JP6879799B2 - Non-aqueous electrolyte for batteries and lithium secondary battery - Google Patents

Description

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

A secondary battery using a non-aqueous electrolyte solution has a high voltage, a high energy density, and high reliability such as storage characteristics, and is therefore widely used as a power source for consumer electronic devices. Furthermore, secondary batteries using non-aqueous electrolytes have begun to be used for power storage and as batteries for automobiles such as electric vehicles (EV), hybrid electric vehicles (HEV), and plug-in hybrid electric vehicles (PHEV). .. Typical examples of the secondary battery using the non-aqueous electrolyte solution include a lithium battery and a lithium ion secondary battery.

The non-aqueous electrolyte solution used in 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 solution transfers ions between the positive electrode and the negative electrode. The non-aqueous electrolyte solution is required to have the following characteristics in order to improve the battery performance of the secondary battery.
First, the non-aqueous electrolyte 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 electrolytic solution is preferably a solution having a high ion transfer rate in order to improve the charge / discharge characteristics of the secondary battery. Specifically, the non-aqueous electrolyte solution has a low viscosity and is prone to mass transfer due to diffusion. It is required to be a liquid.

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

Japanese Unexamined Patent Publication No. 09-12825 Japanese Unexamined Patent Publication No. 10-223258 Japanese Unexamined Patent Publication No. 11-054133 Japanese Unexamined Patent Publication No. 11-12103 JP-A-2002-025609 Japanese Unexamined Patent Publication No. 2002-216844 Japanese Unexamined Patent Publication No. 2003-132946 Japanese Unexamined Patent Publication No. 2003-168476 Japanese Unexamined Patent Publication No. 2008-198542 JP-A-2009-245829

As disclosed in Patent Documents 1 to 10, it is known to add a boron compound to a non-aqueous electrolytic solution in order to improve the battery performance of a secondary battery (for example, a lithium secondary battery). However, it may be required to suppress an increase in battery resistance due to storage of a non-aqueous electrolytic solution to which a boron compound is added and a lithium secondary battery using this non-aqueous electrolytic solution.
Therefore, an object of the present disclosure is to provide a non-aqueous electrolyte solution for a battery capable of suppressing an increase in battery resistance due to storage, and a lithium secondary battery using this non-aqueous electrolyte solution for a battery.

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), and
Additive B, which 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 above formula (Y), and
A non-aqueous electrolyte solution 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 the formula (A1), R ^{1 to} R ³ are independently hydrogen atom, halogen atom, alkyl group having 1 to 12 carbon atoms, alkenyl group having 2 to 12 carbon atoms, or aryl group having 6 to 12 carbon atoms. Represents. In the formula (A1), * represents a binding site with an oxygen atom in the formula (A). ]

Wherein (X), R ⁴ is a hydrocarbon group having 1 to 6 carbon atoms, at least one hydrocarbon group having 1 to 6 carbon atoms which is substituted with a fluorine atom, a hydrocarbon oxy group having 1 to 6 carbon atoms , A hydrocarbon oxy group having 1 to 6 carbon atoms substituted with at least one fluorine atom, or a fluorine atom.
Wherein (Y), R ⁵ is at least one hydrocarbon group with a 1 to 6 carbon atoms substituted with a fluorine atom, at least one hydrocarbon group having 1 to 6 carbon atoms substituted with fluorine atoms, or Represents a fluorine atom. ]
<2> The non-aqueous electrolyte solution for batteries 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 non-aqueous electrolyte solution for batteries.
<3> The non-aqueous electrolyte solution for batteries 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 non-aqueous electrolyte solution for batteries. ..
<4> Further, for a battery according to any one of <1> to <3>, which contains at least one additive C 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 non-aqueous electrolyte solution for batteries 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 non-aqueous electrolyte solution for batteries.

<6> Positive electrode and
Metallic lithium, lithium-containing alloys, metals or alloys that can be alloyed with lithium, oxides that can be doped and dedoped with lithium ions, transition metal nitrogen compounds that can be doped and dedoped with lithium ions, and lithium. A negative electrode containing at least one selected from the group consisting of carbon materials capable of doping and dedoping ions as a negative electrode active material, and a negative electrode.
The non-aqueous electrolyte solution for batteries according to any one of <1> to <5>.
Lithium secondary battery including.

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

Provided are a non-aqueous electrolyte solution for a battery capable of suppressing an increase in battery resistance due to storage, and a lithium secondary battery using the non-aqueous electrolyte solution for a battery.

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

In the present specification, the numerical range represented by using "~" means a range including the numerical values before and after "~" as the lower limit value and the upper limit value.
In the present specification, the amount of each component in the composition is the total amount of the plurality of substances present in the composition unless otherwise specified, when a plurality of substances corresponding to each component are present in the composition. Means.

[Non-aqueous electrolyte for batteries]
The non-aqueous electrolyte solution for batteries (hereinafter, also simply referred to as “non-aqueous electrolyte solution”) of the present disclosure is used.
Additive A, which is at least one selected from the group consisting of boron compounds represented by the following formula (A), and
Additive B, which 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 above formula (Y), and
Contains.

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

Wherein (X), R ⁴ is a hydrocarbon group having 1 to 6 carbon atoms, at least one hydrocarbon group having 1 to 6 carbon atoms which is substituted with a fluorine atom, 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.
Wherein (Y), R ⁵ is at least one hydrocarbon group with a 1 to 6 carbon atoms substituted with a fluorine atom, at least one hydrocarbon group having 1 to 6 carbon atoms substituted with fluorine atoms, or Represents a fluorine atom.

According to the non-aqueous 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 unknown, the boron compound (additive A) represented by the above formula (A) is decomposed by the initial charge, and the oxalate structural part ".O- (C =)". It is conceivable that "O) _2- O." Is generated, which acts on the surface of the electrode (active material) to form an ionic conduction path having high ionic 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 decomposing to form an oxalate structure. ) Is considered to be advantageous. Further, the boron compound represented by the above formula (A) has an oxalate group and a group represented by RO-bonded to a boron atom as a substituent, and has an asymmetric molecular structure centered on the boron atom. Therefore, it is considered that the charge distribution in the molecule can be imbalanced, so that even among the boron compounds, they are easily decomposed by the initial charge, and the above action is effectively exhibited.
In the non-aqueous electrolyte solution of the present disclosure, it is considered that the presence of the additive B improves the durability of the ion conduction path formed by the action of the decomposition product (oxalate structure) of the additive A during storage. .. As a result, it is considered that the increase in battery resistance due to storage is suppressed.

Hereinafter, each component of the non-aqueous electrolytic solution of the present disclosure will be described.

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

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

As the alkyl group having 1 to 12 carbon atoms represented by R, an alkyl group having 1 to 10 carbon atoms is more preferable, an alkyl group having 1 to 8 carbon atoms is further preferable, and an alkyl group having 1 to 6 carbon atoms is further preferable. Alkyl groups having 1 to 4 carbon atoms are preferable, and alkyl groups having 1 to 4 carbon atoms are 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, Examples thereof include sec-octyl group and tert-octyl group.
The alkyl group having 1 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).

As the alkenyl group having 2 to 12 carbon atoms represented by R, an alkenyl group having 2 to 10 carbon atoms is more preferable, an alkenyl group having 2 to 8 carbon atoms is further preferable, and an alkenyl group having 2 to 6 carbon atoms is further preferable. Preferably, an alkenyl group having 2 to 4 carbon atoms is more preferable.
Examples of the alkenyl group include an ethenyl group, a propenyl group, a butenyl group, a pentenyl group, a hexenyl group, a heptenyl group, an 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).

As R, a group represented by the above formula (A1) is preferable. In the formula (A1), R ^{1 to} R ³ are independently hydrogen atom, halogen atom, alkyl group having 1 to 12 carbon atoms, alkenyl group having 2 to 12 carbon atoms, or 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.

As ^{the alkyl group having 1 to 12 carbon atoms represented by R 1 to} R ³ , an alkyl group having 1 to 10 carbon atoms is more preferable, an alkyl group having 1 to 8 carbon atoms is further preferable, and an alkyl group having 1 to 6 carbon atoms is more preferable. Alkyl groups are more preferable, alkyl groups having 1 to 4 carbon atoms are further preferable, and alkyl groups having 1 to 3 carbon atoms are 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, Examples thereof include sec-octyl group and tert-octyl group.
The alkyl group having 1 to 12 carbon atoms represented by R ^{1 to} R ³ may be unsubstituted or substituted with a halogen atom (for example, a fluorine atom or a chlorine atom).

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

As ^{the aryl group having 6 to 12 carbon atoms represented by R 1 to} R ³ , an aryl group having 6 to 10 carbon atoms is more preferable.
Examples of the aryl group include a phenyl group, a group in which one hydrogen atom is removed from alkylbenzene (for example, a benzyl group, a tolyl group, a xsilyl group, a methicyl group, etc.), a naphthyl group, and a hydrogen atom from an alkyl group substituent of naphthalene. Examples include groups in which one is removed.
The aryl group having 6 to 12 carbon atoms represented by R ^{1 to} R ³ may be unsubstituted or 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, Alternatively, it is more preferably an aryl group. In this case, the preferred embodiments of the alkyl group, the alkenyl group, and the aryl group are as described above, and the alkyl group is preferable among the alkyl group, the alkenyl group, and the aryl group.

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, preferably 0.01% by mass to 10% by mass, based on the total amount of the non-aqueous electrolyte 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% by mass is further preferable, 0.5% by mass to 2% by mass is further preferable, and 0.5% by mass to 1% by mass is further preferable.
As the boron compound represented by the general formula (A), one type may be used alone, or two or more types may be mixed and used.

<Additive B>
The non-aqueous electrolyte solution of the present disclosure is at least one selected from the group consisting of lithium monofluorophosphate, lithium difluorophosphate, a compound represented by the formula (X), and a compound represented by the formula (Y). Contains the additive B which is.
The additive B may be only one kind or two or more kinds.

(Lithium monofluorophosphate, lithium difluorophosphate)
The non-aqueous electrolyte solution of the present disclosure has _{at least one of lithium monofluorophosphate (Li 2} PO ₃ F) and lithium difluorophosphate _{(Li PO 2} F ₂ ) as additive B (hereinafter referred to as “lithium fluorophosphate”). May contain).
When the non-aqueous 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 non-aqueous electrolytic solution of the present disclosure may contain a compound represented by the following formula (X) as the additive B.
When the non-aqueous electrolytic solution of the present disclosure contains a compound represented by the following formula (X) as the additive B, only one compound represented by the following formula (X) may be used. There may be two or more types.

Wherein (X), R ⁴ is a hydrocarbon group having 1 to 6 carbon atoms, at least one hydrocarbon group having 1 to 6 carbon atoms which is substituted with a fluorine atom, 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.

The “hydrocarbon group having 1 to 6 carbon atoms” represented by ^{R 4 represents an unsubstituted hydrocarbon group having 1 to 6 carbon atoms.}
The ^{"hydrocarbon group having 1 to 6 carbon atoms" represented by R 4} may be a linear hydrocarbon group, a branched hydrocarbon group, or a cyclic hydrocarbon group.
As the "hydrocarbon group having 1 to 6 carbon atoms" represented by R ^4, an alkyl group or 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.

As "hydrocarbon group having 1 to 6 carbon atoms" represented by R ⁴ include methyl group, an ethyl group, a propyl group, an 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, 3,3-dimethylbutyl group; vinyl group, 1-propenyl group, allyl group, 1 -Buthenyl group, 2-butyl 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 alkenyl groups; etc.

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. , A group having a structure in which an unsubstituted hydrocarbon group having 1 to 6 carbon atoms) is substituted with at least one fluorine atom.

As "the at least one hydrocarbon group with a 1 to 6 carbon atoms substituted with a fluorine atom" represented by R ⁴ is, for example, fluoromethyl group, difluoromethyl group, 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- Fluoroalkenyl groups such as methyl-2-propenyl group, 3-fluoro-2-butenyl group, perfluorovinyl group, perfluoropropenyl group, perfluorobutenyl group; and the like can be mentioned.

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 "hydrocarbon group having 1 to 6 carbon atoms" represented by R ⁴ is preferably an alkoxy group or an alkenyloxy group, an alkoxy group is more preferable.

As "hydrocarbon group having 1 to 6 carbon atoms" represented by R ⁴ include a methoxy group, an ethoxy group, a propoxy group, isopropoxy group, n- butoxy group, 2-butoxy group, tert- butoxy group , Alkoxy groups such as cyclopropyloxy group and cyclopentyloxy group; alkenyloxy groups such as allyloxy group and vinyloxy group; and the like.

In the formula (X), the "hydrocarbon oxy group having 1 to 6 carbon atoms substituted with at least one fluorine atom" represented by ^{R 4} is represented by the above-mentioned "carbon number 1 to 6 carbon atoms" represented by ^{R 4.} A group having a structure in which "hydrocarbon oxy group of 1" (that is, an unsubstituted hydrocarbon oxy group having 1 to 6 carbon atoms) is substituted with at least one fluorine atom can be mentioned.

Wherein (X), as it is R ^4, a hydrocarbon group having 1 to 6 carbon atoms (i.e., unsubstituted hydrocarbon group having 1 to 6 carbon atoms), or carbon atoms which is substituted with at least one fluorine atom Hydrocarbon groups 1 to 6 are preferable, hydrocarbon groups having 1 to 6 carbon atoms are more preferable, and alkyl groups having 1 to 6 carbon atoms are particularly preferable.

The compound represented by the formula (X) includes
Methansulfonyl fluoride, ethanesulfonyl fluoride, propanesulfonyl fluoride, 2-propanesulfonyl fluoride, butane sulfonyl fluoride, 2-butane sulfonyl fluoride, hexanesulfonyl fluoride, trifluoromethanesulfonyl fluoride, perfluoroethanesulfonyl fluoride Do, perfluoropropanesulfonyl fluoride, perfluorobutane sulfonyl fluoride, ethensulfonyl fluoride, 1-propen-1-sulfonyl fluoride, or 2-propen-1-sulfonyl fluoride is preferred.
Methansulfonyl fluoride, ethanesulfonyl fluoride, propanesulfonyl fluoride, 2-propanesulfonyl fluoride, butane sulfonyl fluoride, 2-butane sulfonyl fluoride, hexanesulfonyl fluoride, trifluoromethanesulfonyl fluoride, perfluoroethanesulfonyl fluoride Do, perfluoropropanesulfonyl fluoride, or perfluorobutanesulfonyl fluoride is more preferred.
Methanesulfonyl fluoride, ethanesulfonyl fluoride, propanesulfonyl fluoride, 2-propanesulfonyl fluoride, butane sulfonyl fluoride, 2-butane sulfonyl fluoride, or hexanesulfonyl fluoride are more preferred.
Methanesulfonyl fluoride, ethanesulfonyl fluoride, or propanesulfonyl fluoride are more preferred.
Methanesulfonyl fluoride is particularly preferred.

(Compound represented by formula (Y))
The non-aqueous electrolytic solution of the present disclosure may contain a compound represented by the following formula (Y) as the additive B.
When the non-aqueous electrolytic solution of the present disclosure contains a compound represented by the following formula (Y) as the additive B, only one compound represented by the following formula (Y) may be used. There may be two or more types.

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

Wherein (Y), represented by R ⁵ "at least one hydrocarbon group having 1 to 6 carbon atoms substituted with fluorine atoms", "at least as represented by R ⁴ in the aforementioned formula (X) It is synonymous with "hydrocarbon groups having 1 to 6 carbon atoms substituted with one fluorine atom".
In the formula (Y), the "hydrocarbon oxy group having 1 to 6 carbon atoms substituted with at least one fluorine atom" represented by ^{R 5 is represented by R 4} in the above-mentioned formula (X). It is synonymous with "hydrocarbon oxy group having 1 to 6 carbon atoms substituted with at least one fluorine atom".

Wherein (Y), as is R ^5, at least one hydrocarbon group having 1 to 6 carbon atoms substituted with fluorine atoms are preferable, an alkyl group having 1 to 6 carbon atoms which is substituted with at least one fluorine atom More preferably, a perfluoroalkyl group having 1 to 6 carbon atoms is further preferable, a perfluoromethyl group (also known as a trifluoromethyl group) or a perfluoroethyl group (also known as a pentafluoroethyl group) is further preferable, and a perfluoromethyl group is more preferable. (Also known as: trifluoromethyl group) is particularly preferable.

The compound represented by the formula (Y) preferably contains 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 0.05% by mass to 5% by mass, based on the total amount of the non-aqueous electrolyte solution. More preferably, 0.1% by mass to 5% by mass, further preferably 0.5% by mass to 5% by mass, further preferably 0.5% by mass to 3% by mass, and 0.5% by mass. ~ 2% by mass is more preferable, and 0.5% by mass to 1% by mass is further preferable.

<Electrolyte>
The non-aqueous electrolyte solution of the present disclosure includes an electrolyte that is a lithium monofluorophosphate, lithium difluorophosphate, and a lithium salt other than the compound represented by the above formula (Y) (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.

Examples of specific lithium _{salts, LiPF 6, LiBF 4, LiClO} 4, LiAsF 6, Li 2 SiF 6, LiPF n [C k F (2k + 1)] (6-n) (n = 1~5, k = Lithium salts such as (an integer of 1 to 8) can be mentioned.
Further, a 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 ) (here R ^{27 to} R ³³ may be the same or different from each other and are perfluoroalkyl groups having 1 to 8 carbon atoms). These electrolytes may be used alone or in combination of two or more.

The specific lithium salt preferably contains at least one of _{LiPF 6} and LiBF ₄ , and more preferably contains _{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 preferable.

The concentration of the electrolyte in the non-aqueous electrolyte 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 electrolytic solution of the present disclosure may contain additive C, which is a compound represented by the following formula (C).
When the non-aqueous 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 type selected from the group consisting of the compounds represented by the following formula (C), or may be two or more types.

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, methylvinylene carbonate, ethylvinylene carbonate, bropyrvinylene carbonate, dimethylvinylene carbonate, diethylvinylene carbonate, dipropylvinylene carbonate and the like. Of these, vinylene carbonate is the most preferable.

The content of the additive C (compound represented by the formula (C)) is preferably 0.001% by mass to 10% by mass, preferably 0.01% by mass to 10% by mass, based on the total amount of the non-aqueous electrolyte 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% 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 non-aqueous electrolyte solution of the present disclosure may contain an additive A, an additive B, and other additives other than the additive C (also referred to as "other additives" in the present specification).
When the non-aqueous 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 oxalate compounds (excluding additive A), fluorophosphate compounds (excluding lithium monofluorophosphate and lithium difluorophosphate), and carbonate compounds having a carbon-carbon unsaturated bond. (However, additive C is excluded), at least one selected from the group consisting of a carbonate compound having a fluorine atom, a cyclic sulton compound, and a cyclic sulfate ester compound is preferable.

(Oxalate compound)
Examples of the oxalate compound (excluding additive A) include lithium difluorobis (oxalate), lithium tetrafluoro (oxalate) phosphate, lithium tris (oxalate) phosphate, lithium difluoro (oxalate) borate, and bis (excluding additive A). Oxalato) Lithium borate and the like can be mentioned. Of these, lithium difluorobis (oxalate) phosphate, lithium tetrafluoro (oxalate) phosphate, or lithium bis (oxalate) borate is preferable.

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

(Carbon-carbon unsaturated bond carbonate compound)
Examples of carbonate compounds having a carbon-carbon unsaturated bond (excluding additive C) include methyl vinyl carbonate, ethyl vinyl carbonate, divinyl carbonate, methylpropynyl carbonate, ethylpropynyl carbonate, dipropynyl carbonate, methylphenyl carbonate, and ethyl. Chain carbonates such as phenyl carbonate and diphenyl carbonate; vinyl ethylene carbonate, 4,5-divinylethylene carbonate, 4,5-divinylethylene carbonate, ethynylethylene carbonate, 4,5-diethynylethylene carbonate, 4,5-di Cyclic carbonates such as ethynylethylene carbonate, propynylethylene carbonate, 4,4-dipropynylethylene carbonate, and 4,5-dipropynylethylene carbonate; and the like. Of these, methylphenyl carbonate, ethylphenyl carbonate, diphenyl carbonate, vinylethylene carbonate, 4,5-divinylethylene carbonate, or 4,5-divinylethylene carbonate is preferable, and vinylethylene carbonate is more preferable. ..

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

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

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

In formula (I), R ¹ and R ² are 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 a group represented by formula (III). It represents a group, or represents a group in which R ¹ and R ² are united to form a benzene ring or a cyclohexyl ring together with a carbon atom to ^{which R 1} is bonded and a 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, an alkyl halide group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or the formula (IV). Represents a group. The wavy lines in equations (II), (III), and (IV) represent the coupling positions.
When the compound represented by the formula (I) contains two groups represented by the formula (II), the groups represented by the two formulas (II) are different from each other even if they are the same. May be good.

Specific examples of the "halogen atom" in the formula (II) 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), the "alkyl group having 1 to 6 carbon atoms" is a linear or branched alkyl group having 1 or more and 6 or less carbon atoms, and is a methyl group, an ethyl group, or 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 specific example is a dimethylbutyl group.
As the alkyl group having 1 to 6 carbon atoms, an alkyl group having 1 to 3 carbon atoms is more preferable.

In the formula (II), the "alkyl halide group having 1 to 6 carbon atoms" is a linear or branched alkyl halide group having 1 to 6 carbon atoms, and is a fluoromethyl group, a difluoromethyl group, or the like. Trifluoromethyl group, 2,2,2-trifluoroethyl group, perfluoroethyl group, perfluoropropyl group, perfluorobutyl group, perfluoropentyl group, perfluorohexyl group, perfluoroisopropyl group, perfluoroisobutyl group , Chloromethyl group, chloroethyl group, chloropropyl group, bromomethyl group, bromoethyl group, bromopropyl group, methyl iodide group, ethyl iodide group, propyl iodide group and the like can be mentioned as specific examples.
As the alkyl halide group having 1 to 6 carbon atoms, an alkyl halide group having 1 to 3 carbon atoms is more preferable.

In the formula (II), the "alkoxy group having 1 to 6 carbon atoms" is a linear or branched alkoxy group having 1 or more and 6 or less carbon atoms, and is a methoxy group, an ethoxy group, a propoxy group, or an isopropoxy. 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 groups.
As the alkoxy group having 1 to 6 carbon atoms, an alkoxy group having 1 to 3 carbon atoms is more preferable.

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

^{R 2} in the formula (I) is more preferably a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, and a group represented by the formula (II) (in the formula (II), R ³ is a fluorine atom and carbon. It is more preferably an alkyl group having the number 1 to 3, an alkyl halide group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or a group represented by the formula (IV)), or the formula. It is a group represented by (III), more preferably a hydrogen atom or a methyl group.

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

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

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

When the non-aqueous electrolyte solution of the present disclosure contains other additives, the content thereof (the total content when there are two or more kinds) is not particularly limited, but the effect of the present disclosure is more effective. From the viewpoint of playing, 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, based on the total amount of the non-aqueous electrolyte solution. It is more preferably% to 4% by mass, further preferably 0.1% by mass to 2% by mass, and particularly preferably 0.1% by mass to 1% by mass.

<Non-aqueous solvent>
The non-aqueous electrolyte solution generally contains a non-aqueous solvent.
As the non-aqueous solvent, various known ones can be appropriately selected, but it is preferable to use at least one selected from a cyclic aprotic solvent and a chain aprotic solvent.

When aiming to improve the flash point of the solvent in order to improve the safety of the battery, 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 such a ratio, the conductivity of the electrolytic solution related 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, and 2,3-pentylene carbonate. 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, and alkyl substituents 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, and a high dielectric constant, and can reduce the viscosity of the electrolytic solution without lowering the flash point of the electrolytic solution and the degree of dissociation of the electrolyte. Therefore, it has a 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. It is preferable to use a cyclic carboxylic acid ester as the cyclic aprotic solvent. Among the cyclic carboxylic acid esters, γ-butyrolactone is most preferable.

Further, 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 cyclic sulfone include sulfolane, 2-methylsulfolane, 3-methylsulfolane, dimethylsulfone, diethylsulfone, dipropylsulfone, methylethylsulfone, methylpropylsulfone and the like.
Dioxolane can be mentioned as an example of the cyclic ether.

(Chain aprotic solvent)
As the chain aprotic solvent, a chain carbonate, a chain carboxylic acid ester, a chain ether, a chain phosphate ester and 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.

Specifically, as the chain carbonate, 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 thereof include ethylpentyl carbonate, dipentyl carbonate, methylheptyl carbonate, ethylheptyl carbonate, diheptyl carbonate, methylhexyl carbonate, ethylhexyl carbonate, dihexyl carbonate, methyloctyl carbonate, ethyloctyl carbonate, dioctyl carbonate, methyltrifluoroethyl carbonate and the like. Two or more kinds of these chain carbonates may be mixed and used.

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

(Solvent combination)
The non-aqueous solvent used in the non-aqueous electrolytic solution of the present disclosure may be one type or a mixture of a plurality of types. Further, only one or more kinds of cyclic aprotic solvents may be used, one or more kinds of chain aprotic solvents may be used, or cyclic aprotic solvents and chain protics. Solvents may be mixed and used. When it is particularly intended to improve the load characteristics and low temperature characteristics of the battery, it is preferable to use a combination of a cyclic aprotic solvent and a chain aprotic solvent as the aprotic solvent.

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

Specific combinations of cyclic carbonate and chain carbonate include 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, and propylene carbonate. 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 and 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, methyl ethyl carbonate and diethyl Examples thereof include 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 such a ratio, it is possible to suppress an increase in the viscosity of the electrolytic solution and increase the degree of dissociation of the electrolyte, so that the conductivity of the electrolytic solution related to the charge / discharge characteristics of the battery can be increased. Moreover, the solubility of the electrolyte can be further increased. Therefore, since the electrolytic solution having excellent electrical conductivity at room temperature or low temperature can be obtained, the load characteristics of the battery at room temperature to low temperature can be improved.

Specific examples of combinations of cyclic carboxylic acid ester and cyclic carbonate and / or chain carbonate include γ-butyrolactone and ethylene carbonate, γ-butyrolactone and ethylene carbonate and dimethyl carbonate, γ-butyrolactone and ethylene carbonate and methyl ethyl. 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 and propylene carbonate, γ-butyrolactone, ethylene carbonate, propylene carbonate and dimethyl carbonate, γ-butyrolactone, 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 and diethyl carbonate, γ-butyrolactone, ethylene carbonate, methyl ethyl carbonate and diethyl carbonate, γ-butyrolactone, ethylene carbonate and dimethyl carbonate And methyl ethyl carbonate and diethyl carbonate, γ-butyrolactone and ethylene carbonate and propylene carbonate and dimethyl carbonate and methyl ethyl carbonate, γ-butyrolactone and ethylene carbonate and propylene carbonate and dimethyl carbonate and diethyl carbonate, γ-butyrolactone and ethylene carbonate and propylene carbonate. And methyl ethyl carbonate and diethyl carbonate, γ-butyrolactone and ethylene carbonate and propylene carbonate and dimethyl carbonate and methyl ethyl carbonate and diethyl carbonate, γ-butyrolactone and sulfolane, γ-butyrolactone and ethylene carbonate and sulfolane, γ-butyrolactone and propylene carbonate Sulfolane, γ-butyrolactone, ethylene carbonate, propylene carbonate, sulfolane, γ-buty Examples thereof include lolactone, sulfolane and dimethyl carbonate.

(Other solvents)
Examples of the non-aqueous solvent include other solvents other than the above.
Specific examples of other solvents include amides such as dimethylformamide, chain carbamates such as methyl-N and N-dimethylcarbamate, cyclic amides such as N-methylpyrrolidone, and N, N-dimethylimidazolidinone. Examples thereof include boron compounds such as cyclic urea, trimethyl borate, triethyl borate, tributyl borate, trioctyl borate, and trimethylsilyl borate, and polyethylene glycol derivatives represented by the following general formulas.
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 solution of the present disclosure is not only suitable as a non-aqueous electrolyte solution for a lithium secondary battery, but also a non-aqueous electrolyte solution for a primary battery, a non-aqueous electrolyte solution for an electrochemical capacitor, and an electric double layer capacitor. , 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 a non-aqueous electrolytic solution of the present disclosure.

(Negative electrode)
The negative electrode may include a negative electrode active material and a negative electrode current collector.
Examples of the negative electrode active material in the negative electrode include metallic lithium, lithium-containing alloys, metals or alloys that can be alloyed with lithium, oxides that can be doped / dedoped with lithium ions, and lithium ions that can be doped / dedoped. At least one selected from the group consisting of transition metal nitridants and carbon materials capable of doping and dedoping lithium ions (may be used alone, or a mixture containing two or more of these 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, a carbon material capable of doping and dedoping lithium ions is 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 fibrous, spherical, potato-like, or flake-like.

Specific examples of the amorphous carbon material include hard carbon, coke, mesocarbon microbeads (MCMB) calcined at 1500 ° C. or lower, and mesophase pitch carbon fiber (MCF).
Examples of the graphite material include natural graphite and artificial graphite. As the artificial graphite, graphitized MCMB, graphitized MCF and the like are used. Further, as the graphite material, a material containing boron or the like can also be used. Further, as the graphite material, a material coated with a metal such as gold, platinum, silver, copper or tin, 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 admixture of two or more.
As the carbon material, a carbon material having a surface spacing d (002) of the (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 a property close to that of graphite is also preferable. When the carbon material as described above is used, the energy density of the battery can be further increased.

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. Of 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.
Examples of the positive electrode active material in the positive electrode include transition metal oxides or transition metal sulfides such _{as MoS 2} , TiS ₂ , MnO ₂ , and 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 an α-NaFeO type 2} 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 ] (e.g., 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 composite oxides consisting of lithium and transition metals, Examples thereof include conductive polymer materials such as polyaniline, polythiophene, polypyrrole, polyacetylene, polyacene, dimercaptothiaizole, and polyaniline complex. Among these, a composite oxide composed of lithium and a transition metal is particularly preferable. When the negative electrode is a lithium metal or a lithium alloy, a carbon material can also be used as the positive electrode. Further, as the positive electrode, a mixture of a composite oxide of lithium and a transition metal and a carbon material can also be used.
The positive electrode active material may be used alone or in combination of two or more. When the positive electrode active material has insufficient conductivity, it can be used together with a conductive auxiliary agent 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 metal materials such as aluminum, aluminum alloy, stainless steel, nickel, titanium, and tantalum; carbon materials such as carbon cloth and carbon paper; and the like.

(Separator)
The lithium secondary battery of the present disclosure preferably contains a separator between the negative electrode and the positive electrode.
The separator is a membrane that electrically insulates the positive electrode and the negative electrode and allows lithium ions to pass through, and examples thereof include a porous membrane and a polymer electrolyte.
As the porous film, a microporous polymer film is preferably used, and examples of the material include polyolefin, polyimide, polyvinylidene fluoride, polyester and the like.
In particular, porous polyolefin is preferable, and 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. The porous polyolefin film may be coated with another resin having excellent thermal stability.
Examples of the polymer electrolyte include a polymer in which a lithium salt is dissolved, a polymer inflated with an electrolytic solution, and the like.
The non-aqueous electrolyte solution of the present disclosure may be used for the purpose of swelling a polymer to obtain a polymer electrolyte.

(Battery configuration)
The lithium secondary battery of the present disclosure can take various known shapes, and can be formed into a cylindrical type, a coin type, a square type, a laminated type, a film type, 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.

An example of the lithium secondary battery (non-aqueous electrolyte secondary battery) of the present disclosure is a laminated battery.
FIG. 1 is a schematic perspective view showing an example of a laminated battery which is an example of the lithium secondary battery of the present disclosure, and FIG. 2 is a thickness of a laminated electrode body housed in the laminated battery shown in FIG. It is a schematic sectional view of a direction.
The laminated battery shown in FIG. 1 contains a non-aqueous electrolytic solution (not shown in FIG. 1) and a laminated electrode body (not shown in FIG. 1), and the peripheral edge thereof is sealed. A laminated exterior body 1 whose inside is hermetically sealed is provided. As the laminated exterior body 1, for example, a laminated exterior body made of aluminum is used.
As shown in FIG. 2, the laminated electrode body housed in the laminated exterior body 1 is a laminated body in which a positive electrode plate 5 and a negative electrode plate 6 are alternately laminated via a separator 7, and a laminated body of the laminated body. A separator 8 that surrounds the periphery is provided. The positive electrode plate 5, the negative electrode plate 6, the separator 7, and the separator 8 are impregnated with the non-aqueous 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 the positive electrode tab (not shown), and a part of the positive electrode terminal 2 is the laminated exterior body 1. It protrudes outward from the peripheral end (Fig. 1). A portion of the peripheral end of the laminated exterior body 1 on which the positive electrode terminal 2 protrudes is sealed with an insulating seal 4.
Similarly, the plurality of negative electrode plates 6 in the laminated electrode body are all electrically connected to the negative electrode terminal 3 via the negative electrode tab (not shown), and a part of the negative electrode terminal 3 is the laminated exterior. It protrudes outward from the peripheral end of the body 1 (FIG. 1). A portion of the peripheral end of the laminated exterior body 1 from which the negative electrode terminal 3 protrudes is sealed with an insulating seal 4.
In the laminated battery according to the above example, the number of positive electrode plates 5 is 5 and the number of negative electrode plates 6 is 6, and the positive electrode plate 5 and the negative electrode plate 6 are located on both sides of the battery via the separator 7. The outer layers are all laminated so as to be the negative electrode plate 6. However, it goes without saying that the number of positive electrode plates, the number of negative electrode plates, and the arrangement of the laminated battery are not limited to this example, and various changes may be made.

Another example of the lithium secondary battery of the present disclosure is a coin-type battery.
FIG. 3 is a schematic perspective view showing 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, a disk-shaped negative electrode 12, a separator 15 injected with a non-aqueous electrolyte solution, a disk-shaped positive electrode 11, and, if necessary, spacer plates 17 and 18 made of stainless steel or aluminum are arranged in this order. In a laminated state, it is stored between the positive electrode can 13 (hereinafter, also referred to as “battery can”) and the sealing plate 14 (hereinafter, also referred to as “battery can lid”). The positive electrode can 13 and the sealing plate 14 are caulked and sealed via the gasket 16.
In this example, the non-aqueous electrolytic solution of the present disclosure is used as the non-aqueous electrolytic solution to be injected into the separator 15.

The lithium secondary battery of the present disclosure 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 solution of the present disclosure. It may be a lithium secondary battery.
That is, as the lithium secondary battery of the present disclosure, first, a lithium secondary battery before charging / discharging containing a negative electrode, a positive electrode, and the non-aqueous electrolyte solution of the present disclosure is prepared, and then the lithium secondary battery before charging / discharging is prepared. It may be a lithium secondary battery (charged / discharged lithium secondary battery) manufactured 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 it can be used for various known uses. For example, laptops, mobile computers, mobile phones, headphone stereos, video movies, LCD TVs, handy cleaners, electronic organizers, calculators, radios, backup power supplies, motors, automobiles, electric vehicles, bikes, electric bikes, bicycles, electric It can be widely used regardless of whether it is a small portable device or a large device such as a bicycle, a lighting device, a game machine, a clock, an electric tool, or a camera.

Hereinafter, examples of the present disclosure will be shown, but the present disclosure is not limited to the following examples.
In the following examples, the "addition amount" represents the content in the finally obtained non-aqueous electrolytic solution (that is, the amount with respect to the total amount of the finally obtained non-aqueous electrolytic solution).
Further, "wt%" means mass%.

[Example 1]
A coin-type battery (test battery), which is a lithium secondary battery, was produced by the following procedure.
<Manufacturing of negative electrode>
98 parts by mass of natural graphite, 1 part by mass of carboxymethyl cellulose 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 is 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 composed of the negative electrode current collector and the negative electrode active material layer. A negative electrode was obtained. At this time, the coating density of the negative electrode active material layer was 10 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 92 parts by mass, acetylene black 2.5 parts by mass, polyvinylidene fluoride 2.5 parts by mass and binder 3 parts by mass, N-methylpyrrolidinone as a solvent A paste-like positive mixture mixture slurry was prepared by kneading.
Next, this positive electrode mixture slurry is applied to a positive electrode current collector of a strip-shaped aluminum foil having a thickness of 20 μm, dried, and then compressed by a roll press to form a sheet-shaped positive electrode composed of a positive electrode current collector and a positive electrode active material layer. Got At this time, the coating density of the positive electrode active material layer was 30 mg / cm ² , and the packing density was 2.5 g / ml.

<Preparation of non-aqueous electrolyte solution>
Ethylene carbonate (EC), dimethyl carbonate (DMC) and methyl ethyl carbonate (EMC) were mixed as non-aqueous solvents at a ratio of 28:36:36 (mass ratio) to obtain a mixed solvent.
In the obtained mixed solvent, LiPF ₆ , which is an electrolyte, was dissolved so that the electrolyte concentration in the finally obtained non-aqueous electrolyte solution was 1.2 mol / liter.
For the solution obtained above
Oxalatoborate (exemplified compound (25), addition amount 0.5% by mass) as additive A (3-methyl-2,4-pentanedionato), and lithium difluorophosphate as additive B (hereinafter, "LiDFP"). (Also called) (addition amount 1.0% by mass)
Was added to obtain a non-aqueous electrolyte solution.

<Making coin-type batteries>
A coin-shaped electrode (negative electrode and positive electrode) was obtained by punching the above-mentioned negative electrode with a diameter of 14 mm and the above-mentioned positive electrode with a diameter of 13 mm in a disk shape. 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 a stainless steel battery can (2032 size) in this order, and 20 μl of the non-aqueous electrolytic solution is injected into the separator, the positive electrode, and the negative electrode. It was pickled.
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 crimping the battery can lid via a polypropylene gasket to seal the battery with a diameter of 20 mm and a height of 20 mm. A coin-shaped lithium secondary battery (hereinafter referred to as a test battery) having a structure of 3.2 mm and having the configuration shown in FIG. 3 was produced.

[Evaluation]
The obtained coin-type battery (test battery) was evaluated as follows.

<Resistance increase rate due to storage (-20 ° C)>
The coin-type battery is charged at a constant voltage of 3.9 V, then the charged coin-type battery is cooled to −20 ° C. in a constant temperature bath, discharged at −20 ° C. at a constant current of 0.2 mA, and from the start of discharge. The DC resistance [Ω] of the coin-type battery was measured by measuring the potential drop in 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 at 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 to obtain the above-mentioned initial resistance value (-20 ° C.). The DC resistance [Ω] of the coin cell battery was measured by the same method, and the obtained value was used as the resistance value (-20 ° C.) after storage.
From these results, the "rate of increase in resistance due to storage [%] (-20 ° C)" was determined by the following formula.
The results obtained are shown in Table 1.

Rate of increase in resistance due to storage [%] (-20 ° C)
= ((Resistance value [Ω] (-20 ° C) after storage-Initial resistance value [Ω] (-20 ° C)) / Initial resistance value [Ω] (-20 ° C)) × 100

<Resistance increase rate due to storage (25 ° C)>
Except for changing the temperature at the time of discharge (initial and after storage) from -20 ° C to room temperature (25 ° C), "preservation" is the same as the above-mentioned "resistance increase rate [%] (-20 ° C) due to storage". The rate of increase in resistance [%] (-25 ° C) was determined.
The results are shown in Table 1.

<Recovery capacity maintenance rate>
When the coin-type battery is charged to 4.25 V at a charging 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 constant temperature bath at 25 ° C. 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 constant temperature bath at 25 ° C., and then the temperature of the constant temperature bath was raised 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 constant temperature bath was returned to 25 ° C., the coin-type battery was discharged to 2.85 V at a discharge rate of 0.2 C in the constant temperature bath at 25 ° C., and the discharge capacity at the time of discharge was measured. This discharge capacity was defined as the residual discharge capacity [mAh].
From these results, the "recovery capacity retention rate [%]" was calculated by the following formula.
The results obtained are shown in Table 1.
Recovery capacity maintenance rate [%]
= (Residual discharge capacity [mAh] / Initial discharge capacity [mAh]) × 100 [%]

[Examples 2 to 3]
The same operation as in Example 1 was carried out except that the type and amount of the additive in the preparation of the non-aqueous electrolyte solution were changed as shown in Table 1. The results are shown in Table 1.
[Comparative Example 1]
In the preparation of the non-aqueous electrolyte solution, the same operation as in Example 1 was carried out except that no additive was added. The results are shown in Table 1.

-Explanation of Table 1-
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 a 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 electrolytic solution of Examples 1 to 3 containing both the additive A and the additive B, the non-aqueous electrolytic solution of Comparative Example 1 containing no additive was stored as compared with the non-aqueous electrolytic solution of Comparative Example 1. It was possible to suppress the increase in battery resistance at -20 ° C and the increase in battery resistance at 25 ° C. In addition, the non-aqueous electrolytic solutions of Examples 1 to 3 had low resistance values (-20 ° C. and 25 ° C.) after storage.
The recovery capacity maintenance rate of Examples 1 to 3 was at the same level as the recovery capacity maintenance rate of Comparative Example 1.
Such effects of Examples 1 to 3 are those exhibited by including both Additive A and Additive B.

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

-Explanation 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 electrolytic solution of Examples 101 to 102 containing all of Additive A, Additive B and Additive C, Additive A is not contained and Additive B and Additive C are contained. Compared with the non-aqueous electrolyte solution of Comparative Example 101, it was possible to suppress an increase in battery resistance due to storage.
The recovery capacity maintenance rate of Examples 101 to 102 was at the same level as the recovery capacity maintenance rate of Comparative Example 101.
Such an effect of Examples 101 to 102 is an effect exhibited by including both the additive A and the additive B.

1 Laminated exterior 2 Positive electrode terminal 3 Negative electrode terminal 4 Insulation seal 5 Positive electrode plate 6 Negative electrode plate 7, 8 Separator 11 Positive electrode 12 Negative electrode 13 Positive electrode can 14 Seal plate 15 Separator 16 Gasket 17, 18 Spacer plate

Claims (6)

Additive A, which is at least one selected from the group consisting of boron compounds represented by the following formula (A), and
Additive B, which 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 above formula (Y), and
A non-aqueous electrolyte solution 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 the formula (A1), R ^{1 to} R ³ are independently hydrogen atom, halogen atom, alkyl group having 1 to 12 carbon atoms, alkenyl group having 2 to 12 carbon atoms, or aryl group having 6 to 12 carbon atoms. Represents. In the formula (A1), * represents a binding site with an oxygen atom in the formula (A). ]

Wherein (X), R ⁴ is a hydrocarbon group having 1 to 6 carbon atoms, at least one hydrocarbon group having 1 to 6 carbon atoms which is substituted with a fluorine atom, a hydrocarbon oxy group having 1 to 6 carbon atoms , A hydrocarbon oxy group having 1 to 6 carbon atoms substituted with at least one fluorine atom, or a fluorine atom.
Wherein (Y), R ⁵ is at least one hydrocarbon group with a 1 to 6 carbon atoms substituted with a fluorine atom, at least one hydrocarbon group having 1 to 6 carbon atoms substituted with fluorine atoms, or Represents a fluorine atom. ] The non-aqueous electrolyte solution for batteries 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 non-aqueous electrolyte solution for batteries. The non-aqueous electrolyte solution for batteries according to claim 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 non-aqueous electrolyte solution for batteries. The non-aqueous electrolysis for batteries according to any one of claims 1 to 3, further comprising an additive C which is at least one selected from the group consisting of compounds represented by the 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 non-aqueous electrolyte solution for batteries 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 non-aqueous electrolyte solution for batteries. With the positive electrode
Metallic lithium, lithium-containing alloys, metals or alloys that can be alloyed with lithium, oxides that can be doped and dedoped with lithium ions, transition metal nitrogen compounds that can be doped and dedoped with lithium ions, and lithium A negative electrode containing at least one selected from the group consisting of carbon materials capable of doping and dedoping ions as a negative electrode active material, and a negative electrode.
The non-aqueous electrolyte solution for a battery according to any one of claims 1 to 5.
Lithium secondary battery including.

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