, terminated at 2.0V 3rd cycle: Charge: 2.5mA, 3.6V constant current / constant voltage charge, terminated at 0.5mA ⇒ Discharge: 25mA discharge, terminated at 2.0V

[0120] (Measurement of Self-Discharge Capacity Rate After High-Temperature Storage) Using the obtained evaluation battery, OCV measurements were performed before and after high-temperature storage using the following method. The evaluation battery was charged and discharged under the following conditions (25°C), and the discharge capacity before storage was confirmed. Charging: Constant current / constant voltage charging at 3.6 V and 25 mA, with a 0.5 mA termination ⇒ Constant current discharging: 2.5 mA, 2.0 V termination. For high-temperature storage, the cell after discharge capacity confirmation was subjected to constant current / constant voltage charging at 1 C (25 mA) at room temperature and 0.02 C (0.5 mA) termination at 3.6 V. After fully charging, the cell was stored at 85°C for 10 days. The discharge capacity after storage was determined by constant current discharging at 25°C and 2.5 mA with a 2.0 V termination. The self-discharge amount (%) after high-temperature storage was calculated as the self-discharge capacity rate after 10 days of storage at 85°C using the following formula. The results are shown in Table 5. 100 × {(discharge capacity before storage) − (discharge capacity after storage)} / (discharge capacity before storage)

[0121] (Confirmation of Aluminum Dissolution) After measuring the self-discharge rate, the battery was subjected to a constant current discharge of 0.5 mA (0.02 C) at 25°C with a cutoff voltage of 2.0 V. The discharged cell was disassembled in a glove box, and the negative electrode was washed with MEC and dried. The negative electrode from which the copper foil had been removed was immersed in nitric acid for 24 hours to dissolve it. Each of the resulting nitric acid solutions was filtered and diluted with ultrapure water, and the diluted solution was analyzed by ICP to determine whether aluminum was detected. The results are shown in Table 5.

[0122]

[0123] According to the results in Table 5, the non-aqueous electrolyte is LiPF ６ The lithium ion secondary batteries according to Examples 5-1 to 5-36 containing the compound of formula (1) had suppressed self-discharge during high-temperature storage compared to the lithium ion secondary batteries according to Comparative Examples 5-1 and 5-2 in which the non-aqueous electrolyte solution did not contain the compound of formula (1).

[0124] Furthermore, according to the results in Table 5, the non-aqueous electrolyte is LiPF ６ In the lithium ion secondary batteries according to Examples 5-1 to 5-36 containing the compound of formula (1), no aluminum elution was observed in the positive electrode current collector. ６ The lithium ion secondary batteries according to Examples 5-1 to 5-36 containing the compound of formula (1) had significantly reduced self-discharge during high-temperature storage compared to the lithium ion secondary batteries according to Comparative Examples 5-2 and 5-3 in which the nonaqueous electrolyte solution contained LiFSI alone as the electrolyte.

[0125] Test Example 4: Preparation and evaluation of lithium ion secondary battery including LMFP positive electrode / Gr negative electrode cell In Test Example 4, a lithium ion secondary battery including a cell made from a positive electrode containing lithium manganese iron phosphate (LMFP positive electrode) and a negative electrode (Gr negative electrode) based on graphite was prepared and evaluated.

[0126] (Preparation of Positive Electrode) Commercially available LiMn ０．７ Fe ０．３ P.O. ４, acetylene black (HS-100), and PVdF (Kureha #L7208) were weighed in a composition ratio (mass ratio) of 100:9:6 and dispersed in NMP to prepare a slurry. The obtained slurry was coated on one side of an aluminum foil (coating weight 20.20 mg / cm). ２ ), dried, and roll-pressed to prepare a positive electrode.

[0127] (Preparation of Negative Electrode) First, agglomerated natural graphite (manufactured by Hitachi Chemical Co., Ltd., product name: "SMG") and flake artificial graphite (manufactured by TIMCAL, product name: "SFG-15") were mixed in a mass ratio of 85:15 to obtain a mixed graphite. An aqueous slurry having a composition (mass ratio) of mixed graphite:VGCF:SBR:CMC=100:2:1.5:1.5 was prepared, and the slurry was applied to a copper foil at a coating weight of 8.8 mg / cm. ２ The mixture was coated with the solvent, dried, and roll-pressed to prepare a negative electrode.

[0128] (Preparation of Electrolyte) The electrolyte was prepared by dissolving LiFSI, LiPF in an EC / EMC=3 / 7 (vol / vol) mixed solvent (referred to as "EC / EMC" in the table) or an EC / PP=3 / 7 (vol / vol) mixed solvent (referred to as "EC / PP" in the table) to give the salt concentrations shown in Table 6. ６ and FSO ２ NH ２ was prepared by dissolving

[0129] (Fabrication of Battery) The fabricated positive electrode was placed in a battery with an effective area of ​​12 cm ２ The negative electrode was cut at 13.44 cm², and a polarity lead was welded to the cut positive electrode using an ultrasonic welder. ２The battery was then cut into 1 / 4" pieces, and a polarity lead was welded to the ultrasonically cut negative electrode. The positive and negative electrodes were placed opposite each other with a 25 μm thick polyethylene separator interposed between them, and the three sides were sealed with a laminate exterior. 700 μL of electrolyte solution with the salt concentration shown in Table 6 was added to the unsealed side. After the battery was charged at a constant current of 5 mA for 3 hours, one piece was cleaved and resealed in a vacuum to degas the battery. After degassing, the cell was stored at 25°C for 48 hours and then charged and discharged under the following conditioning conditions to complete the evaluation battery. <Conditioning conditions> 1st cycle: Charge: 2.5mA, 4.2V constant current / constant voltage charge, terminated at 0.25mA ⇒ Discharge: 5mA discharge, terminated at 2.5V 2nd cycle: Charge: 2.5mA, 4.2V constant current / constant voltage charge, terminated at 0.5mA ⇒ Discharge: 5mA discharge, terminated at 2.5V 3rd cycle: Charge: 2.5mA, 4.2V constant current / constant voltage charge, terminated at 0.5mA ⇒ Discharge: 25mA discharge, terminated at 2.5V

[0130] (Measurement of Self-Discharge Capacity Rate After High-Temperature Storage) Using the obtained evaluation battery, OCV measurements were performed before and after high-temperature storage using the following method. The evaluation battery was charged and discharged under the following conditions (25°C), and the discharge capacity before storage was confirmed. Charging: Constant current / constant voltage charging at 3.6 V and 25 mA, with a 0.5 mA termination ⇒ Constant current discharging: 2.5 mA, 2.0 V termination. For high-temperature storage, the cell after discharge capacity confirmation was subjected to constant current / constant voltage charging at 1 C (25 mA) at room temperature and 0.02 C (0.5 mA) termination at 3.6 V, fully charged, and then stored at 85°C for 10 days. The discharge capacity after storage was determined by constant current discharging the battery after 10 days of storage at 25°C under conditions of 2.5 mA and 2.0 V termination. The self-discharge amount (%) after high-temperature storage was calculated as the self-discharge capacity rate after 10 days of storage at 85°C using the following formula. The results are shown in Table 6. 100 × {(discharge capacity before storage) − (discharge capacity after storage)} / (discharge capacity before storage)

[0131] (Confirmation of Aluminum Dissolution) After measuring the self-discharge rate, the battery was subjected to a constant current discharge of 0.5 mA (0.02 C) at 25°C with a cutoff voltage of 2.0 V. The discharged cell was disassembled in a glove box, and the negative electrode was washed with MEC and dried. The negative electrode from which the copper foil had been removed was immersed in nitric acid for 24 hours to dissolve it. Each of the resulting nitric acid solutions was filtered and diluted with ultrapure water, and the diluted solution was analyzed by ICP to determine whether aluminum was detected. The results are shown in Table 6.

[0132]

[0133] According to the results in Table 6, the non-aqueous electrolyte is LiPF ６ The lithium ion secondary batteries according to Examples 6-1 to 6-36 containing the compound of formula (1) had suppressed self-discharge during high-temperature storage compared to the lithium ion secondary batteries according to Comparative Examples 6-1 and 6-2 in which the non-aqueous electrolyte solution did not contain the compound of formula (1).

[0134] Furthermore, according to the results in Table 6, the non-aqueous electrolyte is LiPF ６ In the lithium ion secondary batteries according to Examples 6-1 to 6-36 containing the compound of formula (1), no aluminum elution was observed in the positive electrode current collector. ６ The lithium ion secondary batteries according to Examples 6-1 to 6-36 containing the compound of formula (1) had significantly reduced self-discharge during high-temperature storage compared to the lithium ion secondary batteries according to Comparative Examples 6-2 and 6-3 in which the nonaqueous electrolyte solution contained LiFSI alone as the electrolyte.

Claims

1. A non-aqueous electrolyte solution for a secondary battery, comprising a hexafluorophosphate salt, a compound represented by the following formula (1), and a non-aqueous solvent: FSO ２ NHR １ ...(1) [In formula (1), R １ represents a hydrogen atom or an optionally substituted hydrocarbon group having 1 to 18 carbon atoms.

2. The non-aqueous electrolyte according to claim 1, wherein the content of the compound represented by formula (1) is 0.001% by mass or more and 0.8% by mass or less based on the total amount of the non-aqueous electrolyte.

3. The nonaqueous electrolyte solution according to claim 1, further comprising a salt containing an anion represented by the following formula (2): N － (R ２ SO ２ ) (R ３ SO ２ )...(2) [In formula (2), R ２ and R ３ each independently represents a fluorine atom or an alkyl group having 1 to 6 carbon atoms which may be substituted with a fluorine atom.

4. The non-aqueous electrolyte according to claim 1, further comprising at least one additive selected from the group consisting of unsaturated cyclic carbonates, cyclic sulfonic acid esters, nitrile compounds, ester compounds and fluorine-containing alkali metal salts.

5. The nonaqueous electrolyte according to claim 1, wherein the secondary battery is a lithium ion secondary battery, and the hexafluorophosphate is lithium hexafluorophosphate.

6. A secondary battery comprising the nonaqueous electrolyte solution according to any one of claims 1 to 5, a positive electrode having a positive electrode mixture layer and a positive electrode current collector, and a negative electrode having a negative electrode mixture layer and a negative electrode current collector, wherein the positive electrode mixture layer contains at least one positive electrode active material selected from the group consisting of a positive electrode active material represented by the following formula (3), a positive electrode active material represented by the following formula (4), and a positive electrode active material represented by the following formula (5). M ３ ｖ Ni ｘ Co ｙ Mn ｚ O （２＋ｗ） ...(3) [In formula (3), M ３ represents an alkali metal atom, and v, x, y, z, and w are real numbers indicating the number of moles, where 0.2≦v≦1.2, 0.3≦x≦0.9, 0<y≦0.3, 0<z≦0.4, x+y+z=1, and −0.2≦w≦0.2.] M １ M ２ P.O. ４ ...(4) [In formula (4), M １ represents an alkali metal atom, M ２ represents Ni, Mn, Co or Fe.] Li （１＋ｘ） Mn （１－ｙ－ｚ） Fe ｙ A ｚ P.O. ４ ... (5) [In formula (5), x, y, and z are real numbers indicating the number of moles, -0.1<x<0.1, 0<y<1.0, 0≦z<0.1, and 0<1-y-z, and A represents at least one atom selected from the group consisting of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Ni, Co, Ga, Sn, Sb, Nb, and Ge.] 7. The secondary battery according to claim 6, wherein the positive electrode mixture layer contains at least one positive electrode active material selected from the group consisting of a positive electrode active material represented by the following formula (4-1) and a positive electrode active material represented by the following formula (5-1): M １ M ２ P.O. ４ ...(4-1) [In formula (4-1), M １ represents an alkali metal atom, M ２ represents Ni, Mn, or Fe.] Li （１＋ｘ） Mn （１－ｙ－ｚ） Fe ｙ A ｚ P.O. ４ ...(5-1) [In formula (5-1), x, y, and z are real numbers indicating the number of moles, -0.1<x<0.1, 0<y<1.0, 0≦z<0.1, and 0<1-y-z, and A represents at least one atom selected from the group consisting of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Ni, Ga, Sn, Sb, Nb, and Ge.] 8. The secondary battery according to claim 6, wherein the positive electrode current collector is made of aluminum.

9. The secondary battery according to claim 6, which is a lithium ion secondary battery.

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