JP2018170237A - Nonaqueous electrolyte solution for battery and lithium secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte solution for a battery, by which the rise in battery resistance owing to storing can be suppressed.SOLUTION: A nonaqueous electrolyte solution for a battery comprises: an additive agent A including one or more kinds selected from a group of boron compounds represented by the formula (A); an additive agent B including one or more kinds selected from a group consisting of a lithium monofluorophosphate, a lithium difluorophosphate, a compound represented by the formula (X), and a compound represented by the formula (Y); and an electrolyte which is a Li salt other than the additive agent A and the additive agent B. [R is an alkyl group, an alkenyl group or a group represented by the formula (A1); Rto Rindependently represent H, halogen, an alkyl group, an alkenyl group or an aryl group; * represents a position of coupling with O; Rrepresents a hydrocarbon group which can be substituted with F, a hydrocarbon oxy group, or F; and Ris a hydrocarbon group substituted with one or more F atoms, a hydrocarbon oxy group, or F.]SELECTED DRAWING: None

Description

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

  Secondary batteries using non-aqueous electrolytes are widely used as power sources for consumer electronic devices because of their high voltage, high energy density, and high reliability such as storage characteristics. Furthermore, secondary batteries using non-aqueous electrolytes are beginning to be used for power storage, and batteries for vehicles such as electric vehicles (EV), hybrid vehicles (HEV), and plug-in hybrid vehicles (PHEV). . As a typical example of the secondary battery using the non-aqueous electrolyte, there are a lithium battery and a lithium ion secondary battery.

The non-aqueous electrolyte used for these secondary batteries is a solution in which an electrolyte is mixed with a non-aqueous solvent, and the electrolyte contained in the non-aqueous electrolyte transfers ions between the positive electrode and the negative electrode. The non-aqueous electrolyte is required to have the following characteristics in order to improve the battery performance of the secondary battery.
First, the nonaqueous electrolytic solution needs to be chemically and electrochemically stable with respect to the positive electrode and the negative electrode in order to enhance the storage characteristics and cycle characteristics of the secondary battery.
Further, the non-aqueous electrolyte is preferably a solution having a high ion movement speed in order to enhance the charge / discharge characteristics of the secondary battery. Specifically, the non-aqueous electrolyte has a low viscosity and mass transfer due to diffusion is likely to occur. It must be liquid.

  In order to satisfy the above characteristics required for non-aqueous electrolytes, non-aqueous solvents for non-aqueous electrolytes include high dielectric constant carbonate solvents such as propylene carbonate and ethylene carbonate, diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate and the like. It is known to use low viscosity carbonate solvents. In addition, it is known that a boron compound is added to a non-aqueous electrolyte to improve battery performance such as storage characteristics, cycle characteristics, and charge / discharge characteristics of the secondary battery (see, for example, Patent Documents 1 to 10). .

Japanese Patent Laid-Open No. 09-120825 JP-A-10-223258 Japanese Patent Application Laid-Open No. 11-054133 JP-A-11-121033 JP 2002-025609 A JP 2002-216844 A JP 2003-132946 A JP 2003-168476 A JP 2008-198542 A JP 2009-245829 A

As disclosed in Patent Documents 1 to 10, it is known to add a boron compound to a nonaqueous electrolytic solution in order to improve battery performance of a secondary battery (for example, a lithium secondary battery). However, there are cases where it is required to suppress an increase in battery resistance due to storage in a non-aqueous electrolyte to which a boron compound is added and a lithium secondary battery using the non-aqueous electrolyte.
Therefore, the subject of this indication is providing the non-aqueous electrolyte for batteries which can suppress a raise of battery resistance by storage, and the lithium secondary battery using this non-aqueous electrolyte for batteries.

Means for solving the above problems include the following aspects.
<1> Additive A which is at least one selected from the group consisting of boron compounds represented by the following formula (A);
An additive B that is at least one selected from the group consisting of lithium monofluorophosphate, lithium difluorophosphate, a compound represented by the following formula (X), and a compound represented by the following formula (Y);
An electrolyte that is a lithium salt other than lithium monofluorophosphate, lithium difluorophosphate, and the compound represented by the formula (Y);
A non-aqueous electrolyte for batteries containing

[In the formula (A), R represents an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, or a group represented by the formula (A1). In formula (A1), R ^{1 to} R ³ each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms. Represents. In formula (A1), * represents a bonding site with an oxygen atom in formula (A). ]

[In the formula (X), R ⁴ represents a hydrocarbon group having 1 to 6 carbon atoms, a hydrocarbon group having 1 to 6 carbon atoms substituted with at least one fluorine atom, or a hydrocarbon oxy group having 1 to 6 carbon atoms. Represents a hydrocarbon oxy group having 1 to 6 carbon atoms substituted with at least one fluorine atom, or a fluorine atom.
In formula (Y), R ⁵ represents a hydrocarbon group having 1 to 6 carbon atoms substituted with at least one fluorine atom, a hydrocarbon oxy group having 1 to 6 carbon atoms substituted with at least one fluorine atom, or Represents a fluorine atom. ]
<2> The nonaqueous electrolyte for battery according to <1>, wherein the content of the additive A is 0.001% by mass to 10% by mass with respect to the total amount of the nonaqueous electrolyte for battery.
<3> The battery nonaqueous electrolyte according to <1> or <2>, wherein the content of the additive B is 0.001% by mass to 10% by mass with respect to the total amount of the battery nonaqueous electrolyte. .
<4> The battery according to any one of <1> to <3>, further containing an additive C that is at least one selected from the group consisting of compounds represented by the following formula (C): Non-aqueous electrolyte.

[In Formula (C), Y ¹ and Y ² each independently represent a hydrogen atom, a methyl group, an ethyl group, or a propyl group. ]
<5> The nonaqueous electrolyte for battery according to <4>, wherein the content of the additive C is 0.001% by mass to 10% by mass with respect to the total amount of the nonaqueous electrolyte for battery.

<6> a positive electrode;
Lithium metal, lithium-containing alloys, metals or alloys that can be alloyed with lithium, oxides that can be doped / undoped with lithium ions, transition metal nitrides that can be doped / undoped with lithium ions, 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 ion doping and dedoping;
<1>-<5> any one of the battery non-aqueous electrolyte solutions,
Including lithium secondary battery.

<7> A lithium secondary battery obtained by charging and discharging the lithium secondary battery according to <6>.

  Provided are a nonaqueous electrolyte for a battery that can suppress an increase in battery resistance due to storage, and a lithium secondary battery using the nonaqueous electrolyte for a battery.

It is a schematic perspective view which shows an example of the laminate type battery which is an example of the lithium secondary battery of this indication. It is a schematic sectional drawing of the thickness direction of the laminated electrode body accommodated in the laminate type battery shown in FIG. It is a schematic sectional drawing which shows an example of the coin-type battery which is another example of the lithium secondary battery of this indication.

In this specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
In this specification, the amount of each component in the composition is the total amount of the plurality of substances present in the composition unless there is a specific indication when there are a plurality of substances corresponding to each component in the composition. Means.

[Non-aqueous electrolyte for batteries]
The non-aqueous electrolyte for battery of the present disclosure (hereinafter also simply referred to as “non-aqueous electrolyte”)
An additive A that is at least one selected from the group consisting of boron compounds represented by the following formula (A);
An additive B that is at least one selected from the group consisting of lithium monofluorophosphate, lithium difluorophosphate, a compound represented by the following formula (X), and a compound represented by the following formula (Y);
An electrolyte that is a lithium salt other than lithium monofluorophosphate, lithium difluorophosphate, and the compound represented by the formula (Y);
Containing.

In formula (A), R represents an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, or a group represented by formula (A1). In formula (A1), R ^{1 to} R ³ each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms. Represents. In formula (A1), * represents a bonding site with an oxygen atom in formula (A).

In formula (X), R ⁴ represents a hydrocarbon group having 1 to 6 carbon atoms, a hydrocarbon group having 1 to 6 carbon atoms substituted with at least one fluorine atom, a hydrocarbon oxy group having 1 to 6 carbon atoms, It represents a C 1-6 hydrocarbonoxy group substituted with at least one fluorine atom, or a fluorine atom.
In formula (Y), R ⁵ represents a hydrocarbon group having 1 to 6 carbon atoms substituted with at least one fluorine atom, a hydrocarbon oxy group having 1 to 6 carbon atoms substituted with at least one fluorine atom, or Represents a fluorine atom.

According to the nonaqueous electrolytic solution of the present disclosure, an increase in battery resistance due to storage can be suppressed.
Although the detailed mechanism of action for obtaining such an effect is unclear, the boron compound (additive A) represented by the above formula (A) is decomposed by initial charging to produce an oxalato structure ““ O— (C = O) ₂ -O. "Is generated, and this acts on the surface of the electrode (active material) to form an ion conduction path with high ion conductivity. Among the boron compounds, a boron compound having a structure represented by the above formula (A) (particularly, a boron compound having a substituent represented by the above formula (A1) from the viewpoint of easily generating an oxalato structure portion by decomposition. ) Is considered advantageous. In the boron compound represented by the above formula (A), an oxalato group and a group represented by R—O— are bonded to a boron atom as a substituent, and an asymmetric molecular structure centering on the boron atom. Therefore, since it is possible to cause an imbalance in the charge distribution in the molecule, among the boron compounds, it is easily decomposed by the initial charge, and the above action is considered to be effectively achieved.
In the nonaqueous electrolytic solution of the present disclosure, the presence of the additive B is considered to improve the durability during storage of the ion conduction path formed by the action of the decomposition product (oxalato structure part) of the additive A. . Thereby, it is considered that an increase in battery resistance due to storage is suppressed.

  Hereinafter, each component of the nonaqueous electrolytic solution of the present disclosure will be described.

<Additive A>
The nonaqueous electrolytic solution of the present disclosure contains additive A.
Additive A is at least one selected from the group consisting of boron compounds represented by formula (A).

In formula (A), R represents an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, or a group represented by formula (A1). In formula (A1), R ^{1 to} R ³ each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms. Represents. In formula (A1), * represents a bonding site with an oxygen atom in formula (A).

As a C1-C12 alkyl group represented by R, a C1-C10 alkyl group is more preferable, a C1-C8 alkyl group is still more preferable, and a C1-C6 alkyl group is further An alkyl group having 1 to 4 carbon atoms is more preferable.
Examples of the alkyl group include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, isopentyl group, and neopentyl group. Tert-pentyl group, n-hexyl group, isohexyl group, sec-hexyl group, tert-hexyl group, n-heptyl group, isoheptyl group, sec-heptyl group, tert-heptyl group, n-octyl group, isooctyl group, A sec-octyl group, a tert-octyl group, etc. are mentioned.
The C1-C12 alkyl group represented by R may be unsubstituted or substituted with a halogen atom (for example, a fluorine atom or a chlorine atom).

As a C2-C12 alkenyl group represented by R, a C2-C10 alkenyl group is more preferable, a C2-C8 alkenyl group is still more preferable, and a C2-C6 alkenyl group is further An alkenyl group having 2 to 4 carbon atoms is more preferable.
Examples of the alkenyl group include ethenyl group, propenyl group, butenyl group, pentenyl group, hexenyl group, heptenyl group, octenyl group and the like.
The alkenyl group having 2 to 12 carbon atoms represented by R may be unsubstituted or substituted with a halogen atom (for example, a fluorine atom or a chlorine atom).

R is preferably a group represented by the formula (A1). In the formula (A1), R ^{1 to} R ³ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, or an aryl having 6 to 12 carbon atoms. Represents a group.

Examples of the halogen atom represented by R ^{1 to} R ³ include a fluorine atom, a chlorine atom, and a bromine atom, and a fluorine atom is preferable.

Examples of the alkyl group having 1 to 12 carbon atoms represented by R ¹ to R ^3, and more preferably an alkyl group having 1 to 10 carbon atoms, more preferably an alkyl group having 1 to 8 carbon atoms, 1 to 6 carbon atoms An alkyl group is more preferable, an alkyl group having 1 to 4 carbon atoms is more preferable, and an alkyl group having 1 to 3 carbon atoms is further preferable.
Examples of the alkyl group include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, isopentyl group, and neopentyl group. Tert-pentyl group, n-hexyl group, isohexyl group, sec-hexyl group, tert-hexyl group, n-heptyl group, isoheptyl group, sec-heptyl group, tert-heptyl group, n-octyl group, isooctyl group, A sec-octyl group, a tert-octyl group, etc. are mentioned.
The alkyl group having 1 to 12 carbon atoms represented by R ^{1 to} R ³ may be unsubstituted or may be substituted with a halogen atom (for example, a fluorine atom or a chlorine atom).

The alkenyl group having 2 to 12 carbon atoms represented by R ¹ to R ^3, and more preferably an alkenyl group having 2 to 10 carbon atoms, more preferably an alkenyl group having 2 to 8 carbon atoms, having 2 to 6 carbon atoms An alkenyl group is more preferable, and an alkenyl group having 2 to 4 carbon atoms is more preferable.
Examples of the alkenyl group include ethenyl group, propenyl group, butenyl group, pentenyl group, hexenyl group, heptenyl group, octenyl group and the like.
The alkenyl group having 2 to 12 carbon atoms represented by R ^{1 to} R ³ may be unsubstituted or may be substituted with a halogen atom (for example, a fluorine atom or a chlorine atom).

The aryl group having 6 to 12 carbon atoms represented by R ^{1 to} R ³ is more preferably an aryl group having 6 to 10 carbon atoms.
Examples of the aryl group include a phenyl group, a group in which one hydrogen atom is removed from an alkylbenzene (for example, a benzyl group, a tolyl group, a xylyl group, a methicyl group, etc.), a naphthyl group, and a hydrogen atom from a substituted alkyl group of naphthalene. And the like, and the like.
The aryl group having 6 to 12 carbon atoms represented by R ^{1 to} R ³ may be unsubstituted or may be substituted with a halogen atom (for example, a fluorine atom or a chlorine atom).

In the formula ^(A1), at least one of R 1 to R ³ is an alkyl group, preferably an alkenyl group, or an aryl ^group, at least two R 1 to R ³ is an alkyl group, an alkenyl group, Or it is more preferable that it is an aryl group. In this case, preferred embodiments of the alkyl group, alkenyl group and aryl group are as described above, and among the alkyl group, alkenyl group and aryl group, the alkyl group is preferred.

  Specific examples of the boron compound represented by the formula (A) include the following exemplified compounds (1) to (26).

  The boron compound represented by the formula (A) can be synthesized, for example, by the method described in Chemische Berichte, Volume 68, Issue 6, Pages 1949-55, 1965.

The content of the additive A (boron compound represented by the formula (A)) is preferably 0.001% by mass to 10% by mass, and 0.01% by mass to 10% by mass with respect to the total amount of the nonaqueous electrolytic solution. % Is more preferable, 0.05% by mass to 5% by mass is further preferable, 0.1% by mass to 5% by mass is further preferable, 0.5% by mass to 5% by mass is further preferable, and 0.5% by mass to 0.5% by mass. 3 mass% is still more preferable, 0.5 mass%-2 mass% is still more preferable, and 0.5 mass%-1 mass% is still more preferable.
The boron compound represented by the general formula (A) may be used alone or in combination of two or more.

<Additive B>
The nonaqueous electrolytic solution of the present disclosure is at least one selected from the group consisting of lithium monofluorophosphate, lithium difluorophosphate, a compound represented by formula (X), and a compound represented by formula (Y). Additive B which is
One type of additive B may be used, or two or more types may be used.

(Lithium monofluorophosphate, lithium difluorophosphate)
The non-aqueous electrolyte of the present disclosure has at least one of lithium monofluorophosphate (Li ₂ PO ₃ F) and lithium difluorophosphate (LiPO ₂ F ₂ ) as additive B (hereinafter referred to as “lithium fluorophosphate”). May be included).
When the nonaqueous electrolytic solution of the present disclosure contains lithium fluorophosphate as the additive B, the additive B preferably contains lithium difluorophosphate.

(Compound represented by Formula (X))
The nonaqueous electrolytic solution of the present disclosure may contain a compound represented by the following formula (X) as the additive B.
When the nonaqueous electrolytic solution of the present disclosure contains a compound represented by the following formula (X) as the additive B, the compound represented by the following formula (X) may be only one type, Two or more types may be used.

In formula (X), R ⁴ represents a hydrocarbon group having 1 to 6 carbon atoms, a hydrocarbon group having 1 to 6 carbon atoms substituted with at least one fluorine atom, a hydrocarbon oxy group having 1 to 6 carbon atoms, It represents a C 1-6 hydrocarbonoxy group substituted with at least one fluorine atom, or a fluorine atom.

The “C 1-6 hydrocarbon group” represented by R ⁴ represents an unsubstituted C 1-6 hydrocarbon group.
The “C1-C6 hydrocarbon group” represented by R ⁴ may be a linear hydrocarbon group, a branched hydrocarbon group, or a cyclic hydrocarbon group.
The “C 1-6 hydrocarbon group” represented by R ⁴ is preferably an alkyl group or an alkenyl group, and more preferably an alkyl group.
Carbon number of represented by R ⁴ "hydrocarbon group having 1 to 6 carbon atoms", 1-3, more preferably 1 or 2, 1 is particularly preferred.

Examples of the “C 1-6 hydrocarbon group” represented by R ⁴ include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, Alkyl groups such as pentyl group, 2-methylbutyl group, 1-methylpentyl group, neopentyl group, 1-ethylpropyl group, hexyl group, 3,3-dimethylbutyl 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 group, 1-methyl-2-propenyl group, 2-methyl-1-propenyl group And the like.

As "the at least one hydrocarbon group with a 1 to 6 carbon atoms substituted with a fluorine atom" represented by R ^4, the "hydrocarbon group having 1 to 6 carbon atoms" represented by R ⁴ in the above (i.e. And an unsubstituted hydrocarbon group having 1 to 6 carbon atoms) is substituted with at least one fluorine atom.

Examples of the “C 1-6 hydrocarbon group substituted with at least one fluorine atom” represented by R ⁴ include a fluoromethyl group, a difluoromethyl group, a trifluoromethyl group, 2,2,2- Fluoroalkyl groups such as trifluoroethyl group, perfluoroethyl group, perfluoropropyl group, perfluorobutyl group, perfluoropentyl group, perfluorohexyl group, perfluoroisopropyl group, perfluoroisobutyl group; 2-fluoroethenyl Group, 2,2-difluoroethenyl group, 2-fluoro-2-propenyl group, 3,3-difluoro-2-propenyl group, 2,3-difluoro-2-propenyl group, 3,3-difluoro-2- Methyl-2-propenyl group, 3-fluoro-2-butenyl group, perfluorovinyl group, perfluoropropene And fluoroalkenyl groups such as a nyl group and a perfluorobutenyl group.

Wherein (X), part of the hydrocarbon group in the structure of the "hydrocarbon group having 1 to 6 carbon atoms" represented by R ⁴ is represented by R ⁴ in the aforementioned "1 to 6 carbon atoms It is synonymous with “hydrocarbon group”.
As the “hydrocarbon oxy group having 1 to 6 carbon atoms” represented by R ⁴ , an alkoxy group or an alkenyloxy group is preferable, and an alkoxy group is more preferable.

Examples of the “hydrocarbon oxy group having 1 to 6 carbon atoms” represented by R ⁴ include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, an n-butoxy group, a 2-butoxy group, and a tert-butoxy group. And alkoxy groups such as cyclopropyloxy group and cyclopentyloxy group; alkenyloxy groups such as allyloxy group and vinyloxy group;

Formula (X), examples of the "at least one hydrocarbon group having been 1 to 6 carbon atoms substituted with a fluorine atom" represented by R ^4, "1 to 6 carbon atoms represented by R ⁴ described above Group having a structure in which the “hydrocarbon oxy group” (that is, the unsubstituted hydrocarbon oxy group having 1 to 6 carbon atoms) is substituted with at least one fluorine atom.

In formula (X), R ⁴ represents a hydrocarbon group having 1 to 6 carbon atoms (that is, an unsubstituted hydrocarbon group having 1 to 6 carbon atoms), or a carbon number substituted with at least one fluorine atom. A hydrocarbon group having 1 to 6 carbon atoms is preferable, a hydrocarbon group having 1 to 6 carbon atoms is more preferable, and an alkyl group having 1 to 6 carbon atoms is particularly preferable.

As a compound represented by the formula (X),
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-propene-1-sulfonyl fluoride, or 2-propene-1-sulfonyl fluoride,
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,
More preferred is methanesulfonyl fluoride, ethanesulfonyl fluoride, propanesulfonyl fluoride, 2-propanesulfonyl fluoride, butanesulfonyl fluoride, 2-butanesulfonyl fluoride, or hexanesulfonyl fluoride,
More preferred is methanesulfonyl fluoride, ethanesulfonyl fluoride, or propanesulfonyl fluoride,
Methanesulfonyl fluoride is particularly preferred.

(Compound represented by Formula (Y))
The nonaqueous electrolytic solution of the present disclosure may contain a compound represented by the following formula (Y) as the additive B.
When the nonaqueous electrolytic solution of the present disclosure contains a compound represented by the following formula (Y) as the additive B, the compound represented by the following formula (Y) may be only one type, Two or more types may be used.

In formula (Y), R ⁵ represents a hydrocarbon group having 1 to 6 carbon atoms substituted with at least one fluorine atom, a hydrocarbon oxy group having 1 to 6 carbon atoms substituted with at least one fluorine atom, or Represents a fluorine atom.

In the formula (Y), “the hydrocarbon group having 1 to 6 carbon atoms substituted by at least one fluorine atom” represented by R ⁵ is “at least represented by R ⁴ in the above-described formula (X)”. It is synonymous with a “C1-C6 hydrocarbon group substituted with one fluorine atom”.
In the formula (Y), “the hydrocarbon oxy group having 1 to 6 carbon atoms substituted by at least one fluorine atom” represented by R ⁵ is represented by R ⁴ in the above-described formula (X). It is synonymous with “a hydrocarbon oxy group having 1 to 6 carbon atoms substituted with at least one fluorine atom”.

In formula (Y), R ⁵ is preferably a hydrocarbon group having 1 to 6 carbon atoms substituted with at least one fluorine atom, and an alkyl group having 1 to 6 carbon atoms substituted with at least one fluorine atom. More preferably, a C1-C6 perfluoroalkyl group is still more preferable, a perfluoromethyl group (alias: trifluoromethyl group) or a perfluoroethyl group (alias: pentafluoroethyl group) is still more preferred, and a perfluoromethyl group (Alternative name: trifluoromethyl group) is particularly preferred.

  The compound represented by the formula (Y) preferably includes at least one selected from the group consisting of lithium trifluoromethanesulfonate and lithium pentafluoroethanesulfonate, and lithium trifluoromethanesulfonate is particularly preferable.

  The content of the additive B is preferably 0.001% by mass to 10% by mass, more preferably 0.01% by mass to 10% by mass, and more preferably 0.05% by mass to 5% by mass with respect to the total amount of the nonaqueous electrolytic solution. % By mass is more preferable, 0.1% by mass to 5% by mass is further preferable, 0.5% by mass to 5% by mass is further preferable, 0.5% by mass to 3% by mass is further preferable, and 0.5% by mass. -2 mass% is still more preferable, and 0.5 mass%-1 mass% is still more preferable.

<Electrolyte>
The non-aqueous electrolyte of the present disclosure includes an electrolyte that is a lithium salt other than the compound represented by the above formula (Y) and lithium monofluorophosphate, lithium difluorophosphate (hereinafter also referred to as “specific lithium salt”). contains.
The specific lithium salt as the electrolyte may be only one kind or two or more kinds.

Specific examples of the specific lithium salt include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , Li ₂ SiF ₆ , LiPF _n [C _k F _{(2k + 1)} ] _(6-n) (n = 1 to 5, k = Lithium salt such as an integer of 1 to 8.
Moreover, the lithium salt represented by the following general formula can also be used.

_{^{LiC (SO 2 R 27) (}} SO 2 R 28) (SO 2 R 29), LiN (SO 2 OR 30) (SO 2 OR 31), LiN (SO 2 R 32) (SO 2 R 33) ( where R ^{27 to} R ³³ may be the same as or different from each other, and are a C 1-8 perfluoroalkyl group). These electrolytes may be used alone or in combination of two or more.

The specific lithium salt preferably includes at least one of LiPF ₆ and LiBF ₄ , and more preferably includes LiPF ₆ .
If a particular lithium salt containing LiPF _6, the proportion of LiPF ₆ occupied in particular the lithium salt is preferably from 10 wt% to 100 wt%, more preferably from 50 wt% to 100 wt%, 70 wt% to 100 wt% Is particularly preferred.

  The concentration of the electrolyte in the nonaqueous electrolytic solution is preferably 0.1 mol / L to 3 mol / L, and more preferably 0.5 mol / L to 2 mol / L.

<Additive C>
The non-aqueous electrolyte of the present disclosure may contain an additive C that is a compound represented by the following formula (C).
When the nonaqueous electrolytic solution of the present disclosure contains the additive C, the effect of the combination of the additive A and the additive B is more effectively exhibited.
The additive C may be only one selected from the group consisting of compounds represented by the following formula (C), or may be two or more.

In formula (C), Y ¹ and Y ² each independently represent a hydrogen atom, a methyl group, an ethyl group, or a propyl group.
Examples of the compound represented by the formula (C) include vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, propyl vinylene carbonate, dimethyl vinylene carbonate, diethyl vinylene carbonate, and dipropyl vinylene carbonate. Of these, vinylene carbonate is most preferred.

  The content of the additive C (compound represented by the formula (C)) is preferably 0.001% by mass to 10% by mass, and 0.01% by mass to 10% by mass with respect to the total amount of the nonaqueous electrolytic solution. Is more preferable, 0.05% by mass to 5% by mass is further preferable, 0.1% by mass to 5% by mass is further preferable, 0.5% by mass to 5% by mass is further preferable, and 0.5% by mass to 3% by mass. % By mass is more preferable, 0.5% by mass to 2% by mass is further preferable, and 0.5% by mass to 1% by mass is further preferable.

<Other additives>
The nonaqueous electrolytic solution of the present disclosure may contain an additive other than the additive A, the additive B, and the additive C (also referred to as “other additive” in the present specification).
When the nonaqueous electrolytic solution of the present disclosure contains other additives, the other additives contained may be only one kind or two or more kinds.
Other additives include oxalato compounds (excluding additive A), fluorophosphate compounds (except lithium monofluorophosphate and lithium difluorophosphate), carbonate compounds having a carbon-carbon unsaturated bond (However, the additive C is excluded) At least one selected from the group consisting of a carbonate compound having a fluorine atom, a cyclic sultone compound, and a cyclic sulfate compound is preferable.

(Oxalato compound)
Oxalato compounds (excluding Additive A) include difluorobis (oxalato) lithium phosphate, tetrafluoro (oxalato) lithium phosphate, tris (oxalato) lithium phosphate, difluoro (oxalato) lithium borate, bis ( Oxalato) lithium borate and the like. Of these, preferred is lithium difluorobis (oxalato) phosphate, lithium tetrafluoro (oxalato) phosphate, or lithium bis (oxalato) borate.

(Fluorophosphate compound)
Fluorophosphoric acid compounds (excluding lithium monofluorophosphate and lithium difluorophosphate) include difluorophosphoric acid, monofluorophosphoric acid, methyl difluorophosphate, ethyl difluorophosphate, dimethyl fluorophosphate, and fluorophosphoric acid Examples include diethyl.

(Carbonate compound having a carbon-carbon unsaturated bond)
Carbonate compounds having a carbon-carbon unsaturated bond (excluding additive C) include methyl vinyl carbonate, ethyl vinyl carbonate, divinyl carbonate, methyl propynyl carbonate, ethyl propynyl carbonate, dipropynyl carbonate, methyl phenyl carbonate, and ethyl. Chain carbonates such as phenyl carbonate and diphenyl carbonate; vinyl ethylene carbonate, 4,4-divinyl ethylene carbonate, 4,5-divinyl ethylene carbonate, ethynyl ethylene carbonate, 4,4-diethynyl ethylene carbonate, 4,5-di Ethynyl ethylene carbonate, propynyl ethylene carbonate, 4,4-dipropynyl ethylene carbonate, 4,5-dipropynyl ethylene car Cyclic carbonates such as sulfonate; and the like. Of these, methyl phenyl carbonate, ethyl phenyl carbonate, diphenyl carbonate, vinyl ethylene carbonate, 4,4-divinyl ethylene carbonate, or 4,5-divinyl ethylene carbonate is preferable, and vinyl ethylene carbonate is more preferable. .

(Carbonate compound having fluorine atom)
Examples of the carbonate compound having a fluorine atom include methyl trifluoromethyl carbonate, ethyl trifluoromethyl carbonate, bis (trifluoromethyl) carbonate, methyl (2,2,2-trifluoroethyl) carbonate, ethyl (2,2,2). -Chain carbonates such as trifluoroethyl) carbonate and bis (2,2,2-trifluoroethyl) carbonate; 4-fluoroethylene carbonate, 4,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4 -Cyclic carbonates such as trifluoromethylethylene carbonate; Of these, 4-fluoroethylene carbonate, 4,4-difluoroethylene carbonate, or 4,5-difluoroethylene carbonate is preferable.

(Cyclic sultone compound)
Examples of cyclic sultone compounds include 1,3-propane sultone, 1,4-butane sultone, 1,3-propene sultone, 1-methyl-1,3-propene sultone, 2-methyl-1,3-propene sultone, 3- Examples include sultone such as methyl-1,3-propene sultone. Of these, 1,3-propane sultone or 1,3-propene sultone is preferable.

(Cyclic sulfate compound)
As the cyclic sulfate compound, a compound represented by the following formula (I) is preferable.

In formula (I), R ¹ and R ² are each independently represented by a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a phenyl group, a group represented by formula (II), or formula (III). Represents a group, or R ¹ and R ² together represent a group that forms a benzene ring or a cyclohexyl ring together with the carbon atom to which R ¹ is bonded and the carbon atom to which R ² is bonded.
In formula (II), R ³ is represented by a halogen atom, an alkyl group having 1 to 6 carbon atoms, a halogenated alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or formula (IV). Represents a group. The wavy line in formula (II), formula (III), and formula (IV) represents the bonding position.
When two groups represented by the formula (II) are contained in the compound represented by the formula (I), the two groups represented by the formula (II) may be the same or different from each other. Also good.

In formula (II), examples of the “halogen atom” include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
As the halogen atom, a fluorine atom is preferable.

In the formulas (I) and (II), “an alkyl group having 1 to 6 carbon atoms” is a linear or branched alkyl group having 1 to 6 carbon atoms, and includes a methyl group, an ethyl group, and a propyl group. Group, isopropyl group, butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group, 2-methylbutyl group, 1-methylpentyl group, neopentyl group, 1-ethylpropyl group, hexyl group, 3, 3 -A dimethylbutyl group etc. are mentioned as a specific example.
As a C1-C6 alkyl group, a C1-C3 alkyl group is more preferable.

In the formula (II), the “halogenated alkyl group having 1 to 6 carbon atoms” is a linear or branched halogenated alkyl group having 1 to 6 carbon atoms, such as a fluoromethyl group, a difluoromethyl group, Trifluoromethyl group, 2,2,2-trifluoroethyl group, perfluoroethyl group, perfluoropropyl group, perfluorobutyl group, perfluoropentyl group, perfluorohexyl group, perfluoroisopropyl group, perfluoroisobutyl group Specific examples include chloromethyl group, chloroethyl group, chloropropyl group, bromomethyl group, bromoethyl group, bromopropyl group, methyl iodide group, ethyl iodide group, and propyl iodide group.
As the halogenated alkyl group having 1 to 6 carbon atoms, a halogenated alkyl group having 1 to 3 carbon atoms is more preferable.

In the formula (II), the “C1-C6 alkoxy group” is a linear or branched alkoxy group having 1 to 6 carbon atoms, and includes a methoxy group, an ethoxy group, a propoxy group, and an isopropoxy group. Group, butoxy group, isobutoxy group, sec-butoxy group, tert-butoxy group, pentyloxy group, 2-methylbutoxy group, 1-methylpentyloxy group, neopentyloxy group, 1-ethylpropoxy group, hexyloxy group, Specific examples include 3,3-dimethylbutoxy group.
As a C1-C6 alkoxy group, a C1-C3 alkoxy group is more preferable.

In a preferred embodiment of formula (I), R ¹ is a group represented by formula (II) (in formula (II), R ³ is a fluorine atom, an alkyl group having 1 to 3 carbon atoms, or 1 to 3 carbon atoms. A halogenated alkyl group, an alkoxy group having 1 to 3 carbon atoms, or a group represented by formula (IV).) Or a group represented by formula (III), and R ² is , A hydrogen atom, an alkyl group having 1 to 3 carbon atoms, a group represented by formula (II), or a group represented by formula (III), or R ¹ and R ² are combined, In this embodiment, R ¹ is a group that forms a benzene ring or a cyclohexyl ring together with the carbon atom to which R ¹ is bonded and the carbon atom to which R ² is bonded.

More preferably, R ² in formula (I) is a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a group represented by formula (II) (in formula (II), R ³ is a fluorine atom, carbon It is more preferably a C 1-3 alkyl group, a C 1-3 halogenated alkyl group, a C 1-3 alkoxy group, or a group represented by the formula (IV). And a group represented by (III), more preferably a hydrogen atom or a methyl group.

When R ¹ in formula (I) is a group represented by formula (II), R ³ in formula (II) is a halogen atom, an alkyl group having 1 to 6 carbon atoms, or 1 carbon atom as described above. A halogenated alkyl group of ˜6, an alkoxy group of 1 to 6 carbon atoms, or a group represented by the formula (IV), more preferably as R ³ , a fluorine atom, an alkyl group of 1 to 3 carbon atoms, A halogenated alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or a group represented by the formula (IV), more preferably a fluorine atom, a methyl group, an ethyl group, or trifluoromethyl. A group, a methoxy group, an ethoxy group, or a group represented by the formula (IV).
When R ² in formula (I) is a group represented by formula (II), R ¹ in formula (I) is preferably represented by formula (II) for the preferred range of R ³ in formula (II). This is the same as the preferred range of R ³ in the case of the represented group.

As a preferable combination of R ¹ and R ² in formula (I), R ¹ is a group represented by formula (II) (in formula (II), R ³ is a fluorine atom, an alkyl group having 1 to 3 carbon atoms. A halogenated alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or a group represented by formula (IV)), or a group represented by formula (III) , R ² is a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, a group represented by formula (II) (in formula (II), R ³ is a fluorine atom, an alkyl group having 1 to 3 carbon atoms, or a carbon number A halogenated alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or a group represented by formula (IV).), Or a combination of groups represented by formula (III) is there.
As a more preferable combination of R ¹ and R ² in the formula (I), R ¹ is a group represented by the formula (II) (in the formula (II), R ³ is a fluorine atom, a methyl group, an ethyl group, trifluoro A methyl group, a methoxy group, an ethoxy group, or a group represented by formula (IV)) or a group represented by formula (III), and a combination in which R ² is a hydrogen atom or a methyl group. is there.

  Regarding the compound represented by the formula (I), the description in paragraphs 0040 to 0070 of International Publication No. 2012/053644 can be appropriately referred to.

  When the non-aqueous electrolyte of the present disclosure contains other additives, the content (the total content in the case of two or more) is not particularly limited, but the effect of the present disclosure is more effective. From the viewpoint of performance, it is preferably 0.001% by mass to 10% by mass, more preferably 0.05% by mass to 5% by mass, and 0.1% by mass with respect to the total amount of the non-aqueous electrolyte. % To 4% by mass is more preferable, 0.1% to 2% by mass is further preferable, and 0.1% to 1% by mass is particularly preferable.

<Nonaqueous solvent>
A non-aqueous electrolyte generally contains a non-aqueous solvent.
Various known solvents can be appropriately selected as the non-aqueous solvent, but at least one selected from a cyclic aprotic solvent and a chain aprotic solvent is preferably used.

  In order to improve the safety of the battery, when aiming to improve the flash point of the solvent, it is preferable to use a cyclic aprotic solvent as the non-aqueous solvent.

(Cyclic aprotic solvent)
As the cyclic aprotic solvent, cyclic carbonate, cyclic carboxylic acid ester, cyclic sulfone, and cyclic ether can be used.

The cyclic aprotic solvent may be used alone or in combination of two or more.
The mixing ratio of the cyclic aprotic solvent in the non-aqueous solvent is 10% by mass to 100% by mass, more preferably 20% by mass to 90% by mass, and particularly preferably 30% by mass to 80% by mass. By setting it as such a ratio, the electroconductivity of the electrolyte solution relating to the charge / discharge characteristics of the battery can be increased.

  Specific examples of the cyclic carbonate 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 having a high dielectric constant are preferably used. In the case of a battery using graphite as the negative electrode active material, ethylene carbonate is more preferable. Moreover, you may use these cyclic carbonates in mixture of 2 or more types.

  Specific examples of the cyclic carboxylic acid ester include γ-butyrolactone, δ-valerolactone, alkyl substitution products such as methyl γ-butyrolactone, ethyl γ-butyrolactone, and ethyl δ-valerolactone.

  The cyclic carboxylic acid ester has a low vapor pressure, a low viscosity, a high dielectric constant, and can lower the viscosity of the electrolytic solution without lowering the degree of dissociation between the flash point of the electrolytic solution and the electrolyte. For this reason, since it has the feature that the conductivity of the electrolytic solution, which is an index related to the discharge characteristics of the battery, can be increased without increasing the flammability of the electrolytic solution, when aiming to improve the flash point of the solvent, It is preferable to use a cyclic carboxylic acid ester as the cyclic aprotic solvent. Of the cyclic carboxylic acid esters, γ-butyrolactone is most preferred.

  The cyclic carboxylic acid ester is preferably used by mixing with another cyclic aprotic solvent. For example, a mixture of a cyclic carboxylic acid ester and a cyclic carbonate and / or a chain carbonate can be mentioned.

Examples of the cyclic sulfone include sulfolane, 2-methylsulfolane, 3-methylsulfolane, dimethyl sulfone, diethyl sulfone, dipropyl sulfone, methylethyl sulfone, methylpropyl sulfone and the like.
An example of a cyclic ether is dioxolane.

(Chain aprotic solvent)
As the chain aprotic solvent, a chain carbonate, a chain carboxylic acid ester, a chain ether, a chain phosphate, or the like can be used.

  The mixing ratio of the chain aprotic solvent in the non-aqueous solvent is 10% by mass to 100% by mass, more preferably 20% by mass to 90% by mass, and particularly preferably 30% by mass to 80% by mass.

  Specific examples of the chain carbonate include 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, Examples include ethyl pentyl 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, dioctyl carbonate, and methyltrifluoroethyl carbonate. These chain carbonates may be used as a mixture of two or more.

Specific examples of the chain carboxylic acid ester include methyl pivalate.
Specific examples of the chain ether include dimethoxyethane.
Specific examples of the chain phosphate ester include trimethyl phosphate.

(Solvent combination)
The nonaqueous solvent used in the nonaqueous electrolytic solution of the present disclosure may be used alone or in combination. Further, only one or more types of cyclic aprotic solvents may be used, or only one or more types of chain aprotic solvents may be used, or cyclic aprotic solvents and chain proticity may be used. You may mix and use a solvent. When the load characteristics and low temperature characteristics of the battery are particularly intended to be improved, it is preferable to use a combination of a cyclic aprotic solvent and a chain aprotic solvent as the nonaqueous solvent.

  Furthermore, in view of the electrochemical stability of the electrolytic solution, it is most preferable to apply a cyclic carbonate to the cyclic aprotic solvent and a chain carbonate to the chain aprotic solvent. Further, the conductivity of the electrolytic solution related to the charge / discharge characteristics of the battery can be increased by a combination of the cyclic carboxylic acid ester and the cyclic carbonate and / or the chain carbonate.

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

  The mixing ratio of the cyclic carbonate and the chain carbonate is expressed by mass ratio, and the cyclic carbonate: chain carbonate is 5:95 to 80:20, more preferably 10:90 to 70:30, and particularly preferably 15:85. ~ 55: 45. By setting it as such a ratio, since the raise of the viscosity of electrolyte solution can be suppressed and the dissociation degree of electrolyte can be raised, the conductivity of the electrolyte solution in connection with the charge / discharge characteristic of a battery can be raised. In addition, the solubility of the electrolyte can be further increased. Therefore, since it can be set as the electrolyte solution excellent in the electrical conductivity in normal temperature or low temperature, the load characteristic of the battery from normal temperature to low temperature can be improved.

  Specific examples of combinations of cyclic carboxylic acid esters and cyclic carbonates and / or chain carbonates include γ-butyrolactone and ethylene carbonate, γ-butyrolactone and ethylene carbonate and dimethyl carbonate, and γ-butyrolactone and ethylene carbonate and methylethyl. Carbonate, γ-butyrolactone and ethylene carbonate and diethyl carbonate, γ-butyrolactone and propylene carbonate, γ-butyrolactone and propylene carbonate and dimethyl carbonate, γ-butyrolactone and propylene carbonate and methyl ethyl carbonate, γ-butyrolactone and propylene carbonate and diethyl carbonate, γ-butyrolactone, ethylene carbonate, propylene carbonate, γ-butyrolactone, Tylene carbonate and propylene carbonate and dimethyl carbonate, γ-butyrolactone and ethylene carbonate, propylene carbonate and methyl ethyl carbonate, γ-butyrolactone, ethylene carbonate, propylene carbonate and diethyl carbonate, γ-butyrolactone, ethylene carbonate, dimethyl carbonate and methyl ethyl carbonate, γ-butyrolactone, ethylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, ethylene carbonate, methyl ethyl carbonate, diethyl carbonate, γ-butyrolactone, ethylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, γ-butyrolactone, ethylene carbonate And professional Ren carbonate, dimethyl carbonate and methyl ethyl carbonate, γ-butyrolactone, ethylene carbonate, propylene carbonate, dimethyl carbonate and diethyl carbonate, γ-butyrolactone, ethylene carbonate, propylene carbonate, methyl ethyl carbonate and diethyl carbonate, γ-butyrolactone and ethylene carbonate Propylene carbonate, dimethyl carbonate, methyl ethyl carbonate and diethyl carbonate, γ-butyrolactone and sulfolane, γ-butyrolactone and ethylene carbonate and sulfolane, γ-butyrolactone and propylene carbonate and sulfolane, γ-butyrolactone, ethylene carbonate, propylene carbonate and sulfolane, γ -Butyrolactone and sul Such as orchids and dimethyl carbonate.

(Other solvents)
Examples of the non-aqueous solvent include other solvents other than those described above.
Specific examples of other solvents include amides such as dimethylformamide, chain carbamates such as methyl-N, N-dimethylcarbamate, cyclic amides such as N-methylpyrrolidone, N, N-dimethylimidazolidinone, and the like. Examples thereof include boron compounds such as cyclic urea, trimethyl borate, triethyl borate, tributyl borate, trioctyl borate, trimethylsilyl borate, and polyethylene glycol derivatives represented by the following general formula.
HO (CH ₂ CH ₂ O) _a H
HO [CH ₂ CH (CH ₃ ) O] _b H
CH ₃ O (CH ₂ CH ₂ O) _c H
CH ₃ O [CH ₂ CH (CH ₃ ) O] _d H
CH ₃ O (CH ₂ CH ₂ O) _e CH ₃
CH ₃ O [CH ₂ CH (CH ₃ ) O] _f CH _{3
C 9 H 19 PhO (CH 2} CH 2 O) g [CH (CH 3) O] h CH 3
(Ph is a phenyl group)
CH ₃ O [CH ₂ CH (CH ₃ ) O] _i CO [OCH (CH ₃ ) CH ₂ ] _j OCH ₃
In the above formula, a to f are integers of 5 to 250, g to j are integers of 2 to 249, 5 ≦ g + h ≦ 250, and 5 ≦ i + j ≦ 250.

  The non-aqueous electrolyte of the present disclosure 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, and an electric double layer capacitor. It can also be used as an electrolytic solution for aluminum electrolytic capacitors.

[Lithium secondary battery]
The lithium secondary battery of the present disclosure includes a positive electrode, a negative electrode, and the nonaqueous electrolytic solution of the present disclosure.

(Negative electrode)
The negative electrode may include a negative electrode active material and a negative electrode current collector.
The negative electrode active material in the negative electrode is metal lithium, lithium-containing alloy, metal or alloy that can be alloyed with lithium, oxide that can be doped / undoped with lithium ions, and lithium ion doped / undoped At least one selected from the group consisting of transition metal nitrides and carbon materials capable of doping and undoping lithium ions (may be used alone or a mixture containing two or more of these may be used) Good) can be used.
Examples of metals or alloys that can be alloyed with lithium (or lithium ions) include silicon, silicon alloys, tin, and tin alloys. Further, lithium titanate may be used.
Among these, carbon materials that can be doped / undoped with lithium ions are preferable. Examples of such carbon materials include carbon black, activated carbon, graphite materials (artificial graphite, natural graphite), amorphous carbon materials, and the like. 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 less, and mesophase pitch carbon fiber (MCF).
Examples of the graphite material include natural graphite and artificial graphite. As artificial graphite, graphitized MCMB, graphitized MCF, and the like are used. Further, as the graphite material, a material containing boron can be used. As the graphite material, those coated with a metal such as gold, platinum, silver, copper and tin, those coated with amorphous carbon, and those obtained by mixing amorphous carbon and graphite can 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 (002) plane distance d (002) of 0.340 nm or less as measured by X-ray analysis 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. When the carbon material as described above is used, the energy density of the battery can be further increased.

There is no restriction | limiting in particular in the material of the negative electrode electrical power collector in a negative electrode, A well-known thing can be used arbitrarily.
Specific examples of the negative electrode current collector include metal materials such as copper, nickel, stainless steel, and nickel-plated steel. Among these, 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 , LiNi _X Co _(1-X) O ₂ [0 <X <1], Li _{1 + α} Me _1-α O ₂ having an 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, LiNi _0.33 Co _0.33 Mn _0.33 O ₂ , LiNi _0.5 Co _0.2 Mn _0.3 O _2, etc.), LiFePO ₄ , LiMnPO ₄ and other complex oxides composed of lithium and transition metals, 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.
A positive electrode active material may be used by 1 type, and may mix and use 2 or more types. When the positive electrode active material has insufficient conductivity, it can be used together with a conductive auxiliary agent to constitute a positive electrode. Examples of the conductive assistant include carbon materials such as carbon black, amorphous whiskers, and graphite.

There is no restriction | limiting in particular in the material of the positive electrode electrical power collector in a positive electrode, A well-known thing can be used arbitrarily.
Specific examples of the positive electrode current collector include 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.
A microporous polymer film is preferably used as the porous film, and examples of the material include polyolefin, polyimide, polyvinylidene fluoride, and polyester.
In particular, porous polyolefin is preferable. Specifically, a porous polyethylene film, a porous polypropylene film, or a multilayer film of a porous polyethylene film and a polypropylene film can be exemplified. On the porous polyolefin film, other resin excellent in thermal stability may be coated.
Examples of the polymer electrolyte include a polymer in which a lithium salt is dissolved, a polymer swollen with an electrolytic solution, and the like.
The nonaqueous electrolytic solution 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.

As an example of the lithium secondary battery (nonaqueous electrolyte secondary battery) of the present disclosure, a laminate type battery can be given.
FIG. 1 is a schematic perspective view showing an example of a laminated battery that is an example of the lithium secondary battery of the present disclosure, and FIG. 2 shows the thickness of the laminated electrode body accommodated in the laminated battery shown in FIG. It is a schematic sectional drawing of a direction.
The laminate type 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) inside, and the periphery is sealed. The laminate outer package 1 is sealed inside. As the laminate exterior body 1, for example, an aluminum laminate exterior body is used.
As shown in FIG. 2, the laminated electrode body accommodated in the laminate outer package 1 includes a laminated body in which positive plates 5 and negative plates 6 are alternately laminated with separators 7 interposed therebetween. And a separator 8 surrounding the periphery. The positive electrode plate 5, the negative electrode plate 6, the separator 7, and the separator 8 are impregnated with the nonaqueous electrolytic solution of the present disclosure.
The plurality of positive electrode plates 5 in the laminated electrode body are all electrically connected to the positive electrode terminal 2 via a positive electrode tab (not shown), and a part of the positive electrode terminal 2 is part of the laminate outer package 1. 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 outer package 1 is sealed with an insulating seal 4.
Similarly, each of the plurality of negative electrode plates 6 in the laminated electrode body is electrically connected to the negative electrode terminal 3 through a negative electrode tab (not shown), and a part of the negative electrode terminal 3 is part of the laminate exterior. It protrudes outward from the peripheral edge of the body 1 (FIG. 1). The portion where the negative electrode terminal 3 protrudes at the peripheral end of the laminate outer package 1 is sealed with an insulating seal 4.
In the laminate type battery according to the above example, the number of the positive plates 5 is 5 and the number of the negative plates 6 is 6, and the positive plates 5 and the negative plates 6 are separated from each other through the separators 7. All the outer layers are laminated in an arrangement to be the negative electrode plate 6. However, it is needless to say that the number of positive plates, the number of negative plates, and the arrangement in the laminated battery are not limited to this example, and various changes may be made.

As another example of the lithium secondary battery of the present disclosure, a coin-type battery is also included.
FIG. 3 is a schematic perspective view illustrating an example of a coin-type battery that is another example of the lithium secondary battery of the present disclosure.
In the coin-type battery shown in FIG. 3, a disc-shaped negative electrode 12, a separator 15 into which a non-aqueous electrolyte is injected, a disc-shaped positive electrode 11, and spacer plates 17 and 18 such as stainless steel or aluminum as necessary are arranged in this order. In a laminated state, the positive electrode can 13 (hereinafter also referred to as “battery can”) and a sealing plate 14 (hereinafter also referred to as “battery can lid”) are accommodated. The positive electrode can 13 and the sealing plate 14 are caulked and sealed via a gasket 16.
In this example, the nonaqueous electrolytic solution of the present disclosure is used as the nonaqueous electrolytic solution injected into the separator 15.

In addition, the lithium secondary battery of this indication is obtained by charging / discharging a lithium secondary battery (lithium secondary battery before charging / discharging) containing a negative electrode, a positive electrode, and the non-aqueous electrolyte of the said indication. Lithium secondary batteries may be used.
That is, a lithium secondary battery according to the present disclosure is prepared by first preparing a lithium secondary battery before charge / discharge including a negative electrode, a positive electrode, and the non-aqueous electrolyte according to the present disclosure, and then, before the charge / discharge. It may be a lithium secondary battery (charged / discharged lithium secondary battery) produced by charging / discharging the lithium secondary battery one or more times.

  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 notebooks, calculators, radios, backup power applications, motors, automobiles, electric cars, motorcycles, electric bikes, bicycles, electric motors Bicycles, lighting fixtures, game machines, watches, electric tools, cameras, etc. can be widely used regardless of small portable devices or large devices.

Examples of the present disclosure will be described below, but the present disclosure is not limited to the following examples.
In the following examples, “addition amount” represents the content in the finally obtained non-aqueous electrolyte (that is, the amount relative to the total amount of the finally obtained non-aqueous electrolyte).
“Wt%” means mass%.

[Example 1]
A coin-type battery (test battery), which is a lithium secondary battery, was produced by the following procedure.
<Production of negative electrode>
98 parts by mass of natural graphite, 1 part by mass of carboxymethylcellulose and 1 part by mass of a binder were kneaded with an aqueous solvent to prepare a paste-like negative electrode mixture slurry.
Next, this negative electrode mixture slurry was applied to a negative electrode current collector made of a strip-shaped copper foil having a thickness of 10 μm, dried, and then compressed by a roll press to form a sheet-like material comprising a negative electrode current collector and a negative electrode active material layer. A negative electrode was obtained. The coating density of the negative electrode active material layer at this time was 10 mg / cm ² , and the packing density was 1.5 g / ml.

<Preparation of positive electrode>
92 parts by mass of LiNi _0.5 Mn _0.3 Co _0.2 O ₂ , 2.5 parts by mass of acetylene black, 2.5 parts by mass of polyvinylidene fluoride and 3 parts by mass of a binder, N-methylpyrrolidinone as a solvent As a result, a paste-like positive electrode mixture slurry was prepared.
Next, this positive electrode mixture slurry is applied to a positive electrode current collector made of a strip-shaped aluminum foil having a thickness of 20 μm, dried, and then compressed by a roll press to form a sheet-like positive electrode comprising a positive electrode current collector and a positive electrode active material layer Got. The coating density of the positive electrode active material layer at this time was 30 mg / cm ² , and the packing density was 2.5 g / ml.

<Preparation of non-aqueous electrolyte>
As a non-aqueous solvent, ethylene carbonate (EC), dimethyl carbonate (DMC), and methyl ethyl carbonate (EMC) were mixed at a ratio of 28:36:36 (mass ratio), respectively, to obtain a mixed solvent.
In the obtained mixed solvent, LiPF ₆ as an electrolyte was dissolved so that the electrolyte concentration in the finally obtained nonaqueous electrolytic solution was 1.2 mol / liter.
For the solution obtained above,
Additive A (3-methyl-2,4-pentanedionato) oxalatoborate (Exemplary Compound (25), added amount 0.5 mass%), and Additive B as lithium difluorophosphate (hereinafter referred to as “LiDFP”) (Also referred to as “addition amount 1.0 mass%)
Was added to obtain a non-aqueous electrolyte.

<Production of coin-type battery>
The above-mentioned negative electrode was 14 mm in diameter and the above-mentioned positive electrode was 13 mm in diameter, and each was punched into a disk shape to obtain coin-shaped electrodes (negative electrode and positive electrode). Further, a microporous polyethylene film having a thickness of 20 μm was punched into a disk shape 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 battery can (2032 size) made of stainless steel, and 20 μl of the non-aqueous electrolyte is injected to be contained in the separator, the positive electrode, and the negative electrode. Soaked.
Further, an aluminum plate (thickness 1.2 mm, diameter 16 mm) and a spring are placed on the positive electrode, and the battery can be sealed by caulking the battery can lid through a polypropylene gasket, and the diameter is 20 mm and height. A coin-type lithium secondary battery (hereinafter referred to as a test battery) having a configuration of 3.2 mm shown in FIG. 3 was produced.

[Evaluation]
The following evaluation was implemented about the obtained coin-type battery (battery for a test).

<Rate of increase in resistance due to storage (−20 ° C.)>
The coin-type battery is charged at a constant voltage of 3.9 V, and then the charged coin-type battery is cooled to −20 ° C. in a thermostat, and discharged at −20 ° C. with a 0.2 mA constant current. The direct current resistance [Ω] of the coin-type battery was measured by measuring the potential drop for 10 seconds, and the obtained value was taken as the initial resistance value (−20 ° C.).
The coin-type battery whose initial resistance value was measured was charged with a constant voltage of 4.25 V, and the charged coin-type battery was stored in a constant temperature bath at 60 ° C. for 5 days. The initial resistance value (−20 ° C.) The direct current resistance [Ω] of the coin-type battery was measured by the same method, and the obtained value was defined as the resistance value after storage (−20 ° C.).
From these results, “resistance increase rate due to storage [%] (−20 ° C.)” was determined by the following formula.
The obtained results are shown in Table 1.

Resistance increase rate due to storage [%] (-20 ° C)
= ((Resistance value after storage [Ω] (−20 ° C.) − Initial resistance value [Ω] (−20 ° C.)) / Initial resistance value [Ω] (−20 ° C.)) × 100

<Rate increase by storage (25 ° C)>
Except that the temperature during discharge (initial and after storage) was changed from −20 ° C. to room temperature (25 ° C.), the same as the above “resistance increase rate by storage [%] (−20 ° C.)”. The rate of increase in resistance [%] (−25 ° C.) ”was determined.
The results are shown in Table 1.

<Recovery capacity maintenance rate>
The coin-type battery was charged to 4.25 V at a charge rate of 0.2 C in a constant temperature bath at 25 ° C., and discharged to 2.85 V at a discharge rate of 0.2 C in this 25 ° C. constant temperature bath. The discharge capacity was measured, and this discharge capacity was defined as the initial discharge capacity [mAh].
The coin-type battery whose initial discharge capacity [mAh] was measured was charged to 4.25 V at a charging rate of 0.2 C in a thermostatic chamber at 25 ° C., and then the temperature of the thermostatic chamber was increased to 60 ° C. The coin-type battery was stored in a constant temperature bath at 60 ° C. for 5 days (high temperature storage).
After the high-temperature storage, the temperature of the thermostatic chamber is returned to 25 ° C., and the coin-type battery is discharged at a discharge rate of 0.2 C to 2.85 V in the thermostatic bath at 25 ° C., and the discharge capacity when discharged is measured. This discharge capacity was defined as the remaining discharge capacity [mAh].
From these results, the “recovery capacity retention rate [%]” was determined by the following formula.
The obtained results are shown in Table 1.
Recovery capacity maintenance rate [%]
= (Remaining discharge capacity [mAh] / Initial discharge capacity [mAh]) × 100 [%]

[Examples 2-3]
The same operation as in Example 1 was performed except that the types and amounts of additives in the preparation of the nonaqueous electrolytic solution were changed as shown in Table 1. The results are shown in Table 1.
[Comparative Example 1]
In the preparation of the nonaqueous electrolytic solution, the same operation as in Example 1 was performed except that the additive was not added. The results are shown in Table 1.

-Description of Table 1-
The exemplified compound (25) is (3-methyl-2,4-pentanedionato) oxalatoborate, which is an example of the compound represented by the formula (A).
“LiDFP” is lithium difluorophosphate (LiPO ₂ F ₂ ).
“MSF” is methanesulfonyl fluoride which is an example of a compound represented by the formula (X).
“TFMSLi” is lithium trifluoromethanesulfonate, which is an example of the compound represented by the formula (Y).
“-” In each additive column means that the corresponding additive is not contained.
The same applies to Table 2 described later.

As shown in Table 1, according to the non-aqueous electrolytes of Examples 1 to 3 containing both additive A and additive B, compared to the non-aqueous electrolyte of Comparative Example 1 that does not contain additives, storage The increase in battery resistance at −20 ° C. and the increase in battery resistance at 25 ° C. could be suppressed. Moreover, in the non-aqueous electrolyte of Examples 1-3, the resistance value (-20 degreeC and 25 degreeC) after a preservation | save was also low.
Further, the recovery capacity retention rates of Examples 1 to 3 were at the same level as the recovery capacity retention rate of Comparative Example 1.
Such an effect of Examples 1-3 is an effect exhibited by including both additive A and additive B.

[Examples 101 to 102, Comparative Example 101]
A coin-type battery (test battery) was produced in the same manner as in Example 1 except that the types and amounts of additives in the preparation of the non-aqueous electrolyte were changed as shown in Table 2, and the resistance increase due to storage The rate (−20 ° C.) and the recovery capacity maintenance rate were evaluated. In each example, the resistance after storage was expressed as a relative value (%) when the initial resistance value was 100%.
The results are shown in Table 2.

-Description of Table 2-
“VC” is vinylene carbonate which is an example of a compound represented by the formula (C).

As shown in Table 2, according to the non-aqueous electrolytes of Examples 101 to 102 including all of additive A, additive B, and additive C, additive B and additive C are included without additive A. Compared with the non-aqueous electrolyte of Comparative Example 101, an increase in battery resistance due to storage could be suppressed.
Further, the recovery capacity retention rates of Examples 101 to 102 were at the same level as the recovery capacity retention rate of Comparative Example 101.
Such effects of Examples 101 to 102 are effects exhibited by including both additive A and additive B.

DESCRIPTION OF SYMBOLS 1 Laminate exterior body 2 Positive electrode terminal 3 Negative electrode terminal 4 Insulation seal 5 Positive electrode plate 6 Negative electrode plates 7 and 8 Separator 11 Positive electrode 12 Negative electrode 13 Positive electrode can 14 Sealing plate 15 Separator 16 Gaskets 17 and 18 Spacer plate

Claims (7)

An additive A that is at least one selected from the group consisting of boron compounds represented by the following formula (A);
An additive B that is at least one selected from the group consisting of lithium monofluorophosphate, lithium difluorophosphate, a compound represented by the following formula (X), and a compound represented by the following formula (Y);
An electrolyte that is a lithium salt other than lithium monofluorophosphate, lithium difluorophosphate, and the compound represented by the formula (Y);
A non-aqueous electrolyte for batteries containing

[In the formula (A), R represents an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, or a group represented by the formula (A1). In formula (A1), R ^{1 to} R ³ each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms. Represents. In formula (A1), * represents a bonding site with an oxygen atom in formula (A). ]

[In the formula (X), R ⁴ represents a hydrocarbon group having 1 to 6 carbon atoms, a hydrocarbon group having 1 to 6 carbon atoms substituted with at least one fluorine atom, or a hydrocarbon oxy group having 1 to 6 carbon atoms. Represents a hydrocarbon oxy group having 1 to 6 carbon atoms substituted with at least one fluorine atom, or a fluorine atom.
In formula (Y), R ⁵ represents a hydrocarbon group having 1 to 6 carbon atoms substituted with at least one fluorine atom, a hydrocarbon oxy group having 1 to 6 carbon atoms substituted with at least one fluorine atom, or Represents a fluorine atom. ]   The battery nonaqueous electrolyte solution according to claim 1, wherein the content of the additive A is 0.001% by mass to 10% by mass with respect to the total amount of the battery nonaqueous electrolyte solution.   3. The battery non-aqueous electrolyte according to claim 1, wherein the content of the additive B is 0.001 to 10% by mass with respect to the total amount of the battery non-aqueous electrolyte. Furthermore, the non-aqueous electrolysis for batteries of any one of Claims 1-3 containing the additive C which is at least 1 sort (s) selected from the group which consists of a compound represented by following formula (C). liquid.

[In Formula (C), Y ¹ and Y ² each independently represent a hydrogen atom, a methyl group, an ethyl group, or a propyl group. ]   The battery nonaqueous electrolyte solution according to claim 4, wherein the content of the additive C is 0.001% by mass to 10% by mass with respect to the total amount of the battery nonaqueous electrolyte solution. A positive electrode;
Lithium metal, lithium-containing alloys, metals or alloys that can be alloyed with lithium, oxides that can be doped / undoped with lithium ions, transition metal nitrides that can be doped / undoped with lithium ions, 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 ion doping and dedoping;
The non-aqueous electrolyte for a battery according to any one of claims 1 to 5,
Including lithium secondary battery.   A lithium secondary battery obtained by charging and discharging the lithium secondary battery according to claim 6.