Non-aqueous electrolyte

Abstract

According to the nonaqueous electrolyte, a nonaqueous electrolyte which can balance the reduction effect of the absolute value of the internal resistance at low temperatures and the improvement effect of the battery capacity after the cycle test can be provided, the nonaqueous electrolyte including: a nonaqueous organic solvent, a solute, a specific silicon compound (A), a specific borate (B), and a specific imide salt (C), the content W of the aforementioned borate (B) on a mass basis B The content W of the aforementioned silicon compound (A) on a mass basis A The ratio W B / W A is 1.5 or more and 3 or less, the content W of the aforementioned imide salt (C) on a mass basis C The content W of the aforementioned silicon compound (A) on a mass basis A The ratio W C / W A is 1 or more and 5 or less.

Description

Technical Field

[0001] This disclosure relates to non-aqueous electrolytes. Background Technology

[0002] In recent years, batteries, as electrochemical devices, have seen significant attention regarding small energy storage systems used in information-related devices, communication devices, personal computers, cameras, digital cameras, mobile phones, and smartphones; large energy storage systems for high-energy-density applications; auxiliary power supplies for electric vehicles, hybrid vehicles, and fuel cell vehicles; and energy storage systems for power applications. As a potential candidate, non-aqueous electrolyte batteries, represented by lithium-ion batteries with high energy density, high voltage, and high capacity, are currently under active research and development.

[0003] Non-aqueous electrolytes used in non-aqueous electrolyte batteries, such as lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium tetrafluoroborate (LiBF4), which contain fluorinated electrolytes dissolved in solvents such as cyclic carbonates, chain carbonates, and esters as solutes, are suitable for obtaining batteries with high voltage and high capacity, and are therefore frequently used. However, non-aqueous electrolyte batteries using such electrolytes may not meet the battery characteristics, such as cycle performance and power performance.

[0004] For example, in the case of lithium-ion secondary batteries, during the initial charging process, when lithium cations are inserted into the negative electrode, a reaction occurs between the negative electrode and the lithium cations, or between the negative electrode and the electrolyte solvent, forming a coating on the surface of the negative electrode mainly composed of lithium oxide, lithium carbonate, or alkyl lithium carbonate. This coating on the electrode surface is called a solid electrolyte interface (SEI), and its properties, such as inhibiting further reduction and decomposition of the solvent and suppressing the degradation of battery performance, have a significant impact on battery performance. Similarly, a coating of decomposition products also forms on the surface of the positive electrode, which is known to play an important role in inhibiting the oxidative decomposition of the solvent and suppressing the generation of gases inside the battery.

[0005] In order to improve battery characteristics such as cycle performance and low-temperature performance (below 0°C), it is important to form a stable SEI with high ionic conductivity and low electronic conductivity. Small amounts (usually more than 0.001% by mass and less than 10% by mass) of compounds called additives are added to the electrolyte, thus actively attempting to form a good SEI.

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

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2002-134169 Summary of the Invention

[0010] The problem the invention aims to solve

[0011] However, further improvements in performance are required, such as the reduction in the absolute value of internal resistance (also simply "resistance") at low temperatures (below 0°C) and the retention rate of battery capacity after cycle testing.

[0012] This disclosure is made in view of the above circumstances, and its purpose is to provide a non-aqueous electrolyte that can uniformly and well exert the effect of reducing the absolute value of internal resistance at low temperatures (below 0°C, for example -20°C) and improving the battery capacity after cycle testing.

[0013] Solution for solving the problem

[0014] The inventors have discovered that the above-mentioned problem can be achieved through the following configuration.

[0015] <1> A non-aqueous electrolyte comprising:

[0016] Non-aqueous organic solvents, solutes, silicon compounds (A), borates (B), and imide salts (C),

[0017] The aforementioned silicon compound (A) is a compound represented by the following general formula (1).

[0018] The aforementioned borate (B) is a borate formed by a pair of the following cations and anions, wherein the cation is selected from at least one of the group consisting of alkali metal cations and alkaline earth metal cations, and the anion is selected from at least one of the group consisting of tetrafluoroborate anion and difluorooxalate-borate anion.

[0019] The aforementioned imide salt (C) is an imide salt represented by the following general formula (2).

[0020] The content W of the aforementioned borate (B) as a quality standard B The content W relative to the aforementioned silicon compound (A) mass benchmark A The ratio is W B / W A It is between 1.5 and 3.

[0021] The content W of the aforementioned imide salt (C) as a quality standard C The content W relative to the aforementioned silicon compound (A) mass benchmark A The ratio is W C / W A It is between 1 and 5.

[0022]

[0023] [R 1 ~R 3 Each substituent is independently a substituent having at least one of the following: an unsaturated bond and an aromatic ring.

[0024]

[0025] [Rf 1 and Rf 2 Each independently represents a perfluoroalkyl group, either a straight-chain group with 1 to 4 carbon atoms or a branched group with 3 to 4 carbon atoms, M + This indicates an alkali metal cation.

[0026] <2>

[0027] according to <1> The non-aqueous electrolyte, wherein the aforementioned R 1 ~R 3 Each is independently a group selected from the group consisting of alkenyl, alkynyl, aryl, alkenyloxy, alkynyloxy, and aryloxy groups.

[0028] <3>

[0029] according to <2> The non-aqueous electrolyte, wherein,

[0030] The aforementioned alkenyl group is selected from vinyl and 2-propenyl groups.

[0031] The aforementioned alkynyl group is an ethynyl group.

[0032] The aforementioned aryl group is selected from phenyl, 2-methylphenyl, 4-methylphenyl, 4-fluorophenyl, 4-tert-butylphenyl, and 4-tert-pentylphenyl.

[0033] The aforementioned olefin group is selected from ethyleneoxy and 2-propenoxy groups.

[0034] The aforementioned alkynyloxy group is the propynyloxy group.

[0035] The aforementioned aryloxy group is selected from phenoxy, 2-methylphenoxy, 4-methylphenoxy, 4-fluorophenoxy, 4-tert-butylphenoxy, and 4-tert-pentylphenoxy.

[0036] <4>

[0037] according to <1> The non-aqueous electrolyte, wherein the aforementioned R 1 ~R 3 At least two of them are independently vinyl or ethynyl groups.

[0038] <5>

[0039] according to <1> ~ <4> The non-aqueous electrolyte in any one of the above general formulas (1) is at least one selected from the group consisting of (1a) to (1q) below.

[0040]

[0041] <6>

[0042] according to <5> The non-aqueous electrolyte, wherein the compound represented by the aforementioned general formula (1) is selected from at least one of the group consisting of (1a), (1b), (1c), (1e), (1f), (1g), (1h), (1i), (1j), (1k), (1p), and (1q).

[0043] <7>

[0044] according to <1> ~ <6> The non-aqueous electrolyte in any one of the following methods, wherein the aforementioned borate (B) is at least one selected from the group consisting of lithium tetrafluoroborate and lithium difluorooxalate borate.

[0045] <8>

[0046] according to <1> ~ <7> The non-aqueous electrolyte in any one of the following methods, wherein the aforementioned imide salt (C) is lithium bis(fluorosulfonyl)imide.

[0047] The effects of the invention

[0048] According to this disclosure, a non-aqueous electrolyte can be provided that can uniformly and effectively reduce the absolute value of internal resistance at low temperatures (below 0°C, for example -20°C) and improve battery capacity after cycle testing. Detailed Implementation

[0049] The following embodiments are examples of various components and combinations thereof. Additions, omissions, substitutions, and other modifications to the components may be made without departing from the spirit of this disclosure. Furthermore, this disclosure is not limited to the embodiments.

[0050] In this specification, “~” is used to encompass the values ​​described before and after it as lower and upper limits.

[0051] [1. Non-aqueous electrolyte]

[0052] The non-aqueous electrolyte disclosed herein is a non-aqueous electrolyte.

[0053] It comprises: a non-aqueous organic solvent, a solute, a silicon compound (A), a borate (B), and an imide salt (C).

[0054] The aforementioned silicon compound (A) is a compound represented by the following general formula (1).

[0055] The aforementioned borate (B) is a borate formed by a pair of the following cations and anions, wherein the cation is selected from at least one of the group consisting of alkali metal cations and alkaline earth metal cations, and the anion is selected from at least one of the group consisting of tetrafluoroborate anion and difluorooxalate-borate anion.

[0056] The aforementioned imide salt (C) is an imide salt represented by the following general formula (2).

[0057] The content W of the aforementioned borate (B) as a quality standard B The content W relative to the aforementioned silicon compound (A) mass benchmark A The ratio is W B / W A It is between 1.5 and 3.

[0058] The content W of the aforementioned imide salt (C) as a quality standard C The content W relative to the aforementioned silicon compound (A) mass benchmark A The ratio is W C / W A It is between 1 and 5.

[0059]

[0060] [R 1 ~R 3 Each substituent is independently a substituent having at least one of the following: an unsaturated bond and an aromatic ring.

[0061]

[0062] [Rf 1 and Rf 2 Each independently represents a perfluoroalkyl group, either a straight-chain group with 1 to 4 carbon atoms or a branched group with 3 to 4 carbon atoms, M + This represents an alkali metal cation.

[0063] The following describes the components contained in the non-aqueous electrolyte of this disclosure.

[0064] <Silicon Compound (A)>

[0065] The silicon compound (A) will be described. The silicon compound (A) will also be referred to as component (A).

[0066] Silicon compound (A) is the compound represented by the following general formula (1).

[0067]

[0068] [R 1 ~R 3Each substituent is independently a substituent having at least one of the following: an unsaturated bond and an aromatic ring.

[0069] The above R 1 ~R 3 The number of carbons of the substituents represented, which have at least one of unsaturated bonds and aromatic rings, is not particularly limited. For example, substituents with 2 to 25 carbons can be mentioned, preferably with 2 to 20 carbons, and more preferably with 2 to 15 carbons.

[0070] The above R 1 ~R 3 Preferably, the group is selected from alkenyl, alkynyl, aryl, alkenyloxy, alkynoxy, and aryloxy groups.

[0071] The alkenyl group is preferably selected from vinyl and 2-propenyl (allyl), and the alkynyl group is preferably ethynyl. Additionally, the aryl group is preferably selected from phenyl, 2-methylphenyl, 4-methylphenyl, 4-fluorophenyl, 4-tert-butylphenyl, and 4-tert-pentylphenyl.

[0072] The olefinic group is preferably selected from ethyleneoxy and 2-propenoxy (allyloxy). Additionally, the alkynyloxy group is preferably propynoxy, and the aryloxy group is preferably selected from phenoxy, 2-methylphenoxy, 4-methylphenoxy, 4-fluorophenoxy, 4-tert-butylphenoxy, and 4-tert-pentylphenoxy.

[0073] Furthermore, from the perspective of achieving a high level of durability improvement, R is the preferred choice. 1 ~R 3 At least two of them are independently vinyl or ethynyl groups. Specifically, examples can be found in compounds (1a) to (1q), (1a) to (1d), (1f) to (1k), and (1m) to (1q) described later.

[0074] For the compound represented by general formula (1), specifically, it is preferred to select at least one from the group consisting of compounds (1a) to (1q), wherein, from the viewpoint of the stability of the compound, it is particularly preferred to select at least one from the group consisting of (1a), (1b), (1c), (1e), (1f), (1g), (1h), (1i), (1j), (1k), (1p), and (1q).

[0075]

[0076] There is no particular limitation on the suitable concentration of silicon compound (A) relative to the total amount of the non-aqueous electrolyte containing the aforementioned non-aqueous organic solvent and solute. Generally, the lower limit is 0.01% by mass or more, preferably 0.05% by mass or more, and more preferably 0.1% by mass or more. In addition, the upper limit is generally 3.0% by mass or less, preferably 2.0% by mass or less, and more preferably 1.0% by mass or less.

[0077] In addition, silicon compound (A) can be used alone or in combination.

[0078] <Borate (B)>

[0079] The borate (B) is described. The borate (B) is also referred to as component (B).

[0080] Borate (B) is a borate formed by a pair of the following cations and the following anions, wherein the cation is selected from at least one of the group consisting of alkali metal cations and alkaline earth metal cations, and the anion is selected from at least one of the group consisting of tetrafluoroborate anion and difluorooxalate-borate anion.

[0081] As the cation constituting borate (B), an alkali metal cation is preferred, wherein lithium ion, sodium ion, or potassium ion is more preferred, and lithium ion is even more preferred.

[0082] That is, the borate (B) is preferably selected from at least one of the group consisting of lithium tetrafluoroborate and lithium difluorooxalate borate, and more preferably lithium tetrafluoroborate.

[0083] There is no particular limitation on the suitable concentration of borate (B) relative to the total amount of the non-aqueous electrolyte containing the aforementioned non-aqueous organic solvent and solute. Generally, the lower limit is 0.01% by mass or more, preferably 0.05% by mass or more, and more preferably 0.1% by mass or more. In addition, generally, the upper limit is 9.0% by mass or less, preferably 6.0% by mass or less, and more preferably 3.0% by mass or less.

[0084] In addition, borates (B) can be used alone or in combination.

[0085] <Imidine Salt (C)>

[0086] The imide salt (C) is described. The imide salt (C) is also referred to as component (C).

[0087] The imide salt (C) is the imide salt represented by the following general formula (2).

[0088]

[0089] [Rf 1 and Rf 2Each independently represents a perfluoroalkyl group, either a straight-chain group with 1 to 4 carbon atoms or a branched group with 3 to 4 carbon atoms, M + This indicates an alkali metal cation.

[0090] As the alkali metal cation (M) constituting the imide salt (C) + More preferably, lithium ions, sodium ions, or potassium ions, with lithium ions being the most preferred.

[0091] As the anion constituting the imide salt (C), it is preferably an imide anion selected from at least one of the group consisting of bis(trifluoromethanesulfonyl)imide anion, bis(pentafluoroethanesulfonyl)imide anion, bis(fluorosulfonyl)imide anion, and (trifluoromethanesulfonyl)(fluorosulfonyl)imide anion.

[0092] The imide salt (C) is preferably lithium bis(fluorosulfonyl)imide.

[0093] There is no particular limitation on the suitable concentration of the imide salt (C) relative to the total amount of the non-aqueous electrolyte containing the aforementioned non-aqueous organic solvent and solute. Generally, the lower limit is 0.01% by mass or more, preferably 0.05% by mass or more, and more preferably 0.1% by mass or more. In addition, generally, the upper limit is 15% by mass or less, preferably 10% by mass or less, and more preferably 5% by mass or less.

[0094] In addition, imide salt (C) can be used alone or in combination.

[0095] The content W of borate (B) in the non-aqueous electrolyte of this disclosure is based on a mass standard. B Content W relative to the mass standard of silicon compound (A) A The ratio is W B / W A It is between 1.5 and 3.

[0096] In addition, the mass standard content W of the imide salt (C) in the non-aqueous electrolyte of this disclosure is... C Content W relative to the mass standard of silicon compound (A) A The ratio is W C / W A It is between 1 and 5.

[0097] From the perspective of internal resistance at low temperatures (below 0°C) and battery capacity retention after cycle testing, the aforementioned W B / W A More preferably, the value is 1.7 or more and 3 or less; particularly preferably, it is 2 or more and 3 or less.

[0098] From the perspective of internal resistance at low temperatures (below 0°C) and battery capacity retention after cycle testing, the aforementioned WC / W A More preferably, 1.5 or more and 5 or less; particularly preferably, 2 or more and 5 or less.

[0099] <Solute>

[0100] The solutes contained in the non-aqueous electrolyte of this disclosure are described.

[0101] The solute is preferably an ionic salt, for example, preferably an ionic salt formed by a pair of the following cations and anions, wherein the cation is selected from at least one of the group consisting of alkali metal ions and alkaline earth metal ions, and the anion is selected from at least one of the group consisting of hexafluorophosphate anion, trifluoromethanesulfonate anion, fluorosulfonate anion, bis(difluorophosphono)imide anion, (difluorophosphono)(fluorosulfonate)imide anion and (difluorophosphono)(trifluoromethanesulfonate)imide anion.

[0102] Furthermore, considering the solubility in non-aqueous organic solvents and their electrochemical stability, it is preferred that the cation of the ionic salt of the solute is lithium, sodium, potassium or magnesium, and the anion is at least one selected from the group consisting of hexafluorophosphate anion, trifluoromethanesulfonate anion, bis(difluorophosphonyl)imide anion and (difluorophosphonyl)(fluorosulfonyl)imide anion.

[0103] There are no particular restrictions on the suitable concentration of the solute, but generally, the lower limit is 0.5 mol / L or higher, preferably 0.7 mol / L or higher, and more preferably 0.9 mol / L or higher. Additionally, the upper limit is generally 2.5 mol / L or lower, preferably 2.2 mol / L or lower, and more preferably 2.0 mol / L or lower. By setting it to 0.5 mol / L or higher, the decrease in cycle characteristics and power characteristics of the non-aqueous electrolyte battery caused by the decrease in ionic conductivity can be suppressed. By setting it to 2.5 mol / L or lower, the decrease in ionic conductivity, cycle characteristics, and power characteristics of the non-aqueous electrolyte battery caused by the increase in viscosity can be suppressed.

[0104] In addition, a single solute can be used alone, or multiple solutes can be used in combination.

[0105] <Non-aqueous organic solvents>

[0106] Explanation of non-aqueous organic solvents.

[0107] The types of non-aqueous organic solvents used in the non-aqueous electrolytes disclosed herein are not particularly limited, and any non-aqueous organic solvent can be used. Specifically, it is preferably selected from methyl ethyl 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- The group consisting of at least one of the following: hexafluoro-1-propyl ester, ethylene carbonate (hereinafter also referred to as "EC"), propylene carbonate (hereinafter also referred to as "PC"), butyl 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.

[0108] Furthermore, when the aforementioned non-aqueous organic solvent includes at least one selected from the group consisting of cyclic carbonates and chain carbonates, it is preferable to have excellent cycling characteristics at high temperatures. Additionally, when the aforementioned non-aqueous organic solvent includes an ester, it is preferable to have excellent input / output power characteristics at low temperatures.

[0109] Specific examples of the aforementioned cyclic carbonates include EC, PC, butylene carbonate, and FEC, wherein at least one is preferably selected from the group consisting of EC, PC, and FEC.

[0110] Specific examples of the aforementioned chain carbonates 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, etc., wherein at least one is preferably selected from the group consisting of EMC, DMC, DEC, and methyl propyl carbonate.

[0111] In addition, specific examples of the aforementioned esters include methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl 2-fluoropropionate, and ethyl 2-fluoropropionate.

[0112] The non-aqueous electrolyte disclosed herein may also contain polymers. These polymers may also contain what are commonly referred to as polymer solid electrolytes. Polymer solid electrolytes also include electrolytes containing non-aqueous organic solvents as plasticizers.

[0113] There is no particular limitation as long as the polymer is an aprotic polymer that can dissolve components (A) to (C), the solute, and other additives described below. Examples include polymers containing polyethylene oxide in the main chain or side chain, homopolymers or copolymers of polyvinylidene fluoride, methacrylate polymers, and polyacrylonitrile. When a plasticizer is added to these polymers, an aprotic non-aqueous organic solvent among the aforementioned non-aqueous organic solvents is preferred.

[0114] <Regarding other additives>

[0115] As long as it does not impair the purpose of this disclosure, commonly used additives may be added to the non-aqueous electrolyte of this disclosure in any proportion.

[0116] The non-aqueous electrolyte disclosed herein may contain at least one of the compounds shown in the following general formulas (3) to (5).

[0117]

[0118] In general formula (3), X 1 and X 2 Each halogen atom represents itself independently. A + This indicates an alkali metal cation, ammonium ion, or organic cation.

[0119] In general formula (3), X 1 and X 2 Each halogen atom represents itself independently. As X 1 and X 2 The halogen atom represented can be fluorine, chlorine, bromine, iodine, etc., with fluorine being preferred.

[0120] X 1 and X 2 They can be the same or different, but it is preferred that they are the same, and it is preferred that they are all fluorine atoms.

[0121] In general formula (3), A + It indicates an alkali metal cation, ammonium ion, or organic cation.

[0122] As A + Examples of alkali metal cations that can be represented include lithium cations, sodium cations, and potassium cations.

[0123] A + Preferably, it is an alkali metal cation, and more preferably a lithium cation.

[0124]

[0125] In general formula (4), R 4 This indicates a hydrocarbon group with 2 to 6 carbon atoms. Heteroatoms may be present between the carbon-carbon bonds in this hydrocarbon group. Furthermore, any hydrogen atom in this hydrocarbon group may be replaced by a halogen atom.

[0126] In general formula (4), R 4 This indicates a hydrocarbon group having 2 to 6 carbon atoms. As R 4 Examples of hydrocarbon groups that can be represented include straight-chain or branched alkylene groups, alkenylene groups, and ynylene groups.

[0127] As R 4 When referring to alkylene, specific examples of alkylene include ethylene, n-propylene, isopropylene, n-butylene, secondary butylene, tert-butylene, n-pentylene, -CH2CH(C3H7)-yl, and n-hexylene.

[0128] As R 4 When referring to an alkenyl group, examples of alkenyl groups include vinylene and propene. As R... 4 The term "ethynyl group" can be used to refer to ethynyl groups, specifically, examples include propynyl groups.

[0129] R 4 The hydrocarbon group represented may contain heteroatoms between carbon-carbon bonds. Examples of heteroatoms include oxygen, nitrogen, and sulfur atoms.

[0130] R 4 Any hydrogen atom in the represented hydrocarbon group can be replaced by a halogen atom. Examples of hydrocarbon groups obtained by replacing any hydrogen atom with a fluorine atom include tetrafluoroethylene, 1,2-difluoroethylene, 2,2-difluoroethylene, fluoroethylene, and (trifluoromethyl)ethylene.

[0131] R 4 Preferably, it is an unsubstituted alkylene group having 3 to 4 carbon atoms, more preferably a propylene group.

[0132]

[0133] In general formula (5), R 5 This indicates a hydrocarbon group with 2 to 5 carbon atoms. Heteroatoms may be present between the carbon-carbon bonds in this hydrocarbon group. Furthermore, any hydrogen atom in this hydrocarbon group may be replaced by a halogen atom.

[0134] In general formula (5), R 5 This indicates a hydrocarbon group with 2 to 5 carbon atoms. As R 5Examples of hydrocarbon groups that can be represented include straight-chain or branched alkylene groups, alkenylene groups, and ynylene groups.

[0135] As R 5 When referring to alkylene, specific examples include ethylene, n-propylene, isopropylene, n-butylene, secondary butylene, tert-butylene, n-pentylene, and -CH2CH(C3H7)-yl.

[0136] As R 5 When referring to an alkenyl group, examples of alkenyl groups include vinylidene and propenylidene.

[0137] As R 5 The term "ethynyl group" can specifically refer to ethynylene, propynylene, etc.

[0138] R 5 The hydrocarbon group represented may contain heteroatoms between carbon-carbon bonds. Examples of heteroatoms include oxygen, nitrogen, and sulfur atoms.

[0139] R 5 Any hydrogen atom in the represented hydrocarbon group can be replaced by a halogen atom. Examples of hydrocarbon groups obtained by replacing any hydrogen atom with a fluorine atom include tetrafluoroethylene, 1,2-difluoroethylene, 2,2-difluoroethylene, fluoroethylene, and (trifluoromethyl)ethylene.

[0140] R 5 Preferably, it is an unsubstituted alkylene group having 2 to 3 carbon atoms, more preferably an ethylene group.

[0141] Specific examples of "other additives" other than the compounds shown in the general formulas (3) to (5) above include: cyclohexylbenzene, cyclohexylfluorobenzene, fluorobenzene (hereinafter sometimes referred to as FB), biphenyl, difluoroanisole, tert-butylbenzene, tert-pentylbenzene, 2-fluorotoluene, 2-fluorobiphenyl, vinylene carbonate, dimethyl vinylene carbonate, ethylene ethylene carbonate, fluoroethylene carbonate, methyl propargyl carbonate, ethyl propargyl carbonate, dipropargyl carbonate, maleic anhydride, succinic anhydride, methane disulfonate, dimethyl methane disulfonate, trimethyl methane disulfonate, methyl methanesulfonate, lithium difluorobis(oxalate)phosphate (hereinafter sometimes referred to as LDFBOP), sodium difluorobis(oxalate)phosphate, and difluorobis(oxalate)phosphate. Compounds such as potassium, lithium bis(oxalate)borate, sodium bis(oxalate)borate, potassium bis(oxalate)borate, lithium tetrafluorooxalate phosphate (hereinafter, sometimes abbreviated as LTFOP), sodium tetrafluorooxalate phosphate, potassium tetrafluorooxalate phosphate, lithium tri(oxalate) phosphate, sodium tri(oxalate) phosphate, potassium tri(oxalate) phosphate, lithium ethyl fluorophosphate (hereinafter, sometimes abbreviated as LEFP), lithium propyl fluorophosphate, lithium fluorophosphate, ethylene sulfonyl fluoride (hereinafter, sometimes abbreviated as ESF), trifluoromethane sulfonyl fluoride (hereinafter, sometimes abbreviated as TSF), methane sulfonyl fluoride (hereinafter, sometimes abbreviated as MSF), and phenyl difluorophosphate (hereinafter, sometimes abbreviated as PDFP) have overcharge prevention effects, negative electrode coating formation effects, and positive electrode protection effects.

[0142] The content of the other additives in the non-aqueous electrolyte is not particularly limited, but is preferably 0.01% by mass or more and 8.00% by mass or less relative to the total amount of the non-aqueous electrolyte.

[0143] Alternatively, compounds comprising one or more of the following are preferred: lithium salts containing boron complexes with oxalate groups, lithium salts containing phosphorus complexes with oxalate groups, compounds containing O=SF bonds, and compounds containing O=PF bonds. From the viewpoint that these compounds not only improve capacity retention after long-term cycling at higher temperatures and suppress resistance increases at lower temperatures after high-temperature storage, but also further reduce the dissolution of Ni components from the Ni-containing electrode into the electrolyte when using a Ni-containing electrode, this is preferable.

[0144] When the lithium salt of the phosphorus complex containing the oxalate group is selected from at least one of the group consisting of lithium tetrafluorooxalate phosphate and lithium difluorobis(oxalate) phosphate, in addition to improving the capacity retention rate after long-term cycling at further high temperatures and suppressing the increase in resistance at low temperatures after high-temperature storage, the Ni component has a particularly excellent effect in inhibiting dissolution from the positive electrode, and is therefore more preferred.

[0145] Examples of compounds having an O=SF bond include lithium fluorosulfonate, propyl fluorosulfate, phenyl fluorosulfate, 4-fluorophenyl-fluorosulfonate, 4-tert-butylphenyl-fluorosulfonate, 4-tert-pentylphenyl-fluorosulfonate, ethylene sulfonyl fluoride, trifluoromethane sulfonyl fluoride, methane sulfonyl fluoride, benzene sulfonyl fluoride, 4-fluorophenyl sulfonyl fluoride, 4-tert-butylphenyl sulfonyl fluoride, 4-tert-pentylphenyl sulfonyl fluoride, and 2-methylphenyl sulfonyl fluoride.

[0146] Examples of compounds having an O=PF bond include lithium ethyl fluorophosphate, lithium bis(difluorophosphono)imide, and phenyl difluorophosphate.

[0147] Furthermore, in cases such as those used in non-aqueous electrolyte batteries known as polymer batteries, the non-aqueous electrolyte can be quasi-solidified using a gelling agent or cross-linked polymer.

[0148] The non-aqueous electrolyte of this disclosure may or may not contain the compound shown in general formula (6) below. As one embodiment of the non-aqueous electrolyte of this disclosure, when the amount of the compound shown in general formula (1) is set to 100% by mass, an example is that the content of the compound shown in general formula (6) below is less than 0.05% by mass. Alternatively, the non-aqueous electrolyte of this disclosure may not contain the compound shown in general formula (6).

[0149]

[0150] In general formula (6), R 6 ~R 8 Each substituent is independently a substituent having at least one of the following: an unsaturated bond and an aromatic ring.

[0151] The above R 6 ~R 8 Compared with the aforementioned R 1 ~R 3 same.

[0152] <Preparation Methods of Non-Aqueous Electrolytes>

[0153] The method for preparing the non-aqueous electrolyte disclosed herein is not particularly limited. For example, it can be prepared by dissolving a silicon compound (A), a borate (B), an imide salt (C), and a solute in a non-aqueous organic solvent.

[0154] In the process of dissolving a solute in a non-aqueous organic solvent, from the viewpoint of preventing the deterioration of both the non-aqueous organic solvent and the solute, it is effective to keep the liquid temperature of the non-aqueous organic solvent below 40°C. This is because, by keeping the liquid temperature below 40°C, the formation of free acids such as hydrogen fluoride (HF) produced by the reaction and decomposition of the solute with water in the system can be suppressed. As a result, the decomposition of the non-aqueous organic solvent can also be suppressed. Furthermore, from the viewpoint of suppressing the formation of free acids such as HF, it is also effective to add the solute little by little and dissolve and prepare it.

[0155] When dissolving a solute in a non-aqueous organic solvent, the process can be carried out while the non-aqueous organic solvent is cooled. There is no particular limitation on the liquid temperature, but it is preferably -20 to 40°C, more preferably 0 to 40°C.

[0156] Furthermore, when adding silicon compounds (A), borates (B), imide salts (C), or other additives, it is preferable to control the temperature of the non-aqueous electrolyte to be above -10°C and below 40°C. The upper limit of the liquid temperature is more preferably below 30°C, and particularly preferably below 20°C.

[0157] The non-aqueous electrolyte disclosed herein is preferably used in non-aqueous electrolyte batteries (preferably secondary batteries).

[0158] [2. Non-aqueous electrolyte battery]

[0159] The non-aqueous electrolyte battery contains at least: (a) the non-aqueous electrolyte disclosed herein; (b) a positive electrode; and (c) a negative electrode having at least one of the following: a negative electrode material containing lithium metal, a negative electrode material capable of absorbing, storing, and releasing lithium, sodium, potassium, or magnesium. Preferably, it also includes (d) a separator, a housing, etc.

[0160] <(b) Positive electrode>

[0161] (b) The positive electrode preferably contains at least one oxide and / or polyanionic compound as the positive electrode active material.

[0162] [Positive electrode active material]

[0163] In the case of a lithium-ion secondary battery in which the cations in the non-aqueous electrolyte become the lithium matrix, the positive electrode active material constituting (b) is not particularly limited as long as it is a material that can be charged and discharged. For example, it can contain at least one of the following: (b1) a lithium transition metal composite oxide containing at least one of the metals nickel, manganese and cobalt and having a layered structure; (b2) a lithium manganese composite oxide having a spinel structure; (b3) a lithium-containing olivine-type phosphate; and (b4) a lithium excess layered transition metal oxide having a layered rock salt structure.

[0164] ((b1) Lithium transition metal composite oxide)

[0165] For example, (b1), a lithium transition metal composite oxide containing at least one of the metals nickel, manganese, and cobalt and having a layered structure, can be used as a positive electrode active material. Examples include lithium / cobalt composite oxides, lithium / nickel composite oxides, lithium / nickel / cobalt composite oxides, lithium / nickel / cobalt / aluminum composite oxides, lithium / cobalt / manganese composite oxides, lithium / nickel / manganese composite oxides, and lithium / nickel / manganese / cobalt composite oxides. Alternatively, a portion of the transition metal atoms that will form the main body of these lithium transition metal composite oxides can be replaced by other elements such as Al, Ti, V, Cr, Fe, Cu, Zn, Mg, Ga, Zr, Si, B, Ba, Y, and Sn.

[0166] As specific examples of lithium / cobalt composite oxides and lithium / nickel composite oxides, LiCoO2, LiNiO2, and lithium cobalt oxide (LiCoO2) with added heterogeneous elements such as Mg, Zr, Al, and Ti can be used. 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 0.01 Lithium cobalt oxide, which has rare earth compounds fixed on its surface, as described in Japanese Patent Application Publication No. 2014 / 034043, can also be used, such as that described in Japanese Patent Application Publication No. 2002-151077, which is formed by coating a portion of the surface of LiCoO2 particle powder with alumina.

[0167] For lithium / nickel / cobalt composite oxides and lithium / nickel / cobalt / aluminum composite oxides, the general formula

[11] is used.

[0168] Li a Ni 1-b-c Co b M 11 c O2

[11]

[0169] In formula

[11] , M 11 To select at least one element from the group consisting of Al, Fe, Mg, Zr, Ti, and B, a is 0.9 ≤ a ≤ 1.2, and b and c satisfy the conditions 0.1 ≤ b ≤ 0.3 and 0 ≤ c ≤ 0.1.

[0170] They can be prepared, for example, according to the manufacturing methods described in Japanese Patent Application Publication No. 2009-137834, etc. Specifically, LiNi can be cited as an example. 0.8 Co 0.2 O2, LiNi0.85 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.

[0171] As specific examples of lithium / cobalt / manganese composite oxides and lithium / nickel / manganese composite oxides, LiNi can be cited. 0.5 Mn 0.5 O2, LiCo 0.5 Mn 0.5 O2, etc.

[0172] As a lithium / nickel / manganese / cobalt composite oxide, lithium-containing composite oxides represented by general formula

[12] can be cited.

[0173] Li d Ni e Mn f Co g M 12 h O2

[12]

[0174] In formula

[12] , M 12 To select at least one element 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.

[0175] The lithium / nickel / manganese / cobalt composite oxide improves structural stability and enhances the safety of lithium secondary batteries at high temperatures. Therefore, it is preferable to contain manganese in the range shown in general formula

[12] . In particular, in order to improve the power characteristics of lithium-ion secondary batteries, it is more preferable to further contain cobalt in the range shown in general formula

[12] .

[0176] Specifically, examples include Li[Ni] which has a charge / discharge region above 4.3V. 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[Ni0.49 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.

[0177] ((b2) Lithium-manganese composite oxide with spinel structure)

[0178] For example, (b2) a lithium manganese composite oxide with a spinel structure, which is an example of a positive electrode active material, spinel-type lithium manganese composite oxides represented by general formula

[13] can be cited.

[0179] Li j (Mn 2-k M 13 k )O4

[13]

[0180] In formula

[13] , M 13 The element to be selected is at least one metallic element from the group consisting of Ni, Co, Fe, Mg, Cr, Cu, Al and Ti, where j is 1.05≤j≤1.15 and k is 0≤k≤0.20.

[0181] Specifically, examples include LiMnO2, LiMn2O4, and 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.

[0182] ((b3) Lithium-containing olivine-type phosphate)

[0183] For example, lithium-containing olivine-type phosphates (b3) that are used as positive electrode active materials can be exemplified by those shown in general formula

[14] .

[0184] LiFe 1-n M 14 n PO4

[14]

[0185] In formula

[14] , M 14 It is selected from at least one of Co, Ni, Mn, Cu, Zn, Nb, Mg, Al, Ti, W, Zr and Cd, where n is 0 ≤ n ≤ 1.

[0186] Specifically, for example, LiFePO4, LiCoPO4, LiNiPO4, LiMnPO4, etc. can be cited. Among them, LiFePO4 and / or LiMnPO4 are preferred.

[0187] ((b4) Lithium-excess layered transition metal oxide)

[0188] Regarding the (b4) lithium-excess layered transition metal oxide having a layered rock salt-type structure as an example of the positive electrode active material, for example, those represented by the general formula

[15] can be cited.

[0189] xLiM 15 O2·(1-x)Li2M 16 O3

[15]

[0190] In formula

[15] , x is a number satisfying 0 < x < 1, and M 15 is at least one or more metal elements with an average oxidation number of 3 + , and M 16 is at least one metal element with an average oxidation number of 4 + . In formula

[15] , M 15 is preferably one metal element selected from trivalent Mn, Ni, Co, Fe, V, Cr, but the average oxidation number can be made trivalent with equal amounts of divalent and tetravalent metals.

[0191] In addition, in formula

[15] , M 16 is preferably one or more metal elements selected from Mn, Zr, Ti. Specifically, 0.5[LiNi 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 O2]·0.10[Li2TiO3]·0.45[Li2MnO3], etc. can be cited.

[0192] It is known that the positive electrode active material represented by this general formula

[15] exhibits high capacity under high voltage charging above 4.4V (Li reference) (e.g., US Patent 7135252).

[0193] These positive electrode active materials can be prepared, for example, according to the manufacturing methods described in Japanese Patent Application Publication No. 2008-270201, WO2013 / 118661, and Japanese Patent Application Publication No. 2013-030284.

[0194] As a positive electrode active material, it is sufficient to contain at least one of the above (b1) to (b4) as a main component. Other substances included may include transition element sulfides such as FeS2, TiS2, TiO2, V2O5, MoO3, and MoS2, conductive polymers such as polyacetylene, poly(p-phenylene), polyaniline, and polypyrrole, activated carbon, free radical-generating polymers, and carbon materials.

[0195] [Positive current collector]

[0196] (b) The positive electrode has a positive current collector. For example, aluminum, stainless steel, nickel, titanium, or alloys thereof can be used as the positive current collector.

[0197] [Positive electrode active material layer]

[0198] (b) The positive electrode, for example, has a positive electrode active material layer formed on at least one side of the positive electrode current collector. The positive electrode active material layer is composed, for example, the aforementioned positive electrode active material, a binder, and a conductive agent as needed.

[0199] Examples of adhesives 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.

[0200] As conductive agents, carbon materials such as acetylene black, Ketjen black, furnace black, carbon fiber, graphite (granular graphite, flake graphite), and fluorinated graphite can be used. For the positive electrode, acetylene black and Ketjen black with low crystallinity are preferred.

[0201] <(c) Negative electrode>

[0202] As a negative electrode material, there are no particular limitations. In the case of lithium batteries and lithium-ion batteries, lithium metal, alloys of lithium metal with other metals, intermetallic compounds, various carbon materials (artificial graphite, natural graphite, etc.), metal oxides, metal nitrides, tin (elemental), tin compounds, silicon (elemental), silicon compounds, activated carbon, conductive polymers, etc. can be used.

[0203] Carbon materials include, for example, easily graphitizable carbon, hard carbon (difficult to graphitize) with a (002) plane interplanar spacing of 0.37 nm or more, and graphite with a (002) plane interplanar spacing of 0.34 nm or less. More specifically, they include: pyrolytic carbon, coke, glassy carbon fibers, calcined organic polymer compounds, activated carbon, or carbon black. Among them, coke includes pitch coke, needle coke, or petroleum coke. Calcined organic polymer compounds refer to those produced by calcining and carbonizing phenolic resin, furan resin, etc., at an appropriate temperature. Carbon materials are preferred because they exhibit very little change in crystal structure associated with lithium absorption and release, thus achieving high energy density and excellent cycling characteristics. It should be noted that the shape of carbon materials can be any of fibrous, spherical, granular, or flake-like. In addition, amorphous carbon and graphite materials with amorphous carbon covering their surfaces have lower reactivity with non-aqueous electrolytes, thus they are more preferred.

[0204] (c) The negative electrode preferably contains at least one negative electrode active material.

[0205] [Negative Electrode Active Material]

[0206] In the case of a lithium-ion secondary battery where the cations in the non-aqueous electrolyte are lithium-based, the negative electrode active material constituting (c) the negative electrode is capable of lithium-ion doping / dedoping. Examples include (c1) carbon materials with a d-value of 0.340 nm or less on the (002) lattice plane in X-ray diffraction, (c2) carbon materials with a d-value of more than 0.340 nm on the (002) lattice plane in X-ray diffraction, (c3) oxides of one or more metals selected from Si, Sn, and Al, (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, and (c5) materials containing at least one of lithium titanium oxides. These negative electrode active materials can be used individually or in combination of two or more.

[0207] ((c1) Carbon materials with a d-value of less than 0.340 nm for the (002) plane of the lattice in X-ray diffraction)

[0208] For carbon materials that serve as negative electrode active materials and whose d-value of the (002) lattice plane in X-ray diffraction is 0.340 nm or less, examples include pyrolytic carbon, coke (e.g., pitch coke, needle coke, petroleum coke, etc.), graphite, calcined organic polymer compounds (e.g., those obtained by calcining and carbonizing phenolic resin, furan resin, etc. at an appropriate temperature), carbon fibers, activated carbon, etc., which can also be graphitized. This carbon material is defined as having a (002) interplanar spacing (d002) of 0.340 nm or less as measured by X-ray diffraction, with a preferred true density of 1.70 g / cm³.3 The above refers to graphite or highly crystalline carbon materials with properties similar to those mentioned above.

[0209] ((c2) Carbon materials with a d-value exceeding 0.340 nm in the (002) lattice plane of X-ray diffraction)

[0210] For carbon materials that serve as negative electrode active materials and whose d-value of the (002) lattice plane in (c2) X-ray diffraction exceeds 0.340 nm, amorphous carbon can be cited as an example. Amorphous carbon is a carbon material whose layering order does not change even after heat treatment at temperatures above 2000°C. Examples include hard carbon (difficult-to-graphitize carbon), mesophase carbon microspheres (MCMB) obtained by calcination below 1500°C, and mesophase pitch carbon fibers (MCF). Carbotron (registered trademark) P manufactured by Kureha Corporation is a representative example.

[0211] ((c3) Oxides of one or more metals selected from Si, Sn, and Al)

[0212] For example, (c3) is an oxide of one or more metals selected from Si, Sn, and Al, which can be used as a negative electrode active material. Examples include silicon oxide and tin oxide.

[0213] Yes: SiO has a structure in which ultrafine Si particles are dispersed in SiO2. x Etc. If this material is used as the negative electrode active material, the Si reacting with Li is in the form of ultrafine particles, thus allowing for smooth charging and discharging, and SiO with the above structure... x The particles themselves have a small surface area, therefore, the coating properties of the composition (paste) used to form the negative electrode active material layer are good, and the adhesion of the negative electrode paste layer to the current collector is also good.

[0214] It should be noted that SiO x The volume change during charging and discharging is large; therefore, SiO₂ is used in combination with other materials in a specific ratio in the negative electrode active material. x The graphite, along with the aforementioned negative electrode active material (c1), can achieve both high capacity and good charge-discharge cycle characteristics.

[0215] ((c4) Selected from one or more metals selected from Si, Sn, and Al, or alloys containing these metals, or alloys of these metals or alloys with lithium)

[0216] For example, (c4) as a negative electrode active material is selected from 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 include metals such as silicon, tin, and aluminum, silicon alloys, tin alloys, and aluminum alloys. Their metals and alloys can also be materials alloyed with lithium with charge and discharge.

[0217] Specific examples of preferred materials include: elemental metals such as silicon (Si) and tin (Sn) (e.g., powdered substances), metal alloys, compounds containing such metals, and alloys containing tin (Sn) and cobalt (Co), as described in WO2004 / 100293 and Japanese Patent Application Laid-Open No. 2008-016424. When these metals are used as electrodes, they exhibit high charging capacity and less volume expansion / contraction during charging and discharging, making them preferable. Furthermore, when these metals are used as the negative electrode of a lithium-ion secondary battery, they alloy with Li during charging, thus exhibiting known high charging capacity, which is also preferable.

[0218] Furthermore, for example, negative electrode active materials formed from silicon pillars with submicron diameters, as described in WO2004 / 042851, WO2007 / 083155, and others, or negative electrode active materials formed from silicon fibers, can also be used.

[0219] ((c5) Lithium titanium oxide)

[0220] Examples of (c5) lithium titanium oxides that serve as negative electrode active materials include lithium titanate with a spinel structure and lithium titanate with an orthorhombic manganese oxide structure.

[0221] Lithium titanate with a spinel structure can be exemplified by, for example, Li 4+α Ti5O 12 (α varies within the range of 0 ≤ α ≤ 3 depending on the charge-discharge reaction). Additionally, lithium titanate with an orthorhombic manganese oxide structure, for example, is Li... 2+β Ti3O7 (β varies within the range of 0 ≤ β ≤ 3 depending on the charge-discharge reaction). These negative electrode active materials can be prepared, for example, according to the manufacturing methods described in Japanese Patent Application Publication No. 2007-018883 and Japanese Patent Application Publication No. 2009-176752.

[0222] For example, in sodium-ion secondary batteries where the cations in the non-aqueous electrolyte are sodium-based, oxides such as hard carbon, TiO2, V2O5, and MoO3 are used as negative electrode active materials. Similarly, in sodium-ion secondary batteries where the cations in the non-aqueous electrolyte are sodium-based, positive electrode active materials include sodium-containing transition metal composite oxides such as NaFeO2, NaCrO2, NaNiO2, NaMnO2, and NaCoO2; mixtures of various transition metals such as Fe, Cr, Ni, Mn, and Co from these sodium-containing transition metal composite oxides; oxides where a portion of the transition metals in these sodium-containing transition metal composite oxides is replaced by metals other than other transition metals; phosphate compounds of transition metals such as Na2FeP2O7 and NaCo3(PO4)2P2O7; sulfides such as TiS2 and FeS2; or conductive polymers such as polyacetylene, poly(p-phenylene), polyaniline, and polypyrrole; activated carbon; free radical-generating polymers; and carbon materials.

[0223] [Negative current collector]

[0224] (c) The negative electrode has a negative current collector. For example, copper, stainless steel, nickel, titanium, or alloys thereof can be used as the negative current collector.

[0225] [Negative electrode active material layer]

[0226] (c) The negative electrode, for example, has a negative electrode active material layer formed on at least one surface of the negative electrode current collector. The negative electrode active material layer is composed, for example, of the aforementioned negative electrode active material, a binder, and a conductive agent as needed.

[0227] Examples of adhesives 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.

[0228] As conductive agents, carbon materials such as acetylene black, Ketjen black, furnace black, carbon fiber, graphite (granular graphite, flake graphite), and fluorinated graphite can be used.

[0229] <Manufacturing methods of electrodes ((b) positive electrode and (c) negative electrode)>

[0230] Electrodes can be obtained, for example, by dispersing and mixing active materials, binders, and conductive agents as needed in a prescribed amount in a solvent such as N-methyl-2-pyrrolidone (NMP) and water, coating the resulting paste onto a current collector, and drying it to form an active material layer. Preferably, the obtained electrode is compressed using a roller press or similar method to adjust it to an electrode of appropriate density.

[0231] <(d) Separator>

[0232] The aforementioned non-aqueous electrolyte battery may include (d) a separator. As a separator to prevent contact between (b) the positive electrode and (c) the negative electrode, polyolefins such as polypropylene and polyethylene, nonwoven fabrics made of cellulose, paper, or glass fiber, or porous sheets are used. These films are preferably microporous, allowing the non-aqueous electrolyte to penetrate while ions can easily permeate.

[0233] Examples of polyolefin separators include membranes that provide electrical insulation between the positive and negative electrodes, such as porous polyolefin films or microporous polymer films, while allowing lithium ions to permeate. Specific examples of porous polyolefin films include multilayer films formed by overlapping porous polyethylene films alone or by layering porous polyethylene films with porous polypropylene films. Additionally, films formed by combining porous polyethylene films and polypropylene films can be cited as examples.

[0234] <Outer Shell>

[0235] When constructing a non-aqueous electrolyte battery, the outer casing can be, for example, a coin-shaped, cylindrical, or square metal can, or a laminated casing. Examples of metal can materials include, for example, nickel-plated iron or steel plates, stainless steel plates, nickel-plated stainless steel plates, aluminum or its alloys, nickel, titanium, etc.

[0236] As the outer shell of the laminate, for example, aluminum laminate film, SUS laminate film, polypropylene or polyethylene laminate film coated with silica, etc. can be used.

[0237] The configuration of the non-aqueous electrolyte battery in this embodiment is not particularly limited. For example, it can be configured such that electrode elements with positive and negative electrodes arranged opposite each other and a non-aqueous electrolyte are encapsulated in an outer casing. The shape of the non-aqueous electrolyte battery is not particularly limited, and electrochemical devices in the shapes of coins, cylinders, squares, or aluminum laminates can be assembled from the above elements.

[0238] Example

[0239] The present disclosure will now be described in further detail with reference to embodiments, but the present disclosure is not limited thereto by these descriptions.

[0240] (Preparation of non-aqueous electrolyte No. 1-1)

[0241] As a non-aqueous organic solvent, a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate in a volume ratio of 2.5:4:3.5 was used, and LiPF6 as a solute was added to this solvent to achieve a concentration of 1.0 mol / L.

[0242] Next, the compound shown in formula (1j) as component (A), lithium tetrafluoroborate (LiBF4) as component (B), and lithium bis(fluorosulfonyl)imide (LiFSI) as component (C) were dissolved to concentrations relative to the total amount of the non-aqueous electrolyte, such that component (A) was 0.3% by mass, component (B) was 0.5% by mass, and component (C) was 0.3% by mass, respectively. The preparation was carried out while maintaining the liquid temperature in the range of 20–30°C. The preparation conditions for the non-aqueous electrolyte are shown in Table 1. From now on, “-” in all tables indicates no addition.

[0243] (Preparation of non-aqueous electrolytes No. 1-2 to 1-3)

[0244] The concentrations of components (A) to (C) were changed as shown in Table 1. Otherwise, No.1-2 to No.1-3 were prepared in the same manner as non-aqueous electrolyte No.1-1. The preparation conditions of the non-aqueous electrolyte are shown in Table 1.

[0245] (Preparation of non-aqueous electrolytes No. 1-4 to 1-6)

[0246] As component (A), compounds represented by formulas (1b), (1f), or (1h) were used instead of the compound represented by formula (1j), and the concentrations of components (A) to (C) were changed as described in Table 1. Otherwise, No.1-4 to 1-6 were prepared in the same manner as non-aqueous electrolyte No.1-1. The preparation conditions of the non-aqueous electrolyte are shown in Table 1.

[0247] (Comparison of the preparation of non-aqueous electrolytes No. 1-1 to 1-2)

[0248] The concentrations of components (A) to (C) were changed as shown in Table 1. Otherwise, non-aqueous electrolytes No. 1-1 to 1-2 were prepared in the same manner as non-aqueous electrolyte No. 1-1. The preparation conditions of the non-aqueous electrolytes are shown in Table 1.

[0249] (Comparison of the preparation of non-aqueous electrolytes No. 1-3 to 1-6)

[0250] As component (A), the compound shown in formula (1b) or formula (1f) is used instead of the compound shown in formula (1j), and the concentrations of components (A) to (C) are changed as described in Table 1. Otherwise, comparative non-aqueous electrolytes No. 1-3 to 1-6 are prepared in the same manner as comparative non-aqueous electrolyte No. 1-1. The preparation conditions of the non-aqueous electrolytes are shown in Table 1.

[0251] (Compare the preparation of non-aqueous electrolytes No. 1-7 to 1-9)

[0252] As shown in Table 1, non-aqueous electrolytes No. 1-7 to 1-9 were prepared in the same manner as non-aqueous electrolyte No. 1-1, except that lithium tetrafluoroborate as component (B) or lithium bis(fluorosulfonyl)imide as component (C). The preparation conditions of the non-aqueous electrolytes are shown in Table 1.

[0253] (Comparison of the preparation of non-aqueous electrolytes No. 1-10)

[0254] As shown in Table 1, lithium tetrafluoroborate (component B) and lithium bis(fluorosulfonyl)imide (component C) were not added. Otherwise, comparative non-aqueous electrolyte No. 1-10 was prepared in the same manner as non-aqueous electrolyte No. 1-1. The preparation conditions of the non-aqueous electrolyte are shown in Table 1.

[0255] (Comparison of the preparation of non-aqueous electrolytes No. 1-11 to 1-13)

[0256] As component (A), the compound shown in formula (1j) was replaced by the compound shown in formula (1b), formula (1f), or formula (1h), respectively. Otherwise, comparative electrolytes No. 1-11 to 1-13 were prepared in the same manner as comparative non-aqueous electrolytes No. 1-10. The preparation conditions of the non-aqueous electrolytes are shown in Table 1.

[0257] The content W of component (B) as a quality benchmark B Content W relative to the quality benchmark of component (A) A The ratio is W B / W A The content W of components (C) as a quality benchmark C Content W relative to the quality benchmark of component (A) A The ratio is W C / W A As shown in Table 1.

[0258] [Table 1]

[0259]

[0260] (Fabrication of non-aqueous electrolyte batteries)

[0261] Using the above-mentioned non-aqueous electrolyte, LiNi 0.6 Co 0.2 Mn 0.2 Using O2 as the positive electrode material and graphite as the negative electrode material, a non-aqueous electrolyte battery (experimental single cell) was fabricated.

[0262] In LiNi 0.6 Co 0.2 Mn 0.2O2 powder (90% by mass) is mixed with polyvinylidene fluoride (PVDF) as a binder (5% by mass) and acetylene black (5% by mass) as a conductive material, and further N-methylpyrrolidone (NMP) is added to form a paste. This paste is coated onto aluminum foil and dried to form the experimental positive electrode.

[0263] In addition, 10% by mass of PVDF as a binder is mixed into 90% by mass of graphite powder, and NMP is further added to form a slurry. This slurry is coated onto copper foil and dried at 120°C for 12 hours to form the negative electrode for testing.

[0264] Then, a non-aqueous electrolyte is immersed in a polyethylene separator, and a 50mAh single battery with an aluminum laminated casing is assembled.

[0265] [Initial charge and discharge DC resistance measurement test (resistance evaluation at low temperature)]

[0266] First, using the fabricated single cell, initial charge and discharge were performed at an ambient temperature of 25°C under the following conditions: constant current and constant voltage charging at a rate of 0.1C (5mA) with an upper charging limit of 4.3V, followed by constant current discharging at a rate of 0.2C (10mA) until the discharge termination voltage of 3.0V. Then, constant current and constant voltage charging at a rate of 0.2C (10mA) with an upper charging limit of 4.3V, followed by constant current discharging at a rate of 0.2C (10mA) until the discharge termination voltage of 3.0V was repeated 3 times.

[0267] After the initial charge and discharge cycle, the battery was removed from the charge / discharge device and the 25°C constant temperature bath. It was then connected to an electrochemical measurement device (Electrofield, automated battery evaluation device) and placed in a -20°C constant temperature bath. After standing in this state for 1 hour, an IV measurement was performed to determine the absolute value of the DC resistance.

[0268] As shown in Table 2, for each non-aqueous electrolyte, a comparison was made according to each type of component (A) used. Non-aqueous electrolytes without the addition of components (B) and (C) (comparison non-aqueous electrolytes No. 1-10 to 1-13) were used as the benchmark. The absolute value of the DC resistance of each experimental example was expressed as the relative value when the absolute value of the DC resistance of the benchmark was 100.

[0269] [Capacity determination test after 400 cycles (cycle performance evaluation)]

[0270] The non-aqueous electrolyte battery, having completed the DC resistance measurement test at -20°C, was removed from the electrochemical testing apparatus and the -20°C constant temperature bath, connected to the charge-discharge device, and placed in a 50°C constant temperature bath. After standing in this state for 2 hours, it was charged at a charging rate of 2C until it reached 4.3V. After reaching 4.3V, this voltage was maintained for 1 hour, and then discharged at a discharging rate of 2C until it reached 3.0V. This charge-discharge cycle at 2C in the 50°C environment was repeated for 400 cycles. Then, the battery degradation was evaluated based on the discharge capacity after 400 cycles.

[0271] As shown in Table 2, for each non-aqueous electrolyte, the non-aqueous electrolytes without (B) and (C) components (comparing non-aqueous electrolytes No. 1-10 to 1-13) were classified and compared according to each type of (A) component used. The capacity values ​​of each experimental example after 400 cycles were expressed as relative values ​​when the capacity of the benchmark was 100.

[0272] [Table 2]

[0273]

[0274] The evaluation results shown in Table 2 confirm that, compared with the comparative example, the non-aqueous electrolyte battery using the non-aqueous electrolyte of this disclosure can achieve a balanced and good reduction in the absolute value of internal resistance at low temperature and an improvement in battery capacity after cycle testing.

[0275] Industrial availability

[0276] According to this disclosure, a non-aqueous electrolyte can be provided that can uniformly and effectively reduce the absolute value of internal resistance at low temperatures (below 0°C, for example -20°C) and improve battery capacity after cycle testing.

[0277] This disclosure has been described in detail and with reference to specific embodiments, but it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of this disclosure.

[0278] This application is based on Japanese Patent Application No. 2019-105457, filed on June 5, 2019, the contents of which are incorporated herein by reference.

Claims

1. A non-aqueous electrolyte comprising: Non-aqueous organic solvents, solutes, silicon compounds (A), borates (B), and imide salts (C), The silicon compound (A) is a compound represented by the following general formula (1). The borate (B) is a borate formed by a pair of the following cations and anions, wherein the cation is selected from at least one of the group consisting of alkali metal cations and alkaline earth metal cations, and the anion is a tetrafluoroborate anion. The imide salt (C) is an imide salt represented by the following general formula (2). The content W of the borate (B) as a mass standard B Content W relative to the mass reference of the silicon compound (A) A The ratio is W B / W A It is between 1.7 and 3. The content W of the imide salt (C) as a mass standard C Content W relative to the mass reference of the silicon compound (A) A The ratio is W C / W A It is between 1 and 5. R 1 ~R 3 Each is independently a substituent having at least one of the following: an unsaturated bond and an aromatic ring. Rf 1 and Rf 2 Each independently represents a perfluoroalkyl group, either a straight-chain group with 1 to 4 carbon atoms or a branched group with 3 to 4 carbon atoms, M + Represents alkali metal cations. The concentration of the borate (B) relative to the total amount of the non-aqueous electrolyte is 0.01% by mass or more and 3.0% by mass or less.

2. The non-aqueous electrolyte according to claim 1, wherein, The R 1 ~R 3 Each is independently a group selected from the group consisting of alkenyl, alkynyl, aryl, alkenyloxy, alkynyloxy, and aryloxy groups.

3. The non-aqueous electrolyte according to claim 2, wherein, The alkenyl group is selected from vinyl and 2-propenyl groups. The alkynyl group is an acetylenyl group. The aryl group is selected from phenyl, 2-methylphenyl, 4-methylphenyl, 4-fluorophenyl, 4-tert-butylphenyl, and 4-tert-pentylphenyl. The olefin group is selected from ethyleneoxy and 2-propenoxy groups. The alkynyloxy group is propynyloxy group. The aryloxy group is selected from phenoxy, 2-methylphenoxy, 4-methylphenoxy, 4-fluorophenoxy, 4-tert-butylphenoxy, and 4-tert-pentylphenoxy.

4. The non-aqueous electrolyte according to claim 1, wherein, The R 1 ~R 3 At least two of them are independently vinyl or ethynyl groups.

5. The non-aqueous electrolyte according to any one of claims 1 to 4, wherein, The compound represented by general formula (1) is at least one selected from the group consisting of (1a) to (1q) below.

6. The non-aqueous electrolyte according to claim 5, wherein, The compound represented by the general formula (1) is selected from at least one of the group consisting of (1a), (1b), (1c), (1e), (1f), (1g), (1h), (1i), (1j), (1k), (1p), and (1q).

7. The non-aqueous electrolyte according to any one of claims 1 to 4, wherein, The borate (B) is lithium tetrafluoroborate.

8. The non-aqueous electrolyte according to any one of claims 1 to 4, wherein, The imide salt (C) is lithium bis(fluorosulfonyl)imide.

9. A non-aqueous electrolyte battery comprising: a positive electrode, a negative electrode, and a non-aqueous electrolyte according to any one of claims 1 to 8, wherein the negative electrode has at least one negative electrode material selected from the group consisting of a negative electrode material containing lithium metal and a negative electrode material capable of absorbing, storing, and releasing lithium, sodium, potassium, or magnesium.

10. The non-aqueous electrolyte battery according to claim 9, wherein, The positive electrode contains a lithium / nickel / manganese / cobalt composite oxide as the positive electrode active material.

11. The non-aqueous electrolyte battery according to claim 10, wherein, The lithium / nickel / manganese / cobalt composite oxide is a lithium-containing composite oxide as shown in general formula [12]. Li d Ni e Mr f Co g M 12 h O2 [12] In formula [12], M 12 To select at least one element 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.

12. The non-aqueous electrolyte battery according to claim 9, wherein, The positive electrode contains LiNi 0.6 Co 0.2 Mn 0.2 O2.

13. The non-aqueous electrolyte battery according to claim 9, wherein, The negative electrode contains graphite as the negative electrode active material.

14. The non-aqueous electrolyte battery according to claim 13, wherein, The negative electrode active material is a carbon material with a d value of less than 0.340 nm in the (002) lattice plane of X-ray diffraction.

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