Non-aqueous electrolyte

Abstract

Provided is a nonaqueous electrolyte solution, which comprises a nonaqueous organic solvent, a solute, a specific silicon compound (A), a specific borate (B), and a specific imide salt (C). This nonaqueous electrolyte solution exhibits a good balance between the effects of lowering the absolute value of the low-temperature internal resistance and of improving battery capacity after cycle testing.

Description

[Technical field]

[0001] The present disclosure relates to non-aqueous electrolytes. [Background technology]

[0002] In recent years, batteries, which are electrochemical devices, have been attracting attention as energy storage systems for small, high-energy density applications such as information-related equipment and communication equipment, i.e., personal computers, video cameras, digital cameras, mobile phones, smartphones, etc., as well as large-scale, power storage systems for power applications such as electric vehicles, hybrid vehicles, and fuel cell vehicle auxiliary power sources, power storage, etc. One candidate is non-aqueous electrolyte batteries, including lithium-ion batteries, which have high energy density and voltage and can provide high capacity, and research and development of these batteries is currently being actively conducted.

[0003] As the nonaqueous electrolyte used in nonaqueous electrolyte batteries, a nonaqueous electrolyte in which a fluorine-containing electrolyte such as lithium hexafluorophosphate (hereinafter also referred to as "LiPF6"), lithium bis(fluorosulfonyl)imide (hereinafter also referred to as "LiFSI"), or lithium tetrafluoroborate (hereinafter also referred to as "LiBF4") is dissolved as a solute in a solvent such as a cyclic carbonate, a chain carbonate, or an ester is often used because it is suitable for obtaining a high-voltage and high-capacity battery. However, nonaqueous electrolyte batteries using such a nonaqueous electrolyte are not necessarily satisfactory in terms of battery characteristics such as cycle characteristics and output characteristics.

[0004] For example, in the case of a lithium-ion secondary battery, when lithium cations are inserted into the negative electrode during the initial charge, the negative electrode and lithium cations, or the negative electrode and the electrolyte solvent, react to form a coating on the surface of the negative electrode, mainly composed of lithium oxide, lithium carbonate, or lithium alkyl carbonate. This coating on the surface of the electrode is called the Solid Electrolyte Interface (SEI), and its properties have a significant effect on battery performance, such as suppressing further reductive decomposition of the solvent and suppressing deterioration of battery performance. Similarly, a coating of decomposition products is also formed on the surface of the positive electrode, which is known to play an important role in suppressing oxidative decomposition of the solvent and suppressing gas generation inside the battery.

[0005] In order to improve battery characteristics such as cycle characteristics and low-temperature characteristics (below 0°C), it is important to form a stable SEI with high ionic conductivity and low electronic conductivity, and there have been many attempts to actively form a good SEI by adding small amounts (usually 0.001% by mass or more and 10% by mass or less) of compounds called additives to the electrolyte.

[0006] For example, Patent Document 1 describes an electrolyte solution containing a silicon compound with a specific structure. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2002-134169 Summary of the Invention [Problem to be solved by the invention]

[0008] However, there is a demand for further improvements in performance, such as reducing the absolute value of internal resistance (also simply called "resistance") at low temperatures (below 0°C) and maintaining the battery capacity after cycle testing.

[0009] The present disclosure has been made in consideration of the above circumstances, and aims to provide a nonaqueous electrolyte solution that can achieve a good balance between the effect of reducing the absolute value of internal resistance at low temperatures (below 0°C, for example, −20°C) and the effect of improving battery capacity after cycle testing. [Means for solving the problem]

[0010] The present inventors have found that the above object can be achieved by the following configuration.

[0011] <1> A non-aqueous electrolyte solution, The present invention includes a non-aqueous organic solvent, a solute, a silicon compound (A), a borate (B), and an imide salt (C), The silicon compound (A) is a compound represented by the following general formula (1): the borate (B) is a borate formed from a pair of at least one cation selected from the group consisting of alkali metal cations and alkaline earth metal cations and at least one anion selected from the group consisting of tetrafluoroborate anion and difluorooxalatoborate anion, The imide salt (C) is an imide salt represented by the following general formula (2): Non-aqueous electrolyte.

[0012] [ka]

[0013] [R 1 ~R 3 are each independently a substituent having at least one of an unsaturated bond and an aromatic ring, and R 1 ~R 3 At least one of the groups is a substituent having an aromatic ring.

[0014] [ka]

[0015] [Rf1 and Rf 2 each independently represents a fluorine atom or a linear or branched perfluoroalkyl group having 1 to 4 carbon atoms; M + represents an alkali metal cation. <2> R 1 ~R 3 are each independently a group selected from the group consisting of an alkenyl group, an alkynyl group, an aryl group, an alkenyloxy group, an alkynyloxy group, and an aryloxy group; <1> The non-aqueous electrolyte according to claim 1. <3> the alkenyl group is selected from an ethenyl group and a 2-propenyl group, the alkynyl group is an ethynyl group, the aryl group is selected from a phenyl group, a 2-methylphenyl group, a 4-methylphenyl group, a 4-fluorophenyl group, a 4-tert-butylphenyl group, and a 4-tert-amylphenyl group; the alkenyloxy group is a group selected from a vinyloxy group and a 2-propenyloxy group, the alkynyloxy group is a propargyloxy group, the aryloxy group is selected from a phenoxy group, a 2-methylphenoxy group, a 4-methylphenoxy group, a 4-fluorophenoxy group, a 4-tert-butylphenoxy group, and a 4-tert-amylphenoxy group; <2> The non-aqueous electrolyte according to claim 1. <4> R 1 ~R 3 at least one of the above is a group selected from the group consisting of an alkenyl group, an alkynyl group, an alkenyloxy group, and an alkynyloxy group; <1> The non-aqueous electrolyte according to claim 1. <5> R 1 ~R 3 two of are independently an ethenyl group or an ethynyl group; <1> or <4> The non-aqueous electrolyte according to claim 1. <6> The compound represented by the general formula (1) is at least one selected from the group consisting of the following (1a) to (1e): <1> ~ <5> 13. The non-aqueous electrolyte according to claim 12,

[0016] [ka]

[0017] <7> The compound represented by the general formula (1) is at least one selected from the group consisting of the compounds (1a), (1b), (1c), and (1d). <6> The non-aqueous electrolyte according to claim 1. <8> The borate (B) is at least one selected from the group consisting of lithium tetrafluoroborate and lithium difluorooxalatoborate. <1> ~ <7> 13. The non-aqueous electrolyte according to claim 12, <9> The imide salt (C) is lithium bis(fluorosulfonyl)imide. <1> ~ <8> 13. The non-aqueous electrolyte according to claim 12, Effect of the Invention

[0018] According to the present disclosure, it is possible to provide a nonaqueous electrolyte solution that can achieve a good balance between the effect of reducing the absolute value of internal resistance at low temperatures (0° C. or lower, for example, −20° C.) and the effect of improving battery capacity after cycle testing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The configurations and combinations thereof in the following embodiments are examples, and addition, omission, substitution, and other modifications of the configurations are possible without departing from the spirit of the present disclosure. In addition, the present disclosure is not limited to the embodiments. In this specification, the symbol "to" is used to mean that the numerical values ​​before and after it are included as the lower limit and upper limit.

[0020] [1. Non-aqueous electrolyte] The nonaqueous electrolyte of the present disclosure is The present invention includes a non-aqueous organic solvent, a solute, a silicon compound (A), a borate (B), and an imide salt (C), The silicon compound (A) is a compound represented by the following general formula (1): the borate (B) is a borate formed from a pair of at least one cation selected from the group consisting of alkali metal cations and alkaline earth metal cations and at least one anion selected from the group consisting of tetrafluoroborate anion and difluorooxalatoborate anion, The imide salt (C) is an imide salt represented by the following general formula (2): It is a non-aqueous electrolyte.

[0021] [ka]

[0022] [R 1 ~R 3 are each independently a substituent having at least one of an unsaturated bond and an aromatic ring, and R 1 ~R 3 At least one of the groups is a substituent having an aromatic ring.

[0023] [ka]

[0024] [Rf 1 and Rf 2 each independently represents a fluorine atom or a linear or branched perfluoroalkyl group having 1 to 4 carbon atoms; M + represents an alkali metal cation.

[0025] Hereinafter, each component contained in the nonaqueous electrolyte solution of the present disclosure will be described.

[0026] <Silicon Compound (A)> The silicon compound (A) will be described. The silicon compound (A) is also called component (A). The silicon compound (A) is a compound represented by the following general formula (1).

[0027] [ka]

[0028] [R 1 ~R 3 are each independently a substituent having at least one of an unsaturated bond and an aromatic ring, and R 1 ~R 3 At least one of the groups is a substituent having an aromatic ring.

[0029] Above R 1 ~R 3 The number of carbon atoms of the substituent having at least one of an unsaturated bond and an aromatic ring represented by is not particularly limited, but examples thereof include a substituent having 2 to 25 carbon atoms, preferably 2 to 20 carbon atoms, and more preferably 2 to 15 carbon atoms.

[0030] Above R 1 ~R 3 is preferably a group selected from an alkenyl group, an alkynyl group, an aryl group, an alkenyloxy group, an alkynyloxy group, and an aryloxy group.

[0031] The alkenyl group is preferably a group selected from ethenyl and 2-propenyl (allyl) groups, the alkynyl group is preferably an ethynyl group, and the aryl group is preferably a group selected from phenyl, 2-methylphenyl, 4-methylphenyl, 4-fluorophenyl, 4-tert-butylphenyl, and 4-tert-amylphenyl groups.

[0032] The alkenyloxy group is preferably a group selected from a vinyloxy group and a 2-propenyloxy group (allyloxy group). The alkynyloxy group is preferably a propargyloxy group, and the aryloxy group is preferably a group selected from a phenoxy group, a 2-methylphenoxy group, a 4-methylphenoxy group, a 4-fluorophenoxy group, a 4-tert-butylphenoxy group, and a 4-tert-amylphenoxy group.

[0033] R 1 ~R 3 At least one of these is preferably a group selected from the group consisting of an alkenyl group, an alkynyl group, an alkenyloxy group, and an alkynyloxy group. Also, R 1 ~R 3 In view of a high durability improving effect, it is preferable that two of the groups (1a) to (1e) are each independently an ethenyl group or an ethynyl group. Specific examples include compounds (1a) to (1e) described later.

[0034] The compound represented by general formula (1) is preferably at least one selected from the group consisting of (1a) to (1e), and among these, at least one selected from the group consisting of (1a), (1b), (1c), and (1d) is particularly preferred from the viewpoint of the effect of reducing the absolute value of the internal resistance.

[0035] [ka]

[0036] The suitable concentration of the silicon compound (A) relative to the total amount of the nonaqueous electrolytic solution containing the nonaqueous organic solvent and the solute is not particularly limited, but the lower limit is usually 0.01 mass% or more, preferably 0.05 mass% or more, more preferably 0.1 mass% or more.The upper limit is usually 3.0 mass% or less, preferably 2.0 mass% or less, more preferably 1.0 mass% or less. The silicon compound (A) may be used alone or in combination of two or more kinds.

[0037] <Borates (B)> The borate (B) is also called component (B). The borate (B) is a borate consisting of a pair of at least one cation selected from the group consisting of alkali metal cations and alkaline earth metal cations and at least one anion selected from the group consisting of tetrafluoroborate anion and difluorooxalatoborate anion. The cation constituting the borate (B) is preferably an alkali metal cation, and among these, a lithium ion, a sodium ion, or a potassium ion is more preferable, and a lithium ion is even more preferable. That is, the borate (B) is preferably at least one selected from the group consisting of lithium tetrafluoroborate and lithium difluorooxalatoborate, and more preferably lithium tetrafluoroborate.

[0038] The preferred concentration of the borate (B) relative to the total amount of the nonaqueous electrolytic solution containing the nonaqueous organic solvent and the solute is not particularly limited, but the lower limit is usually 0.01 mass% or more, preferably 0.05 mass% or more, more preferably 0.1 mass% or more, and the upper limit is usually 9.0 mass% or less, preferably 6.0 mass% or less, more preferably 3.0 mass% or less. The borate (B) may be used alone or in combination of two or more kinds.

[0039] <Imide salt (C)> The imide salt (C) will be explained below. The imide salt (C) is also called component (C). The imide salt (C) is an imide salt represented by the following general formula (2).

[0040] [ka]

[0041] [Rf 1 and Rf 2each independently represents a fluorine atom or a linear or branched perfluoroalkyl group having 1 to 4 carbon atoms; M + represents an alkali metal cation.

[0042] The alkali metal cation (M + ) is more preferably a lithium ion, a sodium ion, or a potassium ion, and even more preferably a lithium ion. The anion constituting the imide salt (C) is preferably at least one imide anion selected from the group consisting of bis(trifluoromethanesulfonyl)imide anion, bis(pentafluoroethanesulfonyl)imide anion, bis(fluorosulfonyl)imide anion, and (trifluoromethanesulfonyl)(fluorosulfonyl)imide anion. The imide salt (C) is preferably lithium bis(fluorosulfonyl)imide.

[0043] The suitable concentration of the imide salt (C) relative to the total amount of the nonaqueous electrolytic solution containing the nonaqueous organic solvent and the solute is not particularly limited, but the lower limit is usually 0.01 mass% or more, preferably 0.05 mass% or more, more preferably 0.1 mass% or more, and the upper limit is usually 15 mass% or less, preferably 10 mass% or less, more preferably 5 mass% or less. The imide salt (C) may be used alone or in combination of two or more kinds.

[0044] The mass-based content W of the silicon compound (A) in the nonaqueous electrolyte of the present disclosure A The mass-based content of borate (B) W B The ratio of W B / W A is preferably 1.5 or more and 3 or less. In addition, the mass-based content W of the silicon compound (A) in the nonaqueous electrolyte of the present disclosure A The mass content W of the imide salt (C) relative to C The ratio of W C / WA is preferably 1 or more and 5 or less. The above W B / W A is more preferably 1.7 or more and 3 or less, and particularly preferably 2 or more and 3 or less, from the viewpoints of the internal resistance at low temperatures (0° C. or less) and the battery capacity retention rate after cycle testing. The above W C / W A is more preferably 1.5 or more and 5 or less, and particularly preferably 2 or more and 5 or less, from the viewpoints of the internal resistance at low temperatures (0° C. or less) and the battery capacity retention rate after cycle testing.

[0045] <Solute> The solute contained in the nonaqueous electrolyte of the present disclosure will be described. The solute is preferably an ionic salt, for example, a salt of at least one cation selected from the group consisting of alkali metal ions and alkaline earth metal ions, and a hexafluorophosphate anion, a trifluoromethanesulfonate anion, a fluorosulfonate anion, a bis(difluorophosphoric acid anion, a phosphate ... R (difluorophosphoric acid)imide anion, R (fluorosulfonyl)imide anion, and (difluorophospho R It is preferable that the anion pair is an ionic salt consisting of at least one anion pair selected from the group consisting of (trifluoromethanesulfonyl)imide anion and (trifluoromethanesulfonyl)imide anion.

[0046] In addition, the cation of the ionic salt that is the solute is lithium, sodium, potassium, or magnesium, and the anion is a hexafluorophosphate anion, a trifluoromethanesulfonate anion, a bis(difluorophosphoric acid anion, R (difluorophosphoric acid)imide anion, and R From the viewpoints of high solubility in non-aqueous organic solvents and electrochemical stability, the anion is preferably at least one selected from the group consisting of (fluorosulfonyl)imide anions.

[0047] There is no particular limit to the suitable concentration of the solute, but the lower limit is usually 0.5 mol / L or more, preferably 0.7 mol / L or more, and more preferably 0.9 mol / L or more. The upper limit is usually 2.5 mol / L or less, preferably 2.2 mol / L or less, and more preferably 2.0 mol / L or less. By setting the concentration to 0.5 mol / L or more, it is possible to suppress the deterioration of the cycle characteristics and output characteristics of the nonaqueous electrolyte battery due to the decrease in ion conductivity, and by setting the concentration to 2.5 mol / L or less, it is possible to suppress the deterioration of the cycle characteristics and output characteristics of the nonaqueous electrolyte battery due to the increase in viscosity of the nonaqueous electrolyte. The solutes may be used alone or in combination of two or more kinds.

[0048] <Non-aqueous organic solvent> The non-aqueous organic solvent will now be described. The type of nonaqueous organic solvent used in the nonaqueous electrolyte solution of the present disclosure is not particularly limited, and any nonaqueous organic solvent can be used. Specifically, ethyl methyl carbonate (hereinafter also referred to as "EMC"), dimethyl carbonate (hereinafter also referred to as "DMC"), diethyl carbonate (hereinafter also referred to as "DEC"), methyl propyl carbonate, ethyl propyl carbonate, methyl butyl carbonate, 2,2,2-trifluoroethyl methyl carbonate, 2,2,2-trifluoroethyl ethyl carbonate, 2,2,2-trifluoroethyl propyl carbonate, bis(2,2,2-trifluoroethyl)carbonate, 1,1,1,3,3,3-hexafluoro-1-propyl methyl carbonate, 1,1,1,3,3,3-hexafluoro-1-propyl ethyl carbonate, 1,1,1,3,3,3-hexafluoro-1-propyl propyl carbonate, bis(1,1,1,3,3,3-hexafluoro-1-propyl)carbonate , ethylene carbonate (hereinafter also referred to as "EC"), propylene carbonate (hereinafter also referred to as "PC"), butylene carbonate, fluoroethylene carbonate (hereinafter also referred to as "FEC"), difluoroethylene carbonate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl 2-fluoropropionate, ethyl 2-fluoropropionate, diethyl ether, dibutyl ether, diisopropyl ether, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, furan, tetrahydropyran, 1,3-dioxane, 1,4-dioxane, N,N-dimethylformamide, acetonitrile, propionitrile, dimethyl sulfoxide, sulfolane, γ-butyrolactone, and γ-valerolactone.

[0049] The nonaqueous organic solvent preferably contains at least one selected from the group consisting of cyclic carbonates and chain carbonates, which provides excellent cycle characteristics at high temperatures, and preferably contains an ester, which provides excellent input / output characteristics at low temperatures. Specific examples of the cyclic carbonate include EC, PC, butylene carbonate, FEC, and the like, and among these, at least one selected from the group consisting of EC, PC, and FEC is preferable. Specific examples of the chain carbonate include EMC, DMC, DEC, methyl propyl carbonate, ethyl propyl carbonate, 2,2,2-trifluoroethyl methyl carbonate, 2,2,2-trifluoroethyl ethyl carbonate, 1,1,1,3,3,3-hexafluoro-1-propyl methyl carbonate, and 1,1,1,3,3,3-hexafluoro-1-propyl ethyl carbonate, and among these, at least one selected from the group consisting of EMC, DMC, DEC, and methyl propyl carbonate is preferred. Specific examples of the ester include methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl 2-fluoropropionate, and ethyl 2-fluoropropionate.

[0050] The non-aqueous electrolyte of the present disclosure may also contain a polymer. The polymer may also include what is generally called a polymer solid electrolyte. The polymer solid electrolyte may also include a polymer solid electrolyte that contains a non-aqueous organic solvent as a plasticizer.

[0051] The polymer is not particularly limited as long as it is an aprotic polymer capable of dissolving the above components (A) to (C), the solute, and other additives described below. For example, a polymer having polyethylene oxide in the main chain or side chain, a homopolymer or copolymer of polyvinylidene fluoride, a methacrylic acid ester polymer, polyacrylonitrile, etc. are included. When a plasticizer is added to these polymers, aprotic nonaqueous organic solvents are preferred among the above nonaqueous organic solvents.

[0052] <Other additives> As long as the gist of the present disclosure is not impaired, the nonaqueous electrolyte solution of the present disclosure may further contain commonly used additives in any ratio.

[0053] The nonaqueous electrolyte of the present disclosure may contain at least one of the compounds represented by the following general formulas (3) to (5).

[0054] [ka]

[0055] [In general formula (3), X 1 and X 2 Each independently represents a halogen atom. + represents an alkali metal cation, an ammonium ion, or an organic cation.

[0056] In general formula (3), X 1 and X 2 Each independently represents a halogen atom. 1 and X 2 Examples of the halogen atom represented by include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc., and a fluorine atom is preferable. X 1 and X 2 may be the same or different, but are preferably the same, and are preferably both fluorine atoms.

[0057] In general formula (3), A + represents an alkali metal cation, an ammonium ion or an organic cation. A + Examples of the alkali metal cation represented by the formula (I) include a lithium cation, a sodium cation, and a potassium cation. A + is preferably an alkali metal cation, more preferably a lithium cation.

[0058] [ka]

[0059] [In general formula (4), R 4represents a hydrocarbon group having 2 to 6 carbon atoms. The hydrocarbon group may contain a heteroatom between the carbon atom-carbon atom bond. Any hydrogen atom in the hydrocarbon group may be substituted with a halogen atom.

[0060] In general formula (4), R 4 R represents a hydrocarbon group having 2 to 6 carbon atoms. 4 Examples of the hydrocarbon group represented by include linear or branched alkylene groups, alkenylene groups, and alkynylene groups. R 4 When represents an alkylene group, specific examples of the alkylene group include an ethylene group, an n-propylene group, an i-propylene group, an n-butylene group, an s-butylene group, a t-butylene group, an n-pentylene group, a -CHCH(CH)- group, and an n-hexylene group. R 4 When R represents an alkenylene group, specific examples of the alkenylene group include an ethenylene group and a propenylene group. 4 When represents an alkynylene group, specific examples of the alkynylene group include a propynylene group.

[0061] R 4 The hydrocarbon group represented by may contain a heteroatom between the carbon atom and the carbon atom. Examples of the heteroatom include an oxygen atom, a nitrogen atom, and a sulfur atom.

[0062] R 4 Any hydrogen atom of the hydrocarbon group represented by may be substituted with a halogen atom. Examples of the hydrocarbon group in which any hydrogen atom is substituted with a fluorine atom include a tetrafluoroethylene group, a 1,2-difluoroethylene group, a 2,2-difluoroethylene group, a fluoroethylene group, and a (trifluoromethyl)ethylene group.

[0063] R 4 is preferably an unsubstituted alkylene group having 3 to 4 carbon atoms, and more preferably a propylene group.

[0064] [ka]

[0065] [In general formula (5), R 5 represents a hydrocarbon group having 2 to 5 carbon atoms. The hydrocarbon group may contain a heteroatom between the carbon atom-carbon atom bond. Any hydrogen atom in the hydrocarbon group may be substituted with a halogen atom.

[0066] In general formula (5), R 5 R represents a hydrocarbon group having 2 to 5 carbon atoms. 5 Examples of the hydrocarbon group represented by include linear or branched alkylene groups, alkenylene groups, and alkynylene groups. R 5 When represents an alkylene group, specific examples of the alkylene group include an ethylene group, an n-propylene group, an i-propylene group, an n-butylene group, an s-butylene group, a t-butylene group, an n-pentylene group, and a -CH2CH(C3H7)- group. R 5 When represents an alkenylene group, specific examples of the alkenylene group include an ethenylene group and a propenylene group. R 5 When represents an alkynylene group, specific examples of the alkynylene group include an ethynylene group and a propynylene group.

[0067] R 5 The hydrocarbon group represented by may contain a heteroatom between the carbon atom and the carbon atom. Examples of the heteroatom include an oxygen atom, a nitrogen atom, and a sulfur atom.

[0068] R 5 Any hydrogen atom of the hydrocarbon group represented by may be substituted with a halogen atom. Examples of the hydrocarbon group in which any hydrogen atom is substituted with a fluorine atom include a tetrafluoroethylene group, a 1,2-difluoroethylene group, a 2,2-difluoroethylene group, a fluoroethylene group, and a (trifluoromethyl)ethylene group.

[0069] R 5is preferably an unsubstituted alkylene group having 2 to 3 carbon atoms, and more preferably an ethylene group.

[0070] Specific examples of "other additives" other than the compounds represented by the above general formulas (3) to (5) include cyclohexylbenzene, cyclohexylfluorobenzene, fluorobenzene (hereinafter, may be referred to as FB), biphenyl, difluoroanisole, tert-butylbenzene, tert-amylbenzene, 2-fluorotoluene, 2-fluorobiphenyl, vinylene carbonate, dimethylvinylene carbonate, vinylethylene carbonate, fluoroethylene carbonate, methyl propargyl carbonate, ethyl propargyl carbonate, dipropargyl carbonate, maleic anhydride, succinic anhydride, methylenemethane disulfonate, dimethylmethane disulfonate, trimethylenemethane disulfonate, methyl methanesulfonate, lithium difluorobis(oxalato)phosphate (hereinafter, may be referred to as LDFBOP), sodium difluorobis(oxalato)phosphate, potassium difluorobis(oxalato)phosphate, bis( Oxalate ) Lithium borate, bis( Oxalate ) Sodium borate, bis( Oxalate ) Examples of compounds that have an overcharge prevention effect, a negative electrode film forming effect, or a positive electrode protection effect include potassium borate, lithium tetrafluorooxalatophosphate (hereinafter, may be referred to as LTFOP), sodium tetrafluorooxalatophosphate, potassium tetrafluorooxalatophosphate, lithium tris(oxalato)phosphate, sodium tris(oxalato)phosphate, potassium tris(oxalato)phosphate, lithium ethylfluorophosphate (hereinafter, may be referred to as LEFP), lithium propylfluorophosphate, lithium fluorophosphate, ethenesulfonyl fluoride (hereinafter, may be referred to as ESF), trifluoromethanesulfonyl fluoride (hereinafter, may be referred to as TSF), methanesulfonyl fluoride (hereinafter, may be referred to as MSF), and phenyl difluorophosphate (hereinafter, may be referred to as PDFP).

[0071] The content of the other additives in the non-aqueous electrolyte is not particularly limited, but is preferably 0.01 mass % or more and 8.00 mass % or less with respect to the total amount of the non-aqueous electrolyte.

[0072] In addition, the battery may contain one or more of the following compounds: a lithium salt of a boron complex having an oxalic acid group, a lithium salt of a phosphorus complex having an oxalic acid group, a compound having an O=SF bond, and a compound having an O=PF bond. The battery may contain the above compounds, which is preferable from the viewpoint of not only improving the capacity retention rate after a long-term cycle at a high temperature and suppressing the increase in resistance at a low temperature after high-temperature storage, but also reducing the elution of Ni components from a Ni-containing electrode into the electrolyte when the electrode is used. It is more preferable that the lithium salt of the phosphorus complex having an oxalic acid group is at least one selected from the group consisting of lithium tetrafluorooxalatophosphate and lithium difluorobis(oxalato)phosphate, since this improves the capacity retention rate after long-term cycles at a further high temperature, suppresses the increase in resistance at a low temperature after high-temperature storage, and is particularly effective in suppressing the elution of Ni components from the positive electrode. Examples of the compound having an O=SF bond include lithium fluorosulfonate, propyl fluorosulfate, phenyl fluorosulfate, 4-fluorophenyl fluorosulfate, 4-tert-butylphenyl fluorosulfate, 4-tert-amylphenyl fluorosulfate, ethenesulfonyl fluoride, trifluoromethanesulfonyl fluoride, methanesulfonyl fluoride, benzenesulfonyl fluoride, 4-fluorophenylsulfonyl fluoride, 4-tert-butylphenylsulfonyl fluoride, 4-tert-amylphenylsulfonyl fluoride, and 2-methylphenylsulfonyl fluoride. Examples of the compound having the O=PF bond include lithium ethyl fluorophosphate, bis(difluorophosphoric acid), R Examples of the fluorophosphate include lithium difluorophosphate and phenyl difluorophosphate.

[0073] Furthermore, as in the case of a non-aqueous electrolyte battery called a polymer battery, the non-aqueous electrolyte may be quasi-solidified with a gelling agent or a crosslinked polymer.

[0074] The nonaqueous electrolyte of the present disclosure may or may not contain a compound represented by the following general formula (6). One embodiment of the nonaqueous electrolyte of the present disclosure is an embodiment in which the content of the compound represented by the following general formula (6) is less than 0.05% by mass when the amount of the compound represented by the above-mentioned general formula (1) is taken as 100% by mass. In addition, the nonaqueous electrolyte of the present disclosure may not contain a compound represented by the following general formula (6).

[0075] [ka]

[0076] [In general formula (6), R 6 ~R 8 are each independently a substituent having at least one of an unsaturated bond and an aromatic ring.

[0077] Above R 6 ~R 8 are each independently a substituent having at least one of an unsaturated bond and an aromatic ring, and specific examples thereof include the above-mentioned R 1 ~R 3 Examples of the above include those described in the explanation of the above.

[0078] <Method of preparing non-aqueous electrolyte> The method for preparing the non-aqueous electrolyte of the present disclosure is not particularly limited. For example, the electrolyte can be prepared by dissolving the silicon compound (A), the borate (B), the imide salt (C) and a solute in a non-aqueous organic solvent. In the operation of dissolving a solute in a nonaqueous organic solvent, it is effective from the viewpoint of preventing deterioration of the nonaqueous organic solvent and the solute to keep the liquid temperature of the nonaqueous organic solvent from exceeding 40° C. This is because keeping the liquid temperature at 40° C. or less can suppress the generation of free acids such as hydrogen fluoride (HF) caused by the solute reacting with water in the system and decomposing when the solute dissolves, and as a result, it is possible to suppress the decomposition of the nonaqueous organic solvent. In addition, dissolving and blending the solute by adding it little by little is also effective from the viewpoint of suppressing the generation of free acids such as HF. When dissolving a solute in a non-aqueous organic solvent, the non-aqueous organic solvent may be cooled. The liquid temperature is not particularly limited, but is preferably -20 to 40°C, more preferably 0 to 40°C.

[0079] In addition, when the silicon compound (A), the borate (B), the imide salt (C) and other additives are added, it is preferable to control the temperature of the nonaqueous electrolyte to be −10° C. or higher and 40° C. or lower. The upper limit of the temperature is more preferably 30° C. or lower, and particularly preferably 20° C. or lower.

[0080] The nonaqueous electrolyte of the present disclosure can be preferably used in a nonaqueous electrolyte battery (preferably a secondary battery).

[0081] [2. Non-aqueous electrolyte battery] The nonaqueous electrolyte battery includes at least (a) the nonaqueous electrolyte of the present disclosure, (b) a positive electrode, (c) a negative electrode having at least one material selected from the group consisting of a negative electrode material containing lithium metal and a negative electrode material capable of absorbing and releasing lithium, sodium, potassium, or magnesium, and preferably further includes (d) a separator, an exterior body, and the like.

[0082] <(b) Positive electrode> (b) The positive electrode preferably contains at least one type of oxide and / or polyanion compound as a positive electrode active material.

[0083] [Cathode active material] In the case of a lithium ion secondary battery in which the cations in the non-aqueous electrolyte are mainly lithium, (b) the positive electrode active material constituting the positive electrode is not particularly limited as long as it is a material capable of being charged and discharged. Examples of the positive electrode active material include those containing at least one of (b1) lithium transition metal composite oxides containing at least one metal selected from nickel, manganese, and cobalt and having a layered structure, (b2) lithium manganese composite oxides having a spinel structure, (b3) lithium-containing olivine-type phosphates, and (b4) lithium-excess layered transition metal oxides having a layered rock salt structure.

[0084] ((b1) Lithium transition metal composite oxide) Examples of the positive electrode active material (b1) lithium transition metal composite oxide containing at least one metal selected from nickel, manganese, and cobalt and having a layered structure include lithium-cobalt composite oxide, lithium-nickel composite oxide, lithium-nickel-cobalt composite oxide, lithium-nickel-cobalt-aluminum composite oxide, lithium-cobalt-manganese composite oxide, lithium-nickel-manganese composite oxide, and lithium-nickel-manganese-cobalt composite oxide, etc. In addition, some of the transition metal atoms that are the main components of these lithium transition metal composite oxides may be replaced with other elements such as Al, Ti, V, Cr, Fe, Cu, Zn, Mg, Ga, Zr, Si, B, Ba, Y, and Sn.

[0085] Specific examples of lithium-cobalt composite oxides and lithium-nickel composite oxides include LiCoO2, LiNiO2, and lithium cobalt oxides with added elements such as Mg, Zr, Al, and Ti (LiCo 0.98 Mg 0.01 Zr 0.01 O2, LiCo 0.98 Mg 0.01 Al 0.01 O2, LiCo 0.975 Mg 0.01 Zr 0.005 Al 0.01LiCoO2, etc., lithium cobalt oxide having a rare earth compound fixed to the surface as described in WO2014 / 034043, etc., may be used. Also, as described in JP2002-151077A, etc., LiCoO2 particles having a part of the particle surface coated with aluminum oxide may be used.

[0086] The lithium-nickel-cobalt composite oxide and the lithium-nickel-cobalt-aluminum composite oxide are represented by the general formula

[11] . Li a Ni 1-b-c Co b M 11 c O2

[11] In formula

[11] , M 11 is at least one element selected from the group consisting of Al, Fe, Mg, Zr, Ti, and B, a satisfies the conditions of 0.9≦a≦1.2, and b and c satisfy the conditions of 0.1≦b≦0.3 and 0≦c≦0.1. These can be prepared, for example, according to the manufacturing method described in JP-A-2009-137834. 0.8 Co 0.2 O2, LiNi 0.85 Co 0.10 Al 0.05 O2, LiNi 0.87 Co 0.10 Al 0.03 O2, LiNi 0.6 Co 0.3 Al 0.1 O2, etc.

[0087] Specific examples of lithium-cobalt-manganese composite oxide and lithium-nickel-manganese composite oxide are LiNi 0.5 Mn 0.5 O2, LiCo 0.5 Mn 0.5 O2, etc.

[0088] Lithium-nickel-manganese-cobalt composite oxides include the lithium-containing composite oxides represented by the general formula

[12] . Li dNi e Mn f Co g M 12 h O2

[12] In formula

[12] , M 12 is at least one element selected from the group consisting of Al, Fe, Mg, Zr, Ti, B, and Sn, d is 0.9≦d≦1.2, and e, f, g, and h satisfy the conditions e+f+g+h=1, 0≦e≦0.7, 0≦f≦0.5, 0≦g≦0.5, and h≧0. The lithium-nickel-manganese-cobalt composite oxide preferably contains manganese in the range shown in the general formula

[12] in order to enhance the structural stability and improve the safety of lithium secondary batteries at high temperatures. It is even more preferable that the lithium-nickel-manganese-cobalt composite oxide further contains cobalt in the range shown in the general formula

[12] in order to enhance the high-rate characteristics of lithium-ion secondary batteries. Specifically, for example, Li[Ni 1 / 3 Mn 1 / 3 Co 1 / 3 ]O2, Li[Ni 0.45 Mn 0.35 Co 0.2 ]O2, Li[Ni 0.5 Mn 0.3 Co 0.2 ]O2, Li[Ni 0.6 Mn 0.2 Co 0.2 ]O2, Li[Ni 0.49 Mn 0.3 Co 0.2 Zr 0.01 ]O2, Li[Ni 0.49 Mn 0.3 Co 0.2 Mg 0.01 ]O2, etc.

[0089] ((b2) Lithium manganese composite oxide with spinel structure) An example of the positive electrode active material (b2) lithium manganese composite oxide having a spinel structure is a spinel-type lithium manganese composite oxide represented by the general formula

[13] . Li j (M 2-k M13 k )O4

[13] In formula

[13] , M 13 is at least one metal element selected from the group consisting of Ni, Co, Fe, Mg, Cr, Cu, Al, and Ti; j satisfies 1.05 ≦ j ≦ 1.15; and k satisfies 0 ≦ k ≦ 0.20. Specifically, for example, LiMnO2, LiMn2O4, LiMn 1.95 Al 0.05 O4, LiMn 1.9 Al 0.1 O4, LiMn 1.9 Ni 0.1 O4, LiMn 1.5 Ni 0.5 O4, etc. can be mentioned.

[0090] ((b3) Lithium-containing olivine-type phosphate) As an example of the positive electrode active material, (b3) lithium-containing olivine-type phosphate includes, for example, those represented by the general formula

[14] . LiFe 1-n M 14 n PO4

[14] In formula

[14] , M 14 is at least one selected from Co, Ni, Mn, Cu, Zn, Nb, Mg, Al, Ti, W, Zr, and Cd; and n satisfies 0 ≦ n ≦ 1. Specifically, for example, LiFePO4, LiCoPO4, LiNiPO4, LiMnPO4, etc. can be mentioned, and among them, LiFePO4 and / or LiMnPO4 are preferable.

[0091] ((b4) Lithium-excess layered transition metal oxide) As an example of the positive electrode active material, (b4) lithium-excess layered transition metal oxide having a layered rock salt-type structure includes, for example, those represented by the general formula

[15] . xLiM 15 O2·(1 - x)Li2M 16 O3

[15] In formula

[15] , x is a number satisfying 0 < x < 1; and M 15 has an average oxidation number of 3 +At least one metal element is selected from the group consisting of M 16 has an average oxidation number of 4 + In formula

[15] , M is at least one metal element. 15 is preferably one metal element selected from trivalent Mn, Ni, Co, Fe, V, and Cr, but may be divalent and tetravalent metals in equal amounts to make the average oxidation number trivalent. In addition, in the formula

[15] , M 16 is preferably one or more metal elements selected from Mn, Zr, and Ti. 0.5 Mn 0.5 O2]·0.5[Li2MnO3], 0.5[LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2]·0.5[Li2MnO3], 0.5[LiNi 0.375 Co 0.25 Mn 0.375 O2]·0.5[Li2MnO3], 0.5[LiNi 0.375 Co 0.125 Fe 0.125 Mn 0.375 O2]·0.5[Li2MnO3], 0.45[LiNi 0.375 Co 0.25 Mn 0.375 [Li2O2]·0.10[Li2TiO3]·0.45[Li2MnO3], etc. The positive electrode active material represented by this general formula

[15] is known to exhibit high capacity when charged at a high voltage of 4.4 V (based on Li) or higher (for example, U.S. Patent 7,135,252). These positive electrode active materials can be prepared in accordance with the manufacturing methods described in, for example, JP-A-2008-270201, WO2013 / 118661, JP-A-2013-030284, and the like.

[0092] The positive electrode active material may contain at least one selected from the above (b1) to (b4) as a main component, and other components that may be contained include, for example, transition element chalcogenides such as FeS2, TiS2, TiO2, V2O5, MoO3, and MoS2, conductive polymers such as polyacetylene, polyparaphenylene, polyaniline, and polypyrrole, activated carbon, polymers that generate radicals, and carbon materials.

[0093] [Positive electrode current collector] (b) The positive electrode has a positive electrode current collector. As the positive electrode current collector, for example, aluminum, stainless steel, nickel, titanium, or an alloy thereof can be used.

[0094] [Cathode active material layer] (b) The positive electrode has a positive electrode active material layer formed on at least one surface of a positive electrode current collector. The positive electrode active material layer is composed of, for example, the above-mentioned positive electrode active material, a binder, and, if necessary, a conductive agent. Examples of the binder include polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, styrene butadiene rubber (SBR), carboxymethyl cellulose, methyl cellulose, cellulose acetate phthalate, hydroxypropyl methyl cellulose, and polyvinyl alcohol. As the conductive agent, for example, carbon materials such as acetylene black, ketjen black, furnace black, carbon fiber, graphite (granular graphite or flake graphite), fluorinated graphite, etc. are usable. In the positive electrode, it is preferable to use acetylene black or ketjen black, which has low crystallinity.

[0095] <(c) Negative electrode> The negative electrode material is not particularly limited, but in the case of lithium batteries and lithium ion batteries, lithium metal, alloys and intermetallic compounds of lithium metal and other metals, various carbon materials (artificial graphite, natural graphite, etc.), metal oxides, metal nitrides, tin (element), tin compounds, silicon (element), silicon compounds, activated carbon, conductive polymers, etc. may be used.

[0096] The carbon material may be, for example, graphitizable carbon, non-graphitizable carbon (hard carbon) with a (002) plane spacing of 0.37 nm or more, or graphite with a (002) plane spacing of 0.34 nm or less. More specifically, there are pyrolytic carbon, cokes, glassy carbon fiber, organic polymer compound sintered bodies, activated carbon, or carbon blacks. Among these, cokes include pitch coke, needle coke, or petroleum coke. The organic polymer compound sintered body refers to a phenolic resin, a furan resin, or the like, which is sintered at an appropriate temperature to be carbonized. Carbon materials are preferable because they have very little change in crystal structure due to the absorption and release of lithium, and therefore can provide high energy density and excellent cycle characteristics. The shape of the carbon material may be any of fibrous, spherical, granular, or scaly. In addition, amorphous carbon or graphite materials with amorphous carbon coated on the surface are more preferable because they have low reactivity between the material surface and the nonaqueous electrolyte.

[0097] (c) The negative electrode preferably contains at least one type of negative electrode active material.

[0098] [Negative electrode active material] In the case of a lithium ion secondary battery in which the cations in the non-aqueous electrolyte are mainly lithium, (c) the negative electrode active material constituting the negative electrode is one that can be doped and dedoped with lithium ions, for example, (c1) a lattice plane (002 ) surface Carbon materials with d values ​​of 0.340 nm or less, (c2) lattice plane (002 ) surface Examples of the negative electrode active material include a carbon material having a d value of more than 0.340 nm, (c3) an oxide of one or more metals selected from Si, Sn, and Al, (c4) one or more metals selected from Si, Sn, and Al, an alloy containing these metals, or an alloy of these metals or alloys with lithium, and (c5) a lithium titanium oxide. One of these negative electrode active materials can be used alone, or two or more can be used in combination.

[0099] (c1) Lattice plane (002 ) surface Carbon materials with d value of 0.340 nm or less) An example of a negative electrode active material (c1) X-ray diffraction lattice plane (002 ) surface Examples of carbon materials having a d value of 0.340 nm or less include pyrolytic carbons, cokes (e.g., pitch coke, needle coke, petroleum coke, etc.), graphites, fired organic polymer compounds (e.g., phenolic resins, furan resins, etc. fired at an appropriate temperature and carbonized), carbon fibers, activated carbons, etc., which may be graphitized. The carbon materials in question are those having a (002) plane spacing (d002) of 0.340 nm or less as measured by X-ray diffraction, and among these, those having a true density of 1.70 g / cm 3 Graphite having the above properties or a highly crystalline carbon material having properties similar thereto is preferred.

[0100] (c2) Lattice plane (002 ) surface Carbon materials with d values ​​exceeding 0.340 nm) An example of a negative electrode active material (c2) X-ray diffraction lattice plane (002 ) surface Carbon materials with d values ​​exceeding 0.340 nm include amorphous carbon, which is a carbon material in which the stacking order hardly changes even when heat-treated at high temperatures of 2000° C. or higher. Examples include non-graphitizable carbon (hard carbon), mesocarbon microbeads (MCMB) sintered at 1500° C. or lower, and mesope pitch carbon fiber (MCF). Carbotron (registered trademark) P manufactured by Kureha Corporation is a representative example.

[0101] ((c3) Oxides of one or more metals selected from Si, Sn, and Al) As an example of the negative electrode active material (c3) an oxide of one or more metals selected from Si, Sn and Al, for example, silicon oxide, tin oxide and the like that can be doped / dedoped with lithium ions can be mentioned. SiO2 has a structure in which ultrafine particles of Si are dispersed in SiO2. x When this material is used as the negative electrode active material, charging and discharging are smooth because the Si that reacts with Li is in the form of ultrafine particles, while the SiOx Since the particles themselves have a small surface area, the particles have good paint properties when made into a composition (paste) for forming a negative electrode active material layer, and the negative electrode mixture layer has good adhesion to the current collector. In addition, SiO x Since the volume change during charging and discharging is large, SiO x By using the graphite of the negative electrode active material (c1) in a specific ratio in combination with the negative electrode active material, it is possible to achieve both a high capacity and good charge / discharge cycle characteristics.

[0102] ((c4) One or more metals selected from Si, Sn, and Al, or alloys containing these metals, or alloys of these metals or alloys with lithium) Examples of the negative electrode active material (c4) include one or more metals selected from Si, Sn, and Al, or alloys containing these metals, or alloys of these metals or alloys with lithium, such as metals such as silicon, tin, and aluminum, silicon alloys, tin alloys, and aluminum alloys, and materials in which these metals or alloys are alloyed with lithium during charge and discharge can also be used. Preferred specific examples of these include metal elements (e.g., powders) such as silicon (Si) and tin (Sn), metal alloys, compounds containing the metals, and alloys containing tin (Sn) and cobalt (Co) in the metals, as described in WO2004 / 100293 and JP2008-016424. When the metals are used in electrodes, they are preferred because they can achieve high charge capacity and the volume expansion and contraction associated with charging and discharging is relatively small. In addition, it is known that when these metals are used in the negative electrode of a lithium ion secondary battery, they are alloyed with Li during charging, resulting in high charge capacity, which is also preferred in this respect. Furthermore, negative electrode active materials formed from silicon pillars with submicron diameters, negative electrode active materials made of silicon fibers, etc., as described in, for example, WO2004 / 042851, WO2007 / 083155, etc., may also be used.

[0103] ((c5) Lithium titanium oxide) Examples of the negative electrode active material (c5) lithium titanium oxide include lithium titanate having a spinel structure and lithium titanate having a ramsdellite structure. Examples of lithium titanate having a spinel structure include Li 4+α Ti5O 12 (α varies within the range of 0≦α≦3 depending on the charge / discharge reaction). Examples of lithium titanate having a ramsdellite structure include Li 2+β Ti3O7 (β varies within the range of 0≦β≦3 depending on the charge / discharge reaction) can be exemplified. These negative electrode active materials can be prepared according to the manufacturing methods described in, for example, JP-A-2007-018883 and JP-A-2009-176752. For example, in the case of a sodium ion secondary battery in which the cations in the non-aqueous electrolyte are mainly sodium, oxides such as hard carbon, TiO2, V2O5, and MoO3 are used as the negative electrode active material. For example, in the case of a sodium ion secondary battery in which the cations in the non-aqueous electrolyte are mainly sodium, sodium-containing transition metal composite oxides such as NaFeO2, NaCrO2, NaNiO2, NaMnO2, and NaCoO2, mixtures of transition metals such as Fe, Cr, Ni, Mn, and Co in these sodium-containing transition metal composite oxides, those in which a part of the transition metal in these sodium-containing transition metal composite oxides is replaced with a metal other than the other transition metal, phosphate compounds of transition metals such as Na2FeP2O7 and NaCo3(PO4)2P2O7, sulfides such as TiS2 and FeS2, conductive polymers such as polyacetylene, polyparaphenylene, polyaniline, and polypyrrole, activated carbon, radical-generating polymers, carbon materials, and the like are used as the positive electrode active material.

[0104] [Negative electrode current collector] (c) The negative electrode has a negative electrode current collector. As the negative electrode current collector, for example, copper, stainless steel, nickel, titanium, or an alloy thereof can be used.

[0105] [Negative electrode active material layer] (c) The negative electrode has, for example, a negative electrode active material layer formed on at least one surface of a negative electrode current collector. The negative electrode active material layer is composed of, for example, the above-mentioned negative electrode active material, a binder, and, if necessary, a conductive agent. Examples of the binder include polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, styrene butadiene rubber (SBR), carboxymethyl cellulose, methyl cellulose, cellulose acetate phthalate, hydroxypropyl methyl cellulose, and polyvinyl alcohol. As the conductive agent, for example, carbon materials such as acetylene black, ketjen black, furnace black, carbon fiber, graphite (granular graphite or flake graphite), and fluorinated graphite can be used.

[0106] <Method of manufacturing electrodes ((b) positive electrode and (c) negative electrode)> The electrode can be obtained, for example, by dispersing and kneading the active material, the binder, and optionally the conductive agent in a predetermined blending amount in a solvent such as N-methyl-2-pyrrolidone (NMP) or water, applying the obtained paste to a current collector, and drying to form an active material layer. The obtained electrode is preferably compressed by a method such as a roll press to adjust the density of the electrode to an appropriate value.

[0107] <(d) Separator> The nonaqueous electrolyte battery may include a separator (d). The separator for preventing contact between the positive electrode (b) and the negative electrode (c) may be a nonwoven fabric or porous sheet made of polyolefin such as polypropylene or polyethylene, cellulose, paper, glass fiber, or the like. These films are preferably microporous so that the nonaqueous electrolyte can penetrate and ions can easily pass through. The polyolefin separator may be, for example, a microporous polymer film such as a porous polyolefin film, which electrically insulates the positive electrode and the negative electrode and allows lithium ions to pass through. Specific examples of the porous polyolefin film include a porous polyethylene film alone, or a multi-layer film formed by stacking a porous polyethylene film and a porous polypropylene film. Also, a composite film of a porous polyethylene film and a polypropylene film may be used.

[0108] <Exterior body> In constructing a nonaqueous electrolyte battery, the exterior body of the nonaqueous electrolyte battery may be, for example, a coin-shaped, cylindrical, or rectangular metal can or a laminate exterior body. Examples of the metal can material include nickel-plated steel plate, stainless steel plate, nickel-plated stainless steel plate, aluminum or its alloy, nickel, titanium, etc. As the laminate exterior body, for example, an aluminum laminate film, a SUS laminate film, a silica-coated polypropylene, a polyethylene laminate film, or the like can be used.

[0109] The configuration of the nonaqueous electrolyte battery according to this embodiment is not particularly limited, but may be, for example, a configuration in which an electrode element in which a positive electrode and a negative electrode are arranged opposite each other and a nonaqueous electrolyte are enclosed in an exterior body. The shape of the nonaqueous electrolyte battery is not particularly limited, but an electrochemical device having a shape such as a coin shape, a cylindrical shape, a square shape, or an aluminum laminate sheet shape is assembled from the above-mentioned elements. EXAMPLES

[0110] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these descriptions in any way.

[0111] (Preparation of non-aqueous electrolyte No. 1-1) A mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate in a volume ratio of 2.5:4:3.5 was used as the nonaqueous organic solvent, and LiPF6 was added as a solute to the solvent to a concentration of 1.0 mol / L. Next, a compound represented by formula (1b) as component (A), lithium tetrafluoroborate (LiBF4) as component (B), and lithium bis(fluorosulfonyl)imide (LiFSI) as component (C) were dissolved in the non-aqueous electrolyte to give concentrations of 0.2% by mass for component (A), 0.4% by mass for component (B), and 0.6% by mass for component (C). The above preparation was carried out while maintaining the liquid temperature in the range of 20 to 30°C. The preparation conditions for the non-aqueous electrolyte are shown in Table 1. In all tables hereafter, "-" indicates that no additive was added.

[0112] (Preparation of non-aqueous electrolyte No. 1-2) No.1-2 was prepared in the same manner as nonaqueous electrolyte No.1-1, except that the compound represented by formula (1c) was used as component (A) instead of the compound represented by formula (1b), and the concentrations of components (A) to (C) were changed as shown in Table 1. The preparation conditions for the nonaqueous electrolyte are shown in Table 1.

[0113] (Preparation of Comparative Non-Aqueous Electrolytes No. 1-1 to 1-2) Comparative nonaqueous electrolyte solutions No. 1-1 and 1-2 were prepared in the same manner as nonaqueous electrolyte solution No. 1-1, except that component (C), lithium bis(fluorosulfonyl)imide, was not added as shown in Table 1, and the concentration of component (B) was changed as shown in Table 1. The preparation conditions for the nonaqueous electrolyte solutions are shown in Table 1.

[0114] (Preparation of Comparative Non-Aqueous Electrolytes No. 1-3) Comparative nonaqueous electrolyte No. 1-3 was prepared in the same manner as nonaqueous electrolyte No. 1-1, except that component (B) lithium tetrafluoroborate and component (C) lithium bis(fluorosulfonyl)imide were not added as shown in Table 1. The preparation conditions for the nonaqueous electrolyte are shown in Table 1.

[0115] (Preparation of Comparative Non-Aqueous Electrolytes No. 1-4) Comparative electrolyte No. 1-4 was prepared in the same manner as comparative nonaqueous electrolyte No. 1-3, except that 0.3 mass% of the compound represented by formula (1c) was used as component (A) instead of the compound represented by formula (1b). The preparation conditions of the nonaqueous electrolyte are shown in Table 1.

[0116] For reference, the mass content of component (A) is W A The mass content W of component (B) relative to B The ratio of W B / W A , and the mass-based content W of component (A) A The mass content W of component (C) relative to C The ratio of W C / W A are shown in Table 1.

[0117] [Table 1]

[0118] (Preparation of non-aqueous electrolyte battery) Using the above non-aqueous electrolyte, LiNi 0.6 Co 0.2 Mn 0.2 A non-aqueous electrolyte battery (test cell) was fabricated using O2 as the positive electrode material and graphite as the negative electrode material. LiNi 0.6 Co 0.2 Mn 0.2 90% by mass of O2 powder was mixed with 5% by mass of polyvinylidene fluoride (hereinafter referred to as "PVDF") as a binder and 5% by mass of acetylene black as a conductive material, and N-methylpyrrolidone (hereinafter referred to as "NMP") was added to make a paste. This paste was applied to aluminum foil and dried to make a test cathode body. In addition, 90% by mass of graphite powder was mixed with 10% by mass of PVDF as a binder, and NMP was further added to prepare a slurry. This slurry was applied onto copper foil and dried at 120° C. for 12 hours to prepare a test negative electrode body. A polyethylene separator was then impregnated with the non-aqueous electrolyte to assemble a 50 mAh cell with an aluminum laminate exterior.

[0119] [DC resistance measurement test after initial charge / discharge (resistance evaluation at low temperature)] First, the fabricated cell was subjected to initial charge and discharge under the following conditions at an ambient temperature of 25° C. That is, the cell was charged at a constant current and constant voltage of 0.1 C rate (5 mA) with a charging upper limit voltage of 4.3 V, discharged at a constant current of 0.2 C rate (10 mA) until the discharge end voltage was 3.0 V, and then charged at a constant current and constant voltage of 0.2 C rate (10 mA) with a charging upper limit voltage of 4.3 V, and discharged at a constant current of 0.2 C rate (10 mA) until the discharge end voltage was 3.0 V. This charge and discharge cycle was repeated three times. After completing the initial charge and discharge, the battery was removed from the charge / discharge device and the 25°C thermostatic chamber, then connected to an electrochemical measurement device (Electrofield, automatic battery evaluation device) and placed in a thermostatic chamber at -20°C. After leaving it in that state for 1 hour, IV measurements were performed to determine the absolute value of the DC resistance. As shown in Table 2, the nonaqueous electrolytes were compared according to the type of component (A) used, and the absolute value of the DC resistance of each experimental example was expressed as a relative value when the absolute value of the standard DC resistance was set to 100, using nonaqueous electrolytes (comparative nonaqueous electrolytes No. 1-3 to 1-4) that did not contain component (B) or component (C) as the standard.

[0120] [Capacity measurement test after 400 cycles (cycle characteristic evaluation)] The non-aqueous electrolyte battery after the above-mentioned DC resistance measurement test at -20°C was removed from the electrochemical measurement device and the -20°C thermostatic chamber, connected to a charge / discharge device, and placed in a thermostatic chamber at 50°C. After leaving it in that state for 2 hours, it was charged to 4.3V at a charge rate of 2C. After reaching 4.3V, the voltage was maintained for 1 hour, and then discharged to 3.0V at a discharge rate of 2C. This charge / discharge at 2C in a 50°C environment was repeated 400 cycles. The degree of deterioration of the battery was evaluated based on the discharge capacity after 400 cycles. As shown in Table 2, the nonaqueous electrolytes were compared according to the type of component (A) used, and the capacity value after 400 cycles of each experimental example was expressed as a relative value when the capacity value of the standard was set to 100, with the nonaqueous electrolytes (comparative nonaqueous electrolytes No. 1-3 to 1-4) not containing the components (B) and (C) being used as the standard.

[0121] [Table 2]

[0122] From the evaluation results shown in Table 2, it was confirmed that the nonaqueous electrolyte battery using the nonaqueous electrolyte of the present disclosure can exhibit a well-balanced effect of reducing the absolute value of internal resistance at low temperatures and an effect of improving battery capacity after cycle testing, compared to the comparative example. [Industrial Applicability]

[0123] According to the present disclosure, it is possible to provide a nonaqueous electrolyte solution that can achieve a good balance between the effect of reducing the absolute value of internal resistance at low temperatures (0° C. or lower, for example, −20° C.) and the effect of improving battery capacity after cycle testing.

[0124] Although the present disclosure has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the disclosure. This application is based on a Japanese patent application (Patent Application No. 2019-105459) filed on June 5, 2019, the contents of which are incorporated herein by reference.

Claims

1. A nonaqueous electrolyte for a lithium ion secondary battery, comprising: The present invention comprises a non-aqueous organic solvent, a solute, a silicon compound (A), a borate (B), and an imide salt (C), The silicon compound (A) is a compound represented by the following general formula (1): the borate (B) is a borate formed from a pair of at least one cation selected from the group consisting of alkali metal cations and alkaline earth metal cations and at least one anion selected from the group consisting of tetrafluoroborate anion and difluorooxalatoborate anion, The imide salt (C) is an imide salt represented by the following general formula (2): A non-aqueous electrolyte for lithium-ion secondary batteries. 【Chemistry 1】 [R １ ~R ３ are each independently a substituent having at least one of an unsaturated bond and an aromatic ring, R １ ~R ３ At least one of the groups is a substituent having an aromatic ring. 【Chemistry 2】 [Rf １ and Rf ２ each independently represents a fluorine atom or a linear or branched perfluoroalkyl group having 1 to 4 carbon atoms; M ＋ represents an alkali metal cation.

2. The R １ ~R ３ The nonaqueous electrolyte for a lithium ion secondary battery according to claim 1 , wherein each of the groups independently represents a group selected from the group consisting of an alkenyl group, an alkynyl group, an aryl group, an alkenyloxy group, an alkynyloxy group, and an aryloxy group.

3. the alkenyl group is a group selected from an ethenyl group and a 2-propenyl group, the alkynyl group is an ethynyl group, the aryl group is selected from a phenyl group, a 2-methylphenyl group, a 4-methylphenyl group, a 4-fluorophenyl group, a 4-tert-butylphenyl group, and a 4-tert-amylphenyl group; the alkenyloxy group is a group selected from a vinyloxy group and a 2-propenyloxy group, the alkynyloxy group is a propargyloxy group, The nonaqueous electrolyte for a lithium ion secondary battery according to claim 2, wherein the aryloxy group is selected from a phenoxy group, a 2-methylphenoxy group, a 4-methylphenoxy group, a 4-fluorophenoxy group, a 4-tert-butylphenoxy group, and a 4-tert-amylphenoxy group.

4. The R １ ~R ３ 2. The nonaqueous electrolyte for a lithium ion secondary battery according to claim 1, wherein at least one of the above is a group selected from the group consisting of an alkenyl group, an alkynyl group, an alkenyloxy group, and an alkynyloxy group.

5. The R １ ~R ３ The nonaqueous electrolyte for a lithium ion secondary battery according to claim 1 or 4, wherein two of the above are each independently an ethenyl group or an ethynyl group.

6. The compound represented by the general formula (1) is at least one selected from the group consisting of the following (1a) to (1e): A nonaqueous electrolyte for a lithium ion secondary battery according to any one of claims 1 to 5. 【Chemistry 3】

7. The nonaqueous electrolyte for a lithium ion secondary battery according to claim 6, wherein the compound represented by the general formula (1) is at least one selected from the group consisting of (1a), (1b), (1c), and (1d).

8. The nonaqueous electrolyte for a lithium ion secondary battery according to any one of claims 1 to 7, wherein the borate (B) is at least one selected from the group consisting of lithium tetrafluoroborate and lithium difluorooxalatoborate.

9. The nonaqueous electrolyte for a lithium ion secondary battery according to any one of claims 1 to 8, wherein the imide salt (C) is lithium bis(fluorosulfonyl)imide.

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