Nonaqueous electrolyte battery

Abstract

The purpose of the present invention is to provide a nonaqueous electrolyte that contains a sulfonylimide compound having excellent storage stability in a high-temperature environment. The present invention is a nonaqueous electrolyte characterized by containing a sulfonylimide compound represented by M1N(R1SO2)(R2SO2) (formula 1) (where M1 represents an alkali metal atom, R1 and R2 are the same or different, and represent a fluorine atom, a C1–6 alkyl group, or a C1–6 fluoroalkyl group), and a compound represented by formula (2) (where: R3 to R5 are the same or different, and represent a C1–14 hydrocarbon group, a hydrogen atom, or a halogen atom; and n represents an integer of 2–6).

Description

Non-aqueous electrolytes and batteries

[0001] The present invention relates to a non-aqueous electrolyte and a battery, and more particularly to a non-aqueous electrolyte that can be suitably used as a battery material for lithium ion batteries and the like, and a battery constructed using the same.

[0002] In recent years, growing concern about environmental issues has led to a shift in energy resources away from fossil fuels such as oil and coal, and this has led to an increase in the importance of batteries, with demand expected to grow accordingly. Secondary batteries, which can be repeatedly charged and discharged, are increasingly being used in a variety of fields, including automobiles and aircraft, as well as in electronic devices such as mobile phones and laptops. Research and development is underway on various secondary batteries and the materials used in them. Lithium-ion batteries, which offer high capacity and are lightweight, are particularly expected to see increased use in the future, and are the type of secondary battery that is most actively researched and developed.

[0003] In the research and development of such batteries, technologies for improving the performance of electrolytes have been developed. For example, Patent Document 1 discloses a nonaqueous electrolyte solution for a nonaqueous electrolyte secondary battery having a positive electrode and a negative electrode capable of absorbing and releasing metal ions, the nonaqueous electrolyte solution containing a compound represented by a predetermined formula together with an electrolyte and a nonaqueous solvent. Patent Document 2 discloses a nonaqueous organic electrolyte containing a lithium salt, a nonaqueous organic solvent, and a nonaqueous organic electrolyte additive, the nonaqueous organic electrolyte additive being a mixture of nonaqueous organic electrolyte additives represented by predetermined formulas (I) to (III). Patent Document 3 discloses an electrolyte solution for a lithium ion secondary battery containing a lithium salt of sulfonimide and water, the electrolyte solution containing at least one anion selected from the group consisting of an orthophosphate ion, a pyrophosphate ion, phosphorous acid, or an anion generated by dissociation of a salt thereof, and a phosphinic acid or an anion generated by dissociation of a salt thereof.

[0004] Japanese Patent Publication No. 2017-168443 Chinese Patent No. 103972586 U.S. Patent No. 11069922

[0005] As described above, although various techniques for improving the performance of an electrolyte solution have been reported, there is no description about the stability of the electrolyte solution when stored in a high-temperature environment. The present inventors have discovered a new problem that the sulfonylimide compound decomposes when a non-aqueous electrolyte solution containing the sulfonylimide compound is stored in a high-temperature environment.

[0006] The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a non-aqueous electrolyte solution containing a sulfonylimide compound that has excellent storage stability in a high-temperature environment.

[0007] The present inventors have conducted extensive research into non-aqueous electrolyte solutions containing sulfonylimide compounds and have found that by combining a sulfonylimide compound having a predetermined structure with a phosphate ester having a predetermined structure, the non-aqueous electrolyte solution has excellent stability even when stored in a high-temperature environment. This has led to the realization that the above-mentioned problems can be solved in an excellent manner, and has led to the present invention.

[0008] The present invention encompasses the following non-aqueous electrolytes and the like: [1] A non-aqueous electrolyte represented by the following formula (1); １ N (R １ SO ２ ) (R ２ SO ２ )(1) (wherein, M １ represents an alkali metal atom. １ and R ２ and are the same or different and represent a fluorine atom, an alkyl group having 1 to 6 carbon atoms, or a fluoroalkyl group having 1 to 6 carbon atoms, (In the formula, R ３ ~R ５ are the same or different and represent a hydrocarbon group having 1 to 14 carbon atoms, a hydrogen atom, or a halogen atom; and n represents an integer of 2 to 6. [2] A nonaqueous electrolyte solution containing a compound represented by the formula (2) above. ３ ~R ５ are the same or different and are an alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 14 carbon atoms, a hydrogen atom, or a halogen atom. [3] The nonaqueous electrolyte according to [1] or [2] above, wherein n in formula (2) is 2. [4] The nonaqueous electrolyte according to [1] above, wherein R in formula (2) is３ ~R ５ are the same or different and are an aryl group having 6 to 14 carbon atoms. [5] The nonaqueous electrolyte according to any one of [1] to [4] above, wherein the water concentration is 1000 ppm or less. [6] The nonaqueous electrolyte according to any one of [1] to [5] above, wherein the water concentration is 100 ppm or less. [7] The nonaqueous electrolyte according to any one of [1] to [6] above, wherein the content of the compound represented by formula (2) is 0.05 mass % or more and less than 5.0 mass % relative to 100 mass % of the nonaqueous electrolyte. [8] The nonaqueous electrolyte according to any one of [1] to [6] above, wherein M ２ PF ６ , M ２ BF ４ , M ２ P.O. ２ F ２ and M ２ FSO ３ (M ２ represents an alkali metal atom.) [9] A battery comprising the nonaqueous electrolyte solution according to any one of [1] to [8] above.

[10] The battery is characterized by comprising a nonaqueous electrolyte solution according to any one of [1] to [8] above.

[11] The battery is characterized by comprising a nonaqueous electrolyte solution according to the following formula (3): LiNi ｘ Co ｙ Mn ｚ O ２ (3) A composite metal oxide represented by the formula (wherein x, y, and z are numbers satisfying x+y+z=1, 0≦x≦1, 0≦y≦1, and 0≦z≦1) and / or LiFePO ４ The battery according to [9] above, which is configured with a positive electrode comprising:

[0009] The nonaqueous electrolyte solution of the present invention has the above-mentioned constitution and is excellent in stability when stored in a high-temperature environment, and therefore can be suitably used as a battery material for lithium-ion batteries and the like.

[0010] Preferred embodiments of the present invention will be specifically described below, but the present invention is not limited to the following description and can be appropriately modified and applied within the scope of the present invention. Note that a combination of two or more of the individual preferred embodiments of the present invention described below also falls within the scope of the present invention.

[0011] 1. Nonaqueous Electrolyte The nonaqueous electrolyte of the present invention contains a sulfonylimide compound represented by the above formula (1) (hereinafter also simply referred to as a sulfonylimide compound) and a phosphate ester represented by the above formula (2) (hereinafter also simply referred to as a phosphate ester). By combining the sulfonylimide compound with the phosphate ester, decomposition of the sulfonylimide compound is suppressed even when the nonaqueous electrolyte is stored in a high-temperature environment, resulting in excellent storage stability. If decomposition of the sulfonylimide compound progresses, battery characteristics may deteriorate due to an increase in direct current resistance (DCR) during repeated charging, a decrease in capacity retention, an increase in initial interface resistance, etc. However, a battery using such a nonaqueous electrolyte has reduced interface resistance and is also excellent in DCR increase rate and capacity retention rate.

[0012] In the nonaqueous electrolyte, the concentration of the sulfonylimide compound is not particularly limited, but is preferably 0.1 to 6.0 mol / L. This allows the effects of the present invention to be more fully exhibited. The concentration is more preferably 0.2 to 3.0 mol / L, even more preferably 0.4 to 2.0 mol / L, even more preferably 0.6 to 2.0 mol / L, and particularly preferably 0.8 to 2.0 mol / L.

[0013] The concentration of the sulfonylimide compound is preferably 0.1 to 6.0 mol / kg, more preferably 0.2 to 3.0 mol / kg, still more preferably 0.4 to 2.0 mol / kg, even more preferably 0.6 to 2.0 mol / kg, and particularly preferably 0.8 to 2.0 mol / kg.

[0014] The content of the phosphate ester in the non-aqueous electrolyte is not particularly limited, but is preferably 0.05% by mass or more and less than 5.0% by mass, relative to 100% by mass of the non-aqueous electrolyte. This not only provides the excellent storage stability of the non-aqueous electrolyte, but also further reduces the interfacial resistance in the battery, thereby further improving the DCR increase rate and capacity retention rate. The content of the phosphate ester is more preferably 0.1 to 3.0% by mass, even more preferably 0.2 to 2.0% by mass, even more preferably 0.5 to 1.5% by mass, and particularly preferably 0.5 to 1.0% by mass.

[0015] The non-aqueous electrolyte solution contains the sulfonylimide compound as an alkali metal salt, but may also contain an alkali metal salt other than the sulfonylimide compound. The concentration of the alkali metal salt other than the sulfonylimide compound in the non-aqueous electrolyte solution is not particularly limited, but is preferably 0.1 to 1.5 mol / L, more preferably 0.2 to 1.0 mol / L, and even more preferably 0.2 to 0.6 mol / L. The concentration of the alkali metal salt other than the sulfonylimide compound is preferably 0.1 to 1.5 mol / kg, more preferably 0.2 to 1.0 mol / kg, and even more preferably 0.2 to 0.6 mol / kg.

[0016] In the non-aqueous electrolyte, the total alkali metal concentration of the sulfonylimide compound and the alkali metal salt other than the sulfonylimide compound is preferably 0.8 to 6.0 mol / L, more preferably 1.0 to 3.0 mol / L, and even more preferably 1.2 to 2.0 mol / L. The total alkali metal concentration of the sulfonylimide compound and the alkali metal salt other than the sulfonylimide compound is preferably 0.8 to 6.0 mol / kg, more preferably 1.0 to 3.0 mol / kg, and even more preferably 1.2 to 2.0 mol / kg.

[0017] The sulfonylimide compound is preferably present in an amount of 5 to 100 mol% relative to 100 mol% of the electrolyte (the sulfonylimide compound and other alkali metal salts) in the nonaqueous electrolyte. This allows the effects of the present invention to be more fully exhibited. The amount is more preferably 10 to 95 mol%, even more preferably 20 to 90 mol%, even more preferably 30 to 85 mol%, even more preferably 40 to 85 mol%, particularly preferably 50 to 85 mol%, and especially preferably 60 to 85 mol%. In one embodiment, the sulfonylimide compound may be present in an amount of 70 mol% or more, 80 mol% or more, or 90 mol% or more relative to 100 mol% of the electrolyte.

[0018] The nonaqueous electrolyte contains a nonaqueous solvent as a solvent, but may contain water at a rate of 10% or less. The water content is preferably 1% or less. This allows the effects of the present invention to be more fully exhibited. The water content is more preferably 1000 ppm or less, and even more preferably 100 ppm or less. The water content can be measured using a Karl Fischer water content analyzer.

[0019] The proportion of the non-aqueous solvent in the non-aqueous electrolytic solution is not particularly limited, but is preferably 100 parts by mass to 5000 parts by mass, more preferably 150 parts by mass to 2500 parts by mass, and even more preferably 200 parts by mass to 2000 parts by mass, per 100 parts by mass of the electrolyte (the sulfonylimide compound and other alkali metal salts).

[0020] The non-aqueous electrolyte may contain other components other than the sulfonylimide compound, the phosphate ester, an alkali metal salt other than the sulfonylimide compound, and the solvent. The content of the other components is not particularly limited, but is preferably 0 to 20% by mass, more preferably 0 to 10% by mass, and even more preferably 0 to 5% by mass, relative to 100% by mass of the non-aqueous electrolyte.

[0021] The essential components and optional components contained in the non-aqueous electrolyte solution of the present invention will be further described below. <Sulfonylimide Compound> The sulfonylimide compound is a compound represented by the following formula (1); M １ N (R １ SO ２ ) (R ２ SO ２ )(1) (wherein, M １ represents an alkali metal atom. １ and R ２ are the same or different and represent a fluorine atom, an alkyl group having 1 to 6 carbon atoms, or a fluoroalkyl group having 1 to 6 carbon atoms.

[0022] The above M １The alkali metal in the formula (I) includes lithium, sodium, potassium, rubidium, cesium, and francium. Preferred are lithium, sodium, and potassium, and more preferred is lithium.

[0023] The above R １ Examples of the alkyl group having 1 to 6 carbon atoms in the formula (I) include straight-chain alkyl groups such as methyl, ethyl, n-propyl, n-butyl, n-pentyl (amyl), and n-hexyl; branched-chain alkyl groups such as i-propyl, sec-butyl, i-butyl, t-butyl, 1-methylbutyl, 1-ethylpropyl, 2-methylbutyl, i-amyl, neopentyl, 1,2-dimethylpropyl, 1,1-dimethylpropyl, t-amyl, 1,3-dimethylbutyl, 3,3-dimethylbutyl, and 2-ethylbutyl; and cyclic alkyl groups such as cyclopropyl, cyclopropylmethyl, cyclobutyl, cyclobutylmethyl, cyclopentyl, and cyclohexyl. Of these, straight-chain alkyl groups are preferred.

[0024] The above R １ and R ２ The alkyl group preferably has 1 to 4 carbon atoms, more preferably 1 to 3 carbon atoms, and even more preferably 1 or 2 carbon atoms.

[0025] The above R １ and R ２ The fluoroalkyl group having 1 to 6 carbon atoms in the formula (I) may be one in which at least a portion of the hydrogen atoms bonded to carbon atoms of an alkyl group having 1 to 6 carbon atoms have been substituted with fluorine atoms. Specific examples of the alkyl group are as described above. Examples of the fluoroalkyl group having 1 to 6 carbon atoms include a fluoromethyl group, a difluoromethyl group, a trifluoromethyl group, a fluoroethyl group, a difluoroethyl group, a trifluoroethyl group, a pentafluoroethyl group, a fluoropropyl group, a fluoropentyl group, and a fluorohexyl group.

[0026] The above R １ and R ２ The fluoroalkyl group preferably has 1 to 4 carbon atoms, more preferably 1 to 3 carbon atoms, and even more preferably 1 or 2 carbon atoms.

[0027] The above R １ and R ２ is preferably a fluorine atom, a trifluoromethyl group, or a pentafluoroethyl group, more preferably a fluorine atom, and １ and R ２ It is preferable that at least one of R is a fluorine atom. １ and R ２ In one preferred embodiment of the present invention, both of are fluorine atoms.

[0028] Examples of the sulfonylimide compound include lithium bis(fluorosulfonyl)imide (hereinafter also referred to as LiFSI), lithium (fluorosulfonyl) (trifluoromethylsulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium (fluorosulfonyl) (pentafluoroethylsulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, potassium bis(fluorosulfonyl)imide, potassium (fluorosulfonyl) (trifluoromethylsulfonyl)imide, potassium bis(trifluoromethylsulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium (fluorosulfonyl) (trifluoromethylsulfonyl)imide, sodium bis(trifluoromethylsulfonyl)imide, etc. Among these, preferred are lithium bis(fluorosulfonyl)imide, lithium (fluorosulfonyl) (trifluoromethylsulfonyl)imide, and lithium (fluorosulfonyl) (pentafluoroethylsulfonyl)imide, and more preferably lithium bis(fluorosulfonyl)imide.

[0029] <Phosphate Ester> The phosphate ester is represented by the following formula (2):

[0030]

[0031] (In the formula, R ３ ~R ５ are the same or different and represent a hydrocarbon group having 1 to 14 carbon atoms, a hydrogen atom, or a halogen atom; and n represents an integer of 2 to 6.

[0032] The above R ３ ~R ５ Examples of the hydrocarbon group having 1 to 14 carbon atoms include an aliphatic alkyl group having 1 to 14 carbon atoms, an alicyclic alkyl group having 3 to 14 carbon atoms, an alkenyl group having 2 to 14 carbon atoms, an alkynyl group having 2 to 14 carbon atoms, and an aryl group having 6 to 14 carbon atoms.

[0033] Examples of the aliphatic alkyl group having 1 to 14 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group (an amyl group), an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, an n-tridecyl group, an n-tetradecyl group, an i-propyl group, a sec-butyl group, an i-butyl group, a t-butyl group, a 1-methylbutyl group, a 1-ethylpropyl group, a 2-methylbutyl ... Examples of such groups include an isopropyl group, an i-amyl group, a neopentyl group, a 1,2-dimethylpropyl group, a 1,1-dimethylpropyl group, a t-amyl group, a 1,3-dimethylbutyl group, a 3,3-dimethylbutyl group, a 2-ethylbutyl group, a 2-ethyl-2-methylpropyl group, a 1-methylheptyl group, a 2-ethylhexyl group, a 1,5-dimethylhexyl group, a t-octyl group, a branched nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, and a tetradecyl group.

[0034] Examples of the alicyclic alkyl group having 3 to 14 carbon atoms include a cyclopropyl group, a cyclopropylmethyl group, a cyclobutyl group, a cyclobutylmethyl group, a cyclopentyl group, a cyclohexyl group, a cyclohexylmethyl group, a cycloheptyl group, a cyclooctyl group, a cyclohexylpropyl group, a cyclododecyl group, a norbornyl group (C7), an adamantyl group (C10), and a cyclopentylethyl group.

[0035] Examples of the alkenyl group having 2 to 14 carbon atoms include a vinyl group, an allyl group, a 1-butenyl group, a 2-butenyl group, a pentenyl group, a hexenyl group, a heptenyl group, an octenyl group, a nonenyl group, a decenyl group, a dodecenyl group, and a tetradecenyl group.

[0036] Examples of the alkynyl group having 2 to 14 carbon atoms include an ethynyl group, a 1-propynyl group, a 2-propynyl group, a butynyl group, a pentynyl group, a hexynyl group, a heptynyl group, an octynyl group, a nonynyl group, a decynyl group, a dodecynyl group, and a tetradecynyl group.

[0037] Examples of the aryl group having 6 to 14 carbon atoms include a phenyl group, a naphthyl group, a benzyl group, a 1-phenylethyl group, a 2-phenylethyl group, a 3-phenylpropyl group, a 4-phenylbutyl group, a styryl group (Ph-CH=C- group), a cinnamyl group (Ph-CH=CHCH ２ - group), etc. Preferred are a phenyl group and a benzyl group.

[0038] The alkyl group preferably has 1 to 10 carbon atoms, more preferably 1 to 8, and even more preferably 1 to 4. The alkenyl group and alkynyl group preferably have 2 to 10 carbon atoms, more preferably 2 to 8, and even more preferably 2 to 4. The aryl group preferably has 6 to 10 carbon atoms, more preferably 6 to 8, and even more preferably 6 to 7.

[0039] The above R ３ ~R ５ Examples of the halogen atom in include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0040] The above R ３ ~R ５ is preferably an alkyl group having 1 to 14 carbon atoms or an aryl group having 6 to 14 carbon atoms, and more preferably an aryl group having 6 to 14 carbon atoms.

[0041] Specific examples of the phosphate ester include tetramethyl pyrophosphate, tetraethyl pyrophosphate, tetrapropyl pyrophosphate, tetrabutyl pyrophosphate, tetravinyl pyrophosphate, tetraallyl pyrophosphate, tetraphenyl pyrophosphate, tetrabenzyl pyrophosphate, etc. Among these, tetraethyl pyrophosphate, tetraphenyl pyrophosphate, and tetrabenzyl pyrophosphate are preferred, tetraphenyl pyrophosphate and tetrabenzyl pyrophosphate are more preferred, and tetrabenzyl pyrophosphate is particularly preferred.

[0042] <Other Alkali Metal Salts> The other alkali metal salts are not particularly limited as long as they are alkali metal salts other than the above-mentioned sulfonylimide compounds. For example, LiPF ６ , LiPO ２ F ２ Alkali metal salts of fluorophosphates such as LiFSO ３ alkali metal salts of fluorosulfonic acid such as LiCF ３ SO ３ alkali metal salts of trifluoromethanesulfonic acid such as LiC(CF ３ SO ２ ) ３ alkali metal salts of perfluoroalkanesulfonylmethides such as LiPF ａ (C ｍ F ２ｍ＋１ ) ６－ａ Fluorophosphates such as LiClO (0≦a≦6, 1≦m≦2); ４ alkali metal perchlorates such as LiBF ｂ (C ｎ F ２ｎ＋１ ) ４－ｂ fluoroborates such as (0≦b≦4, 1≦n≦2); alkali metal salts of oxalatoborates such as LiBOB; cyanoborates such as lithium tetracyanoborate; LiAsF ６ , LiI, LiSbF ６ and the like alkali metal salts.

[0043] As the other alkali metal salts, M ２ PF ６ , M ２ BF ４ , M ２P.O. ２ F ２ or M ２ FSO ３ (M ２ represents an alkali metal atom, and M ２ PF ６ , M ２ BF ４ , M ２ P.O. ２ F ２ and M ２ FSO ３ In one preferred embodiment of the present invention, at least one selected from the group consisting of: ２ PF ６ Specific examples and preferred forms of the alkali metal atom are the same as those of the alkali metal atom in the sulfonylimide compound.

[0044] <Solvent> The solvent in the non-aqueous electrolytic solution of the present invention is not particularly limited as long as it is non-aqueous and can dissolve the electrolyte (sulfonylimide compound and other alkali metal salts), phosphate ester, and other components described below. Examples of the solvent include chain carbonates such as dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate; cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and chloroethylene carbonate; tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,1-dimethoxyethane, 1,2-dimethoxyethane, and 1,2-diethoxyethane. ethers such as 1,2-dibutoxyethane; lactones such as γ-butyrolactone, γ-valerolactone, and α-methyl-γ-butyrolactone; chain carboxylic acid esters such as methyl propionate and methyl butyrate; fluorinated cyclic carbonates such as fluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4,4-difluoroethylene carbonate, tetrafluoroethylene carbonate, and 4-fluoro-5-methylethylene carbonate; and fluorinated chain carbonates such as trifluorodimethyl carbonate, trifluorodiethyl carbonate, and trifluoroethylmethyl carbonate. These nonaqueous solvents may be used in combination of two or more. Of these, chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethylmethyl carbonate are preferred.

[0045] <Other Components> The other components in the non-aqueous electrolyte solution of the present invention are components other than the sulfonylimide compound, the phosphate ester, the alkali metal salt other than the sulfonylimide compound, and the solvent, and are not particularly limited. Examples of the other components include carbonate compounds such as phenylethylene carbonate and erythritane carbonate; sulfonic acid esters such as 1,3-propane sultone, 1,4-butane sultone, 1,5-pentane sultone, 1,4-hexane sultone, 4,6-heptane sultone, methyl methanesulfonate, methyl benzenesulfonate, and methyl trifluoromethanesulfonate; sulfolane, 3-methylsulfolane, ethyl methyl sulfone, diphenyl sulfone, bis( sulfone compounds such as succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, diglycolic anhydride, cyclohexanedicarboxylic anhydride, cyclopentanetetracarboxylic dianhydride, phenylsuccinic anhydride, and the like; nitrogen-containing compounds such as 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone, N-methylsuccinimide, and the like; phosphates such as monofluorophosphates, difluorophosphates, and the like; hydrocarbon compounds such as heptane, octane, and cycloheptane, and the like.

[0046] 2. Battery The nonaqueous electrolyte solution of the present invention has the above-described configuration and exhibits excellent stability when stored in a high-temperature environment, making it suitable for use as a battery material for lithium-ion batteries and the like. The present invention also relates to a battery configured using the nonaqueous electrolyte solution of the present invention. The battery is preferably a battery including a positive electrode and a negative electrode, more preferably a battery in which a separator impregnated with the nonaqueous electrolyte solution of the present invention is provided between the positive electrode and the negative electrode, and even more preferably a battery in which these are housed in an exterior case.

[0047] The shape of the battery according to the present invention is not particularly limited, and any of the conventionally known battery shapes can be used, such as cylindrical, prismatic, laminated, coin, large, etc. Furthermore, when used as a high-voltage power supply (several tens of volts to several hundreds of volts) to be mounted on electric vehicles, hybrid electric vehicles, etc., the battery can also be made into a battery module constructed by connecting individual batteries in series.

[0048] The battery is preferably an alkali metal battery, and an alkali metal battery comprising the nonaqueous electrolyte solution of the present invention also constitutes one aspect of the present invention. The battery is more preferably a secondary battery, and a preferred embodiment of the present invention is one in which the battery is a lithium ion secondary battery.

[0049] The positive electrode constituting the battery is not particularly limited, but is a positive electrode active material composition containing a positive electrode active material, a conductive additive, a binder, a dispersion solvent, etc., supported on a positive electrode current collector, and is usually formed into a sheet shape.

[0050] Examples of methods for producing a positive electrode include a method in which a positive electrode active material composition is applied to a positive electrode current collector by a doctor blade method or the like, or the positive electrode current collector is immersed in a positive electrode active material composition and then dried; a method in which a sheet obtained by kneading and molding a positive electrode active material composition and drying it is bonded to a positive electrode current collector via a conductive adhesive, followed by pressing and drying; and a method in which a positive electrode active material composition to which a liquid lubricant has been added is applied or cast onto a positive electrode current collector, molded into a desired shape, the liquid lubricant is removed, and then the positive electrode current collector is stretched in uniaxial or multiaxial directions.

[0051] The material of the positive electrode current collector is not particularly limited, and for example, conductive metals such as aluminum, aluminum alloys, SUS (stainless steel), titanium, etc. Among these, aluminum is preferred from the viewpoints of ease of processing into a thin film and low cost.

[0052] The positive electrode active material may be any known positive electrode active material as long as it can absorb and release ions. ３ CoO ２ , M ３ NiO ２ , M ３ MnO２ , M ３ Ni ｘ Co ｙ Mn ｚ O ２ and M ３ Ni ｘ Co ｙ Al ｚ O ２ (x, y, z are numbers satisfying x+y+z=1, 0≦x≦1, 0≦y≦1, 0≦z≦1), composite metal oxides such as ternary oxides represented by ３ ｐ Ni ｑ Mn （２－ｑ） O ４ (0.9≦p≦1.1, 0<q<1), M ３ APO ４ Compounds with an olivine structure such as (A = Fe, Mn, Ni, Co), solid solution materials incorporating multiple transition metals (electrochemically inactive layered M ３ ２ MnO3 and electrochemically active layered M ３ M″O ([M″=transition metal such as Co, Ni] solid solution) (M ３ The positive electrode active material may be, for example, a compound represented by the following formula (3): LiNi ｘ Co ｙ Mn ｚ O ２ (3) A composite metal oxide represented by the formula (wherein x, y, and z are numbers satisfying x+y+z=1, 0≦x≦1, 0≦y≦1, and 0≦z≦1) and / or LiFePO ４ A battery comprising a positive electrode containing such a positive electrode active material is one of the preferred embodiments of the present invention.

[0053] Examples of the conductive additive include acetylene black, carbon black, graphite, metal powder materials, single-walled carbon nanotubes, multi-walled carbon nanotubes, and vapor-grown carbon fibers.

[0054] Examples of binders include fluorine-based resins such as 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. These binders may be used alone or in combination. These binders may be dissolved in a solvent or dispersed in a solvent when used.

[0055] The amounts of the conductive additive and binder can be adjusted appropriately in consideration of the intended use of the battery (focus on output, focus on energy, etc.), ion conductivity, and the like.

[0056] When producing a positive electrode, examples of solvents used in the positive electrode active material composition include N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methyl ethyl ketone, tetrahydrofuran, acetonitrile, acetone, ethanol, ethyl acetate, and water. These solvents may be used in combination. The amount of solvent used is not particularly limited and may be determined appropriately depending on the production method and materials used.

[0057] The negative electrode constituting the battery is not particularly limited, but is a negative electrode active material composition containing a negative electrode active material, a dispersion solvent, a binder, and, if necessary, a conductive additive, etc., supported on a negative electrode current collector, and is usually formed into a sheet shape.

[0058] The material of the negative electrode current collector may be a conductive metal such as copper, iron, nickel, silver, stainless steel (SUS), etc. Copper is preferred from the viewpoint of ease of processing into a thin film.

[0059] The negative electrode active material may be any conventionally known negative electrode active material used in batteries, as long as it is capable of absorbing and releasing ions. Specifically, examples of the negative electrode active material include alkali metals, metal alloys such as alkali metal-aluminum alloys, graphite materials such as artificial graphite and natural graphite, mesophase sintered bodies made from coal or petroleum pitch, carbon materials such as non-graphitizable carbon, Si-based negative electrode materials such as Si, Si alloys, and SiO, and Sn-based negative electrode materials such as Sn alloys.

[0060] The negative electrode can be manufactured by the same method as the positive electrode, and the conductive additive, binder, and material dispersion solvent used in manufacturing the negative electrode are also the same as those used in manufacturing the positive electrode.

[0061] The separator is disposed to separate the positive electrode and the negative electrode. The separator constituting the battery is not particularly limited, and a commonly used separator can be used. Examples of separators include porous sheets made of polymers capable of absorbing and retaining non-aqueous electrolytes (e.g., polyolefin-based microporous separators, cellulose-based separators, etc.), nonwoven fabric separators, porous metal bodies, etc. Among these, polyolefin-based microporous separators are preferred because they are chemically stable against organic solvents.

[0062] Examples of the material for the porous sheet include polyethylene, polypropylene, and a laminate having a three-layer structure of polypropylene / polyethylene / polypropylene.

[0063] Examples of materials for the nonwoven fabric separator include cotton, rayon, acetate, nylon, polyester, polypropylene, polyethylene, polyimide, aramid, and glass. Depending on the mechanical strength required of the nonaqueous electrolyte layer, the above-exemplified materials can be used alone or in combination.

[0064] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" means "parts by weight" and "%" means "% by mass."

[0065] The physical properties of the non-aqueous electrolyte and the battery characteristics were evaluated as follows: (Measurement of Water Content of Non-aqueous Electrolyte) The water content of the non-aqueous electrolyte was measured using a Karl Fischer water content analyzer AQ-2000 (manufactured by Hiranuma Sangyo Co., Ltd.) and Aqualite RS-A (manufactured by Hiranuma Sangyo Co., Ltd.) as the generating liquid and Aqualite CN (manufactured by Hiranuma Sangyo Co., Ltd.) as the counter electrode liquid.

[0066] (Evaluation of storage stability of non-aqueous electrolyte) 10 ml of non-aqueous electrolyte was placed in a PFA (fluorine-based resin) container, the PFA container was sealed, wrapped with aluminum laminate zip, and stored in a thermostatic chamber set at 60°C for a given period of time. The electrolyte after storage was diluted 100 times with ultrapure water, and sulfate ions (SO ) were measured by ion chromatography as follows. ４ ２－ The sulfate ion concentration in the electrolyte solution containing no added phosphate ester was set at 100, and the storage stability was evaluated based on the sulfate ion concentration. (Ion Chromatography Measurement) The non-aqueous electrolyte solution was diluted 100 times with ultrapure water to prepare a measurement solution, and the sulfate ion (SO ) concentration in the non-aqueous electrolyte solution was measured under the following measurement conditions using an ion chromatography system ICS-3000 (manufactured by Nippon Dionex Co., Ltd.). ４ ２－ Measurement conditions: Separation mode: ion exchange; Eluent: 7 to 18 mM KOH aqueous solution; Detector: electrical conductivity detector; Column: anion analysis column Ion PAC AS-17C (manufactured by Nippon Dionex Co., Ltd.).

[0067] (Evaluation of Interface Resistance) The aged lithium ion secondary battery (cell) was CC charged at 1 C (30 mA) for 30 minutes at room temperature. The cell was then transferred to a thermostatic chamber at -30°C and the temperature was adequately adjusted. Then, an impedance analyzer (manufactured by Bio Logic, product number: VSP-300) was used to measure impedance at frequencies from 1 GHz to 1 mHz. The interface resistance was determined from the frequency at which the arc of the obtained measured value diverged. The frequency at which the arc diverged refers to the frequency at which the imaginary axis value reached a minimum between 10 Hz and 0.001 Hz.

[0068] (DCR Increase Rate, Capacity Retention Rate) (i) DCR: The aged lithium ion secondary battery (cell) was CCCV charged at 4.2 V, 1 C (30 mA) at room temperature. After 30 minutes, it was discharged at 0.2 C (6 mA) for 10 seconds, then left for 30 minutes, discharged at 1 C (30 mA) for 10 seconds, and then left for another 30 minutes, followed by CC discharge at 3 C (90 mA) for 10 seconds. Each discharge current was plotted on the horizontal axis, and the difference in closed-circuit voltage (ΔV) between the start of discharge and 10 seconds after discharge at each discharge current was plotted on the vertical axis. The slope of the IV line was taken as the DCR of the cell. (ii) Cycle Charge / Discharge: After DCR measurement, the cell was CCCV charged at 4.2 V, 0.5 C (15 mA) at 45°C, followed by CC discharge at 2.75 V, 0.2 C (6 mA). Subsequently, the cells were subjected to CCCV charging at 4.2 V, 1 C (30 mA), followed by CC discharging at 2.75 V, 1 C (30 mA). This 1 C charge / discharge cycle was repeated a total of 500 times. The capacity retention rate at the 500th cycle was calculated using the following formula (4). In addition, the DCR of the cells after the cycle charge / discharge was measured again, and the DCR increase rate was calculated using the following formula (5). Capacity retention rate (%) = 500th 1 C discharge capacity / 1st 1 C discharge capacity × 100 (4) DCR increase rate (%) = DCR after cycle charge / discharge / DCR after aging × 100 (5)

[0069] (Preparation of Electrolyte Solutions: Examples 1 to 33, Comparative Examples 1 to 33) Electrolyte salts having a simple salt composition containing only LiFSI (manufactured by Nippon Shokubai Co., Ltd.) in a mixed solvent (manufactured by Kishida Chemical Co., Ltd.) with a composition of ethylene carbonate (EC):ethyl methyl carbonate (EMC) = 3:7 (volume ratio), LiFSI and LiPF ６ (manufactured by Stella Chemifa Corporation) or LiPF ６Non-aqueous electrolyte solutions (hereinafter simply referred to as "electrolytes") with various salt concentrations were prepared by dissolving electrolyte salts having simple salt compositions containing only phosphate esters. To some of the electrolyte solutions, phosphate esters were further added to the concentrations shown in Tables 1 and 2 to prepare non-aqueous electrolyte solutions. Furthermore, ultrapure water (greater than 18.2 Ω cm) was added to the various electrolyte solutions prepared to prepare non-aqueous electrolyte solutions with the water contents shown in Tables 1 to 4. The phosphate esters used in preparing the above non-aqueous electrolyte solutions are as follows: TBP: tribenzyl phosphate TEPP: tetraethyl pyrophosphate TPPP: tetraphenyl pyrophosphate TBPP: tetrabenzyl pyrophosphate

[0070] The water content of the obtained non-aqueous electrolyte solution was measured, and the stability of the electrolyte solution was evaluated after storage for 3 months and 6 months at 60° C. The results are shown in Tables 1 to 4.

[0071] (Fabrication of Lithium Ion Secondary Battery 1) (i) Fabrication of Positive Electrode (NMC111) 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 = 93:2:2:3 (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 it reached a thickness of 83 μm, thereby obtaining a sheet-like positive electrode (thickness: 83 μm).

[0072] (ii) Preparation of Negative Electrode Graphite (natural graphite), 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: SBR: CMC = 97.3: 1.5: 1.2 (solid mass ratio)). Subsequently, the obtained negative electrode mixture slurry was applied to a copper foil (negative electrode current collector, manufactured by Fukuda Metal Foil & Powder Co., Ltd., thickness 15 μm) so that the coating weight after drying was 9.8 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 press-molded until a sheet-like negative electrode (thickness: 113 μm) was obtained.

[0073] (iii) Fabrication of Lithium-Ion Secondary Battery The positive and negative electrodes obtained in (i) and (ii) above were cut, and the polarity lead wires were ultrasonically welded. The positive and negative electrodes were placed opposite each other via a 25 μm polyethylene (PE) separator, and the three sides were sealed with a laminate exterior to fabricate a non-filled battery. Subsequently, 700 μL of each electrolyte solution from the Examples or Comparative Examples was added to one of the unsealed sides of the non-filled battery. After the electrolyte solution was injected, the battery was vacuum sealed to fabricate a 4.2 V, 30 mAh capacity lithium-ion secondary battery (cell) 1.

[0074] (iv) Cell Aging Process The cell obtained in (iii) above was aged using a charge / discharge tester (manufactured by Asuka Electronics Co., Ltd., product number: ACD-01, the same applies hereinafter). Specifically, the cell was charged at a constant current (CC) of 0.1 C (3 mA) for 3 hours at room temperature (25°C, the same applies hereinafter), and then left at room temperature for 48 hours. After leaving the cell, the excess laminate was cleaved and vacuum sealed to degas the cell. Furthermore, the cell was charged at a constant current / constant voltage (CCCV) of 4.2 V and 0.5 C (15 mA) at room temperature, and then CC discharged at 2.75 V and 0.2 C (6 mA). After the same CCCV charging, the cells were discharged at 2.75 V, 1 C (30 mA), and then discharged at 2.75 V, 2 C (60 mA), followed by a final CC discharge at 2.75 V, 0.2 C (6 mA). This was the aging process for the cells.

[0075] (Fabrication of Lithium-Ion Secondary Battery 2) (i) Fabrication of Positive Electrode (LFP) LiFePO 4, an iron phosphate-based positive electrode active material ４ Acetylene black and graphite powder (manufactured by Nippon Graphite Industries Co., Ltd., product number: SP270) as conductive additives, and polyvinylidene fluoride (PVdF, manufactured by Kureha Corporation, product number: KF1120) as a binder were dispersed in N-methyl-2-pyrrolidone (NMP) to prepare a positive electrode mixture slurry (positive electrode active material: AB: graphite powder: PVdF = 89:3:3:5 (solid content mass ratio)). Subsequently, the obtained positive electrode mixture slurry was applied to a carbon-coated aluminum foil (positive electrode current collector, manufactured by Nippon Graphite Industries Co., Ltd., thickness 20 μm) so that the coating weight after drying was 17.6 mg / cm ２ The mixture was coated on one side with an applicator so that the density was 1.6 g / cm 3 and dried on a hot plate at 110°C for 10 minutes. The mixture was then dried in a vacuum drying oven at 110°C for 12 hours. Thereafter, the density was adjusted to 1.6 g / cm 3 using a roll press. ３ The mixture was press-molded until it reached a thickness of 111 μm, thereby obtaining a sheet-shaped positive electrode (thickness: 111 μm).

[0076] (ii) Preparation of Negative Electrode Graphite (natural graphite) was used as the negative electrode active material, fibrous graphite as a conductive aid, and 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: fibrous graphite: SBR: CMC = 96:2:1:1 (solid mass ratio)). Subsequently, the obtained negative electrode mixture slurry was applied to a copper foil (negative electrode current collector, manufactured by Fukuda Metal Foil & Powder Co., Ltd., thickness 15 μm) so that the coating weight after drying was 8.0 mg / cm ２ The mixture was coated on one side with an applicator so that the density was 1.2 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 1.2 g / cm 3 using a roll press. ３ The mixture was press-molded until it reached a thickness of 65 μm, thereby obtaining a sheet-shaped negative electrode (thickness: 65 μm).

[0077] (iii) Fabrication of Lithium-Ion Secondary Battery The positive and negative electrodes obtained in (i) and (ii) above were cut, and the polarity leads were ultrasonically welded. The positive and negative electrodes were placed opposite each other via a 25 μm polyethylene (PE) separator, and the three sides were sealed with a laminate exterior to fabricate a non-filled battery. Subsequently, 700 μL of each electrolyte solution from the Examples or Comparative Examples was added to one of the unsealed sides of the non-filled battery. After the electrolyte solution was injected, the battery was vacuum sealed to fabricate a 3.6 V, 21 mAh capacity lithium-ion secondary battery (cell) 2.

[0078] (iv) Cell Aging Process The cell obtained in (iii) above was aged using a charge / discharge tester. Specifically, the cell was charged at 0.1 C (2.1 mA) for 3 hours at room temperature (25 ° C, the same below) and then left at room temperature for 48 hours. After leaving the cell, the excess laminate was cleaved and vacuum sealed to degas the cell. The cell was then charged at 3.6 V, 0.1 C (2.1 mA) at room temperature using constant current constant voltage (CCCV), followed by CC discharge at 2.0 V, 0.2 C (4.2 mA). In addition, after CCCV charging at 3.6 V, 0.5 C (10.5 mA), CC discharging was performed at 2.00 V, 1 C (21 mA), and after similar CCCV charging, CC discharging was performed at 2.00 V, 2 C (42 mA), and finally CC discharging was performed at 2.0 V, 0.2 C (4.2 mA). This was the cell aging process.

[0079] The resulting lithium ion secondary batteries 1 and 2 were used to measure the interface resistance, DCR increase rate, and capacity retention rate. The results are shown in Tables 1 to 4.

[0080]

[0081]

[0082]

[0083]

[0084] From Tables 1 to 4, it is clear that by adding the phosphate ester represented by the formula (2) to a nonaqueous electrolyte solution containing the sulfonylimide compound represented by the formula (1), the stability when stored in a high-temperature environment is excellent.

[0085] (Discussion) (Storage Stability of Electrolyte Solution) Compared with electrolyte solutions not containing the phosphate ester represented by formula (2) (e.g., electrolyte solution 48), electrolyte solutions containing the phosphate ester (e.g., electrolyte solutions 2, 6, 10, 18, 21, 24, 30, 33, and 36) contained fewer sulfate ions, suppressing electrolyte decomposition. This trend remained unchanged regardless of the type or amount of compound added, as long as the phosphate ester satisfied formula (2). However, electrolyte solutions containing TBP, a monomer of the phosphate ester (e.g., electrolyte solutions 14, 27, and 39), showed almost no sulfate ion reduction effect. Therefore, it is presumed that the condensed phosphate structure in the phosphate ester is an important factor in the manifestation of this effect.

[0086] (NMC111 series) (Evaluation of interfacial resistance) When the phosphate ester represented by the above formula (2) was added to the TBP monomer, which does not satisfy the requirements of the above formula (2), the interfacial resistance was small and the impedance was reduced. As with the storage stability of the electrolyte solution, this tendency remains the same regardless of the type or amount of compound added, as long as the phosphate ester satisfies the formula (2).

[0087] (Capacity Retention Rate During Cycle Charge and Discharge) When the phosphate ester represented by the above formula (2) was added to the TBP monomer, which does not satisfy the requirements of the above formula (2), the capacity retention rate was high and the battery life was improved. As with the storage stability of the electrolyte solution, this tendency remains the same regardless of the type or amount of compound added, as long as the phosphate ester satisfies the formula (2).

[0088] (DCR Increase Rate) When the phosphate ester represented by the above formula (2) was added to the TBP monomer, which does not satisfy the requirements of the above formula (2), the DCR increase rate was small, and the increase in resistance during cycle charge / discharge was suppressed. Similar to the storage stability of the electrolyte solution, this tendency remains the same regardless of the type or amount of compound added, as long as the phosphate ester satisfies the formula (2).

[0089] (LFP Series) (Evaluation of Interface Resistance) The electrolytes containing the phosphate ester represented by the formula (2) exhibited low interface resistance and reduced impedance. This tendency was the same even when the amount of phosphate ester added was changed, as was the case with the storage stability of the electrolyte solution.

[0090] (Capacity Retention Rate During Cycle Charge / Discharge) The addition of the phosphate ester represented by formula (2) resulted in a high capacity retention rate and improved battery life. This tendency was the same regardless of the amount of phosphate ester added, as with the storage stability of the electrolyte solution.

[0091] (DCR Increase Rate) The addition of the phosphate ester represented by the above formula (2) resulted in a small DCR increase rate, suppressing the increase in resistance during cycle charge / discharge. This tendency remained the same even when the amount of phosphate ester added was changed, as with the storage stability of the electrolyte solution.

[0092] (Summary) From the above results, it was confirmed that the storage stability of the electrolyte solution was improved by adding the phosphate ester represented by the above formula (2) to the electrolyte solution containing LiFSI. Furthermore, it was confirmed that the battery performance of the lithium ion secondary battery using the electrolyte solution was improved in terms of reduced interfacial resistance, improved capacity retention during cycle charging and discharging, reduced DCR increase rate, etc.

Claims

1. The following formula (1): M １ N(R １ SO ２ )(R ２ SO ２ )(1) (In the formula, M １ represents an alkali metal atom. １ and R ２ and are the same or different and represent a fluorine atom, an alkyl group having 1 to 6 carbon atoms, or a fluoroalkyl group having 1 to 6 carbon atoms, 【Chemistry 1】 (In the formula, R ３ ~R ５ are the same or different and represent a hydrocarbon group having 1 to 14 carbon atoms, a hydrogen atom, or a halogen atom; and n represents an integer of 2 to 6.

2. R in the formula (2) ３ ~R ５ 2. The nonaqueous electrolyte according to claim 1, wherein: are the same or different and are an alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 14 carbon atoms, a hydrogen atom, or a halogen atom.

3. 3. The nonaqueous electrolyte according to claim 1, wherein n in the formula (2) is 2.

4. R in the formula (2) ３ ~R ５ and are the same or different and are an aryl group having 6 to 14 carbon atoms.

5. 3. The nonaqueous electrolyte according to claim 1, wherein the water concentration is 1000 ppm or less.

6. 3. The nonaqueous electrolyte according to claim 1, wherein the water concentration is 100 ppm or less.

7. 3. The non-aqueous electrolyte according to claim 1, wherein the content of the compound represented by formula (2) is 0.05% by mass or more and less than 5.0% by mass, relative to 100% by mass of the non-aqueous electrolyte.

8. Further M ２ P.F. ６ , M. ２ BF ４ , M. ２ P.O. ２ F ２ and M. ２ FSO ３ (M ２ 3. The nonaqueous electrolyte solution according to claim 1, further comprising at least one selected from the group consisting of:

9. A battery comprising the nonaqueous electrolyte according to claim 1 or 2.

10. The battery has the following formula (3): L)) ｘ Co ｙ Mn ｚ O ２ (3) (wherein x, y, and z are numbers satisfying x+y+z=1, 0≦x≦1, 0≦y≦1, and 0≦z≦1) and / or LiFePO ４ The battery of claim 9 , comprising a positive electrode comprising:

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