WO2020026853A1

WO2020026853A1 - Non-aqueous electrolytic solution for batteries, and lithium secondary battery

Info

Publication number: WO2020026853A1
Application number: PCT/JP2019/028479
Authority: WO
Inventors: 敬菅原; 藤山　聡子; 仁志大西
Original assignee: 三井化学株式会社
Priority date: 2018-07-30
Filing date: 2019-07-19
Publication date: 2020-02-06
Also published as: JPWO2020026853A1; JP7264899B2

Abstract

A non-aqueous electrolytic solution for batteries, which comprises an electrolyte containing LiPF₆ and LiFSI and an additive comprising at least one component selected from the group consisting of compounds (A) to (D). R^a1 represents a fluorine atom, a C1-6 hydrocarbon group, a C1-6 hydrocarbonoxy group, or a C1-6 fluorinated hydrocarbon group. R^b1 represents a hydrogen atom, a fluorine atom, a C1-6 hydrocarbon group, a C1-6 hydrocarbonoxy group, or a C1-6 fluorinated hydrocarbon group. R^c1 to R^c4 independently represent a hydrogen atom, a halogen atom, a C1-6 hydrocarbon group, a C1-6 halogenated hydrocarbon group, a C1-6 hydrocarbonoxy group, or a C1-6 halogenated hydrocarbonoxy group. R^d21 to R^d24 independently represent a hydrogen atom, a C1-6 hydrocarbon group, a group (a), or a group (b). In group (a) and group (b), "*" represents a binding position.

Description

Non-aqueous electrolyte for batteries and lithium secondary batteries

The present disclosure relates to a non-aqueous electrolyte for a battery and a lithium secondary battery.

2. Description of the Related Art In recent years, lithium secondary batteries have been widely used as electronic devices such as mobile phones and notebook computers, or as electric power sources for electric vehicles and power storage. Particularly in recent years, demand for batteries with high capacity, high output, and high energy density, which can be mounted on hybrid vehicles and electric vehicles, has been rapidly expanding.
The lithium secondary battery includes, for example, a positive electrode and a negative electrode containing a material capable of inserting and extracting lithium, and a non-aqueous electrolyte for a battery containing a lithium salt and a non-aqueous solvent.
As the positive electrode active material used for the positive electrode, for example, a lithium metal oxide such as LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , and LiFePO ₄ is used.
Examples of the non-aqueous electrolyte for a battery include a mixed solvent (non-aqueous solvent) of carbonates such as ethylene carbonate, propylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, and LiPF ₆ , LiBF ₄ , and LiN (SO ₂ CF ₃ ). ₂ , a solution in which a Li electrolyte such as LiN (SO ₂ CF ₂ CF ₃ ) ₂ is mixed is used.
On the other hand, as the negative electrode active material used for the negative electrode, metal lithium, metal compounds capable of occluding and releasing lithium (such as simple metals, oxides, and alloys with lithium) and carbon materials are known. Lithium secondary batteries employing coke, artificial graphite, and natural graphite, which can be inserted and released, have been put to practical use.

In order to improve the performance of a battery containing a nonaqueous electrolyte for a battery (for example, a lithium secondary battery), various additives have been added to the nonaqueous electrolyte for a battery.
For example, as a non-aqueous electrolyte for a battery that can improve storage characteristics after charging of the battery, a non-aqueous electrolyte for a battery containing at least one of lithium monofluorophosphate and lithium difluorophosphate as an additive is known. (For example, see Patent Document 1 below).
Further, as a non-aqueous electrolyte for a battery that can improve the charge / discharge characteristics and life characteristics of the battery, a non-aqueous electrolyte for a battery containing a sultone compound having a specific structure is known (for example, Patent Document 2 below) reference).
In addition, a non-aqueous electrolyte for a battery containing a cyclic sulfate ester compound having a specific structure is used as a non-aqueous electrolyte for a battery that can improve the capacity maintenance performance of the battery and suppress a decrease in the open-circuit voltage during charge storage of the battery. A liquid is known (for example, see Patent Document 3 below).

Patent Document 1: Japanese Patent No. 3439085 Patent Document 2: Japanese Patent No. 4442495 Patent Document 3: Japanese Patent No. 5524347

However, in some cases, it is required to further reduce the battery resistance of the conventional non-aqueous electrolyte for batteries and batteries after storage.
Accordingly, an object of the present disclosure is to provide a non-aqueous electrolyte for a battery that can reduce the battery resistance after storage, and a lithium secondary battery using the non-aqueous electrolyte for a battery.

<1> an electrolyte containing lithium hexafluorophosphate and lithium bis (fluorosulfonyl) imide,
Selected from the group consisting of a compound represented by the following formula (A), a compound represented by the following formula (B), a compound represented by the following formula (C), and a compound represented by the following formula (D) At least one additive,
Non-aqueous electrolyte for batteries containing.

In the formula (A), ^Ra1 represents a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, a hydrocarbon oxy group having 1 to 6 carbon atoms, or a fluorinated hydrocarbon group having 1 to 6 carbon atoms.

In the formula (B), R ^b1 represents a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, a hydrocarbonoxy group having 1 to 6 carbon atoms, or a fluorinated hydrocarbon group having 1 to 6 carbon atoms. Represent.

In the formula (C), R ^c1 to R ^c4 each independently represent a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 6 carbon atoms, a halogenated hydrocarbon group having 1 to 6 carbon atoms, Or a halogenated hydrocarbon oxy group having 1 to 6 carbon atoms.

In the formula (D), R ^d21 to R ^d24 each independently represent a hydrogen atom, a hydrocarbon group having 1 to 6 carbon atoms, a group represented by the formula (a), or a group represented by the formula (b) Represents In the formulas (a) and (b), * represents a bonding position.

<2> The content molar ratio of the lithium bis (fluorosulfonyl) imide to the total of the lithium hexafluorophosphate and the lithium bis (fluorosulfonyl) imide is 0.01 or more and 0.85 or less according to <1>. Non-aqueous electrolyte for batteries.
<3> The content molar ratio of the lithium bis (fluorosulfonyl) imide to the total of the lithium hexafluorophosphate and the lithium bis (fluorosulfonyl) imide is 0.08 or more and 0.85 or less <1> or <2> The non-aqueous electrolyte for a battery according to the above.

<4> an electrolyte containing lithium hexafluorophosphate and lithium bis (fluorosulfonyl) imide;
An additive which is at least one selected from the group consisting of compounds represented by the following formula (E):
Containing
A nonaqueous electrolyte solution for a battery, wherein the molar ratio of the lithium bis (fluorosulfonyl) imide to the total of the lithium hexafluorophosphate and the lithium bis (fluorosulfonyl) imide is 0.050 to 0.85.

In the formula (E), R ¹¹ to R ¹⁴ each independently represent a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 3 carbon atoms, or a fluorinated hydrocarbon group having 1 to 3 carbon atoms.

<5> The method according to any one of <1> to <4>, wherein a total concentration of the lithium hexafluorophosphate and the lithium bis (fluorosulfonyl) imide is 0.1 mol / L or more and 3 mol / L or less. Non-aqueous electrolyte for batteries.
<6> The battery according to any one of <1> to <5>, wherein the content of the additive is 0.001% by mass or more and 10% by mass or less based on the total amount of the nonaqueous electrolyte for a battery. For non-aqueous electrolyte.

<7> a positive electrode,
Lithium metal, lithium-containing alloy, metal or alloy capable of being alloyed with lithium, oxide capable of doping / dedoping lithium ion, transition metal nitride capable of doping / dedoping lithium ion, and lithium A negative electrode containing, as a negative electrode active material, at least one selected from the group consisting of carbon materials capable of doping and undoping ions;
A non-aqueous electrolyte for a battery according to any one of <1> to <6>,
Including lithium secondary batteries.
<8> A lithium secondary battery obtained by charging and discharging the lithium secondary battery according to <7>.

According to the present disclosure, a non-aqueous electrolyte for a battery that can reduce the battery resistance after storage, and a lithium secondary battery using the non-aqueous electrolyte for a battery are provided.

FIG. 1 is a schematic perspective view illustrating an example of a laminated battery, which is an example of a lithium secondary battery of the present disclosure. FIG. 2 is a schematic cross-sectional view in a thickness direction of a laminated electrode body housed in the laminated battery shown in FIG. 1. 1 is a schematic cross-sectional view illustrating an example of a coin-type battery, which is another example of the lithium secondary battery of the present disclosure.

In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit and an upper limit.
In the present specification, the amount of each component in the composition is, if there are a plurality of substances corresponding to each component in the composition, unless otherwise specified, the total amount of the plurality of substances present in the composition Means

Hereinafter, as the non-aqueous electrolyte for a battery according to the present disclosure, the non-aqueous electrolyte for a battery according to the first embodiment and the second embodiment of the present disclosure will be sequentially described.

[Non-aqueous electrolyte for battery (first embodiment)]
The non-aqueous electrolyte for a battery according to the first embodiment of the present disclosure (hereinafter, also simply referred to as “non-aqueous electrolyte of the first embodiment”) includes:
An electrolyte comprising lithium hexafluorophosphate and lithium bis (fluorosulfonyl) imide;
Selected from the group consisting of a compound represented by the following formula (A), a compound represented by the following formula (B), a compound represented by the following formula (C), and a compound represented by the following formula (D) At least one additive,
It contains.

According to the non-aqueous electrolyte of the first embodiment, the battery resistance after storage can be reduced.
It is not clear why such an effect is exerted, but the compound represented by the formula (A), the compound represented by the formula (B), the compound represented by the formula (C), and the compound represented by the formula (C) Use of a combination of lithium hexafluorophosphate and lithium bis (fluorosulfonyl) imide as an electrolyte for a nonaqueous electrolyte containing at least one additive selected from the compounds represented by D) It is considered that, by doing so, a good quality film having low resistance after storage of the battery is formed on the electrode surface.

Therefore, in the non-aqueous electrolyte of the first embodiment, by using lithium hexafluorophosphate and lithium bis (fluorosulfonyl) imide in combination as the electrolyte, the case where lithium hexafluorophosphate is used alone as the electrolyte is used. In comparison, it is considered that the stability of the electrolyte during storage is improved. As a result, the storage characteristics (particularly, high-temperature storage characteristics) of the battery are excellent. Specifically, the battery resistance after storage (particularly after high-temperature storage) is reduced.

Hereinafter, each component of the non-aqueous electrolyte of the first embodiment will be described.

<Electrolyte>
The non-aqueous electrolyte of the first embodiment contains an electrolyte containing both lithium hexafluorophosphate (hereinafter, also referred to as LiPF ₆ ) and lithium bis (fluorosulfonyl) imide (hereinafter, also referred to as LiFSI).

In the electrolyte in the nonaqueous electrolytic solution of the first embodiment, the molar ratio of the content of LiFSI to the sum of LiPF ₆ and LiFSI (hereinafter, also referred to as the molar ratio [LiFSI _/ (LiPF 6 + LiFSI)]) is a high-temperature storage characteristics of the battery From the viewpoint of further improving, it is preferably 0.01 or more and 0.85 or less.
When the molar ratio [LiFSI / (LiPF ₆ + LiFSI)] is 0.01 or more, the battery resistance after storage is further reduced. From the viewpoint of further reducing the battery resistance after storage, the molar ratio [LiFSI / (LiPF ₆ + LiFSI)] is more preferably 0.08 or more, further preferably 0.10 or more, and still more preferably 0.1% or more. 15 or more.
On the other hand, when the molar ratio [LiFSI / (LiPF ₆ + LiFSI)] is 0.85 or less, it is advantageous in terms of electric conductivity, oxidation resistance, and the like. From the viewpoints of electrical conductivity and oxidation resistance, the molar ratio [LiFSI / (LiPF ₆ + LiFSI)] may be 0.50 or less, may be less than 0.50, or may be 0.40 or less. , 0.30 or less, or 0.20 or less.

In the non-aqueous electrolyte of the first embodiment, the total concentration of lithium hexafluorophosphate and lithium bis (fluorosulfonyl) imide is not particularly limited, but the total concentration is preferably 0.1 mol / L to 3 mol / L. And more preferably from 0.5 mol / L to 2 mol / L.

The electrolyte in the first embodiment may contain at least one compound other than lithium hexafluorophosphate and lithium bis (fluorosulfonyl) imide.
Other compounds include LiBF ₄ , LiClO ₄ , LiAsF ₆ , Li ₂ SiF ₆ , and LiPF _n [C _k F _{(2k + 1)} ] _(6-n) (n = 1 to 5, k = 1 to 8) , LiC (SO ₂ R ²⁷ ) (SO ₂ R ²⁸ ) (SO ₂ R ²⁹ ) (where R ²⁷ to R ²⁹ may be the same or different and are perfluoroalkyl groups having 1 to 8 carbon atoms) ), LiN (SO ₂ OR ³⁰ ) (SO ₂ OR ³¹ ) (where R ³⁰ and R ³¹ may be the same or different and are perfluoroalkyl groups having 1 to 8 carbon atoms), LiN (SO ₂ OR ³⁰ ) ₂ R ³² ) (SO ₂ R ³³ ) wherein R ³² and R ³³ may be the same or different and are perfluoroalkyl groups having 1 to 8 carbon atoms; provided that R ³² is or If it is 2 perfluoroalkyl group, R ³³ represents a perfluoroalkyl group having 3 to 8 carbon atoms), and the like.

The total mass ratio of lithium hexafluorophosphate and lithium bis (fluorosulfonyl) imide in the electrolyte in the first embodiment is preferably 50% by mass to 100% by mass, more preferably 80% by mass to 100% by mass. %, More preferably 90 to 100% by mass.

<Additives>
The non-aqueous electrolyte for a battery according to the first embodiment includes a compound represented by the following formula (A) (hereinafter, also referred to as “additive A”) and a compound represented by the following formula (B) (hereinafter, “additive”). Agent B "), a compound represented by the following formula (C) (hereinafter also referred to as" additive C "), and a compound represented by the following formula (D) (hereinafter also referred to as" additive D ") )), Which contains at least one additive selected from the group consisting of:

The content of the additive is preferably 0.001% by mass to 10% by mass, more preferably 0.003% by mass to 5% by mass, and more preferably 0.003% by mass to 3% by mass, based on the total amount of the nonaqueous electrolyte. %, More preferably from 0.03 to 3% by mass, particularly preferably from 0.3 to 3% by mass.

The additive A is at least one selected from the group consisting of compounds represented by the following formula (A).

The “fluorocarbon group having 1 to 6 carbon atoms” represented by R ^a1 has a structure in which an unsubstituted hydrocarbon group having 1 to 6 carbon atoms is substituted with at least one fluorine atom.
Examples of the unsubstituted hydrocarbon group having 1 to 6 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, 1-ethylpropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl, 2-methylbutyl, 3,3-dimethylbutyl, n-pentyl, isopentyl, neopentyl, 1-methylpentyl, n-hexyl, isohexyl, sec-hexyl, tert-butyl Alkyl group such as hexyl group; vinyl group, 1-propenyl group, allyl group, 1-butenyl group, 2-butenyl group, 3-butenyl group, pentenyl group, hexenyl group, isopropenyl group, 2-methyl-2-propenyl Alkenyl groups such as a group, a 1-methyl-2-propenyl group and a 2-methyl-1-propenyl group;

The “fluorocarbon group having 1 to 6 carbon atoms” represented by R ^a1 includes, for example, fluoromethyl group, difluoromethyl group, trifluoromethyl group, 2,2,2-trifluoroethyl group, perfluoro Fluoroalkyl groups such as ethyl group, perfluoropropyl group, perfluorobutyl group, perfluoropentyl group, perfluorohexyl group, perfluoroisopropyl group, perfluoroisobutyl group; 2-fluoroethenyl group, 2,2-difluoro Ethenyl, 2-fluoro-2-propenyl, 3,3-difluoro-2-propenyl, 2,3-difluoro-2-propenyl, 3,3-difluoro-2-methyl-2-propenyl, 3-fluoro-2-butenyl group, perfluorovinyl group, perfluoropropenyl group, perfluorobutenyl group And the like.

The “fluorinated hydrocarbon group having 1 to 6 carbon atoms” represented by R ^a1 is preferably an alkyl group substituted with at least one fluorine atom or an alkenyl group substituted with at least one fluorine atom. Alkyl groups substituted with two fluorine atoms are more preferred.
The “fluorocarbon group having 1 to 6 carbon atoms” represented by R ^a1 may be substituted with at least one fluorine atom, and is preferably a perfluorohydrocarbon group.
The number of carbon atoms of the “fluorocarbon group having 1 to 6 carbon atoms” represented by R ^a1 is preferably 1 to 3, more preferably 1 or 2, and particularly preferably 1.

In the formula (A), the “hydrocarbon group having 1 to 6 carbon atoms” represented by R ^a1 represents an unsubstituted hydrocarbon group having 1 to 6 carbon atoms.
The “hydrocarbon group having 1 to 6 carbon atoms” represented by R ^a1 may be a linear hydrocarbon group, a branched hydrocarbon group, or a cyclic hydrocarbon group.

Examples of the “hydrocarbon group having 1 to 6 carbon atoms” represented by R ^a1 include, for example,
Methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, 2-methylbutyl, 1-methylpentyl, neopentyl, 1-ethylpropyl Alkyl groups such as, hexyl group, and 3,3-dimethylbutyl group;
Vinyl, 1-propenyl, allyl, 1-butenyl, 2-butenyl, 3-butenyl, pentenyl, hexenyl, isopropenyl, 2-methyl-2-propenyl, 1-methyl-2 Alkenyl groups such as -propenyl group and 2-methyl-1-propenyl group;
A phenyl group;
And the like.
The “hydrocarbon group having 1 to 6 carbon atoms” represented by R ^a1 is preferably an alkyl group, an alkenyl group, or a phenyl group, more preferably an alkyl group or an alkenyl group, and still more preferably an alkyl group.
The carbon number of the “hydrocarbon group having 1 to 6 carbon atoms” represented by ^Ra1 is preferably 1 to 3, more preferably 1 or 2, and particularly preferably 1.

Specific examples and preferred embodiments of the "hydrocarbon group having 1 to 6 carbon atoms" in the structure of the "hydrocarbon group having 1 to 6 carbon atoms" represented by R ^a1 may previously described, represented by R ^a1 This is the same as the specific examples and preferred embodiments of the “hydrocarbon group having 1 to 6 carbon atoms”.

R ^a1 is preferably a fluorocarbon group having 1 to 6 carbon atoms, more preferably a fluoroalkyl group having 1 to 6 carbon atoms, further preferably a perfluoroalkyl group having 1 to 6 carbon atoms, and more preferably perfluoromethyl. A group (alias: trifluoromethyl group) or a perfluoroethyl group (alias: pentafluoroethyl group) is more preferable, and a perfluoromethyl group (alias: trifluoromethyl group) is particularly preferable.

As the compound represented by the formula (A), lithium trifluoromethylsulfonate or lithium pentafluoroethylsulfonate is preferable, and lithium trifluoromethylsulfonate is particularly preferable.
Further, the compounds represented by the formula (A) include compounds represented by the following formulas (A-1) to (A-5) (hereinafter, compounds (A-1) to (A- 5) is also preferred.

The additive B is at least one selected from the group consisting of compounds represented by the following formula (B).

The “hydrocarbon group having 1 to 6 carbon atoms” represented by R ^b1 represents an unsubstituted hydrocarbon group having 1 to 6 carbon atoms.
The “hydrocarbon group having 1 to 6 carbon atoms” represented by R ^b1 may be a linear hydrocarbon group, a branched hydrocarbon group, or a cyclic hydrocarbon group.
The “hydrocarbon group having 1 to 6 carbon atoms” represented by R ^b1 is preferably an alkyl group, an alkenyl group, or a phenyl group, more preferably an alkyl group or an alkenyl group, and still more preferably an alkyl group.
The carbon number of the “hydrocarbon group having 1 to 6 carbon atoms” represented by R ^b1 is preferably 1 to 3, more preferably 1 or 2, and particularly preferably 1.

Examples of the “hydrocarbon group having 1 to 6 carbon atoms” represented by R ^b1 include, for example, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, tert-butyl group, Alkyl groups such as pentyl group, 2-methylbutyl group, 1-methylpentyl group, neopentyl group, 1-ethylpropyl group, hexyl group and 3,3-dimethylbutyl group; vinyl group, 1-propenyl group, allyl group, -Butenyl group, 2-butenyl group, 3-butenyl group, pentenyl group, hexenyl group, isopropenyl group, 2-methyl-2-propenyl group, 1-methyl-2-propenyl group, 2-methyl-1-propenyl group An alkenyl group; and the like.

Specific examples and preferred embodiments of the "hydrocarbon group having 1 to 6 carbon atoms" in the structure of the "hydrocarbon group having 1 to 6 carbon atoms" represented by R ^b1 is mentioned above, is represented by R ^b1 This is the same as the specific examples and preferred embodiments of the “hydrocarbon group having 1 to 6 carbon atoms”.

Specific examples and preferred embodiments of the “fluorocarbon group having 1 to 6 carbon atoms” represented by R ^b1 are described in the above-mentioned “fluorocarbon group having 1 to 6 carbon atoms” represented by R ^a1 in the formula (A). It is the same as the preferable embodiment of the "hydrocarbon group".

In the formula (B), R ^b1 is preferably a hydrocarbon group having 1 to 6 carbon atoms (that is, an unsubstituted hydrocarbon group having 1 to 6 carbon atoms), and particularly preferably an alkyl group having 1 to 6 carbon atoms. .

As the compound represented by the formula (B),
Methanesulfonyl fluoride, ethanesulfonyl fluoride, propanesulfonyl fluoride, 2-propanesulfonyl fluoride, butanesulfonyl fluoride, 2-butanesulfonyl fluoride, hexanesulfonyl fluoride, trifluoromethanesulfonyl fluoride, perfluoroethanesulfonyl fluoride , Perfluoropropanesulfonyl fluoride, perfluorobutanesulfonyl fluoride, ethenesulfonyl fluoride, 1-propen-1-sulfonyl fluoride, or 2-propene-1-sulfonyl fluoride is preferred,
Methanesulfonyl fluoride, ethanesulfonyl fluoride, propanesulfonyl fluoride, 2-propanesulfonyl fluoride, butanesulfonyl fluoride, 2-butanesulfonyl fluoride, hexanesulfonyl fluoride, trifluoromethanesulfonyl fluoride, perfluoroethanesulfonyl fluoride , Perfluoropropanesulfonyl fluoride, or perfluorobutanesulfonyl fluoride is more preferable,
Methanesulfonyl fluoride, ethanesulfonyl fluoride, propanesulfonyl fluoride, 2-propanesulfonyl fluoride, butanesulfonyl fluoride, 2-butanesulfonyl fluoride, or hexanesulfonyl fluoride is more preferable,
Methanesulfonyl fluoride, ethanesulfonyl fluoride, or propanesulfonyl fluoride is more preferable,
Methanesulfonyl fluoride is particularly preferred.

The additive C is at least one selected from the group consisting of compounds represented by the following formula (C).

In the formula (C), as the halogen atom, a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom is preferable, a fluorine atom, a chlorine atom, or a bromine atom is more preferable, a fluorine atom or a chlorine atom is more preferable, and a fluorine atom is preferable. Is more preferred.

In the formula (C), the hydrocarbon group having 1 to 6 carbon atoms represented by R ^c1 to R ^c4 may be a linear hydrocarbon group or a hydrocarbon group having a branched and / or cyclic structure. It may be.
Specific examples of the hydrocarbon group having 1 to 6 carbon atoms represented by R ^c1 to R ^c4 in the formula (C) are the hydrocarbon groups having 1 to 6 carbon atoms represented by R ^b1 in the formula (B). This is the same as the specific example.
In the formula (C), the hydrocarbon group having 1 to 6 carbon atoms represented by R ^c1 to R ^c4 is preferably an alkyl group, an alkenyl group or an alkynyl group, more preferably an alkyl group or an alkenyl group, and more preferably an alkyl group. Is particularly preferred.
In the formula (C), the number of carbon atoms of the hydrocarbon group having 1 to 6 carbon atoms represented by R ^c1 to R ^c4 is preferably 1 to 3, more preferably 1 or 2, and still more preferably 1.

In the formula (C), the halogenated hydrocarbon group having 1 to 6 carbon atoms represented by R ^c1 to R ^c4 means a hydrocarbon group having 1 to 6 carbon atoms substituted by at least one halogen atom.
As the halogen atom in the halogenated hydrocarbon group, a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom is preferable, a fluorine atom, a chlorine atom, or a bromine atom is more preferable, a fluorine atom or a chlorine atom is more preferable, and a fluorine atom Is more preferred.

In the formula (C), the halogenated hydrocarbon group having 1 to 6 carbon atoms represented by R ^c1 to R ^c4 may be a straight-chain halogenated hydrocarbon group, or may have a branched and / or cyclic structure. And a halogenated hydrocarbon group having the same.
In the formula (C), as the halogenated hydrocarbon group having 1 to 6 carbon atoms represented by R ^c1 to R ^c4 , a halogenated alkyl group, a halogenated alkenyl group, or a halogenated alkynyl group is preferable. Groups or alkenyl halide groups are more preferred, and halogenated alkyl groups are particularly preferred.
In the formula (C), the number of carbon atoms of the halogenated hydrocarbon group having 1 to 6 carbon atoms represented by R ^c1 to R ^c4 is preferably 1 to 3, more preferably 1 or 2, and still more preferably 1.

In the formula (C), the hydrocarbon oxy group having 1 to 6 carbon atoms represented by R ^c1 to R ^c4 may be a straight-chain hydrocarbon oxy group or a hydrocarbon having a branched and / or cyclic structure. It may be a hydrogenoxy group.
In the formula (C), the hydrocarbon oxy group having 1 to 6 carbon atoms represented by R ^c1 to R ^c4 is preferably an alkoxy group, an alkenyloxy group, or an alkynyloxy group, and more preferably an alkoxy group or an alkenyloxy group. Preferably, an alkoxy group is particularly preferred.
In the formula (C), the number of carbon atoms of the hydrocarbon oxy group having 1 to 6 carbon atoms represented by R ^c1 to R ^c4 is preferably 1 to 3, more preferably 1 or 2, and still more preferably 1.

In the formula (C), the halogenated hydrocarbon oxy group having 1 to 6 carbon atoms represented by R ^c1 to R ^c4 means a hydrocarbon oxy group having 1 to 6 carbon atoms substituted by at least one halogen atom. I do.
As the halogen atom in the halogenated hydrocarbon oxy group, a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom is preferable, a fluorine atom, a chlorine atom, or a bromine atom is more preferable, a fluorine atom or a chlorine atom is more preferable, and fluorine Atoms are more preferred.

In the formula (C), the halogenated hydrocarbon oxy group having 1 to 6 carbon atoms represented by R ^c1 to R ^c4 may be a straight-chain halogenated hydrocarbon oxy group, or may be a branched and / or cyclic ring. It may be a halogenated hydrocarbon oxy group having a structure.
In the formula (C), the halogenated hydrocarbon oxy group having 1 to 6 carbon atoms represented by R ^c1 to R ^c4 is preferably a halogenated alkoxy group, a halogenated alkenyloxy group, or a halogenated alkynyloxy group, A halogenated alkoxy group or a halogenated alkenyloxy group is more preferable, and a halogenated alkoxy group is particularly preferable.
In the formula (C), the number of carbon atoms of the halogenated hydrocarbon oxy group having 1 to 6 carbon atoms represented by R ^c1 to R ^c4 is preferably 1 to 3, more preferably 1 or 2, and still more preferably 1. .

In the formula (C), R ^c1 to R ^c4 each independently represent a hydrogen atom, a fluorine atom, a chlorine atom, a methyl group, an ethyl group, a vinyl group, an ethynyl group, an allyl group, a trifluoromethyl group, or a methoxy group. Is preferable, and a hydrogen atom is particularly preferable.

Specific examples of the compound represented by the formula (C) include:
Sulfobenzoic anhydride,
Fluorosulfobenzoic anhydride,
Chlorobenzoic anhydride,
Difluorosulfobenzoic anhydride,
Dichlorosulfobenzoic anhydride,
Trifluorosulfobenzoic anhydride,
Tetrafluorosulfobenzoic anhydride,
Methylsulfobenzoic anhydride,
Dimethylsulfobenzoic anhydride,
Trimethylsulfobenzoic anhydride,
Ethylsulfobenzoic anhydride,
Propylsulfobenzoic anhydride,
Vinylsulfobenzoic anhydride,
Ethynyl sulfobenzoic anhydride,
Allyl sulfobenzoic anhydride,
(Trifluoromethyl) sulfobenzoic anhydride,
Di (trifluoro) (methyl) sulfobenzoic anhydride,
(Trifluoromethoxy) sulfobenzoic anhydride,
(Fluoro) (methyl) sulfobenzoic anhydride,
(Chloro) (methyl) sulfobenzoic anhydride,
(Fluoro) (methoxy) sulfobenzoic anhydride,
(Chloro) (methoxy) sulfobenzoic anhydride,
Di (fluoro) (methoxy) sulfobenzoic anhydride,
Di (trifluoro) (vinyl) sulfobenzoic anhydride,
(Fluoro) (vinyl) sulfobenzoic anhydride,
Di (trifluoro) (ethynyl) sulfobenzoic anhydride,
(Fluoro) (ethynyl) sulfobenzoic anhydride,
And the like.
Among these, sulfobenzoic anhydride (hereinafter also referred to as “compound (C-1)”) is particularly preferred.

The additive D is at least one selected from the group consisting of compounds represented by the following formula (D).

In the formula (D), the hydrocarbon group having 1 to 6 carbon atoms represented by R ^d21 to R ^d24 is preferably an alkyl group, an alkenyl group or an alkynyl group, more preferably an alkyl group or an alkenyl group, and more preferably an alkyl group. Is particularly preferred.
In the formula (D), the number of carbon atoms of the hydrocarbon group having 1 to 6 carbon atoms represented by R ^d21 to R ^d24 is preferably 1 or 2, and particularly preferably 1.

Specific examples of the compound represented by the formula (D) include compounds represented by the following formulas (D2-1) to (D2-4) (hereinafter, compounds (D2-1) to (D2), respectively) -4)), but the compound represented by the formula (D) is not limited to these specific examples.
Among these, compounds (D2-1) to (D2-3) are particularly preferred.

<Non-aqueous solvent>
The non-aqueous electrolyte generally contains a non-aqueous solvent.
The non-aqueous solvent contained in the non-aqueous electrolyte may be only one kind or two or more kinds.
Various known nonaqueous solvents can be appropriately selected.
As the non-aqueous solvent, for example, the non-aqueous solvents described in paragraphs 0069 to 0087 of JP-A-2017-45723 can be used.

The non-aqueous solvent preferably contains a cyclic carbonate compound and a chain carbonate compound.
In this case, each of the cyclic carbonate compound and the chain carbonate compound contained in the non-aqueous solvent may be only one kind or two or more kinds.

Examples of the cyclic carbonate compound include ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate and the like.
Of these, ethylene carbonate and propylene carbonate, which have a high dielectric constant, are preferred. In the case of a battery using a negative electrode active material containing graphite, the non-aqueous solvent more preferably contains ethylene carbonate.

As the chain carbonate compound, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, ethyl propyl carbonate, dipropyl carbonate, methyl butyl carbonate, ethyl butyl carbonate, dibutyl carbonate, methyl pentyl carbonate, ethyl pentyl Examples thereof include carbonate, dipentyl carbonate, methyl heptyl carbonate, ethyl heptyl carbonate, diheptyl carbonate, methyl hexyl carbonate, ethyl hexyl carbonate, dihexyl carbonate, methyl octyl carbonate, ethyl octyl carbonate, and dioctyl carbonate.

As a combination of a cyclic carbonate and a chain carbonate, specifically, ethylene carbonate and dimethyl carbonate, ethylene carbonate and methyl ethyl carbonate, ethylene carbonate and diethyl carbonate, propylene carbonate and dimethyl carbonate, propylene carbonate and methyl ethyl carbonate, propylene carbonate and Diethyl carbonate, ethylene carbonate, propylene carbonate, and methyl ethyl carbonate, ethylene carbonate, propylene carbonate, and diethyl carbonate, ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate, ethylene carbonate, dimethyl carbonate, and diethyl carbonate, ethylene carbonate and methyl ethyl carbonate And diethyl carbonate, ethylene carbonate and dimethyl carbonate and methyl ethyl carbonate and diethyl carbonate, ethylene carbonate and propylene carbonate and dimethyl carbonate and methyl ethyl carbonate, ethylene carbonate and propylene carbonate and dimethyl carbonate and diethyl carbonate, ethylene carbonate and propylene carbonate and methyl ethyl Examples include carbonate and diethyl carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate.

The mixing ratio of the cyclic carbonate compound and the chain carbonate compound is represented by mass ratio, and the ratio of the cyclic carbonate compound to the chain carbonate compound is, for example, 5:95 to 80:20, preferably 10:90 to 70:30, and more preferably. Is from 15:85 to 55:45. With such a ratio, the increase in the viscosity of the non-aqueous electrolyte can be suppressed, and the degree of dissociation of the electrolyte can be increased. Therefore, the conductivity of the non-aqueous electrolyte relating to the charge and discharge characteristics of the battery can be increased. . Further, the solubility of the electrolyte can be further increased. Therefore, a non-aqueous electrolyte having excellent electrical conductivity at normal temperature or low temperature can be obtained, and the load characteristics of the battery at normal temperature to low temperature can be improved.

The non-aqueous solvent may contain other compounds other than the cyclic carbonate compound and the chain carbonate compound.
In this case, the other compound contained in the non-aqueous solvent may be only one kind or two or more kinds.
Other compounds include a cyclic carboxylate compound (eg, γ-butyrolactone), a cyclic sulfone compound, a cyclic ether compound, a linear carboxylate compound, a linear ether compound, a linear phosphate ester compound, an amide compound, and a linear carbamate. Compounds, cyclic amide compounds, cyclic urea compounds, boron compounds, polyethylene glycol derivatives, and the like.
Regarding these compounds, the description in paragraphs 0069 to 0087 of JP-A-2017-45723 can be appropriately referred to.

The proportion of the cyclic carbonate compound and the chain carbonate compound in the nonaqueous solvent is preferably 80% by mass or more, more preferably 90% by mass or more, and further preferably 95% by mass or more.
The proportion of the cyclic carbonate compound and the chain carbonate compound in the nonaqueous solvent may be 100% by mass.

The proportion of the non-aqueous solvent in the non-aqueous electrolyte is preferably at least 60% by mass, more preferably at least 70% by mass.
Although the upper limit of the proportion of the nonaqueous solvent in the nonaqueous electrolyte depends on the content of other components (additives, electrolytes, etc.), the upper limit is, for example, 99% by mass, and preferably 97% by mass. And more preferably 90% by mass.

The non-aqueous electrolyte of the first embodiment is not only suitable as a non-aqueous electrolyte for a lithium secondary battery, but also a non-aqueous electrolyte for a primary battery, a non-aqueous electrolyte for an electrochemical capacitor, It can also be used as an electrolyte for multilayer capacitors and aluminum electrolytic capacitors.

[Non-aqueous electrolyte for battery (second embodiment)]
The non-aqueous electrolyte for a battery according to the second embodiment of the present disclosure (hereinafter, also simply referred to as “non-aqueous electrolyte of the second embodiment”) is
An electrolyte comprising lithium hexafluorophosphate and lithium bis (fluorosulfonyl) imide;
And at least one additive selected from the group consisting of compounds represented by the following formula (E).

According to the non-aqueous electrolyte of the second embodiment, the battery resistance after storage can be reduced.
The reason why such an effect is exhibited is not clear, but a non-aqueous electrolytic solution containing at least one additive selected from the group consisting of the compounds represented by the above formula (E), as an electrolyte, It is considered that by using a combination of lithium hexafluorophosphate and lithium bis (fluorosulfonyl) imide, a good quality film having low resistance after storage of the battery is formed on the electrode surface.

Therefore, in the non-aqueous electrolyte of the second embodiment, by using lithium hexafluorophosphate and lithium bis (fluorosulfonyl) imide in combination as the electrolyte, the case where lithium hexafluorophosphate is used alone as the electrolyte is used. In comparison, it is considered that the stability of the electrolyte during storage is improved. As a result, the storage characteristics (particularly, high-temperature storage characteristics) of the battery are excellent.

Hereinafter, each component of the nonaqueous electrolyte of the second embodiment will be described.

<Electrolyte>
The non-aqueous electrolyte of the second embodiment contains an electrolyte containing both lithium hexafluorophosphate (hereinafter also referred to as LiPF ₆ ) and lithium bis (fluorosulfonyl) imide (hereinafter also referred to as LiFSI).

In the electrolyte in the nonaqueous electrolytic solution of the second embodiment, the molar ratio of the content of LiFSI to the sum of LiPF ₆ and LiFSI (hereinafter, also referred to as the molar ratio [LiFSI _/ (LiPF 6 + LiFSI)]) is 0.050 0. 85 or less.
When the molar ratio [LiFSI / (LiPF ₆ + LiFSI)] is 0.050 or more, the battery resistance after storage is reduced. From the viewpoint of further reducing the battery resistance after storage, the molar ratio [LiFSI / (LiPF ₆ + LiFSI)] is preferably 0.080 or more, more preferably 0.10 or more, and still more preferably 0.15 or more. That is all.
On the other hand, the fact that the molar ratio [LiFSI / (LiPF ₆ + LiFSI)] is 0.85 or less is advantageous in terms of electrical conductivity, oxidation resistance, and the like. From the viewpoints of electrical conductivity and oxidation resistance, the molar ratio [LiFSI / (LiPF ₆ + LiFSI)] may be 0.50 or less, may be less than 0.50, or may be 0.40 or less. , May be 0.30 or less, or may be 0.20 or less.

In the non-aqueous electrolyte of the second embodiment, the total concentration of lithium hexafluorophosphate and lithium bis (fluorosulfonyl) imide is not particularly limited, but the total concentration is preferably 0.1 mol / L to 3 mol / L. And more preferably from 0.5 mol / L to 2 mol / L.

The electrolyte in the nonaqueous electrolyte of the second embodiment may contain at least one compound other than lithium hexafluorophosphate and lithium bis (fluorosulfonyl) imide.
Examples of other compounds that can be included in the electrolyte according to the second embodiment are the same as the examples of other compounds that can be included in the electrolyte according to the first embodiment.

The total mass ratio of lithium hexafluorophosphate and lithium bis (fluorosulfonyl) imide in the electrolyte in the second embodiment is preferably 50% by mass to 100% by mass, and more preferably 80% by mass to 100% by mass. %, More preferably 90 to 100% by mass.

<Additives>
The non-aqueous electrolyte solution of the second embodiment contains at least one additive selected from the group consisting of compounds represented by the following formula (E) (hereinafter, also referred to as “additive E”).

The content of the above-mentioned additive E is preferably 0.001% by mass to 10% by mass, more preferably 0.003% by mass to 5% by mass, and more preferably 0.003% by mass to the total amount of the nonaqueous electrolyte. The content is more preferably 3% by mass, more preferably 0.03% by mass to 3% by mass, and particularly preferably 0.1% to 3% by mass.

The additive E is at least one selected from the group consisting of compounds represented by the following formula (E).

In Formula (E), the hydrocarbon group having 1 to 3 carbon atoms represented by R ¹¹ to R ¹⁴ is preferably an alkyl group, an alkenyl group, or an alkynyl group, more preferably an alkyl group or an alkenyl group, and more preferably an alkyl group. Is particularly preferred.
In the formula (A), the number of carbon atoms of the hydrocarbon group having 1 to 3 carbon atoms represented by R ¹¹ to R ¹⁴ is preferably 1 or 2, and particularly preferably 1.

In the formula (E), the fluorocarbon group having 1 to 3 carbon atoms represented by R ¹¹ to R ¹⁴ is preferably an alkyl fluoride group, an alkenyl fluoride group, or an alkynyl fluoride group. Groups or alkenyl fluoride groups are more preferred, and fluorinated alkyl groups are particularly preferred.
In the formula (E), the number of carbon atoms of the fluorocarbon group having 1 to 3 carbon atoms represented by R ¹¹ to R ¹⁴ is preferably 1 or 2, and particularly preferably 1.

In the formula (E), R ¹¹ to R ¹⁴ are each independently preferably a hydrogen atom, a fluorine atom, a methyl group, an ethyl group, a trifluoromethyl group, or a pentafluoroethyl group, more preferably a hydrogen atom or a methyl group. And a hydrogen atom is particularly preferred.

Specific examples of the compound represented by the formula (E) include compounds represented by the following formulas (E-1) to (E-21) (hereinafter, compounds (E-1) to (E), respectively) -21)), but the compound represented by the formula (E) is not limited to these specific examples.
Among these, compound (E-1) (that is, 1,3-propene sultone; hereinafter, also referred to as “PRS”) is particularly preferred.

<Non-aqueous solvent>
The non-aqueous electrolyte of the second embodiment generally contains a non-aqueous solvent.
Preferred aspects of the non-aqueous solvent contained in the non-aqueous electrolyte of the second embodiment are the same as preferred aspects of the non-aqueous solvent contained in the non-aqueous electrolyte of the first embodiment.

The non-aqueous electrolyte of the second embodiment is not only suitable as a non-aqueous electrolyte for a lithium secondary battery, but also a non-aqueous electrolyte for a primary battery, a non-aqueous electrolyte for an electrochemical capacitor, It can also be used as an electrolyte for multilayer capacitors and aluminum electrolytic capacitors.

[Lithium secondary battery]
Next, the lithium secondary battery of the present disclosure will be described.
The lithium secondary battery of the present disclosure includes a positive electrode, a negative electrode, and a non-aqueous electrolyte of the present disclosure (that is, the non-aqueous electrolyte of the first embodiment or the non-aqueous electrolyte of the second embodiment described above. The same applies hereinafter. ).

(Negative electrode)
The negative electrode may include a negative electrode active material and a negative electrode current collector.
As the negative electrode active material of the negative electrode, metallic lithium, a lithium-containing alloy, a metal or alloy capable of being alloyed with lithium, an oxide capable of doping / undoping lithium ions, and capable of doping / dedoping lithium ions At least one selected from the group consisting of a transition metal nitride and a carbon material capable of doping / dedoping lithium ions (may be used alone, or a mixture containing two or more thereof may be used. Good) can be used.
Examples of the metal or alloy that can be alloyed with lithium (or lithium ion) include silicon, a silicon alloy, tin, and a tin alloy. Further, lithium titanate may be used.
Among these, carbon materials capable of doping / dedoping lithium ions are preferable. Examples of such a carbon material include carbon black, activated carbon, graphite materials (artificial graphite, natural graphite), and amorphous carbon materials. The form of the carbon material may be any of a fibrous form, a spherical form, a potato form, and a flake form.

Specific examples of the amorphous carbon material include hard carbon, coke, mesocarbon microbeads (MCMB) fired at 1500 ° C. or lower, mesophase pitch carbon fiber (MCF), and the like.
Examples of the graphite material include natural graphite and artificial graphite. As artificial graphite, graphitized MCMB, graphitized MCF and the like are used. As the graphite material, a material containing boron or the like can be used. As the graphite material, a material coated with a metal such as gold, platinum, silver, copper, tin, etc., a material coated with amorphous carbon, or a mixture of amorphous carbon and graphite can also be used.

These carbon materials may be used alone or in combination of two or more.
As the carbon material, a carbon material having a plane distance d (002) of (002) plane measured by X-ray analysis of 0.340 nm or less is particularly preferable. Further, as the carbon material, graphite having a true density of 1.70 g / cm ³ or more, or a highly crystalline carbon material having properties close thereto is also preferable. The use of such a carbon material can further increase the energy density of the battery.

The material of the negative electrode current collector in the negative electrode is not particularly limited, and any known material can be used.
Specific examples of the negative electrode current collector include metal materials such as copper, nickel, stainless steel, and nickel-plated steel. Among them, copper is particularly preferable from the viewpoint of ease of processing.

(Positive electrode)
The positive electrode may include a positive electrode active material and a positive electrode current collector.
As the positive electrode active material in the positive electrode, transition metal oxides or transition metal sulfides such as MoS ₂ , TiS ₂ , MnO ₂ , V ₂ O ₅ , LiCoO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , and LiNi _X Co _(1-X) O ₂ [0 <X <1], Li _{1 + α} Me _1-α O ₂ having α-NaFeO ₂ type crystal structure (Me is a transition metal element containing Mn, Ni and Co, 1.0 ≤ (1 + α) / (1-α) ≤1.6), LiNi _x Co _y Mn _z O ₂ [x + y + z = 1, 0 <x <1, 0 <y <1, 0 <z <1] (for example, A composite oxide composed of lithium and a transition metal, such as LiNi _0.33 Co _0.33 Mn _0.33 O ₂ , LiNi _0.5 Co _0.2 Mn _0.3 O ₂ ), LiFePO ₄ , LiMnPO ₄ , Polyaniline, Li thiophene, polypyrrole, polyacetylene, polyacene, dimercaptothiadiazoles, conductive polymer materials such as polyaniline complex thereof. Among these, a composite oxide composed of lithium and a transition metal is particularly preferable. When the negative electrode is lithium metal or a lithium alloy, a carbon material can be used as the positive electrode. In addition, a mixture of a composite oxide of lithium and a transition metal and a carbon material can be used as the positive electrode.
One type of the positive electrode active material may be used, or two or more types may be mixed and used. When the positive electrode active material has insufficient conductivity, the positive electrode can be used together with a conductive auxiliary to form a positive electrode. Examples of the conductive auxiliary agent include carbon materials such as carbon black, amorphous whiskers, and graphite.

The material of the positive electrode current collector in the positive electrode is not particularly limited, and any known material can be used.
Specific examples of the positive electrode current collector include, for example, metal materials such as aluminum, aluminum alloy, stainless steel, nickel, titanium, and tantalum; carbon materials such as carbon cloth and carbon paper;

(Separator)
The lithium secondary battery of the present disclosure preferably includes a separator between the negative electrode and the positive electrode.
The separator is a film that electrically insulates the positive electrode and the negative electrode and transmits lithium ions, and examples thereof include a porous film and a polymer electrolyte.
As the porous film, a microporous polymer film is suitably used, and examples of the material include polyolefin, polyimide, polyvinylidene fluoride, polyester, and the like.
In particular, a porous polyolefin is preferable, and specific examples thereof include a porous polyethylene film, a porous polypropylene film, and a multilayer film of a porous polyethylene film and a polypropylene film. Another resin having excellent thermal stability may be coated on the porous polyolefin film.
Examples of the polymer electrolyte include a polymer in which a lithium salt is dissolved, a polymer swelled with an electrolytic solution, and the like.
The non-aqueous electrolyte of the present disclosure may be used for the purpose of obtaining a polymer electrolyte by swelling a polymer.

(Battery configuration)
The lithium secondary battery of the present disclosure can take various known shapes, and can be formed into a cylindrical shape, a coin shape, a square shape, a laminate shape, a film shape, or any other shape. However, the basic structure of the battery is the same regardless of the shape, and the design can be changed according to the purpose.

Examples of the lithium secondary battery (nonaqueous electrolyte secondary battery) of the present disclosure include a laminated battery.
FIG. 1 is a schematic perspective view illustrating an example of a laminated battery that is an example of the lithium secondary battery of the present disclosure. FIG. 2 is a diagram illustrating a thickness of a laminated electrode body housed in the laminated battery illustrated in FIG. It is a schematic sectional drawing of a direction.
The laminated battery shown in FIG. 1 contains a non-aqueous electrolyte (not shown in FIG. 1) and a laminated electrode body (not shown in FIG. 1), and the peripheral edge is sealed. And a laminate exterior body 1 the inside of which is sealed. As the laminate case 1, for example, a laminate case made of aluminum is used.
As shown in FIG. 2, the laminated electrode body accommodated in the laminate exterior body 1 includes a laminated body in which a positive electrode plate 5 and a negative electrode plate 6 are alternately laminated with a separator 7 interposed therebetween. And a separator 8 surrounding the periphery. The non-aqueous electrolyte of the present disclosure is impregnated in the positive electrode plate 5, the negative electrode plate 6, the separator 7, and the separator 8.
Each of the plurality of positive plates 5 in the stacked electrode body is electrically connected to the positive terminal 2 via a positive tab (not shown). It protrudes outward from the peripheral end (FIG. 1). The portion where the positive electrode terminal 2 protrudes at the peripheral end of the laminate exterior body 1 is sealed by an insulating seal 4.
Similarly, each of the plurality of negative electrodes 6 in the stacked electrode body is electrically connected to the negative electrode terminal 3 via a negative electrode tab (not shown). It protrudes outward from the peripheral end of the body 1 (FIG. 1). The portion where the negative electrode terminal 3 protrudes at the peripheral end of the laminate exterior body 1 is sealed with an insulating seal 4.
In the laminated battery according to the above-described example, the number of the positive electrode plates 5 is five and the number of the negative electrode plates 6 is six. The outer layers are all laminated so as to be the negative electrode plate 6. However, the number of positive electrodes, the number of negative electrodes, and the arrangement in the laminated battery are not limited to this example, and it goes without saying that various changes may be made.

Another example of the lithium secondary battery of the present disclosure includes a coin-type battery.
FIG. 3 is a schematic perspective view illustrating an example of a coin-type battery which is another example of the lithium secondary battery of the present disclosure.
In the coin-type battery shown in FIG. 3, the disc-shaped negative electrode 12, the separator 15 into which a non-aqueous electrolyte is injected, the disc-shaped positive electrode 11, and

spacer plates

17 and 18 made of stainless steel or aluminum are arranged in this order. In a stacked state, it is housed between a positive electrode can 13 (hereinafter, also referred to as a “battery can”) and a sealing plate 14 (hereinafter, also referred to as a “battery can lid”). The positive electrode can 13 and the sealing plate 14 are caulked and sealed via a gasket 16.
In this example, the non-aqueous electrolyte of the present disclosure is used as the non-aqueous electrolyte injected into the separator 15.

Note that the lithium secondary battery of the present disclosure is obtained by charging and discharging a lithium secondary battery (a lithium secondary battery before charging and discharging) including a negative electrode, a positive electrode, and the nonaqueous electrolyte of the present disclosure. Lithium secondary battery may be used.
That is, the lithium secondary battery of the present disclosure is, first, a negative electrode, a positive electrode, the non-aqueous electrolyte of the present disclosure, to prepare a lithium secondary battery before charging and discharging, and then, before this charging and discharging A lithium secondary battery (charged / discharged lithium secondary battery) manufactured by charging / discharging a lithium secondary battery at least once may be used.

用途 The use of the lithium secondary battery of the present disclosure is not particularly limited, and can be used for various known uses. For example, notebook computers, mobile computers, mobile phones, headphone stereos, video movies, LCD TVs, handy cleaners, electronic organizers, calculators, radios, backup power supplies, motors, automobiles, electric vehicles, motorcycles, electric motorcycles, bicycles, electric vehicles It can be widely used for small portable devices and large devices such as bicycles, lighting equipment, game machines, watches, power tools, cameras and the like.

Hereinafter, examples of the present disclosure will be described, but the present disclosure is not limited to the following examples.
In the following examples, “addition amount” means the content in the finally obtained non-aqueous electrolyte (that is, the amount based on the total amount of the finally obtained non-aqueous electrolyte).
Further, “wt%” means mass%.

Hereinafter, Examples 1 to 6 and Comparative Examples 1 to 6, A and B are Examples and Comparative Examples of the non-aqueous electrolyte solution of the first embodiment, and Example 101 and Comparative Examples 101 to 104 are Examples and comparative examples of the non-aqueous electrolyte according to the second embodiment.

[Example 1]
A coin-type battery (test battery) as a lithium secondary battery was manufactured in the following procedure.
<Preparation of negative electrode>
Amorphous natural graphite (97 parts by mass), carboxymethylcellulose (1 part by mass) and SBR latex (2 parts by mass) were kneaded with an aqueous solvent to prepare a paste-like negative electrode mixture slurry.
Next, the negative electrode mixture slurry was applied to a 10 μm-thick strip-shaped copper foil negative electrode current collector, dried, and then compressed by a roll press to form a sheet-shaped negative electrode comprising the negative electrode current collector and the negative electrode active material layer. I got At this time, the coating density of the negative electrode active material layer was 12 mg / cm ² , and the packing density was 1.5 g / ml.

<Preparation of positive electrode>
LiNi _0.5 Mn _0.3 Co _0.2 O ₂ (90 parts by mass), acetylene black (5 parts by mass), and polyvinylidene fluoride (5 parts by mass) are kneaded using N-methylpyrrolidinone as a solvent to form a paste. Was prepared.
Next, this positive electrode mixture slurry is applied to a 20 μm-thick strip-shaped aluminum foil positive electrode current collector, dried, and then compressed by a roll press to form a sheet-shaped positive electrode comprising a positive electrode current collector and a positive electrode active material layer. I got At this time, the coating density of the positive electrode active material layer was 22 mg / cm ² , and the packing density was 2.5 g / ml.

<Preparation of non-aqueous electrolyte>
As non-aqueous solvents, ethylene carbonate (EC), dimethyl carbonate (DMC), and methyl ethyl carbonate (EMC) were mixed at a ratio of 30:35:35 (mass ratio), respectively, to obtain a mixed solvent.
In the obtained mixed solvent, LiPF ₆ and LiFSI (lithium bis (fluoromethylsulfonyl) imide) as electrolytes are used, and the concentration of LiPF _{6 in} the finally obtained non-aqueous electrolyte is 1.0 mol / L, and Was dissolved so that the concentration of LiFSI in the finally obtained non-aqueous electrolyte was 0.2 mol / L, that is, the total concentration of LiPF ₆ and LiFSI in the finally obtained non-aqueous electrolyte. Is 1.2 mol / L, and the molar ratio [LiFSI / (LiPF ₆ + LiFSI)] is 0.17.
For the solution obtained above,
Lithium trifluoromethylsulfonate (hereinafter also referred to as “TFMSL”; a specific example of additive A) (addition amount: 0.5% by mass) was added as an additive to obtain a non-aqueous electrolyte.

<Preparation of coin battery>
The above-mentioned negative electrode was punched into a disk shape with a diameter of 14 mm and the above-mentioned positive electrode with a diameter of 13 mm, to obtain a coin-shaped negative electrode and a coin-shaped positive electrode, respectively. Further, a microporous polyethylene film having a thickness of 20 μm was punched into a disk having a diameter of 17 mm to obtain a separator.
The obtained coin-shaped negative electrode, separator, and coin-shaped positive electrode are laminated in this order in a stainless steel battery can (2032 size), and then 20 μL of the above-described non-aqueous electrolyte is placed in the battery can. It was injected and impregnated in the separator, the positive electrode and the negative electrode.
Next, an aluminum plate (thickness: 1.2 mm, diameter: 16 mm) and a spring were placed on the positive electrode, and the battery can was sealed by caulking the battery can lid via a polypropylene gasket.
As described above, a coin-type battery (that is, a coin-type lithium secondary battery) having a configuration shown in FIG. 3 having a diameter of 20 mm and a height of 3.2 mm was obtained.

<Evaluation of battery resistance>
Conditioning was performed on the obtained coin-type battery, and the battery resistance of the conditioned coin-type battery was evaluated.
Here, “conditioning” means that the coin-type battery is repeatedly charged and discharged three times between 2.75 V and 4.2 V at 25 ° C. in a thermostat.
Hereinafter, “high temperature storage” means an operation of storing coin type batteries at 80 ° C. for 48 hours in a thermostat.
Hereinafter, the battery resistance (DCIR) was measured under a temperature condition of −20 ° C.

(Measurement of battery resistance (DCIR) before high temperature storage)
The SOC (State of Charge) of the coin-type battery after conditioning was adjusted to 80%, and then the DCIR (Direct current internal resistance; DC resistance) of the coin-type battery before storage at high temperature was measured by the following method.
Using the coin-type battery adjusted to the above-mentioned SOC of 80%, CC10s discharge was performed at a discharge rate of 0.2C.
Here, the CC10s discharge means discharging at a constant current (Constant Current) for 10 seconds.
The current value (that is, the current value corresponding to a discharge rate of 0.2 C) and the voltage drop amount (= voltage before the start of discharge−10 seconds after the start of the discharge) in the “CC10s discharge at a discharge rate of 0.2 C” described above ), And the obtained DC resistance (Ω) was defined as the battery resistance (Ω) of the coin-type battery before storage at high temperature.

(Measurement of battery resistance (DCIR) after high temperature storage)
CC-CV charging of the coin-type battery after conditioning and before adjusting the SOC to 80% to 4.25 V at a charging rate of 0.2 C at 25 ° C. in a thermostat, and then performing high-temperature storage. The battery resistance (Ω) after the high-temperature storage was measured in the same manner as the measurement of the battery resistance before the high-temperature storage described above, except that was added.
Table 1 shows the results.
Here, the CC-CV charging means a constant current-constant voltage.

(Measurement of rise rate of battery resistance due to high temperature storage)
The rate of increase in battery resistance due to high-temperature storage (in Table 1, simply referred to as “rate of increase (%)”) was calculated by the following equation. Table 1 shows the results.
Increase rate of battery resistance due to high temperature storage (%)
= [(Battery resistance after high temperature storage (Ω)-battery resistance before high temperature storage (Ω)) / battery resistance before high temperature storage (Ω)] x 100

The rise rate (%) may be not only a positive value, but also a negative value or 0.
A positive rise rate (%) means that the battery resistance increased due to high-temperature storage, and a negative rise rate (%) means that the battery resistance decreased due to high-temperature storage. The fact that the rate of increase (%) is 0 means that the battery resistance did not change due to high-temperature storage.

[Examples 2 to 6, Comparative Examples 1 to 6, A and B]
The same operation as in Example 1 was performed except that the combination of the type of the electrolyte, the concentration of the electrolyte, and the amount of the additive was changed as shown in Table 1.
Table 1 shows the results.

In Table 1, "-" means that the corresponding component is not contained.
In Table 1, the numerical value in parentheses below the abbreviation of the additive means the amount (% by mass) of the additive. For example, “TFMSL (0.5)” means lithium trifluoromethylsulfonate (addition amount: 0.5% by mass). “MSF (0.5)” means methanesulfonyl fluoride (addition amount: 0.5% by mass).
In Table 1, sulfobenzoic acid is a compound represented by the formula (C) in which all of R ^c1 to R ^c4 are each a hydrogen atom. In Table 1, (D2-1), (D2-2), and (D2-3) are specific examples of the compound represented by the formula (D), and specifically, the following compounds.

As shown in Table 1, in the batteries of Examples 1 to 6 containing LiPF ₆ and LiFSI as electrolytes in the non-aqueous electrolyte and containing additives (at least one of additives A to D), The battery resistance after high-temperature storage was reduced as compared with the batteries of Comparative Examples 1 to 6, A and B, which did not satisfy any one of these conditions.
In particular, the batteries of Examples 1 to 6 each contained LiPF ₆ and LiFSI, but had lower battery resistance after high-temperature storage than the batteries of Comparative Example A, which contained no additives.
Further, when comparing the battery of Example 1 with the battery of Comparative Example 1 containing the same additive as in Example 1 but not containing LiFSI, the battery of Example 1 has a battery resistance after high-temperature storage. Had been reduced. Further, in the battery of Example 1, the rate of increase in battery resistance due to high-temperature storage was suppressed as compared with the battery of Comparative Example 1 containing the same additive. Similar results were obtained for the batteries of the other Examples 2 to 6.

(Example 101)
A coin-type battery (test battery) as a lithium secondary battery was manufactured in the following procedure.
<Preparation of negative electrode>
A negative electrode was produced in the same manner as in the production of the negative electrode in Example 1.

<Preparation of positive electrode>
A positive electrode was produced in the same manner as in the production of the positive electrode in Example 1.

<Preparation of non-aqueous electrolyte>
As non-aqueous solvents, ethylene carbonate (EC), dimethyl carbonate (DMC), and methyl ethyl carbonate (EMC) were mixed at a ratio of 30:35:35 (mass ratio), respectively, to obtain a mixed solvent.
In the obtained mixed solvent, LiPF ₆ and LiFSI (lithium bis (fluoromethylsulfonyl) imide) as electrolytes are used, and the concentration of LiPF _{6 in} the finally obtained non-aqueous electrolyte is 1.0 mol / L, and Was dissolved so that the concentration of LiFSI in the finally obtained non-aqueous electrolyte was 0.2 mol / L, that is, the total concentration of LiPF ₆ and LiFSI in the finally obtained non-aqueous electrolyte. Is 1.2 mol / L, and the molar ratio [LiFSI / (LiPF ₆ + LiFSI)] is 0.17.
For the solution obtained above,
As an additive, 1,3-propene sultone (hereinafter also referred to as “PRS”; a specific example of the additive E) (addition amount: 0.5% by mass) was added to obtain a non-aqueous electrolyte.

<Preparation of coin battery>
A coin-type battery was obtained in the same manner as in the production of the coin-type battery in Example 1, except that the non-aqueous electrolyte in Example 101 was used as the non-aqueous electrolyte.

<Evaluation of battery resistance>
With respect to the coin-type battery obtained above, the evaluation of the battery resistance was performed in the same manner as the evaluation of the battery resistance in Example 1 except that the temperature condition of the battery resistance (DCIR) was changed from −20 ° C. to 25 ° C. Was done.
Table 2 shows the results.

[Comparative Examples 101 to 104]
The same operation as in Example 101 was performed, except that the combination of the type of the electrolyte, the concentration of the electrolyte, and the amount of the additive was changed as shown in Table 2.
Table 2 shows the results.

In Table 2, "-" means that the corresponding component was not contained.
In Table 2, the numerical value in parentheses below the abbreviation of the additive means the amount (% by mass) of the additive. For example, “PRS (0.5)” means 1,3-propene sultone (addition amount: 0.5% by mass).

As shown in Table 2, LiPF ₆ and LiFSI as electrolytes in the non-aqueous electrolyte and additive E were contained, and the molar ratio [LiFSI / (LiPF ₆ + LiFSI)] was 0.050 or more and 0.85 or less. In the battery of Example 101 falling within the range, the battery resistance after high-temperature storage was reduced as compared with Comparative Examples 101 to 104 which did not satisfy any one of these conditions. Similarly, in the battery of Example 101, the increase in battery resistance due to high-temperature storage was suppressed as compared with the batteries of Comparative Examples 101 to 104 (see “Rise rate” in Table 2).

The disclosure of Japanese Patent Application No. 2018-171411 filed on September 13, 2018 and the disclosure of Japanese Patent Application No. 2018-142884 filed on July 30, 2018 are incorporated herein by reference in their entirety. It is captured.
All documents, patent applications, and technical standards mentioned herein are to the same extent as if each individual document, patent application, and technical standard were specifically and individually stated to be incorporated by reference. Incorporated herein by reference.

Claims

An electrolyte comprising lithium hexafluorophosphate and lithium bis (fluorosulfonyl) imide;
Selected from the group consisting of a compound represented by the following formula (A), a compound represented by the following formula (B), a compound represented by the following formula (C), and a compound represented by the following formula (D) At least one additive,
Non-aqueous electrolyte for batteries containing.

[In the formula (A), R a1 represents a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, a hydrocarbon oxy group having 1 to 6 carbon atoms, or a fluorinated hydrocarbon group having 1 to 6 carbon atoms. . ]

[In the formula (B), R b1 represents a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, a hydrocarbonoxy group having 1 to 6 carbon atoms, or a fluorinated hydrocarbon group having 1 to 6 carbon atoms. Represents ]

[In the formula (C), R c1 to R c4 each independently represent a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 6 carbon atoms, a halogenated hydrocarbon group having 1 to 6 carbon atoms, 6 represents a hydrocarbon oxy group or a halogenated hydrocarbon oxy group having 1 to 6 carbon atoms. ]

[In the formula (D), R d21 to R d24 each independently represent a hydrogen atom, a hydrocarbon group having 1 to 6 carbon atoms, a group represented by the formula (a), or a formula (b) Represents a group. In the formulas (a) and (b), * represents a bonding position. ]
2. The battery according to claim 1, wherein a molar ratio of the lithium bis (fluorosulfonyl) imide to the total of the lithium hexafluorophosphate and the lithium bis (fluorosulfonyl) imide is 0.01 to 0.85. 3. Non-aqueous electrolyte.
The content molar ratio of the lithium bis (fluorosulfonyl) imide to the total of the lithium hexafluorophosphate and the lithium bis (fluorosulfonyl) imide is 0.08 or more and 0.85 or less. The non-aqueous electrolyte for a battery according to the above.
An electrolyte comprising lithium hexafluorophosphate and lithium bis (fluorosulfonyl) imide;
An additive which is at least one selected from the group consisting of compounds represented by the following formula (E):
Containing
A nonaqueous electrolyte solution for a battery, wherein the molar ratio of the lithium bis (fluorosulfonyl) imide to the total of the lithium hexafluorophosphate and the lithium bis (fluorosulfonyl) imide is 0.050 to 0.85.

[In the formula (E), R 11 to R 14 each independently represent a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 3 carbon atoms, or a fluorinated hydrocarbon group having 1 to 3 carbon atoms. ]
The non-battery for a battery according to any one of claims 1 to 4, wherein a total concentration of the lithium hexafluorophosphate and the lithium bis (fluorosulfonyl) imide is 0.1 mol / L or more and 3 mol / L or less. Water electrolyte.
The non-aqueous solution for a battery according to any one of claims 1 to 5, wherein the content of the additive is 0.001% by mass or more and 10% by mass or less based on the total amount of the non-aqueous electrolyte for a battery. Electrolyte.
A positive electrode,
Lithium metal, lithium-containing alloy, metal or alloy capable of being alloyed with lithium, oxide capable of doping / dedoping lithium ion, transition metal nitride capable of doping / dedoping lithium ion, and lithium A negative electrode containing, as a negative electrode active material, at least one selected from the group consisting of carbon materials capable of doping and undoping ions;
A non-aqueous electrolyte for a battery according to any one of claims 1 to 6,
Including lithium secondary batteries.
A lithium secondary battery obtained by charging and discharging the lithium secondary battery according to claim 7.