Nonaqueous electrolyte and nonaqueous electrolyte secondary battery containing nonaqueous electrolyte

Abstract

To provide a non-aqueous electrolyte that can improve the restored capacity of a non-aqueous electrolyte secondary battery after high-temperature storage and can significantly suppress the amount of gas generation.SOLUTION: A non-aqueous electrolyte solution includes an electrolyte, a non-aqueous solvent, a compound represented by the following general formula (A), and a compound represented by the following general formula (B).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a nonaqueous electrolyte solution and a nonaqueous electrolyte secondary battery containing the nonaqueous electrolyte solution. [Background technology]

[0002] In recent years, electricity storage devices, particularly non-aqueous electrolyte secondary batteries such as lithium batteries, have been widely used in small electronic devices such as mobile phones and notebook computers, electric vehicles, and power storage. Due to the expansion of applications of non-aqueous electrolyte secondary batteries, non-aqueous electrolyte secondary batteries are required to operate in even harsher environments. In particular, the required characteristics of secondary batteries mounted on electric vehicles are becoming increasingly higher, and there is a high demand for improved recovery capacity after high-temperature storage and suppression of gas generation.

[0003] Non-aqueous electrolyte secondary batteries are mainly composed of positive and negative electrodes containing materials capable of absorbing and releasing metal ions, and a non-aqueous electrolyte consisting of a metal salt as an electrolyte and a non-aqueous solvent. The metal salt used is, for example, lithium hexafluorophosphate (LiPF6), and the non-aqueous solvent is a carbonate such as ethylene carbonate or propylene carbonate. Known materials for the negative electrode of nonaqueous electrolyte secondary batteries include metals, metal compounds (metal elements, metal oxides, alloys, etc.) capable of absorbing and releasing metal ions, and carbon materials. In particular, nonaqueous electrolyte secondary batteries using carbon materials capable of absorbing and releasing metal ions, such as coke and graphite (artificial graphite and natural graphite), have been widely used. Carbon materials such as coke and graphite store and release metal ions and electrons at an extremely base potential equivalent to that of the metals contained in the electrolyte, and therefore many solvents have the potential to undergo reductive decomposition. The positive electrode of the non-aqueous electrolyte secondary battery is made of a composite metal oxide containing one or more elements selected from the group consisting of cobalt, manganese, and nickel, which can absorb and release metal ions. Heavy metals in the positive electrode active material may dissolve into the electrolyte during high-temperature storage in a charged state, and if the dissolved metals are redeposited on the negative electrode, the decomposition of the electrolyte is further accelerated. For this reason, attempts have been made to improve battery characteristics by forming a coating on the electrode surface.

[0004] For example, Patent Document 1 discloses that the addition of an organosilicon compound to a non-aqueous electrolyte solution improves the battery capacity and output characteristics after cycle testing.

[0005] Patent Document 2 discloses that the battery capacity after cycle testing can be improved by adding an organosilicon compound or the like to a non-aqueous electrolyte solution. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2005-353579 A [Patent Document 2] JP 2019-106362 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, the non-aqueous electrolyte solutions containing the organosilicon compounds described in Patent Documents 1 and 2 have a problem in that the restored capacity decreases after high-temperature storage. Therefore, the present invention provides a nonaqueous electrolyte that solves the above problems in nonaqueous electrolyte secondary batteries, improves the restored capacity of nonaqueous electrolyte secondary batteries after high-temperature storage, and can significantly suppress the amount of gas generation. [Means for solving the problem]

[0008] As a result of intensive research aimed at solving the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by adding a compound represented by the following general formula (A) and a compound represented by the following general formula (B) to a non-aqueous electrolyte solution, and have arrived at the present invention.

[0009] That is, the gist of the present invention lies in the following. [1] A non-aqueous electrolyte solution comprising an electrolyte, a non-aqueous solvent, a compound represented by the following general formula (A), and a compound represented by the following general formula (B): [ka] (In formula (A), R 1 and R 2 each independently represents a hydrocarbon group having 3 to 12 carbon atoms and a carbon-carbon unsaturated bond, X represents a hydrogen atom, -R 3 -OR 3 R 3 represents a hydrocarbon group having 1 to 12 carbon atoms. [ka] (In formula (B), R 45 is a hydrogen atom or -SiR 4 R 5 R 6 R represents a silyl group represented by the formula: 4 ~R 6 R each independently represents a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 12 carbon atoms which may have a substituent, or an alkoxy group having 1 to 12 carbon atoms which may have a substituent. 7 represents a hydrogen atom, a hydrocarbon group having 1 to 12 carbon atoms which may have a substituent, or -SiR 8 R 9 R 10 R represents a silyl group represented by the formula: 8 ~R 10each independently represents a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 12 carbon atoms which may have a substituent, or an alkoxy group having 1 to 12 carbon atoms which may have a substituent. Y represents a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 12 carbon atoms which may have a substituent, an alkoxy group having 1 to 12 carbon atoms which may have a substituent, -N(R 11 )SiR 12 R 13 R 14 or -N(R 11 ) H, R 11 represents a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms which may have a substituent, R 12 ~R 14 R each independently represents a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 12 carbon atoms which may have a substituent, or an alkoxy group having 1 to 12 carbon atoms which may have a substituent. 7 and R 11 may be bonded to each other to form a ring. [2] R in general formula (A) 1 and R 2 The nonaqueous electrolyte solution according to [1], wherein is a 2-propenyl group. [3] In the general formula (A), X is -R 3 -OR 3 and R 3 is a methyl group or a 2-propenyl group. [4] The nonaqueous electrolyte solution according to any one of [1] to [3], further comprising a compound represented by the following general formula (C): [ka] (In formula (C), R 15 ~R 17 each independently represents a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 12 carbon atoms which may have a substituent, or an alkoxy group having 1 to 12 carbon atoms which may have a substituent. x represents an integer of 1 to 3, p, q and r each represent an integer of 0 to 3, and x+p+q+r=4. [5] The nonaqueous electrolyte solution according to any one of [1] to [4], wherein the content of the compound represented by the general formula (A) is 0.01% by mass or more and 10% by mass or less. [6] The nonaqueous electrolyte solution according to any one of [1] to [5], wherein the content of the compound represented by general formula (B) is 0.001% by mass or more and 1.0% by mass or less. [7] A nonaqueous electrolyte secondary battery comprising a positive electrode and a negative electrode capable of absorbing and releasing metal ions, and a nonaqueous electrolyte solution, the nonaqueous electrolyte solution being the nonaqueous electrolyte solution according to any one of [1] to [6]. [8] The nonaqueous electrolyte secondary battery according to [7], wherein the positive electrode contains a positive electrode active material, and the positive electrode active material is a lithium transition metal oxide represented by the following composition formula (11): Li a1 Ni b1 Co c1 M' d1 O2···(11) (In the composition formula (11), the numerical values ​​are 0.9≦a1≦1.1, 0.30≦b1≦0.98, 0.01≦c1≦0.50, and 0.0≦d1≦0.5, and 0.5≦b1+c1 and b1+c1+d1=1 are satisfied. M' contains at least one element selected from the group consisting of Mn, Al, Mg, Zr, Fe, Ti, and Er.) Effect of the Invention

[0010] According to the present invention, it is possible to provide a nonaqueous electrolyte solution capable of improving the restored capacity after high-temperature storage and suppressing the amount of gas generation after high-temperature storage, and also to provide a nonaqueous electrolyte secondary battery including the nonaqueous electrolyte solution. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the embodiment of the present invention will be described in detail. However, the following description is merely an example of the embodiment of the present invention, and the present invention is not limited to the contents thereof as long as it does not depart from the gist of the claims.

[0012] In this specification, "α to β" means a numerical range of α or more and β or less.

[0013] [1.Non-aqueous electrolyte] The nonaqueous electrolyte solution of the present invention contains an electrolyte, a compound represented by the following formula (A), and a compound represented by the following formula (B).

[0014] The reason why the nonaqueous electrolyte solution of the present invention can improve the restored capacity after high-temperature storage and suppress the amount of gas generation after high-temperature storage is not clear, but the present inventors speculate as follows. The compound represented by formula (A) contained in the non-aqueous electrolyte of the present invention contains a plurality of different types of unsaturated bonds in the same molecule, and forms a solid electrolyte interphase (hereinafter also referred to as "SEI") having a complex structure on the negative electrode during charging and discharging of the non-aqueous electrolyte secondary battery. When the compound represented by formula (B) is further contained in the non-aqueous electrolyte, the Si-NC=O structure or HNC=O structure derived from the compound represented by formula (B) acts specifically on the SEI formed by the compound represented by formula (A), forming an SEI having a higher density, stronger and more complex structure, which is considered to improve the recovery capacity after high-temperature storage and suppress the amount of gas generation after high-temperature storage. Each component will be described below.

[0015] [1-1. Compound represented by formula (A)]

[0016] [ka]

[0017] In formula (A), R 1 and R 2 each independently represents a hydrocarbon group having 3 to 12 carbon atoms and a carbon-carbon unsaturated bond, X represents a hydrogen atom, -R 3 -OR 3 R 3 represents a hydrocarbon group having 1 to 12 carbon atoms.

[0018] R 1 and R 2The hydrocarbon group having 3 to 12 carbon atoms and a carbon-carbon unsaturated bond as the alkyl group is not particularly limited, and specific examples include chain alkenyl groups such as 2-propenyl group (allyl group), isopropenyl group, 2-butenyl group, and 3-butenyl group; cyclic alkenyl groups such as 2-cyclopentenyl group, 2-cyclohexenyl group, and 3-cyclohexenyl group; chain alkynyl groups such as 2-propynyl group, 1-butynyl group, 2-butynyl group, 3-butynyl group, 1-pentynyl group, 2-pentynyl group, 3-pentynyl group, and 4-pentynyl group; and aryl groups such as phenyl group, 3-methoxyphenyl group, 4-methoxyphenyl group, 3,5-dimethoxyphenyl group, 4-phenoxyphenyl group, 1-naphthyl group, and 2-naphthyl group. There are no particular limitations on the position of the carbon-carbon unsaturated bond in the hydrocarbon group having 3 to 12 carbon atoms, but it is preferable for the bond to be present at the molecular end from the viewpoints of suppressing the amount of gas generation after high-temperature storage and improving the recovery capacity.

[0019] Among the above, from the viewpoint of suppressing gas generation amount after high temperature storage and improving recovery capacity, R 1 and R 2 The number of carbon atoms in the hydrocarbon group having a carbon-carbon unsaturated bond is preferably 6 or less, more preferably 5 or less, and even more preferably 4 or less. 1 and R 2 is more preferably selected from 2-propenyl and 2-propynyl groups, with 2-propenyl being particularly preferred.

[0020] R 3The hydrocarbon group having 1 to 12 carbon atoms as the alkyl group is not particularly limited, and specific examples thereof include chain alkyl groups such as methyl group, ethyl group, propyl group, butyl group, isopropyl group, pentyl group, hexyl group, heptyl group, and octyl group; cyclic alkyl groups such as cyclopentyl group and cyclohexyl group; chain alkenyl groups such as vinyl group, 2-propenyl group, isopropenyl group, 2-butenyl group, and 3-butenyl group, 2-cyclopentenyl group, 2-cyclohexenyl group, and the like. chain alkynyl groups, such as 2-propynyl, 1-butynyl, 2-butynyl, 3-butynyl, 1-pentynyl, 2-pentynyl, 3-pentynyl, and 4-pentynyl groups; and aryl groups, such as phenyl, 3-methoxyphenyl, 4-methoxyphenyl, 3,5-dimethoxyphenyl, 4-phenoxyphenyl, 1-naphthyl, and 2-naphthyl groups.

[0021] Among the X's, from the viewpoint of suppressing the amount of gas generation after high-temperature storage and improving the recovery capacity, -R 3 -OR 3 is preferred, and R 3 Among these, methyl, ethyl, vinyl and 2-propenyl groups are more preferred, with methyl and 2-propenyl groups being particularly preferred.

[0022] Specific examples of the compound represented by formula (A) include the following compounds A1 to A112.

[0023] [ka]

[0024] [ka]

[0025] [ka]

[0026] [ka]

[0027] [ka]

[0028] From the viewpoints of improving the restored capacity after high-temperature storage and suppressing the amount of gas generation after high-temperature storage, compounds A2 to A4, A6, A9 to A12, A17 to A24, A26 to A33, A35 to A42, A44 to A51, A53 to A60, A62 to A69, A74 to A81, A86 to A93, and A101 to A108 are preferred, compounds A2, A6, A9, A12, A17, A20, A21, and A24 are more preferred, and compounds A2 and A12 are particularly preferred.

[0029] There are no particular limitations on the content of the compound represented by formula (A) in the non-aqueous electrolyte solution, but from the viewpoint of improving the restored capacity after high-temperature storage and suppressing the amount of gas generation after high-temperature storage, it is preferable that the content be usually 0.01 mass % or more, preferably 0.05 mass % or more, and more preferably 0.1 mass % or more, based on the total amount of the non-aqueous electrolyte solution, and on the other hand, it is usually 10 mass % or less, preferably 5 mass % or less, more preferably 2 mass % or less, and even more preferably 1 mass % or less.

[0030] The compound represented by formula (A) in the non-aqueous electrolyte solution is identified and its content is measured by nuclear magnetic resonance (NMR) spectroscopy.

[0031] [1-2. Compound represented by formula (B)]

[0032] [ka]

[0033] In formula (B), R 45 is a hydrogen atom or -SiR 4 R 5 R 6 R represents a silyl group represented by the formula: 4 ~R 6R each independently represents a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 12 carbon atoms which may have a substituent, or an alkoxy group having 1 to 12 carbon atoms which may have a substituent. 7 represents a hydrogen atom, a hydrocarbon group having 1 to 12 carbon atoms which may have a substituent, or -SiR 8 R 9 R 10 R represents a silyl group represented by the formula: 8 ~R 10 each independently represents a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 12 carbon atoms which may have a substituent, or an alkoxy group having 1 to 12 carbon atoms which may have a substituent. Y represents a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 12 carbon atoms which may have a substituent, an alkoxy group having 1 to 12 carbon atoms which may have a substituent, -N(R 11 )SiR 12 R 13 R 14 or -N(R 11 ) H, R 11 represents a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms which may have a substituent, R 12 ~R 14 each independently represents a hydrogen atom, a halogen atom, an optionally substituted hydrocarbon group having 1 to 12 carbon atoms, or an optionally substituted alkoxy group having 1 to 12 carbon atoms.

[0034] R 4 ~R 6 Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, etc. A fluorine atom is preferable from the viewpoint of causing fewer electrochemical side reactions.

[0035] R 4 ~R 6 Examples of the hydrocarbon group having 1 to 12 carbon atoms which may have a substituent as the substituent include an alkyl group, an alkenyl group, an alkynyl group, an aralkyl group, and an aryl group.

[0036] Specific examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a tert-butyl group, an n-pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, and a decyl group. Among these, from the viewpoint of effectively forming an SEI on the negative electrode, a methyl group, an ethyl group, an n-propyl group, an n-butyl group, a tert-butyl group, an n-pentyl group, and a hexyl group are preferable, a methyl group, an ethyl group, an n-propyl group, an n-butyl group, a tert-butyl group, and an n-pentyl group are more preferable, and a methyl group, an ethyl group, an n-butyl group, and a tert-butyl group are particularly preferable.

[0037] Specific examples of the alkenyl group include a vinyl group, a 2-propenyl group, a methallyl group, a 2-butenyl group, a 3-methyl-2-butenyl group, a 3-butenyl group, a 4-pentenyl group, etc. Among these, from the viewpoint of effectively forming an SEI on the negative electrode, preferred are a vinyl group, a 2-propenyl group, a methallyl group, and a 2-butenyl group, more preferred are a vinyl group, a 2-propenyl group, and a methallyl group, and particularly preferred are a vinyl group and a 2-propenyl group.

[0038] Specific examples of the alkynyl group include an ethynyl group, a 2-propynyl group, a 2-butynyl group, a 3-butynyl group, a 4-pentynyl group, a 5-hexynyl group, etc. Among these, from the viewpoint of effectively forming an SEI on the negative electrode, an ethynyl group, a 2-propynyl group, a 2-butynyl group, and a 3-butynyl group are preferable, a 2-propynyl group and a 3-butynyl group are more preferable, and a 2-propynyl group is particularly preferable.

[0039] Specific examples of the aralkyl group include a benzyl group and a phenethyl group.

[0040] Specific examples of the aryl group include a phenyl group and a tolyl group, etc. Among these, the phenyl group is preferred from the viewpoint of effectively forming an SEI on the negative electrode.

[0041] Specific examples of the alkoxy group having 1 to 12 carbon atoms include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, and an isopropoxy group, etc. Among these, a methoxy group and an ethoxy group are preferable from the viewpoint of effectively forming an SEI on the negative electrode because they cause less steric hindrance to the compound.

[0042] In the optionally substituted hydrocarbon group having 1 to 12 carbon atoms, examples of the substituent include halogen atoms such as fluorine atom, chlorine atom and bromine atom, with the fluorine atom being preferred in view of fewer electrochemical side reactions.

[0043] R 45 is a hydrogen atom or -SiR 4 R 5 R 6 R is preferably a silyl group represented by the formula: 45 Ga-SiR 4 R 5 R 6 When R 4 ~R 6 From the viewpoint of effectively forming an SEI on the negative electrode with the compound represented by general formula (B), it is preferable that at least one of R 4 ~R 6 All of the groups are alkyl groups having 1 to 12 carbon atoms. R 4 ~R 6 may be the same or different, but it is preferable that at least two or more are the same in terms of ease of synthesis of the compound, and it is even more preferable that all three are the same from the above-mentioned viewpoint.

[0044] R 7 Specific examples of the hydrocarbon group having 1 to 12 carbon atoms which may have a substituent as R 4 ~R 6 The hydrocarbon groups having 1 to 12 carbon atoms which may have a substituent, as mentioned above, are similarly illustrated. R 7 -SiR as 8 R 9 R 10 In the silyl group represented by the formula 8 ~R10 Specific examples of the halogen atom, the hydrocarbon group having 1 to 12 carbon atoms which may have a substituent, and the alkoxy group having 1 to 12 carbon atoms which may have a substituent include R 4 ~R 6 The items listed in are shown similarly.

[0045] R 7 Among these, from the viewpoint of effectively forming an SEI on the negative electrode, a hydrogen atom, an alkyl group having 1 to 12 carbon atoms which may have a substituent, or a trimethylsilyl group is preferred, a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a tert-butyl group, a vinyl group, or a 2-propenyl group is more preferred, and a hydrogen atom or a methyl group is even more preferred.

[0046] Specific examples of the hydrocarbon group having 1 to 12 carbon atoms which may have a halogen atom substituent and the alkoxy group having 1 to 12 carbon atoms which may have a substituent as Y include R 4 ~R 6 The items listed in are shown similarly. R 11 Specific examples of the hydrocarbon group having 1 to 12 carbon atoms which may have a substituent as R 4 ~R 6 The hydrocarbon groups having 1 to 12 carbon atoms which may have a substituent, as mentioned above, are similarly illustrated. R 12 ~R 14 Specific examples of the hydrocarbon group having 1 to 12 carbon atoms which may have a halogen atom substituent and the alkoxy group having 1 to 12 carbon atoms which may have a substituent as R 4 ~R 6 The items listed in are shown similarly. R 7 and R 11 is a hydrocarbon group having 1 to 12 carbon atoms which may have a substituent, R 7 and R 11 may be bonded to each other to form a ring. 7 and R 11 When they are bonded to each other to form a ring, the ring is preferably a five- or six-membered ring, and more preferably a five-membered ring.

[0047] Among the above-mentioned Y, from the viewpoints of suppressing the amount of gas generation after high-temperature storage and improving the recovery capacity, a hydrocarbon group having 1 to 12 carbon atoms which may have a substituent, -N(R 11 )SiR 12 R 13 R 14 or -N(R 11 )H is preferred, with a methyl group, a trifluoromethyl group, an ethyl group, a tert-butyl group, -N(H)Si(CH3)3, -N(CH3)Si(CH3)3, -NH2 or -N(CH3)H being more preferred, and a methyl group, a trifluoromethyl group, -N(H)Si(CH3)3, -N(CH3)Si(CH3)3, -NH2 or -N(CH3)H being particularly preferred.

[0048] Specific examples of the compound represented by formula (B) include the following compounds B1 to B66.

[0049] [ka]

[0050] [ka]

[0051] [ka]

[0052] From the viewpoints of improving the restored capacity after high-temperature storage and suppressing the amount of gas generation after high-temperature storage, the compounds B1 to B4, B6, B7, B9 to B14, B19, B21 to B33, B35 to B40, B44 to B51, B53, B55 to B60, B63, B64, and B66 are preferred, of which the compounds B1, B4, B9, B12, B19, B21 to B28, B35 to B37, B44 to B46, B55, B60, and B66 are more preferred, and the compounds B4, B12, B15, B19, B21 to B27, and B66 are particularly preferred.

[0053] There are no particular limitations on the content of the compound represented by formula (B) in the non-aqueous electrolyte solution, but from the viewpoint of improving the restored capacity after high-temperature storage and suppressing the amount of gas generation after high-temperature storage, the content is usually 0.001 mass % or more, preferably 0.005 mass % or more, and more preferably 0.01 mass % or more, and on the other hand, usually 1 mass % or less, preferably 0.5 mass % or less, and more preferably 0.2 mass % or less, based on the total amount of the non-aqueous electrolyte solution.

[0054] The compound represented by formula (B) in the non-aqueous electrolyte solution is identified and its content is measured by nuclear magnetic resonance (NMR) spectroscopy.

[0055] In the nonaqueous electrolyte solution of the present invention, the mass ratio of the content of the compound represented by formula (A) to the content of the compound represented by formula (B) ([content of the compound represented by formula (A)] / [content of the compound represented by formula (B)]) is not particularly limited, but is usually 0.1 or more, preferably 0.2 or more, more preferably 0.4 or more, particularly preferably 0.5 or more, and is usually 1000 or less, preferably 500 or less, more preferably 200 or less, particularly preferably 100 or less. By setting it in the above range, the balance between the complexity of the SEI formed by the compound represented by formula (A) and the density and strength of the SEI brought about by the compound represented by formula (B) is good, and it is considered that the effect of the SEI is fully exerted.

[0056] [1-3. Fluorosilane compounds] In the nonaqueous electrolyte solution of the present invention, it is preferable to further contain a fluorosilane compound in the nonaqueous electrolyte solution, since this promotes the formation of an SEI on the negative electrode through interaction with the negative electrode active material, thereby further improving the gas suppression effect.

[0057] The fluorosilane compound of the present invention is not particularly limited as long as it is a compound having at least one Si-F bond, and specifically, it is a compound represented by general formula (C).

[0058] [ka]

[0059] In formula (C), R 15 ~R 17 each independently represents a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 12 carbon atoms which may have a substituent, or an alkoxy group having 1 to 12 carbon atoms which may have a substituent. x represents an integer of 1 to 3, p, q and r each represent an integer of 0 to 3, and x+p+q+r=4.

[0060] R 15 ~R 17 Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, etc. A fluorine atom is preferable from the viewpoint of causing fewer electrochemical side reactions.

[0061] R 15 ~R 17 Examples of the hydrocarbon group having 1 to 12 carbon atoms which may have a substituent include an alkyl group, an alkenyl group, an alkynyl group, an aralkyl group, and an aryl group. Specific examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a tert-butyl group, an n-pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, and a decyl group. Among these, from the viewpoint of effectively forming an SEI on the negative electrode, a methyl group, an ethyl group, an n-propyl group, an n-butyl group, a tert-butyl group, an n-pentyl group, and a hexyl group are preferable, a methyl group, an ethyl group, an n-propyl group, an n-butyl group, a tert-butyl group, and an n-pentyl group are more preferable, and a methyl group, an ethyl group, an n-butyl group, and a tert-butyl group are particularly preferable.

[0062] Specific examples of the alkenyl group include a vinyl group, a 2-propenyl group, a methallyl group, a 2-butenyl group, a 3-methyl-2-butenyl group, a 3-butenyl group, a 4-pentenyl group, etc. Among these, from the viewpoint of effectively forming an SEI on the negative electrode, preferred are a vinyl group, a 2-propenyl group, a methallyl group, and a 2-butenyl group, more preferred are a vinyl group, a 2-propenyl group, and a methallyl group, and particularly preferred are a vinyl group or a 2-propenyl group.

[0063] Specific examples of the alkynyl group include an ethynyl group, a 2-propynyl group, a 2-butynyl group, a 3-butynyl group, a 4-pentynyl group, a 5-hexynyl group, etc. Among these, from the viewpoint of effectively forming an SEI on the negative electrode, an ethynyl group, a 2-propynyl group, a 2-butynyl group, and a 3-butynyl group are preferable, a 2-propynyl group and a 3-butynyl group are more preferable, and a 2-propynyl group is particularly preferable.

[0064] Specific examples of the aralkyl group include a benzyl group and a phenethyl group.

[0065] Specific examples of the aryl group include a phenyl group and a tolyl group, etc. Among these, the phenyl group is preferred from the viewpoint of effectively forming an SEI on the negative electrode.

[0066] Specific examples of the alkoxy group having 1 to 12 carbon atoms include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, and an isopropoxy group, etc. Among these, a methoxy group and an ethoxy group are preferable from the viewpoint of effectively forming an SEI on the negative electrode because they cause less steric hindrance to the compound.

[0067] Substituents for the hydrocarbon group having 1 to 12 carbon atoms and the alkoxy group having 1 to 12 carbon atoms include a cyano group, an isocyanato group, an acyl group (-(C=O)-R s ), acyloxy group (-O(C=O)-R s ), alkoxycarbonyl group (-(C=O)OR s ), sulfonyl group (-SO2-R s), sulfonyloxy group (-O(SO2)-R s ), alkoxysulfonyl group (-(SO2)-OR s ), alkoxysulfonyloxy group (-O-(SO2)-OR s ), alkoxycarbonyloxy group (-O-(C=O)-OR s ), ether group (-OR s ), an acrylic group, a methacrylic group, a trifluoromethyl group, etc. s R represents an alkyl group having 1 to 10 carbon atoms, an alkylene group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an alkynyl group having 2 to 10 carbon atoms. s When is an alkylene group, it may be bonded to a part of the hydrocarbon group which substitutes it to form a ring.

[0068] Among these substituents, a cyano group, an isocyanato group, an acyloxy group (-O(C=O)-R s ), alkoxycarbonyl group (-(C=O)OR s ), alkoxycarbonyloxy group (-O-(C=O)-OR s ), and a trifluoromethyl group, and more preferably an isocyanato group, an acyloxy group (-O(C=O)-R s ), alkoxycarbonyl group (-(C=O)OR s ), alkoxycarbonyloxy group (-O-(C=O)-OR s ), and a trifluoromethyl group, and particularly preferably an acyloxy group (-O(C=O)-R s ), alkoxycarbonyloxy group (-O-(C=O)-OR s ), alkoxycarbonyloxy group (-O-(C=O)-OR s ), and the trifluoromethyl group.

[0069] R 15 ~R 17 may be the same or different, but it is preferable that at least two of them are the same in terms of facilitating the synthesis of the compound. Also, R 15 ~R17 From the viewpoint of allowing the compound represented by general formula (C) to effectively form an SEI on the negative electrode, it is preferable that at least one of these is an alkyl group having 1 to 12 carbon atoms which may have a substituent.

[0070] Specific examples of the compound represented by formula (C) include the following compounds C1 to C21.

[0071] [ka]

[0072] Among these, from the viewpoints of improving the restored capacity after high-temperature storage and suppressing the amount of gas generation after high-temperature storage, compounds C1, C4, C7, C10, C13 to C15, C17, C18 and C19 to C21 are preferred, compounds C1, C4, C7, C10, C13 to C15, C17, C18 and C19 are more preferred, compounds C1, C4, C7, C10, C13 to C15 and C19 are further preferred, and compounds C1, C10, C13 and C19 are particularly preferred.

[0073] When the nonaqueous electrolyte solution of the present invention contains a fluorosilane compound, there are no particular limitations on the content of the fluorosilane compound in the nonaqueous electrolyte solution, but from the viewpoint of improving the recovery capacity after high-temperature storage and suppressing the amount of gas generation after high-temperature storage, it is preferable that the fluorosilane compound is contained in the total amount of the nonaqueous electrolyte solution in an amount of usually 0.001 mass% or more, preferably 0.005 mass% or more, and more preferably 0.01 mass% or more, and generally 10 mass% or less, preferably 5 mass% or less, more preferably 3 mass% or less, and even more preferably 1 mass% or less.

[0074] When the non-aqueous electrolyte of the present invention contains a fluorosilane compound, the mass ratio of the content of the compound represented by formula (A) to the content of the compound represented by formula (C) in the non-aqueous electrolyte ([content of the compound represented by formula (A)] / [content of the compound represented by formula (C)]) is not particularly limited, but is usually 0.001 or more, preferably 0.005 or more, more preferably 0.01 or more, particularly preferably 0.02 or more, and is usually 1000 or less, preferably 500 or less, more preferably 200 or less, particularly preferably 100 or less. By setting it to the above range, the balance between the complexity of the SEI formed by the compound represented by formula (A) and the density and strength of the SEI brought about by the compound represented by formula (C) is good, and it is considered that the effect of the SEI is fully exerted. In addition, when the non-aqueous electrolyte of the present invention contains a fluorosilane compound, the mass ratio of the content of the compound represented by formula (B) to the content of the compound represented by formula (C) in the non-aqueous electrolyte ([content of the compound represented by formula (B)] / [content of the compound represented by formula (C)]) is not particularly limited, but is usually 0.0001 or more, preferably 0.0003 or more, more preferably 0.0005 or more, particularly preferably 0.001 or more, while it is usually 500 or less, preferably 200 or less, more preferably 100 or less, particularly preferably 50 or less. By setting it to the above range, the balance between the complexity of the SEI formed by the compound represented by formula (B) and the density and strength of the SEI brought about by the compound represented by formula (C) is good, and it is considered that the effect of the SEI is fully exerted.

[0075] The fluorosilane compound in the non-aqueous electrolyte solution is identified and its content is measured by nuclear magnetic resonance (NMR) spectroscopy.

[0076] [1-4. Electrolytes] The electrolyte in the non-aqueous electrolyte solution is usually a salt of an anion and a metal cation, preferably an alkali metal cation such as lithium, sodium or potassium, more preferably a lithium cation.

[0077] There are no particular limitations on the anion, so long as it is known to be used for this application, and any anion can be used. Specific examples of the anion include the following anions: Fluoroborates, PF6 - Examples of anions include phosphate anions having a PF bond and a P=O bond, tungstate anions, carboxylate anions, anions having an S=O bond, oxalate complex anions, and fluorine-containing organic anions.

[0078] Among them, at least one anion selected from phosphate anions having a PF bond and a P=O bond, anions having an S=O bond, and oxalate complex anions (hereinafter also referred to as "specific anions"), and PF6 - However, this is more preferable since it has the effect of improving low-temperature output characteristics, high-rate charge / discharge characteristics, impedance characteristics, high-temperature storage characteristics, cycle characteristics, and the like.

[0079] Examples of phosphate anions having a PF bond and a P=O bond include PO3F 2- Monofluorophosphate anion, such as PO2F2 - Among these, the difluorophosphate anion is preferred from the viewpoint of the balance between the output characteristics of the battery and the protection of the electrode interface.

[0080] Examples of anions having an S=O bond include FSO3 - , CH3SO3 - Fluorosulfonate anion such as CH3SO4 - , C2H5SO4 - , etc. alkyl sulfate anion; (FSO2)2N - , (FSO2)(CF3SO2)N - , (CF3SO2)2N - , (C2F5SO2)2N - Fluorosulfonylimide anions such as cyclic 1,2-perfluoroethanedisulfonylimide anion, cyclic 1,3-perfluoropropanedisulfonylimide anion, etc.; (FSO2)3C- , (CF3SO2)3C - , (C2F5SO2)3C - Among these, from the viewpoint of the balance between the output characteristics of the battery and the protection of the electrode interface, the fluorosulfonate anion, the alkyl sulfate anion, and the fluorosulfonylimide anion are preferred, the fluorosulfonate anion and the alkyl sulfate anion are more preferred, and the fluorosulfonate anion is even more preferred.

[0081] The oxalate complex anion is not particularly limited as long as it is an anion having an oxalate complex in the molecule.The oxalate complex anion is an anion of an acid in which oxalic acid is coordinated or bonded to a central atom to form a complex, and examples thereof include boron oxalate complex anion in which oxalic acid is coordinated or bonded to a boron atom, and phosphorus oxalate complex anion in which oxalic acid is coordinated or bonded to a phosphorus atom.

[0082] Examples of the boron oxalate complex anion include bis(oxalate)borate anion, difluorooxalateborate anion, etc., and examples of the phosphorus oxalate complex anion include tetrafluorooxalate phosphate anion, difluorobis(oxalate)phosphate anion, tris(oxalate)phosphate anion, etc. Among these, from the viewpoint of forming a stable composite coating on the surface of the electrode, the boron oxalate complex anion is preferred, and the bis(oxalate)borate anion is more preferred.

[0083] The above anions may be used alone or in combination of two or more. When two or more of the above anions are used in combination, the above specific anions are preferably used in combination with PF6 - It is preferable to use two or more kinds of anions in combination with PF6. - When using PF6 as the total anion content (mass%), - It is preferable that the content of is the second highest or higher, and more preferably the highest. There are no particular restrictions on the combination of two or more electrolyte salts, but PF6 - and PO2F2 - , PF6 - and FSO3 - , PF6 - and CH3SO4 - , PF6 - and C2H5SO4 - , PF6 - and N(FSO2)2 - , PF6 - and bis(oxalato)borate anion, PF6 - and PO2F2 - and FSO3 - , PF6 - and PO2F2 - and bis(oxalato)borate anion. - and PO2F2 - , PF6 - and FSO3 - , PF6 - and N(FSO2)2 - , PF6 - and PO2F2 - and FSO3 - is preferred.

[0084] The total concentration of the electrolyte in the non-aqueous electrolyte is not particularly limited, but is usually 8% by mass or more, preferably 8.5% by mass or more, more preferably 9% by mass or more, and is usually 18% by mass or less, preferably 17% by mass or less, more preferably 16% by mass or less, based on the total amount of the non-aqueous electrolyte. If the total concentration of the electrolyte is within the above range, the electrical conductivity becomes appropriate for the battery operation, and therefore sufficient output characteristics tend to be obtained.

[0085] (Specific anion content) When the non-aqueous electrolyte contains the specific anions, the content of the specific anions in the total amount of the non-aqueous electrolyte is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, even more preferably 0.1% by mass or more, and also preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less. The content of the specific anions in the total amount of the non-aqueous electrolyte is preferably 0.001% by mass or more and 5% by mass or less, more preferably 0.01% by mass or more and 4% by mass or less, and even more preferably 0.1% by mass or more and 3% by mass or less. If the content of the specific anions is within the above range, the battery characteristics, particularly the internal resistance retention rate after high-temperature storage, can be significantly improved, and the increase in the amount of gas generated after high-temperature storage can be significantly suppressed. Although the reason for this is unclear, it is believed that the content of the specific anions within the above mass ratio range can minimize excessive side reactions of the components of the non-aqueous electrolyte on the electrodes. The identification and content of the specific anions are determined by nuclear magnetic resonance (NMR) spectroscopy.

[0086] (Mass ratio of specific anions to electrolyte) When the non-aqueous electrolyte contains the specific anions, the mass ratio of the content of the specific anions to the content of the electrolyte (content of specific anions [g] / content of electrolyte [g]) is usually 0.00005 or more, preferably 0.001 or more, more preferably 0.01 or more, even more preferably 0.02 or more, even more preferably 0.025 or more, and usually 0.5 or less, preferably 0.45 or less, more preferably 0.4 or less, even more preferably 0.35 or less. The mass ratio (content of specific anions [g] / electrolyte salt [g]) is usually 0.00005 or more and 0.5 or less, preferably 0.001 or more and 0.45 or less, more preferably 0.01 or more and 0.4 or less, even more preferably 0.02 or more and 0.35 or less, even more preferably 0.025 or more and 0.35 or less. When the mass ratio is within the above range, the battery characteristics, particularly the internal resistance retention rate after high-temperature storage, can be significantly improved, and the increase in the amount of gas generated after high-temperature storage can be significantly suppressed. Although the reason for this is unclear, it is believed that by containing the specific anions within the above mass ratio range, the side reaction of the electrolyte in the battery system can be minimized.

[0087] [1-5. Solvent] The non-aqueous electrolyte of the present invention, like a general non-aqueous electrolyte, usually contains a non-aqueous solvent that dissolves the above-mentioned electrolyte as its main component. The non-aqueous solvent used here is not particularly limited as long as it dissolves the above-mentioned electrolyte, and a known organic solvent can be used. Examples of organic solvents include, but are not limited to, saturated cyclic carbonates, chain carbonates, chain carboxylate esters, cyclic carboxylate esters, ether compounds, and sulfone compounds. These can be used alone or in combination of two or more.

[0088] The combination of two or more organic solvents is not particularly limited, and examples thereof include saturated cyclic carbonates and chain carboxylates, cyclic carboxylates and chain carbonates, and saturated cyclic carbonates, chain carbonates and chain carboxylates. Among these, saturated cyclic carbonates and chain carbonates, and saturated cyclic carbonates, chain carbonates and chain carboxylates are preferred.

[0089] [1-5-1. Saturated cyclic carbonates] The saturated cyclic carbonate may generally have an alkylene group having 2 to 4 carbon atoms, and from the viewpoint of improving battery characteristics resulting from an improvement in the degree of dissociation of lithium ions, saturated cyclic carbonates having 2 to 3 carbon atoms are preferably used.

[0090] Examples of the saturated cyclic carbonate include ethylene carbonate, propylene carbonate, butylene carbonate, etc. Among them, ethylene carbonate and propylene carbonate are preferred, and ethylene carbonate, which is less susceptible to oxidation and reduction, is more preferred. The saturated cyclic carbonate may be used alone or in any combination and ratio of two or more kinds.

[0091] The content of the saturated cyclic carbonate is not particularly limited and may be any content as long as it does not significantly impair the effects of the present invention, but the lower limit is usually 3% by volume or more, preferably 5% by volume or more, more preferably 15% by volume or more, and even more preferably 20% by volume or more, based on the total amount of the solvent in the nonaqueous electrolyte, while it is usually 90% by volume or less, preferably 85% by volume or less, more preferably 80% by volume or less, even more preferably 60% by volume or less, particularly preferably 45% by volume or less, and most preferably 50% by volume or less. By setting it in this range, the decrease in electrical conductivity due to the decrease in the dielectric constant of the nonaqueous electrolyte is avoided, and the large current discharge characteristics, stability to the negative electrode, and cycle characteristics of the nonaqueous electrolyte secondary battery are easily in a good range, and the oxidation / reduction resistance of the nonaqueous electrolyte is improved, and the stability during high-temperature storage tends to be improved. In the present embodiment, the volume % refers to the volume at 25° C. and 1 atmospheric pressure.

[0092] [1-5-2. Chain carbonate] As the chain carbonate, one having 3 to 7 carbon atoms is usually used, and in order to adjust the viscosity of the non-aqueous electrolyte solution within an appropriate range, a chain carbonate having 3 to 5 carbon atoms is preferably used.

[0093] Specific examples of the chain carbonate include dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, ethyl methyl carbonate, methyl-n-propyl carbonate, etc. Dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate are particularly preferred.

[0094] In addition, chain carbonates having fluorine atoms (hereinafter, sometimes abbreviated as "fluorinated chain carbonate") can also be suitably used. The number of fluorine atoms in the fluorinated chain carbonate is not particularly limited as long as it is 1 or more, but is usually 6 or less, and preferably 4 or less. When the fluorinated chain carbonate has multiple fluorine atoms, they may be bonded to the same carbon or different carbons. Examples of the fluorinated chain carbonate include fluorinated dimethyl carbonate derivatives such as fluoromethyl methyl carbonate, fluorinated ethyl methyl carbonate derivatives such as 2-fluoroethyl methyl carbonate, and fluorinated diethyl carbonate derivatives such as ethyl-(2-fluoroethyl) carbonate.

[0095] The chain carbonate may be used alone or in any combination of two or more kinds in any ratio.

[0096] The content of the chain carbonate is not particularly limited, but is usually 15% by volume or more, preferably 20% by volume or more, more preferably 25% by volume or more, even more preferably 35% by volume or more, particularly preferably 55% by volume or more, most preferably 65% ​​by volume or more, and usually 90% by volume or less, preferably 85% by volume or less, more preferably 80% by volume or less, based on the total amount of the solvent in the nonaqueous electrolyte. By setting the content of the chain carbonate within the above range, the viscosity of the nonaqueous electrolyte can be set to an appropriate range, the decrease in ion conductivity can be suppressed, and the output characteristics of the nonaqueous electrolyte secondary battery can be easily set to a good range.

[0097] [1-5-3. Chain carboxylate esters] Examples of the chain carboxylate include methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, methyl valerate, methyl isobutyrate, ethyl isobutyrate, and methyl pivalate. Among them, methyl acetate, ethyl acetate, propyl acetate, and butyl acetate are preferred from the viewpoint of improving battery characteristics. Chain carboxylates in which a portion of the hydrogen of the above-mentioned compounds is replaced with fluorine (e.g., methyl trifluoroacetate, ethyl trifluoroacetate, etc.) can also be used suitably.

[0098] [1-5-4. Cyclic carboxylate esters] Examples of the cyclic carboxylate include γ-butyrolactone and γ-valerolactone. Among these, γ-butyrolactone is more preferable. Cyclic carboxylates in which some of the hydrogen atoms of the above-mentioned compounds are replaced with fluorine can also be used suitably.

[0099] [1-5-5. Ether compounds] Preferred examples of the ether compounds include chain ethers having 3 to 10 carbon atoms, such as dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether, and cyclic ethers having 3 to 6 carbon atoms, such as tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, 1,3-dioxane, 2-methyl-1,3-dioxane, 4-methyl-1,3-dioxane, and 1,4-dioxane.

[0100] Among these, as the chain ethers having 3 to 10 carbon atoms, dimethoxymethane, diethoxymethane, and ethoxymethoxymethane are preferred because they have a high solvation ability for lithium ions, improve ion dissociation, have low viscosity, and provide high ionic conductivity, and as the cyclic ethers having 3 to 6 carbon atoms, tetrahydrofuran, 1,3-dioxane, 1,4-dioxane, and the like are preferred because they provide high ionic conductivity.

[0101] The content of the ether-based compound is not particularly limited and may be any content as long as it does not significantly impair the effects of the present invention according to this embodiment, but is usually 1% by volume or more, preferably 2% by volume or more, more preferably 3% by volume or more, and usually 30% by volume or less, preferably 25% by volume or less, more preferably 20% by volume or less, in 100% by volume of the non-aqueous solvent. If the content of the ether-based compound is within the above-mentioned preferred range, it is easy to ensure the effect of improving the lithium ion dissociation degree of the ether and improving the ion conductivity due to the viscosity reduction. In addition, when the negative electrode active material is a carbonaceous material, the phenomenon in which the chain ether is co-inserted with the lithium ion can be suppressed, so that the input / output characteristics and the charge / discharge rate characteristics can be set to appropriate ranges.

[0102] [1-5-6. Sulfone compounds] The sulfone compound is not particularly limited, whether it is a cyclic sulfone or a chain sulfone, but in the case of a cyclic sulfone, the carbon number is usually 3 to 6, preferably 3 to 5, and in the case of a chain sulfone, the carbon number is usually 2 to 6, preferably 2 to 5. The number of sulfonyl groups in one molecule of the sulfone compound is not particularly limited, but is usually 1 or 2.

[0103] Examples of cyclic sulfones include monosulfone compounds such as trimethylene sulfones, tetramethylene sulfones, and hexamethylene sulfones; and disulfone compounds such as trimethylene disulfones, tetramethylene disulfones, and hexamethylene disulfones. Among these, from the viewpoints of dielectric constant and viscosity, tetramethylene sulfones, tetramethylene disulfones, hexamethylene sulfones, and hexamethylene disulfones are more preferred, and tetramethylene sulfones (sulfolanes) are particularly preferred.

[0104] As the sulfolane, sulfolane and / or a sulfolane derivative (hereinafter, sulfolane may be abbreviated as "sulfolane" including sulfolane) are preferable. As the sulfolane derivative, one or more of the hydrogen atoms bonded to the carbon atoms constituting the sulfolane ring are substituted with a fluorine atom or an alkyl group are preferable. Among them, 2-methylsulfolane, 3-methylsulfolane, 2-fluorosulfolane, 3-fluorosulfolane, 2,3-difluorosulfolane, 2-trifluoromethylsulfolane, 3-trifluoromethylsulfolane, etc. are preferable in terms of high ionic conductivity and high input / output.

[0105] Examples of the chain sulfone include dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, monofluoromethyl methyl sulfone, difluoromethyl methyl sulfone, trifluoromethyl methyl sulfone, pentafluoroethyl methyl sulfone, etc. Among these, dimethyl sulfone, ethyl methyl sulfone, and monofluoromethyl methyl sulfone are preferred in terms of improving the high-temperature storage stability of the nonaqueous electrolyte solution.

[0106] The content of the sulfone-based compound is not particularly limited and may be any as long as it does not significantly impair the effect of the present invention, but is usually 0.3% by volume or more, preferably 0.5% by volume or more, more preferably 1% by volume or more, and is usually 40% by volume or less, preferably 35% by volume or less, more preferably 30% by volume or less, based on the total amount of the solvent in the nonaqueous electrolyte. If the content of the sulfone-based compound is within the above range, a nonaqueous electrolyte having excellent high-temperature storage stability tends to be obtained.

[0107] [1-6. Auxiliaries] The non-aqueous electrolyte according to the present invention may contain various auxiliary agents within the range that does not impair the effects of the present invention. As the auxiliary agent, any conventionally known one may be used. The auxiliary agent may be used alone or in combination of two or more kinds at any ratio. Examples of the auxiliary include cyclic carbonates having a carbon-carbon unsaturated bond, fluorine-containing cyclic carbonates, compounds having an isocyanate group, compounds having an isocyanuric acid skeleton, sulfur-containing organic compounds, phosphorus-containing organic compounds, silicon-containing compounds, aromatic compounds, organic compounds having a cyano group, fluorine-free carboxylic acid esters, cyclic compounds having an ether bond, acid anhydrides, triple bond-containing compounds, phosphazene compounds, etc. For example, compounds described in International Publication No. 2015 / 111676 can be mentioned.

[0108] The content of the auxiliary is not particularly limited, and is arbitrary as long as it does not significantly impair the effects of the present invention, but is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and is usually 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 1% by mass or less, and particularly preferably less than 1% by mass. The content of the auxiliary is usually 0.001% by mass or more and 10% by mass or less, preferably 0.01% by mass or more and 5% by mass or less, more preferably 0.1% by mass or more and 3% by mass or less, even more preferably 0.1% by mass or more and 1% by mass or less, and particularly preferably 0.1% by mass or more and 1% by mass or less, based on the total amount of the nonaqueous electrolyte. If the content of the auxiliary agent is within the above range, the battery characteristics, especially the durability, can be improved. Although the reason for this is unclear, it is thought that the inclusion of the auxiliary agent in this ratio forms a coating on the electrode, minimizing side reactions of the components of the non-aqueous electrolyte solution. The identification and content determination of the auxiliary agents is carried out by nuclear magnetic resonance (NMR) spectroscopy.

[0109] The cyclic compound having an ether bond can be used as an auxiliary in a non-aqueous electrolyte solution, and some of them can be used as a non-aqueous solvent as described in the section [1-5. Solvent]. When a cyclic compound having an ether bond is used as an auxiliary agent, it is preferable to use it in an amount of less than 4 mass % based on the total amount of the nonaqueous electrolyte solution.

[0110] [1-6-1. Specific carbonate compounds] The non-aqueous electrolyte may contain at least one carbonate compound (hereinafter also referred to as a specific carbonate compound) selected from the group consisting of cyclic carbonates having a carbon-carbon unsaturated bond and cyclic carbonates having a fluorine atom. Among these, it is preferable to contain a cyclic carbonate having a carbon-carbon unsaturated bond, and it is more preferable to contain vinylene carbonate. These can be used alone or in combination of two or more in any ratio, and it is preferable to combine an unsaturated cyclic carbonate and a fluorinated cyclic carbonate, and it is more preferable to combine a vinylene carbonate and a fluorinated cyclic carbonate, and it is even more preferable to combine an unsaturated cyclic carbonate and a monofluoroethylene carbonate, and it is even more preferable to combine vinylene carbonate and a monofluoroethylene carbonate.

[0111] [1-6-1-1. Cyclic carbonates having carbon-carbon unsaturated bonds] The cyclic carbonate having a carbon-carbon unsaturated bond (hereinafter also referred to as "unsaturated cyclic carbonate") is not particularly limited as long as it is a cyclic carbonate having a carbon-carbon double bond or a carbon-carbon triple bond. Cyclic carbonates having an aromatic ring are also included in the unsaturated cyclic carbonate.

[0112] Examples of the unsaturated cyclic carbonate include vinylene carbonates, ethylene carbonates substituted with a substituent having an aromatic ring, a carbon-carbon double bond or a carbon-carbon triple bond, phenyl carbonates, vinyl carbonates, allyl carbonates, catechol carbonates, etc. Among these, vinylene carbonates and ethylene carbonates substituted with a substituent having an aromatic ring, a carbon-carbon double bond or a carbon-carbon triple bond are preferred.

[0113] Examples of vinylene carbonates include vinylene carbonate, methylvinylene carbonate, 4,5-dimethylvinylene carbonate, phenylvinylene carbonate, 4,5-diphenylvinylene carbonate, vinylvinylene carbonate, 4,5-vinylvinylene carbonate, allylvinylene carbonate, and 4,5-diallylvinylene carbonate. Examples of ethylene carbonates substituted with a substituent having an aromatic ring or a carbon-carbon double bond or a carbon-carbon triple bond include vinyl ethylene carbonate, 4,5-divinyl ethylene carbonate, 4-methyl-5-vinyl ethylene carbonate, 4-allyl-5-vinyl ethylene carbonate, ethynyl ethylene carbonate, 4,5-diethynyl ethylene carbonate, 4-methyl-5-ethynyl ethylene carbonate, 4-vinyl-5-ethynyl ethylene carbonate, 4-allyl-5-ethynyl ethylene carbonate, phenyl ethylene carbonate, 4,5-diphenyl ethylene carbonate, 4-phenyl-5-vinyl ethylene carbonate, 4-allyl-5-phenyl ethylene carbonate, allyl ethylene carbonate, 4,5-diallyl ethylene carbonate, and 4-methyl-5-allyl ethylene carbonate. Among these, vinylene carbonate, vinyl ethylene carbonate, and ethynyl ethylene carbonate are preferred since they form a more stable composite coating on the electrode, and one or more selected from vinylene carbonate and vinyl ethylene carbonate are more preferred, with vinylene carbonate being even more preferred. The unsaturated cyclic carbonates can be used alone or in combination of two or more kinds in any ratio.

[0114] [1-6-1-2. Cyclic carbonates containing fluorine atoms] The fluorine atom-containing cyclic carbonate is not particularly limited as long as it has a cyclic carbonate structure and contains a fluorine atom. Examples of cyclic carbonates having fluorine atoms include fluorinated cyclic carbonates having an alkylene group with 2 to 6 carbon atoms, and derivatives thereof, such as fluorinated ethylene carbonate (fluoroethylene carbonate) and derivatives thereof, and ethylene carbonate having a fluorine-containing group. Examples of derivatives of fluorinated ethylene carbonate include fluorinated ethylene carbonate substituted with an alkyl group (e.g., an alkyl group with 1 to 4 carbon atoms). Among these, fluoroethylene carbonate having 1 to 8 fluorine atoms and derivatives thereof are preferred.

[0115] Examples of fluoroethylene carbonate and derivatives thereof having 1 to 8 fluorine atoms, as well as ethylene carbonate having a fluorine-containing group, include monofluoroethylene carbonate, 4,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4-fluoro-4-methylethylene carbonate, 4,5-difluoro-4-methylethylene carbonate, 4-fluoro-5-methylethylene carbonate, 4,4-difluoro-5-methylethylene carbonate, 4-(fluoromethyl)-ethylene carbonate, 4-(difluoromethyl)-ethylene carbonate, 4-(trifluoromethyl)-ethylene carbonate, 4-(fluoromethyl)-4-fluoroethylene carbonate, 4-(fluoromethyl)-5-fluoroethylene carbonate, 4-fluoro-4,5-dimethylethylene carbonate, 4,5-difluoro-4,5-dimethylethylene carbonate, and 4,4-difluoro-5,5-dimethylethylene carbonate. Among these, from the viewpoints of imparting high ionic conductivity to the non-aqueous electrolyte and facilitating the formation of a stable interface protective film, one or more selected from monofluoroethylene carbonate, 4,4-difluoroethylene carbonate, and 4,5-difluoroethylene carbonate are preferred. The fluorine atom-containing cyclic carbonates can be used alone or in combination of two or more kinds in any ratio.

[0116] [1-6-2. Organic compounds containing isocyanate groups] The organic compound having an isocyanate group is not particularly limited as long as it is an organic compound having at least one isocyanate group in the molecule. The number of isocyanate groups in one molecule is preferably 1 to 4, more preferably 2 or 3, and even more preferably 2. Examples of organic compounds having an isocyanate group include monoisocyanate compounds such as methyl isocyanate, ethyl isocyanate, butyl isocyanate, vinyl isocyanate, propargyl isocyanate, cyclohexyl isocyanate, phenyl isocyanate, 2-isocyanatoethyl acrylate, and 2-isocyanatoethyl methacrylate; and diisocyanate compounds such as monomethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, octamethylene diisocyanate, 1,4-phenylene diisocyanate, 1,3-diisocyanatopropane, 1,3-bis(isocyanatomethyl)cyclohexane, carbonyl diisocyanate, and 1,4-diisocyanato-2-fluorobutane. In particular, from the viewpoint of forming a stable interface protective coating, an organic compound having at least two isocyanate groups is preferred, hexamethylene diisocyanate and 1,3-bis(isocyanatomethyl)cyclohexane are more preferred, and 1,3-bis(isocyanatomethyl)cyclohexane is even more preferred.

[0117] [1-6-3. Organic compounds with an isocyanuric acid skeleton] The organic compound having an isocyanuric acid skeleton (hereinafter also referred to as "isocyanurate compound") is not particularly limited as long as it is an organic compound having at least one isocyanuric acid skeleton in the molecule. Examples of the organic compound having an isocyanuric acid skeleton include the following compounds.

[0118] [ka]

[0119] In particular, from the viewpoint of forming a stable interface protective coating, an isocyanurate compound having a saturated or unsaturated aliphatic hydrocarbon group which may have a halogen atom is preferred, an isocyanurate compound having an unsaturated aliphatic hydrocarbon group containing a carbon-carbon unsaturated bond at the terminal is more preferred, and triallyl isocyanurate is even more preferred.

[0120] [1-6-4. Sulfur-containing organic compounds] The sulfur-containing organic compound is not particularly limited as long as it is an organic compound having at least one sulfur atom (S) in the molecule. It is preferably an organic compound having at least one S=O bond, and more preferably, an ester compound having an S=O bond such as a chain sulfonate ester, a cyclic sulfonate ester, a chain sulfate ester, a cyclic sulfate ester, a chain sulfite ester, and a cyclic sulfite ester. However, anions having an S=O bond are not "sulfur-containing organic compounds" but are included in the above "anions having an S=O bond". Examples of sulfur-containing organic compounds include: Chain sulfonate esters such as alkyl disulfonate esters, such as methyl fluorosulfonate, methyl methanesulfonate, ethyl methanesulfonate, busulfan, methyl methanesulfonyloxyacetate, methyl vinylsulfonate, allyl vinylsulfonate, propargyl allylsulfonate, methoxycarbonylmethyl methanedisulfonate, ethoxycarbonylmethyl methanedisulfonate, methoxycarbonylmethyl 1,3-butanedisulfonate, ethoxycarbonylmethyl 1,3-butanedisulfonate, 1-methoxycarbonylethyl 1,3-butanedisulfonate, and 1-ethoxycarbonylethyl 1,3-butanedisulfonate; cyclic sulfonate esters such as 1,3-propane sultone, 1-fluoro-1,3-propane sultone, 1-methyl-1,3-propane sultone, 1-propene-1,3-sultone, 2-propene-1,3-sultone, 1-fluoro-1-propene-1,3-sultone, 1-methyl-1-propene-1,3-sultone, 1,3-butane sultone, 2,4-butane sultone, 1,4-butane sultone, 1,5-pentane sultone, methylene methane disulfonate, ethylene methane disulfonate, and 2,2-dioxide-1,2-oxathiolan-4-yl acetate; chain sulfate esters such as dimethyl sulfate, ethyl methyl sulfate, and diethyl sulfate; Cyclic sulfates such as 1,2-ethylene sulfate, 1,2-propylene sulfate, 1,3-propylene sulfate, 1,2-butylene sulfate, etc.; Chain sulfites such as dimethyl sulfite, ethyl methyl sulfite, and diethyl sulfite; Examples of the sulfurous acid ester include cyclic sulfite esters such as 1,2-ethylene sulfite, 1,2-propylene sulfite, 1,3-propylene sulfite, and 1,2-butylene sulfite; cyclic sulfones such as 1,1-dioxidetetrahydrothiophen-3-yl methanesulfonate and 1,1-dioxide-2,3-dihydrothiophen-3-yl methanesulfonate; sulfonic acid esters such as butane-2,3-diyl dimethanesulfonate, butane-1,4-diyl dimethanesulfonate, and methylene methane disulfonate; and vinyl sulfone compounds such as divinyl sulfone, 1,2-bis(vinylsulfonyl)ethane, and bis(2-vinylsulfonylethyl)ether. In particular, from the viewpoint of forming a stable interface protective coating, linear or cyclic sulfonate esters, cyclic sulfate esters, or cyclic sulfite esters are more preferred, cyclic sulfonate esters or cyclic sulfate esters are particularly preferred, and 1,3-propane sultone, methylenemethane disulfonate, and 1,2-ethylene sulfate are most preferred.

[0121] [1-6-5. Phosphorus-containing organic compounds] There are no particular limitations on the phosphorus-containing organic compound, so long as it is an organic compound that has at least one phosphorus atom in the molecule. However, compounds that fall under the category of anion-containing compounds having a PF bond and a P=O bond are not "phosphorus-containing organic compounds" but are included in the above "anion-containing compounds having a PF bond and a P=O bond." Examples of phosphorus-containing organic compounds include trimethyl phosphate, tributyl phosphate, trioctyl phosphate, tris(2,2,2-trifluoroethyl) phosphate, ethyl 2-(diethoxyphosphoryl)acetate, and 2-propynyl 2-(diethoxyphosphoryl)acetate.

[0122] In particular, ethyl 2-(diethoxyphosphoryl)acetate or 2-propynyl 2-(diethoxyphosphoryl)acetate is preferred, with 2-propynyl 2-(diethoxyphosphoryl)acetate being more preferred.

[0123] [1-6-6. Silicon-containing compounds] The silicon-containing compound is not particularly limited as long as it is a compound having at least one silicon atom in the molecule. However, those that fall under the category of fluorosilane compounds are not considered to be "silicon-containing compounds" but are included in the above-mentioned "fluorosilane compounds." Examples of silicon-containing compounds include: borate compounds such as tris(trimethylsilyl) borate, tris(trimethoxysilyl) borate, tris(triethylsilyl) borate, and tris(dimethylvinylsilyl) borate; Phosphate compounds such as tris(trimethylsilyl) phosphate, tris(triethylsilyl) phosphate, tris(triphenylsilyl) phosphate, tris(trimethoxysilyl) phosphate, and tris(dimethylvinylsilyl) phosphate; Phosphite compounds such as tris(trimethylsilyl) phosphite, tris(triethylsilyl) phosphite, tris(triphenylsilyl) phosphite, tris(trimethoxysilyl) phosphite, and tris(dimethylvinylsilyl) phosphite; Sulfonic acid compounds such as trimethylsilyl methanesulfonate and trimethylsilyl tetrafluoromethanesulfonate; Silane compounds such as tetramethylsilane, trimethylvinylsilane, dimethyldivinylsilane, methyltrivinylsilane, and tetravinylsilane; Disilane compounds such as hexamethyldisilane, hexaethyldisilane, 1,1,2,2-tetramethyldisilane, and 1,2-diphenyltetramethyldisilane; Disiloxane compounds such as hexamethyldisiloxane, 1,3-divinyltetramethyldisiloxane, and 1,1,3,3-tetramethyl-1,3-diphenyldisiloxane; etc. In particular, from the viewpoint of forming a stable interface protective coating, disilane compounds and disiloxane compounds are preferred, disiloxane compounds are more preferred, hexamethyldisiloxane and 1,3-divinyltetramethyldisiloxane are even more preferred, and 1,3-divinyltetramethyldisiloxane is particularly preferred.

[0124] [1-6-7. Aromatic compounds] The aromatic compound is not particularly limited as long as it is a compound having aromaticity in the molecule.The aromatic compound may be, for example, an aromatic compound having a branched alkyl group such as cyclohexylbenzene, tert-butylbenzene, tert-amylbenzene or 1-fluoro-4-tert-butylbenzene, or an aromatic compound such as biphenyl, terphenyl (o-, m-, p-isomer), fluorobenzene, methylphenyl carbonate, ethylphenyl carbonate or diphenyl carbonate.

[0125] In particular, biphenyl, terphenyl (o-, m-, p-isomer), fluorobenzene, cyclohexylbenzene, tert-butylbenzene, and tert-amylbenzene are more preferred, and biphenyl, o-terphenyl, fluorobenzene, cyclohexylbenzene, and tert-amylbenzene are more preferred.

[0126] [1-6-8. Organic compounds containing a cyano group] The organic compound having a cyano group is not particularly limited as long as it is an organic compound having at least one cyano group in the molecule. Examples of organic compounds having a cyano group include: Organic compounds having one cyano group in the molecule, such as acetonitrile, propionitrile, butyronitrile, pentanenitrile, hexanenitrile, decanenitrile, undecanenitrile, dodecanenitrile, cyclohexanecarbonitrile, acrylonitrile, methacrylonitrile, and crotononitrile; Organic compounds having two cyano groups in the molecule, such as succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, sebaconitrile, methylmalononitrile, ethylmalononitrile, bicyclohexyl-1,1-dicarbonitrile, 1,4-dicyanopentane, and 1,2-dicyanobenzene; Organic compounds having three cyano groups in the molecule, such as 1,2,3-propanetricarbonitrile, 1,2,3-tris(2-cyanoethoxy)propane, 1,3,5-cyclohexanetricarbonitrile, and 1,3,5-benzenetricarbonitrile; etc. In particular, from the viewpoint of forming a stable interface protective film, an organic compound having two cyano groups is preferred, succinonitrile and adiponitrile are more preferred, and adiponitrile is even more preferred.

[0127] [1-6-9. Fluorine-free carboxylic acid esters] The fluorine-free carboxylate is not particularly limited as long as it is a carboxylate that does not have a fluorine atom in the molecule.Preferably, it is a fluorine-free chain carboxylate, more preferably, it is a fluorine-free saturated chain carboxylate.The total carbon number of the fluorine-free chain carboxylate is preferably 3 or more, more preferably 4 or more, preferably 7 or less, more preferably 6 or less, and even more preferably 5 or less. Examples of the chain carboxylate ester include methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, methyl propionate, ethyl propionate, n-propyl propionate, isopropyl propionate, n-butyl propionate, methyl pivalate, ethyl pivalate, n-propyl pivalate, isopropyl pivalate, n-butyl pivalate, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, methyl crotonate, ethyl crotonate, and methyl 2-propionate. In particular, from the viewpoint of improving the output characteristics of the battery, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, and n-propyl propionate are preferred, with methyl propionate being more preferred.

[0128] [1-6-10. Cyclic compounds with ether bonds] The cyclic compound having an ether bond is not particularly limited as long as it is a compound having one or more ether bonds in the molecule. Examples of the cyclic compound having an ether bond include cyclic acetal compounds such as 1,3-dioxolane, 1,3-dioxane, and 1,3,5-trioxane.

[0129] In particular, cyclic acetal compounds are preferred, 1,3-dioxolane or 1,3-dioxane is preferred, and 1,3-dioxane is more preferred.

[0130] [1-6-11. Acid anhydride] The acid anhydride is not particularly limited as long as it has a "C(=O)-OC(=O) group," a "C(=O)-OS(=O)2 group," or a "S(=O)2-OS(=O)2 group" in the molecule. Examples of acid anhydrides include chain carboxylic acid anhydrides such as acetic anhydride, acrylic anhydride, methacrylic anhydride, cyclohexanecarboxylic anhydride, propynoic anhydride, benzoic anhydride, fluoroacetic anhydride, 4-fluorobenzoic anhydride, and acetic propionic anhydride, succinic anhydride, maleic anhydride, citraconic anhydride, glutaric anhydride, itaconic anhydride, fluorosuccinic anhydride, allylsuccinic anhydride, 1,2-oxathiolan-5-one 2,2-dioxide, and 1,2,6-oxadithiane 2,2,6,6-tetraoxide. In particular, from the viewpoint of forming a stable interface protective film, methacrylic anhydride, succinic anhydride, maleic anhydride, and allylsuccinic anhydride are preferred, with succinic anhydride and allylsuccinic anhydride being more preferred.

[0131] [1-6-12. Triple bond-containing compounds] The triple bond-containing compound is not particularly limited as long as it is a compound having at least one triple bond in the molecule.Examples of the triple bond-containing compound include 2-propynyl methyl carbonate, 2-propynyl acetate, 2-propynyl formate, 2-propynyl methacrylate, 2-propynyl methanesulfonate, 2-propynyl vinylsulfonate, 2-propynyl 2-(methanesulfonyloxy)propionate, di(2-propynyl)oxalate, 2-butyne-1,4-diyl dimethanesulfonate and 2-butyne-1,4-diyl diformate.

[0132] In particular, 2-propynyl methyl carbonate, 2-propynyl methacrylate, 2-propynyl methanesulfonate, 2-propynyl vinylsulfonate, di(2-propynyl)oxalate, and 2-butyne-1,4-diyl dimethanesulfonate are preferred, and 2-propynyl methanesulfonate, 2-propynyl vinylsulfonate, di(2-propynyl)oxalate, and 2-butyne-1,4-diyl dimethanesulfonate are more preferred.

[0133] [1-6-13.Phosphazene compounds] The phosphazene compound is not particularly limited as long as it has an "N=PN group" in the molecule. Examples of the phosphazene compound include cyclic phosphazene compounds such as methoxypentafluorocyclotriphosphazene, ethoxypentafluorocyclotriphosphazene, phenoxypentafluorocyclotriphosphazene, and ethoxyheptafluorocyclotetraphosphazene.

[0134] In particular, cyclic phosphazene compounds such as methoxypentafluorocyclotriphosphazene, ethoxypentafluorocyclotriphosphazene, and phenoxypentafluorocyclotriphosphazene are preferred, with methoxypentafluorocyclotriphosphazene and ethoxypentafluorocyclotriphosphazene being more preferred.

[0135] (Mass ratio of electrolyte to auxiliary agent) When the non-aqueous electrolyte contains an auxiliary, the mass ratio of the content of the auxiliary (total amount when two or more kinds are used) to the content of the electrolyte in the non-aqueous electrolyte (auxiliary [g] / electrolyte [g]) is usually 0.00005 or more, preferably 0.001 or more, more preferably 0.01 or more, even more preferably 0.02 or more, even more preferably 0.025 or more, and usually 0.5 or less, preferably 0.45 or less, more preferably 0.4 or less, even more preferably 0.35 or less. If the mass ratio is within the above range, the increase in the battery characteristics, especially the internal resistance, can be suppressed. The reason for this is unclear, but it is thought that by containing the auxiliary and electrolyte within the above mass ratio range, a coating is formed on the electrode, and the side reaction of the electrolyte in the battery system is minimized.

[0136] [2. Non-aqueous electrolyte secondary battery] A nonaqueous electrolyte secondary battery according to another embodiment of the present invention is a nonaqueous electrolyte secondary battery including a positive electrode having a positive electrode active material capable of absorbing and releasing metal ions, and a negative electrode having a negative electrode active material capable of absorbing and releasing metal ions, and contains the above-mentioned nonaqueous electrolyte.

[0137] [2-1. Non-aqueous electrolyte] As the non-aqueous electrolyte solution, the above-mentioned non-aqueous electrolyte solution is used. Note that, within the scope of the present invention, it is also possible to mix the above-mentioned non-aqueous electrolyte solution with other non-aqueous electrolyte solutions.

[0138] [2-2. Negative electrode] The negative electrode refers to an electrode having a negative electrode active material on at least a portion of the surface of a current collector.

[0139] [2-2-1. Negative electrode active material] The negative electrode active material used in the negative electrode is not particularly limited as long as it can electrochemically absorb and release metal ions. Specific examples include carbonaceous materials, particles containing metal elements and / or metalloid elements that can be alloyed with Li, lithium-containing metal composite oxide materials, and mixtures thereof. Among these, it is preferable to use a mixture of carbonaceous materials, metal particles that can be alloyed with Li, and particles containing metal elements and / or metalloid elements that can be alloyed with Li, and graphite particles, in terms of good cycle characteristics and safety, and excellent continuous charging characteristics. These may be used alone or in any combination of two or more.

[0140] [2-2-1-1. Carbon-based materials] Examples of carbonaceous materials include natural graphite, artificial graphite, amorphous carbon, carbon-coated graphite, graphite-coated graphite, and resin-coated graphite. Of these, natural graphite is preferred. The carbonaceous materials may be used alone or in any combination and ratio of two or more. Examples of natural graphite include scaly graphite, scaly graphite, and / or graphite particles obtained by treating such graphite as a raw material with a process such as spheroidization or densification. Among these, from the viewpoints of particle packing and charge / discharge rate characteristics, spherical or ellipsoidal graphite particles that have been subjected to a spheroidization process are particularly preferred. The average particle size (d50) of the graphite particles is usually 1 μm or more and usually 100 μm or less.

[0141] [2-2-1-2. Properties of carbon-based materials] The carbonaceous material as the negative electrode active material preferably satisfies at least one of the characteristics such as the physical properties and shape shown in the following (1) to (4), and particularly preferably satisfies a plurality of the characteristics simultaneously. (1) X-ray parameters The d value (interlayer distance) of the lattice plane (002 plane) of carbon-based materials determined by X-ray diffraction using the Gakushin method is usually 0.335 nm to 0.360 nm. Also, the crystallite size (Lc) of carbonaceous materials determined by X-ray diffraction using the Gakushin method is 1.0 nm or more. (2) Volume-based average particle size The volume-based average particle size of a carbon-based material is the volume-based average particle size (median diameter) determined by a laser diffraction / scattering method, and is usually 1 μm or more and 100 μm or less. (3) Raman R value, Raman half-width The Raman R value of the carbonaceous material is a value measured using an argon ion laser Raman spectroscopy method, and is usually 0.01 or more and 1.5 or less. In addition, the carbonaceous material has a peak at 1580 cm -1 The Raman half-width in the vicinity is not particularly limited, but is usually 10 cm -1 More than 100cm -1 The following is the result. (4) BET specific surface area The BET specific surface area of ​​a carbonaceous material is the value of the specific surface area measured using the BET method, and is usually 0.1 m 2 ·g -1 More than 100m 2 ·g -1 The following is the result.

[0142] The negative electrode active material may contain two or more carbonaceous materials with different properties, where the properties refer to one or more characteristics selected from the group consisting of X-ray diffraction parameters, median diameter, Raman R value, and BET specific surface area.

[0143] Preferred examples include a particle size distribution on a volume basis that is not symmetrical about the median diameter, the material containing two or more carbon-based materials with different Raman R values, and different X-ray parameters.

[0144] [Particles Containing Metal Elements and / or Metalloid Elements Capable of Alloying with Li] Any of the conventionally known particles containing metal elements and / or metalloid elements capable of alloying with Li can be used. However, from the viewpoints of capacity and cycle life, the metal particles are preferably a metal selected from the group consisting of, for example, Sb, Si, Sn, Al, As, and Zn, or a compound thereof. Further, when the particles containing metal elements and / or metalloid elements capable of alloying with Li contain two or more kinds of metals, the particles may be alloy particles composed of an alloy of these metals.

[0145] Examples of the compound of the metal element and / or metalloid element capable of alloying with Li include metal oxides, metal nitrides, and metal carbides. The compound may contain two or more kinds of metal elements and / or metalloid elements capable of alloying with Li.

[0146] Among them, metallic Si (hereinafter sometimes referred to as Si) or a Si-containing inorganic compound is preferable from the viewpoint of achieving a high capacity.

[0147] Further, the compound of the metal element and / or metalloid element capable of alloying with Li may already be alloyed with Li during the production of the negative electrode described later, and Si or a Si-containing inorganic compound is preferable from the viewpoint of achieving a high capacity.

[0148] In this specification, Si or a Si-containing inorganic compound is collectively referred to as a Si compound. Specific examples of the Si compound include SiO x (0 ≦ x ≦ 2), etc. Specific examples of the metal compound alloyed with Li include Li y Si(0 < y ≦ 4.4), Li 2z SiO 2+z (0 < z ≦ 2), etc. As the Si compound, Si metal oxide (SiO x1 , 0 < x1 ≦ 2) is preferable in that the theoretical capacity is larger than that of graphite, or amorphous Si or nano-sized Si crystals are preferable in that alkali ions such as lithium ions can easily enter and exit, and a high capacity can be obtained. The average particle size (d50) of metal particles that can be alloyed with Li is usually 0.01 μm or more and usually 10 μm or less, from the viewpoint of cycle life.

[0149] [2-2-1-4. Mixture of particles containing metallic elements and / or semi-metallic elements capable of being alloyed with Li and graphite particles] The mixture of particles containing a metal element and / or a metalloid element capable of being alloyed with Li and graphite particles used as the negative electrode active material may be a mixture in which the particles containing a metal element and / or a metalloid element capable of being alloyed with Li and the graphite particles are mixed in the state of independent particles, or it may be a composite in which particles containing a metal element and / or a metalloid element capable of being alloyed with Li are present on the surface or inside of graphite particles.

[0150] The content ratio of particles containing metal elements and / or metalloid elements that can be alloyed with Li to the total of particles containing metal elements and / or metalloid elements that can be alloyed with Li and graphite particles is usually 1 mass% or more and 99 mass% or less.

[0151] [2-2-1-5. Lithium-containing metal composite oxide materials] The lithium-containing metal composite oxide material used as the negative electrode active material is not particularly limited as long as it is capable of absorbing and releasing lithium. From the viewpoint of high current density charge / discharge characteristics, however, a lithium-containing composite metal oxide material containing titanium is preferable, a composite oxide of lithium and titanium (hereinafter sometimes abbreviated as "lithium titanium composite oxide") is more preferable, and a lithium titanium composite oxide having a spinel structure is particularly preferable since it significantly reduces the output resistance.

[0152] In addition, the lithium or titanium of the lithium titanium composite oxide may be substituted with another metal element, for example, at least one element selected from the group consisting of Al, Ga, Cu, and Zn. 4 / 3 Ti 5 / 3 O4, Li1Ti2O4 and Li 4 / 5 Ti 11 / 5O4 is preferred. In addition, examples of lithium titanium composite oxides in which part of the lithium titanium is replaced with other elements include Li 4 / 3 Ti 4 / 3 Al 1 / 3 O4 is preferred.

[0153] [2-2-2. Negative electrode composition and manufacturing method] The negative electrode can be produced by any known method as long as it does not significantly impair the effects of the present invention. For example, the negative electrode can be produced by adding a binder, a liquid medium such as an aqueous solvent or an organic solvent, and if necessary, a thickener, a conductive material, a filler, etc. to the negative electrode active material to form a slurry, which is applied to a current collector, dried, and then pressed to form a negative electrode active material layer.

[0154] [2-2-2-1. Active material content] The content of the negative electrode active material in the negative electrode active material layer is usually 80% by mass or more and 99.5% by mass or less.

[0155] [2-2-2-2. Electrode density] The negative electrode active material layer obtained by coating and drying is preferably compacted by hand press, roller press, etc. to increase the packing density of the negative electrode active material. There are no particular restrictions on the electrode structure when the negative electrode active material is made into an electrode, but the density of the negative electrode active material layer present on the current collector is usually 1 g cm -3 More than 2.2g cm -3 The following is the result.

[0156] [2-2-2-3. Thickener] The thickener is usually used to adjust the viscosity of the slurry. The thickener is not particularly limited, but specifically includes carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, etc. These may be used alone or in any combination and ratio of two or more.

[0157] Furthermore, when a thickener is used, the ratio of the thickener to the negative electrode active material is usually 0.1% by mass or more and 5% by mass or less.

[0158] [2-2-2-4. Binder] There are no particular limitations on the binder that binds the negative electrode active material, so long as it is a material that is stable to the non-aqueous electrolyte solution and the solvent used in the production of the electrode.

[0159] Specific examples include rubber-like polymers such as SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluororubber, NBR (acrylonitrile-butadiene rubber), and ethylene-propylene rubber, as well as fluoropolymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene-ethylene copolymers. These may be used alone or in any combination and ratio of two or more.

[0160] The ratio of the binder to the negative electrode active material is usually 0.1% by mass or more and 20% by mass or less.

[0161] In particular, when the main component is a rubber-like polymer such as SBR, the ratio of the binder to the negative electrode active material is usually 0.1% by mass to 5% by mass, and when the main component is a fluorine-based polymer such as polyvinylidene fluoride, the ratio to the negative electrode active material is usually 1% by mass to 15% by mass.

[0162] [2-2-2-5. Current collector] Any known current collector can be used for holding the negative electrode active material. Examples of the current collector for the negative electrode include metal materials such as aluminum, copper, nickel, stainless steel, and nickel-plated steel, and copper is particularly preferred from the viewpoints of ease of processing and cost.

[0163] The shape of the current collector may be metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punched metal, foamed metal, etc. Among these, metal foil or metal thin film is preferable. The metal thin film may be appropriately formed into a mesh shape. When the negative electrode current collector has a plate or film shape, the current collector may have any thickness, but it is usually 1 μm or more and 1 mm or less.

[0164] [2-2-2-6. Thickness of negative electrode plate] The thickness of the negative electrode plate is designed to match the positive electrode plate to be used and is not particularly limited, but the thickness of the composite layer minus the thickness of the metal foil of the core material is usually 15 μm or more and 300 μm or less.

[0165] [2-2-2-7. Surface coating of negative electrode plate] In addition, a substance having a different composition from the negative electrode plate may be attached to the surface of the negative electrode plate (surface-attached substance). Examples of the surface-attached substance include oxides such as aluminum oxide, sulfates such as lithium sulfate, and carbonates such as lithium carbonate.

[0166] [2-3. Positive electrode] The positive electrode refers to a current collector having a positive electrode active material on at least a portion of its surface.

[0167] [2-3-1. Positive electrode active material] The positive electrode active material (lithium transition metal compound) used in the positive electrode will be described below.

[0168] [2-3-1-1. Lithium transition metal compounds] The lithium transition metal compound is a compound having a structure capable of desorbing and inserting lithium ions, and examples thereof include sulfides, phosphate compounds, silicate compounds, borate compounds, lithium transition metal composite oxides, etc. Among these, lithium transition metal composite oxides are preferred.

[0169] Lithium transition metal composite oxides include those with a spinel structure that allows three-dimensional diffusion and those with a layered structure that allows two-dimensional diffusion of lithium ions. Those with a spinel structure are represented as LixM'2O4 (M' contains at least one transition metal), and specific examples include LiMn2O4, LiCoMnO4, LiNi 0.5 Mn 1.5O4, LiCoVO4, etc. Those with a layered structure are generally represented as LixMO2 (M is at least one transition metal). Specifically, LiCoO2, LiNiO2, LiNi 0.85 Co 0.10 Al 0.05 O2, LiNi 0.80 Co 0.15 Al 0.05 O2, LiNi 0.33 Co 0.33 Mn 0.33 O2, Li 1.05 Ni 0.33 Co 0.33 Mn 0.33 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, Li 1.05 Ni 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.91 Co 0.06 Mn 0.03 O2, LiNi 0.91 Co 0.06 Al 0.03 O2, LiNi 0.90 Co 0.03 Al 0.07 O2, LiNi 0.61 Co 0.20 Al 0.19 Examples include O2.

[0170] Among these, lithium transition metal composite oxides having a layered structure are preferred, and lithium transition metal oxides represented by the following composition formula (11) are more preferred. Li a1 Ni b1 Co c1 M' d1 O2···(11) (In the composition formula (11), the numerical values ​​are 0.9≦a1≦1.1, 0.30≦b1≦0.98, 0.01≦c1≦0.50, and 0.0≦d1≦0.5, and 0.5≦b1+c1 and b1+c1+d1=1 are satisfied. M' contains at least one element selected from the group consisting of Mn, Al, Mg, Zr, Fe, Ti, and Er.)

[0171] A specific example of the lithium transition metal oxide represented by the composition formula (11) is LiNi 0.85 Co 0.10 Al 0.05 O2, LiNi 0.80 Co 0.15 Al 0.05 O2, LiNi 0.33 Co 0.33 Mn 0.33 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, Li 1.05 Ni 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.91 Co 0.06 Mn 0.03 O2, LiNi 0.91 Co 0.06 Al 0.03 O2, LiNi 0.90 Co 0.03 Al 0.07 O2, LiNi 0.61 Co 0.20 Al 0.19 O2, etc.

[0172] In particular, when a positive electrode active material having a ratio of Ni atomic concentration to the total atomic concentration of all transition metal elements in the positive electrode active material of 50 atomic% or more is used, the decomposition of the nonaqueous solvent occurs on the positive electrode surface due to the catalytic action of Ni, and the resistance of the battery tends to increase. In particular, the electrochemical characteristics tend to deteriorate in a high temperature environment, but the lithium secondary battery according to the present invention is preferable because it can suppress the deterioration of these electrochemical characteristics. In particular, when a positive electrode active material is used in which the content of Ni atoms to the total amount of atoms of the transition metal elements in the positive electrode active material, in other words, the ratio of the atomic concentration of Ni to the total atomic concentration of all transition metal elements in the positive electrode active material, exceeds 50 atomic%, the above effect becomes remarkable, and it is preferable that it is 60 atomic% or more, more preferably 70 atomic% or more, and particularly preferably 80 atomic% or more.

[0173] Among these, from the viewpoint of improving the battery capacity, a lithium transition metal oxide represented by the following composition formula (12) is particularly preferable. Li a2 Ni b2 Co c2 M' d2 O2···(12) (In the composition formula (12), a2, b2, c2, and d2 are numerical values ​​that satisfy 0.90≦a2≦1.10, 0.50≦b2≦0.98, 0.01≦c2<0.50, and 0.01≦d2<0.50, respectively, and b2+c2+d2=1 is satisfied. M' contains at least one element selected from the group consisting of Mn, Al, Mg, Zr, Fe, Ti, and Er.)

[0174] A specific example of the lithium transition metal oxide represented by the composition formula (12) is LiNi 0.85 Co 0.10 Al 0.05 O2, LiNi 0.80 Co 0.15 Al 0.05 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, Li 1.05 Ni 0.5 Co 0.2 Mn 0.3O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.91 Co 0.06 Mn 0.03 O2, LiNi 0.91 Co 0.06 Al 0.03 O2, LiNi 0.90 Co 0.03 Al 0.07 O2, LiNi 0.61 Co 0.20 Al 0.19 Suitable examples of the oxygen atom include O. The ratio of the content of Ni atoms (Ni atomic concentration) to the total amount of all transition metal elements (Ni, Co, Mn) (total amount) in the specific positive electrode active materials is 50 atomic%, 60 atomic%, 80 atomic%, and 84 atomic%, respectively.

[0175] In each composition formula, M' is preferably Mn or Al. This increases the structural stability of the lithium transition metal oxide and suppresses structural deterioration during repeated charge and discharge.

[0176] The total amount of transition metal element atoms (total transition metal concentration) and the Ni atom content (Ni atom concentration) in the positive electrode active material can be measured and calculated by X-ray photoelectron spectroscopy (XPS).

[0177] [2-3-1-2. Introduction of different elements] The lithium transition metal compound may contain elements other than those defined in the above composition formulas (11) and (12).

[0178] [2-3-1-3. Surface coating] The positive electrode active material may have a different composition (surface-attached material) attached to its surface. Examples of the surface-attached material include oxides such as aluminum oxide, sulfates such as lithium sulfate, and carbonates such as lithium carbonate. Carbonates are preferred because they improve the affinity between the compound represented by formula (I) and the positive electrode.

[0179] These surface-adhering substances can be attached to the surface of the positive electrode active material, for example, by dissolving or suspending them in a solvent, adding them to the positive electrode active material by impregnation, and drying them.

[0180] The amount of the surface-attached substance is preferably 1 μmol / g or more, more preferably 10 μmol / g or more, and is usually 1 mmol / g or less, by mass relative to the positive electrode active material.

[0181] In this specification, a positive electrode active material having a substance of a different composition attached to its surface is also referred to as a "positive electrode active material".

[0182] [2-3-1-4. Blend] These positive electrode active materials may be used alone or in any combination of two or more in any ratio.

[0183] [2-3-2. Positive electrode structure and manufacturing method] The configuration of the positive electrode will be described below. In this embodiment, the positive electrode can be prepared by forming a positive electrode active material layer containing a positive electrode active material and a binder on a current collector. The positive electrode using the positive electrode active material can be manufactured by a conventional method. That is, the positive electrode active material and the binder, and if necessary, a conductive material and a thickener, etc. are mixed in a dry state to form a sheet, which is then pressed onto the positive electrode current collector, or these materials are dissolved or dispersed in a liquid medium to form a slurry, which is then applied to the positive electrode current collector and dried to form a positive electrode active material layer on the current collector, thereby obtaining a positive electrode. In addition, for example, the above-mentioned positive electrode active material may be roll-formed into a sheet electrode, or may be compression-formed into a pellet electrode. Hereinafter, the case where the slurry is applied to the positive electrode current collector and then dried will be described.

[0184] [2-3-2-1. Active material content] The content of the positive electrode active material in the positive electrode active material layer is usually 80% by mass or more and 99.5% by mass or less.

[0185] [2-3-2-2. Electrode density] The positive electrode active material layer obtained by coating and drying is preferably compressed by a hand press, a roller press, or the like in order to increase the packing density of the positive electrode active material. The density of the positive electrode active material layer present on the current collector is usually 1.5 g / cm 3 More than 4.5g / cm 3 The following is the result.

[0186] [2-3-2-3.Conductive materials] Any known conductive material can be used as the conductive material. Specific examples include metal materials such as copper and nickel; graphite such as natural graphite and artificial graphite; carbon black such as acetylene black; and carbon-based materials such as amorphous carbon such as needle coke. These may be used alone or in any combination and ratio of two or more. The conductive material is usually used in an amount of 0.01% by mass or more and 50% by mass or less in the positive electrode active material layer.

[0187] [2-3-2-4. Binder] The binder used in producing the positive electrode active material layer is not particularly limited, and in the case of a coating method, the type is not particularly limited as long as it is a material that is dissolved or dispersed in the liquid medium used in producing the electrode. In view of weather resistance, chemical resistance, heat resistance, flame retardancy, and the like, preferred are fluorine-based resins such as polyvinyl fluoride, polyvinylidene fluoride, and polytetrafluoroethylene; and CN group-containing polymers such as polyacrylonitrile and polyvinylidene cyanide.

[0188] In addition, mixtures, modified products, derivatives, random copolymers, alternating copolymers, graft copolymers, block copolymers, etc. of the above polymers can also be used. The binder may be used alone or in any combination and ratio of two or more kinds.

[0189] Furthermore, when a resin is used as a binder, the weight average molecular weight of the resin is optional as long as it does not significantly impair the effects of the present invention, but is usually from 10,000 to 3,000,000. When the molecular weight is in this range, the strength of the electrode is improved, and the electrode can be suitably formed.

[0190] The proportion of the binder in the positive electrode active material layer is usually 0.1% by mass or more and 80% by mass or less.

[0191] [2-3-2-5. Current collector] The material of the positive electrode current collector is not particularly limited, and any known material can be used. Specific examples include metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum. Among them, aluminum is preferable.

[0192] The shape of the current collector may be a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, an expanded metal, a punched metal, a foamed metal, etc. Among these, a metal thin film is preferable. The thin film may be appropriately formed into a mesh shape.

[0193] When the positive electrode current collector has a plate or film shape, the current collector may have any thickness, but it is usually 1 μm or more and 1 mm or less.

[0194] [2-3-2-6. Thickness of positive electrode plate] The thickness of the positive electrode plate is not particularly limited, but from the viewpoint of high capacity and high output, the thickness of the composite layer minus the thickness of the metal foil of the core material is usually 10 μm or more and 500 μm or less on one side of the current collector.

[0195] [2-3-2-7. Surface coating of positive electrode plate] In addition, the positive electrode plate may have a substance having a different composition from that of the positive electrode plate attached to its surface, and the substance in question may be the same as the surface-attached substance that may be attached to the surface of the positive electrode active material.

[0196] [2-4. Separator] A separator is usually interposed between the positive electrode and the negative electrode to prevent short circuiting. In this case, the non-aqueous electrolyte is usually impregnated into the separator before use.

[0197] There are no particular limitations on the material and shape of the separator, and any known material can be used as long as it does not significantly impair the effects of the present invention.

[0198] [2-5.Battery design] [2-5-1. Electrode group] The electrode group may be either a laminated structure of the positive electrode plate and the negative electrode plate with the separator interposed therebetween, or a structure of the positive electrode plate and the negative electrode plate wound in a spiral shape with the separator interposed therebetween. The ratio of the volume of the electrode group to the internal volume of the battery (hereinafter referred to as the electrode group occupancy rate) is usually 40% or more and 90% or less.

[0199] [2-5-2. Current collection structure] In the case where the electrode group has the above-mentioned laminated structure, a structure formed by bundling the metal core parts of each electrode layer and welding them to a terminal is preferably used. It is also preferably used to reduce resistance by providing multiple terminals in the electrode. In the case where the electrode group has the above-mentioned wound structure, the internal resistance can be reduced by providing multiple lead structures on each of the positive electrode and the negative electrode and bundling them to a terminal.

[0200] [2-5-3.Protection elements] The protective element may be a PTC (Positive Temperature Coefficient) element whose resistance increases when abnormal heat is generated or an excessive current flows, a thermal fuse, a thermistor, a valve (current cutoff valve) that cuts off the current flowing in the circuit due to a sudden increase in the internal pressure or temperature of the battery when abnormal heat is generated, etc. It is preferable to select the above protective element so that it will not operate under normal use at a high current, and it is even more preferable to design it so that abnormal heat generation or thermal runaway does not occur even without the protective element.

[0201] [2-5-4. Exterior body] A non-aqueous electrolyte secondary battery is usually constructed by housing the above-mentioned non-aqueous electrolyte, negative electrode, positive electrode, separator, etc. in an exterior body (exterior case). There are no limitations on this exterior body, and any known exterior body can be used as long as it does not significantly impair the effects of the present invention.

[0202] The material of the exterior case is not particularly limited as long as it is a substance that is stable against the non-aqueous electrolyte solution used, but from the viewpoint of weight reduction, metals such as aluminum or aluminum alloys, and laminate films are preferably used.

[0203] Examples of exterior cases using the above metals include those in which the metals are welded together by laser welding, resistance welding, or ultrasonic welding to form a sealed, airtight structure, and those in which the above metals are used with a resin gasket in between to form a crimped structure.

[0204] [2-5-5. Shape] The shape of the exterior case is also arbitrary, and may be, for example, cylindrical, rectangular, laminated, coin-shaped, large, or the like. EXAMPLES

[0205] Next, specific embodiments of the present invention will be described in more detail with reference to examples, but the present invention is not limited to these.

[0206] [Preparation of non-aqueous electrolyte secondary battery] <Preparation of non-aqueous electrolyte> The compounds used in Examples 1 and 2 and Comparative Examples 2 and 3 are as follows.

[0207] [ka]

[0208] [ka]

[0209] [ka]

[0210] [Preparation of reference electrolyte] Under a dry argon atmosphere, thoroughly dried LiPF6 was dissolved at 1 mol / L (final concentration in the non-aqueous electrolyte) in a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (volume ratio of EC:EMC = 3:7) to prepare a reference electrolyte.

[0211] [Example 1] A non-aqueous electrolyte solution was prepared by adding 1.0 mass % of compound A12, 0.05 mass % of compound B19, and 1.0 mass % of lithium difluorophosphate to the reference electrolyte solution, based on the total mass of the non-aqueous electrolyte solution.

[0212] [Example 2] A non-aqueous electrolyte solution was prepared by adding 1.0 mass% of compound A12, 0.05 mass% of compound B19, 0.5 mass% of compound C19, and 1.0 mass% of lithium difluorophosphate to the reference electrolyte solution, based on the total mass of the non-aqueous electrolyte solution.

[0213] [Comparative Example 1] Lithium difluorophosphate was added to the reference electrolyte solution so that the amount was 1.0% by mass relative to the total mass of the nonaqueous electrolyte solution, thereby preparing a nonaqueous electrolyte solution.

[0214] [Comparative Example 2] A non-aqueous electrolyte solution was prepared by adding compound A12 to the reference electrolyte solution so that the amount of compound A12 was 1.0% by mass and lithium difluorophosphate was 1.0% by mass relative to the total mass of the non-aqueous electrolyte solution.

[0215] [Comparative Example 3] A non-aqueous electrolyte solution was prepared by adding compound B19 to the reference electrolyte solution so that the compound B19 and lithium difluorophosphate were present in amounts of 0.05% by mass and 1.0% by mass, respectively, based on the total mass of the non-aqueous electrolyte solution.

[0216] <Preparation of positive electrode> LiNi 0.8 Co 0.1 Mn0.1 90 parts by mass of O2 (positive electrode active material) and 6 parts by mass of carbon-based conductive agent were mixed, and added to a solution in which 4 parts by mass of polyvinylidene fluoride (binder) had been dissolved in 1-methyl-2-pyrrolidone, and mixed to prepare a positive electrode mixture paste. This positive electrode mixture paste was applied to one side of an aluminum foil (current collector), dried, pressure-treated, and cut to a specified size to form a rectangular positive electrode.

[0217] <Preparation of negative electrode> A negative electrode mixture paste was prepared by adding 98 parts by mass of natural graphite (negative electrode active material) to a suspension in which 1 part by mass of carboxymethyl cellulose (thickener) and 1% by mass of styrene-butadiene rubber (binder) were dissolved and suspended in water, and mixing them. This negative electrode mixture paste was applied to one side of a copper foil (current collector), dried, pressed, and cut to the specified size to form a rectangular negative electrode.

[0218] <Manufacture of non-aqueous electrolyte secondary battery> The positive electrode, the negative electrode, and the microporous polyethylene film separator were laminated in this order, and the battery element thus obtained was wrapped in an aluminum laminate film, and the nonaqueous electrolyte was injected and then vacuum sealed to prepare a sheet-shaped nonaqueous electrolyte secondary battery.

[0219] [Evaluation of non-aqueous electrolyte secondary batteries] The nonaqueous electrolyte secondary batteries produced in the above Examples and Comparative Examples were evaluated as follows. ·Initial charge / discharge In a thermostatic bath at 25°C, the nonaqueous electrolyte secondary battery was charged at a constant current of 0.05C (the current value at which the rated capacity based on the discharge capacity at one-hour rate is discharged in one hour is defined as 1C. The same applies below.) up to 3.72V, and then discharged at a constant current of 0.2C down to 2.8V. Furthermore, the non-aqueous electrolyte secondary battery was stabilized by charging at a constant current and constant voltage at 0.2C to 4.1V, and then storing at 60°C for 24 hours. Thereafter, the battery was discharged at a constant current of 0.2C to 2.8V at 25°C, and then charged at a constant current and constant voltage of 0.2C to a voltage of 4.3V. Further, the battery was discharged at a constant current of 0.2C to 2.8V at 25°C, and then charged at a constant current and constant voltage of 0.2C to a voltage of 4.2V. Finally, the battery was discharged at a constant current of 0.2C to 2.5V. The cutoff current for constant voltage charging is 0.05C in all cases.

[0220] High temperature storage test At 25°C, constant current-constant voltage charging was performed at 0.2C up to a voltage of 4.2V. The cutoff current for constant voltage charging was 0.05C. After that, the battery was left to stand in a thermostatic chamber at 60°C for one week, and then discharged at a constant current of 0.2C up to 2.8V at 25°C. This cycle was repeated four times to perform a four-week high-temperature storage test.

[0221] Recovery capacity evaluation The constant current discharge capacity up to 2.8 V at 25° C. and 0.2 C performed at the end of the initial charge / discharge was defined as the “initial discharge capacity”, and the constant current discharge capacity up to 2.8 V at 25° C. and 0.2 C performed at the end of the fourth cycle of the high-temperature storage test was defined as the “discharge capacity after high-temperature storage”. The “recovery capacity after high-temperature storage” was defined as “discharge capacity after high-temperature storage” / “initial discharge capacity”. The restored capacities after high-temperature storage shown in Examples 1 and 2 and Comparative Examples 2 and 3 in Table 1 are shown as relative values ​​when Comparative Example 1 is taken as 100.

[0222] -Evaluation of gas generation rate after high temperature storage Before the initial charge / discharge and after the high-temperature storage test, the nonaqueous electrolyte secondary batteries were immersed in an ultrapure water bath at room temperature (25°C) to measure their volumes, and the change in volume before and after the test was recorded as the "amount of gas generated after high-temperature storage" of the battery. The amounts of gas generated in Examples 1 and 2 and Comparative Examples 2 and 3 in Table 1 are shown as relative values ​​when the amount of gas generated in Comparative Example 1 is taken as 100.

[0223] [Table 1]

[0224] As is clear from the results shown in Table 1, it can be said that the nonaqueous electrolyte solution containing the compound represented by general formula (A) and the compound represented by general formula (B) improves the recovery capacity of a nonaqueous electrolyte secondary battery containing the nonaqueous electrolyte solution after high-temperature storage and significantly suppresses the amount of gas generation. Furthermore, a comparison between Example 1 and Example 2 shows that the nonaqueous electrolyte solution of the present invention containing the compound represented by general formula (C) further improves the recovery capacity of a nonaqueous electrolyte secondary battery containing the nonaqueous electrolyte solution after high-temperature storage and further suppresses the amount of gas generation.

Claims

1. A non-aqueous electrolyte solution comprising an electrolyte, a non-aqueous solvent, a compound represented by the following general formula (A), and a compound represented by the following general formula (B): 【Chemistry 1】 (In formula (A), R １ and R ２ each independently represents a hydrocarbon group having 3 to 12 carbon atoms and a carbon-carbon unsaturated bond; X represents a hydrogen atom; ３ , or -OR ３ indicates R ３ represents a hydrocarbon group having 1 to 12 carbon atoms. 【Chemistry 2】 (In formula (B), R ４５ is a hydrogen atom or -SiR ４ R ５ R ６ R represents a silyl group represented by the formula: ４ ~R ６ R each independently represents a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 12 carbon atoms which may have a substituent, or an alkoxy group having 1 to 12 carbon atoms which may have a substituent. ７ represents a hydrogen atom, a hydrocarbon group having 1 to 12 carbon atoms which may have a substituent, or -SiR ８ R ９ R １０ R represents a silyl group represented by the formula: ８ ~R １０ each independently represents a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 12 carbon atoms which may have a substituent, or an alkoxy group having 1 to 12 carbon atoms which may have a substituent. Y represents a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 12 carbon atoms which may have a substituent, an alkoxy group having 1 to 12 carbon atoms which may have a substituent, -N(R １１ )SiR １２ R １３ R １４ or a group represented by -N(R １１ ) H; R １１ represents a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms which may have a substituent; R １２ ~R １４ R each independently represents a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 12 carbon atoms which may have a substituent, or an alkoxy group having 1 to 12 carbon atoms which may have a substituent. ７ and R １１ may be bonded to each other to form a ring.)

2. R in general formula (A) １ and R ２ The nonaqueous electrolyte according to claim 1, characterized in that is a 2-propenyl group.

3. In the general formula (A), X is -R ３ Or -OR ３ and R ３ 2. The nonaqueous electrolyte according to claim 1, wherein is a methyl group or a 2-propenyl group.

4. 2. The nonaqueous electrolyte solution according to claim 1, further comprising a compound represented by the following general formula (C): 【Chemistry 3】 (In formula (C), R １５ ~R １７ each independently represents a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 12 carbon atoms which may have a substituent, or an alkoxy group having 1 to 12 carbon atoms which may have a substituent. x represents an integer of 1 to 3, p, q and r each represent an integer of 0 to 3, and x+p+q+r=4.

5. The nonaqueous electrolyte solution according to claim 1 , wherein the content of the compound represented by the general formula (A) is 0.01% by mass or more and 10% by mass or less.

6. The nonaqueous electrolyte solution according to claim 1 , wherein the content of the compound represented by the general formula (B) is 0.001% by mass or more and 1.0% by mass or less.

7. A non-aqueous electrolyte secondary battery comprising a positive electrode and a negative electrode capable of absorbing and releasing metal ions, and a non-aqueous electrolyte solution, the non-aqueous electrolyte solution being the non-aqueous electrolyte solution according to any one of claims 1 to 6.

8. 8. The nonaqueous electrolyte secondary battery according to claim 7, wherein the positive electrode comprises a positive electrode active material, and the positive electrode active material is a lithium transition metal oxide represented by the following composition formula (11): Li ａ１ Ni ｂ１ Co ｃ１ M' ｄ１ O ２ ・・・(11) (In the composition formula (11), the numerical values ​​are 0.9≦a1≦1.1, 0.30≦b1≦0.98, 0.01≦c1≦0.50, and 0.0≦d1≦0.5, and 0.5≦b1+c1 and b1+c1+d1=1 are satisfied. M′ contains at least one element selected from the group consisting of Mn, Al, Mg, Zr, Fe, Ti, and Er.)

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