JP7326681B2 - Non-aqueous electrolyte for batteries and lithium secondary batteries - Google Patents

Description

TECHNICAL FIELD The present disclosure relates to non-aqueous electrolytes for batteries and lithium secondary batteries.

BACKGROUND ART Conventionally, from the viewpoint of improving the performance of batteries, studies have been made to incorporate various additives into non-aqueous electrolyte solutions for batteries.
For example, Patent Document 1 discloses a battery non-aqueous electrolyte containing a sultone compound having a carbon-carbon double bond as a battery non-aqueous electrolyte capable of improving the charge/discharge characteristics and life characteristics of the battery. disclosed.

Japanese Patent No. 4424895

However, in some cases, the technology described in Patent Document 1 is required to further reduce the resistance of the battery after storage.
An object of one aspect of the present disclosure is to provide a non-aqueous electrolyte for a battery that can reduce the resistance of the battery after storage.
An object of another aspect of the present disclosure is to provide a lithium secondary battery with reduced resistance after storage.

Means for solving the above problems include the following aspects.
<1> the following sultone compound (A),
a boron compound (B) which is at least one selected from the group consisting of the following compounds (1) to (6);
A non-aqueous electrolyte for batteries containing

In compound (A), R ^a1 to R ^a4 each independently represent a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 3 carbon atoms, or a fluorohydrocarbon group having 1 to 3 carbon atoms.
Among compounds (1) to (6),
R ³¹ to R ³³ each independently represent a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, or a fluorohydrocarbon group having 1 to 6 carbon atoms,
R ⁴¹ to R ⁴³ each independently represents a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, or a fluorohydrocarbon group having 1 to 6 carbon atoms,
R ⁵¹ represents a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, or a fluorohydrocarbon group having 1 to 6 carbon atoms,
R ⁵² represents a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, or a fluorohydrocarbon group having 1 to 6 carbon atoms,
n represents an integer of 1 to 3;

<2> The non-aqueous electrolyte for a battery according to <1>, wherein the boron compound (B) contains the compound (1).
<3> The non-aqueous battery according to <1> or <2>, wherein the content of the sultone compound (A) is 0.001% by mass to 10% by mass with respect to the total amount of the non-aqueous electrolyte for batteries. Electrolyte.
<4> Any one of <1> to <3>, wherein the content of the boron compound (B) is 0.001% by mass to 10% by mass with respect to the total amount of the battery non-aqueous electrolyte non-aqueous electrolyte for batteries.
<5> Any one of <1> to <4>, further containing an additive (C) that is at least one selected from the group consisting of the following compounds (C1) to (C7): non-aqueous electrolyte for batteries.

In compound (C1), R ^c11 and R ^c12 each independently represent a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, or a fluorohydrocarbon group having 1 to 6 carbon atoms.
In compound (C2), R ^c21 to R ^c24 each independently represent a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, or a fluorohydrocarbon group having 1 to 6 carbon atoms. However, R ^c21 to R ^c24 are not hydrogen atoms at the same time.
In the compound (C3), R ^c31 to R ^c33 each independently represent a fluorine atom or a —OLi group, and at least one of R ^c31 to R ^c33 is a —OLi group.
In the compound (C4), R ^c41 to R ^c43 each independently represent a hydrocarbon group having 1 to 6 carbon atoms, a fluorohydrocarbon group having 1 to 6 carbon atoms, or a group (s), and n is Represents 0 or 1.
In group (s), R ^c44 to R ^c46 each independently represent a hydrocarbon group having 1 to 6 carbon atoms, and * represents a bonding position.
In compound (C5), R ^c51 to R ^c54 each independently represent a hydrogen atom, a hydrocarbon group having 1 to 6 carbon atoms, group (a), or group (b). In group (a) and group (b), * represents a bonding position.
In compound (C6), R ^c61 represents a fluorine atom or a fluorohydrocarbon group having 1 to 6 carbon atoms.
In compound (C7), R ^c71 and R ^c72 each independently represent a fluorine atom or a fluorohydrocarbon group having 1 to 6 carbon atoms.

<6> The battery according to <5>, wherein the additive (C) comprises the compound (C1) and at least one selected from the group consisting of the compounds (C2) to (C7). non-aqueous electrolyte.
<7> 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 batteries <5> or <6> Nonaqueous for batteries according to Electrolyte.

<8> a positive electrode;
Metallic lithium, lithium-containing alloys, metals or alloys that can be alloyed with lithium, oxides that can be doped/dedoped with lithium ions, transition metal nitrides that can be doped/dedoped 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 batteries according to any one of <1> to <7>,
Lithium secondary battery including.
<9> The lithium secondary battery according to <8>, wherein the content of Si in the negative electrode is 5% by mass or less with respect to the entire negative electrode.
<10> A lithium secondary battery obtained by charging and discharging the lithium secondary battery according to <8> or <9>.

According to one aspect of the present disclosure, there is provided a non-aqueous electrolyte for a battery that can reduce the resistance of the battery after storage.
According to another aspect of the present disclosure, a lithium secondary battery with reduced resistance after storage is provided.

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

In this specification, a numerical range represented by "to" means a range including the numerical values before and after "to" as lower and upper limits.
As used herein, the amount of each component in the composition refers to the total amount of the multiple substances present in the composition unless otherwise specified when there are multiple substances corresponding to each component in the composition. means

[Non-aqueous electrolyte for batteries]
The non-aqueous electrolyte for batteries of the present disclosure (hereinafter also simply referred to as “non-aqueous electrolyte”) is
the following sultone compound (A),
a boron compound (B) which is at least one selected from the group consisting of the following compounds (1) to (6);
contains

In compound (A), R ^a1 to R ^a4 each independently represent a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 3 carbon atoms, or a fluorohydrocarbon group having 1 to 3 carbon atoms.
Among compounds (1) to (6),
R ³¹ to R ³³ each independently represent a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, or a fluorohydrocarbon group having 1 to 6 carbon atoms,
R ⁴¹ to R ⁴³ each independently represents a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, or a fluorohydrocarbon group having 1 to 6 carbon atoms,
R ⁵¹ represents a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, or a fluorohydrocarbon group having 1 to 6 carbon atoms,
R ⁵² represents a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, or a fluorohydrocarbon group having 1 to 6 carbon atoms,
n represents an integer of 1 to 3;

According to the non-aqueous electrolyte of the present disclosure, it is possible to reduce the resistance of the battery after storage.
The reason why such an effect is produced is presumed as follows.

According to the non-aqueous electrolyte of the present disclosure, it is believed that the action of the sultone compound (A) can suppress an increase in resistance during storage of the battery. Although the reason for this is not clear, during storage of the battery, a film derived from the sultone compound (A) is formed on the surface of the electrode (negative electrode and/or positive electrode). This is probably because deterioration of the electrode during storage is prevented and an increase in resistance is suppressed.
Furthermore, according to the non-aqueous electrolyte solution of the present disclosure, it is believed that the initial resistance of the battery (that is, the resistance before storage) can be reduced by the action of the boron compound (B). Although the reason for this is not clear, it is considered that the boron compound (B) has higher reductive reactivity than the sultone compound (A). That is, since the boron compound (B) has high reductive reactivity, it is thought that before the battery is stored, it forms a film on the surface of the negative electrode more quickly than the sulfone compound (A). It is believed that the initial resistance of the battery (resistance before storage) is reduced due to the action of the film formed before the battery is stored.

<Sultone compound (A)>
The sultone compound (A) is as follows.

In compound (A), R ^a1 to R ^a4 each independently represent a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 3 carbon atoms, or a fluorohydrocarbon group having 1 to 3 carbon atoms.

The hydrocarbon group having 1 to 3 carbon atoms represented by R ^a1 to R ^a4 is preferably an alkyl group, an alkenyl group, or an alkynyl group, more preferably an alkyl group or an alkenyl group, and particularly preferably an alkyl group.
The number of carbon atoms in the hydrocarbon groups having 1 to 3 carbon atoms represented by R ^a1 to R ^a4 is preferably 1 or 2, and particularly preferably 1.

The fluorinated hydrocarbon group having 1 to 3 carbon atoms represented by R ^a1 to R ^a4 is preferably a fluorinated alkyl group, a fluorinated alkenyl group, or a fluorinated alkynyl group, and is a fluorinated alkyl group or fluorinated alkenyl group. is more preferred, and a fluorinated alkyl group is particularly preferred.
The number of carbon atoms in the fluorohydrocarbon groups having 1 to 3 carbon atoms represented by R ^a1 to R ^a4 is preferably 1 or 2, and particularly preferably 1.

In this disclosure:
The fluorohydrocarbon group means a group in which at least one of the hydrogen atoms contained in the hydrocarbon group is replaced with a fluorine atom,
A fluorinated alkyl group means a group in which at least one of hydrogen atoms contained in an alkyl group is replaced with a fluorine atom,
Fluorinated alkenyl group means a group in which at least one of the hydrogen atoms contained in the alkenyl group is replaced with a fluorine atom,
A fluorinated alkynyl group means a group in which at least one of hydrogen atoms contained in an alkynyl group is replaced with a fluorine atom.

R ^a1 to R ^a4 are each independently preferably a hydrogen atom, a fluorine atom, a methyl group, an ethyl group, a trifluoromethyl group, or a pentafluoroethyl group, more preferably a hydrogen atom or a methyl group, and particularly preferably a hydrogen atom. .

Specific examples of the sultone compound (A) include compounds (A-1) to (A-21) below, but the sultone compound (A) is not limited to these specific examples.
Among these, compound (A-1) (ie, 1,3-propenesultone; hereinafter also referred to as "PRS") is particularly preferred.

The content of the sultone compound (A) is preferably 0.001% by mass to 10% by mass, more preferably 0.003% by mass to 5% by mass, and 0.003% by mass to It is more preferably 3% by mass, more preferably 0.03% by mass to 3% by mass, even more preferably 0.1% by mass to 3% by mass, and 0.1% by mass to 2% by mass. % is more preferred.

<Boron compound (B)>
The boron compound (B) is at least one selected from the group consisting of compounds (1) to (6) below.
Compounds (1) to (6) are described below.

(Compound (1))
Compound (1) is as follows.
Compound (1) is lithium difluorooxalatoborate (hereinafter also referred to as “LiFOB”).

(Compound (2))
Compound (2) is as follows.
Compound (1) is lithium bis(oxalato)borate (hereinafter also referred to as “LiBOB”).

(Compound (3))
Compound (3) is as follows.

In compound (3), R ³¹ to R ³³ each independently represent a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, or a fluorohydrocarbon group having 1 to 6 carbon atoms.

In the compound (3), the hydrocarbon group having 1 to 6 carbon atoms represented by R ³¹ to R ³³ may be a linear hydrocarbon group or a hydrocarbon group having a branched and/or cyclic structure. may be
Examples of hydrocarbon groups having 1 to 6 carbon atoms represented by R ³¹ to R ³³ include;
methyl group, ethyl group, n-propyl group, isopropyl group, 1-ethylpropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, 2-methylbutyl group, 3,3-dimethylbutyl group , n-pentyl group, isopentyl group, neopentyl group, 1-methylpentyl group, n-hexyl group, isohexyl group, sec-hexyl group, alkyl group such as tert-hexyl group;
vinyl group, 1-propenyl group, allyl group, 1-butenyl group, 2-butenyl group, 3-butenyl group, pentenyl group, hexenyl group, isopropenyl group, 2-methyl-2-propenyl group, 1-methyl-2 - alkenyl groups such as a propenyl group and a 2-methyl-1-propenyl group;
phenyl group;
etc.

Hydrocarbon groups having 1 to 6 carbon atoms represented by R ³¹ to R ³³ include:
A phenyl group, an alkyl group having 1 to 6 carbon atoms, or an alkenyl group having 2 to 6 carbon atoms is preferable,
more preferably an alkyl group having 1 to 6 carbon atoms or an alkenyl group having 2 to 6 carbon atoms,
Alkyl groups having 1 to 6 carbon atoms are more preferred.

The number of carbon atoms in the hydrocarbon group having 1 to 6 carbon atoms represented by R ³¹ to R ³³ is preferably 1 to 4, more preferably 1 to 3, still more preferably 1 or 2, especially 1 is preferred.

In the compound (3), the fluorohydrocarbon group having 1 to 6 carbon atoms represented by R ³¹ to R ³³ may be a linear fluorohydrocarbon group, or may have a branched and/or cyclic structure. may be a fluorinated hydrocarbon group having

In the present disclosure, a fluorohydrocarbon group means a hydrocarbon group substituted with at least one fluorine atom.

Examples of fluorohydrocarbon groups having 1 to 6 carbon atoms represented by R ³¹ to R ³³ include;
fluoromethyl group, difluoromethyl group, trifluoromethyl group, 2,2,2-trifluoroethyl group, 1,1,2,2-tetrafluoroethyl group, perfluoroethyl group, 2,2,3,3- Fluoroalkyl groups such as a tetrafluoropropyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, a perfluorohexyl group, a perfluoroisopropyl group, and a 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, perfluoropropenyl group, fluoroalkenyl group such as perfluorobutenyl group;
fluorophenyl groups such as a monofluorophenyl group, a difluorophenyl group, a trifluorophenyl group, a tetrafluorophenyl group, a pentafluorophenyl group (that is, a perfluorophenyl group);
etc.

The fluorohydrocarbon groups having 1 to 6 carbon atoms represented by R ³¹ to R ³³ include:
A fluorophenyl group, a fluoroalkyl group having 1 to 6 carbon atoms, or a fluoroalkenyl group having 2 to 6 carbon atoms is preferable,
A fluoroalkyl group having 1 to 6 carbon atoms or a fluoroalkenyl group having 2 to 6 carbon atoms is more preferable,
A fluoroalkyl group having 1 to 6 carbon atoms is more preferred.

The number of carbon atoms in the fluorohydrocarbon groups having 1 to 6 carbon atoms represented by R ³¹ to R ³³ is preferably 1 to 4, more preferably 1 to 3, still more preferably 1 or 2. , particularly preferably 1.

In compound (3), R ³¹ to R ³³ are particularly preferably a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

Specific examples of the compound (3) are shown below, but the compound (3) is not limited to the following specific examples.

(Compound (4))
Compound (4) is as follows.

In compound (4), R ⁴¹ to R ⁴³ each independently represent a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, or a fluorohydrocarbon group having 1 to 6 carbon atoms.

Specific examples and preferred embodiments of the hydrocarbon group having 1 to 6 carbon atoms represented by R ⁴¹ to R ⁴³ in the compound (4) are 1 carbon atom represented by R ³¹ to R ³³ in the compound (3). It is the same as the specific examples and preferred embodiments of the hydrocarbon group of 1 to 6.

Specific examples and preferred embodiments of the fluorohydrocarbon groups having 1 to 6 carbon atoms represented by R ⁴¹ to R ⁴³ in the compound (4) are the fluorocarbon groups represented by R ³¹ to R ³³ in the compound (3). Specific examples and preferred embodiments of the hydrocarbon group having 1 to 6 carbon atoms are the same.

In compound (4), R ⁴¹ to R ⁴³ are preferably alkyl groups having 1 to 6 carbon atoms.

Specific examples of compound (4) are shown below, but compound (4) is not limited to the following specific examples.

(Compound (5))
Compound (5) is as follows.

In compound (5),
R ⁵¹ represents a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, or a fluorohydrocarbon group having 1 to 6 carbon atoms,
R ⁵² represents a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, or a fluorohydrocarbon group having 1 to 6 carbon atoms,
n represents an integer of 1 to 3;

Specific examples and preferred embodiments of the hydrocarbon group having 1 to 6 carbon atoms represented by R ⁵¹ and R ⁵² in the compound (5) are the hydrocarbon groups having 1 carbon atom represented by R ³¹ to R ³³ in the compound (3) It is the same as the specific examples and preferred embodiments of the hydrocarbon group of 1 to 6.

Specific examples and preferred embodiments of the fluorohydrocarbon groups having 1 to 6 carbon atoms represented by R ⁵¹ and R ⁵² in the compound (5) are the fluorocarbon groups represented by R ³¹ to R ³³ in the compound (3). Specific examples and preferred embodiments of the hydrocarbon group having 1 to 6 carbon atoms are the same.

In compound (5), R ⁵¹ is preferably an alkyl group having 1 to 6 carbon atoms or an alkenyl group having 2 to 6 carbon atoms.
In compound (5), R ⁵² is preferably a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, or a fluorohydrocarbon group having 1 to 6 carbon atoms, an alkyl group having 1 to 6 carbon atoms, or 2 to 6 alkenyl groups are more preferred.
In compound (5), n represents an integer of 1 to 3, preferably 2 or 3.

Specific examples of compound (5) are shown below, but compound (5) is not limited to the following specific examples.

(Compound (6))
Compound (6) is as follows.
contains

The content of the boron compound (B) is preferably 0.001% by mass to 10% by mass, more preferably 0.003% by mass to 5% by mass, relative to the total amount of the non-aqueous electrolyte, and 0.003% by mass to It is more preferably 3% by mass, more preferably 0.03% by mass to 3% by mass, even more preferably 0.1% by mass to 3% by mass, and 0.1% by mass to 2% by mass. % is more preferred.

These ranges of the content of the boron compound (B) are also applicable as the ranges of the content of each of the compounds (1) to (6).

In the non-aqueous electrolytic solution of the present disclosure, the ratio of the content mass of the boron compound (B) to the content mass of the sultone compound (A) (hereinafter referred to as the content mass ratio [boron compound (B)/sultone compound (A)]) is It is preferably 0.1 to 10, more preferably 0.2 to 5.0, even more preferably 0.5 to 3.0, still more preferably 1.0 to 2.5.

Boron compound (A) preferably contains compound (1).
That is, the boron compound (A) consists of the compound (1), or the compound (1) and at least one selected from the group consisting of the compounds (2) to (6). preferable.
In this case, the proportion of compound (1) in the total boron compound (A) is preferably 50% by mass to 100% by mass, more preferably 60% by mass to 100% by mass, and still more preferably 80% by mass. ~100% by mass.

<Other additives>
The nonaqueous electrolytic solution of the present disclosure may contain additives other than the sultone compound (A) and the boron compound (B).
Other additives are not particularly limited, and known additives contained in non-aqueous electrolytes for lithium secondary batteries can be used without particular limitations.

<Additive (C)>
Another additive is preferably an additive (C) that is at least one selected from the group consisting of the following compounds (C1) to (C7).
When the non-aqueous electrolyte of the present disclosure contains the additive (C), the initial resistance of the battery is further reduced.
Compounds (C1) to (C1) are described below.

(Compound (C1))
Compound (C1) is as follows.

In compound (C1), R ^c11 and R ^c12 each independently represent a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, or a fluorohydrocarbon group having 1 to 6 carbon atoms.

Specific examples and preferred embodiments of the hydrocarbon groups having 1 to 6 carbon atoms represented by R ^c11 and R ^c12 in the compound (C1) are those of 1 carbon atom represented by R ³¹ to R ³³ in the compound (3). It is the same as the specific examples and preferred embodiments of the hydrocarbon group of 1 to 6.

Specific examples and preferred embodiments of the fluorohydrocarbon groups having 1 to 6 carbon atoms represented by R ^c11 and R ^c12 in the compound (C1) are the fluorocarbon groups represented by R ³¹ to R ³³ in the compound (3). Specific examples and preferred embodiments of the hydrocarbon group having 1 to 6 carbon atoms are the same.

In the compound (C1), R ^c11 and R ^c12 are
A hydrogen atom, an alkyl group having 1 to 6 carbon atoms or an alkenyl group having 2 to 6 carbon atoms is preferable,
A hydrogen atom or an alkyl group having 1 to 6 carbon atoms is more preferable,
Hydrogen atoms are particularly preferred.

Specific examples of the compound (C1) are shown below, but the compound (C1) is not limited to the following specific examples.
Among these, the compound (C1-1) (vinylene carbonate; hereinafter also referred to as "VC") is particularly preferred.

(Compound (C2))
Compound (C2) is as follows.

In compound (C2), R ^c21 to R ^c24 each independently represent a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, or a fluorohydrocarbon group having 1 to 6 carbon atoms. However, R ^c21 to R ^c24 are not hydrogen atoms at the same time.

Specific examples and preferred embodiments of the hydrocarbon group having 1 to 6 carbon atoms represented by R ^c21 to R ^c24 in the compound (C2) are 1 carbon atom represented by R ³¹ to R ³³ in the compound (3). It is the same as the specific examples and preferred embodiments of the hydrocarbon group of 1 to 6.

Specific examples and preferred embodiments of the fluorohydrocarbon groups having 1 to 6 carbon atoms represented by R ^c21 to R ^c24 in the compound (C2) are the fluorocarbon groups represented by R ³¹ to R ³³ in the compound (3). Specific examples and preferred embodiments of the hydrocarbon group having 1 to 6 carbon atoms are the same.

In the compound (C2), R ^c21 to R ^c24 are
A hydrogen atom, a fluorine atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, a fluorinated alkyl group having 1 to 6 carbon atoms, or a fluorinated alkenyl group having 2 to 6 carbon atoms is preferable.
A hydrogen atom, a fluorine atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or a fluorinated alkyl group having 1 to 6 carbon atoms is more preferable.
A hydrogen atom or a fluorine atom is particularly preferred.
Among compounds (C2), R ^c21 to R ^c24 preferably contain at least one fluorine atom.

Specific examples of the compound (C2) are shown below, but the compound (C2) is not limited to the following specific examples.

(Compound (C3))
Compound (C3) is as follows.

In the compound (C3), R ^c31 to R ^c33 each independently represent a fluorine atom or a —OLi group, and at least one of R ^c31 to R ^c33 is a —OLi group.

Specific examples of the compound (C3) are shown below, but the compound (C3) is not limited to the following specific examples.
Compound (C3-1) is lithium difluorophosphate (hereinafter also referred to as “LiDFP”).

(Compound (C4))
Compound (C4) is as follows.

In the compound (C4), R ^c41 to R ^c43 each independently represent a hydrocarbon group having 1 to 6 carbon atoms, a fluorohydrocarbon group having 1 to 6 carbon atoms, or a group (s), and n is Represents 0 or 1.
In group (s), R ^c44 to R ^c46 each independently represent a hydrocarbon group having 1 to 6 carbon atoms, and * represents a bonding position.

Specific examples and preferred embodiments of the hydrocarbon group having 1 to 6 carbon atoms represented by R ^c41 to R ^c43 in the compound (C4) are 1 carbon atom represented by R ³¹ to R ³³ in the compound (3). It is the same as the specific examples and preferred embodiments of the hydrocarbon group of 1 to 6.

Specific examples and preferred embodiments of the fluorohydrocarbon group having 1 to 6 carbon atoms represented by R ^c41 to R ^c43 in the compound (C4) are the fluorocarbon groups represented by R ³¹ to R ³³ in the compound (3). Specific examples and preferred embodiments of the hydrocarbon group having 1 to 6 carbon atoms are the same.

Specific examples and preferred embodiments of the hydrocarbon group having 1 to 6 carbon atoms represented by R ^c44 to R ^c46 in the group (s) are the 1 carbon atom represented by R ³¹ to R ³³ in the compound (3). It is the same as the specific examples and preferred embodiments of the hydrocarbon group of 1 to 6.

n represents 0 or 1 in the compound (C4).
The compound (C4) when n is 1 is the following compound (C4A) which is a phosphate, and the compound (C4) when n is 0 is the following compound (C4B) which is a phosphite. is.

R ^c41 to R ^c43 in compound (C4A) have the same definitions as R ^c41 to R ^c43 in compound (C4).
R ^c41 to R ^c43 in compound (C4B) have the same definitions as R ^c41 to R ^c43 in compound (C4).

Specific examples of the compound (C4) are shown below, but the compound (C4) is not limited to the following specific examples.

(Compound (C5))
Compound (C5) is as follows.

In compound (C5), R ^c51 to R ^c54 each independently represent a hydrogen atom, a hydrocarbon group having 1 to 6 carbon atoms, group (a), or group (b). In group (a) and group (b), * represents a bonding position.

Specific examples and preferred embodiments of the hydrocarbon group having 1 to 6 carbon atoms represented by R ^c51 to R ^c54 in the compound (C5) are 1 carbon atom represented by R ³¹ to R ³³ in the compound (3). It is the same as the specific examples and preferred embodiments of the hydrocarbon group of 1 to 6.

Specific examples of the compound (C5) are shown below, but the compound (C5) is not limited to the following specific examples.
Among these, compounds (C5-1) to (C5-3) are particularly preferred.

(Compound (C6))
Compound (C6) is as follows.

In compound (C6), R ^c61 represents a fluorine atom or a fluorohydrocarbon group having 1 to 6 carbon atoms.

Specific examples and preferred embodiments of the fluorohydrocarbon group having 1 to 6 carbon atoms represented by R ^c61 in the compound (C6) are those represented by R ³¹ to R ³³ in the compound (3) having 1 to Specific examples and preferred embodiments of the fluorohydrocarbon group of 6 are the same.

Specific examples of the compound (C6) are shown below, but the compound (C6) is not limited to the following specific examples.

(Compound (C7))
Compound (C7) is as follows.

In compound (C7), R ^c71 and R ^c72 each independently represent a fluorine atom or a fluorohydrocarbon group having 1 to 6 carbon atoms.

Specific examples and preferred embodiments of the fluorohydrocarbon groups having 1 to 6 carbon atoms represented by R ^c71 and R ^c72 in the compound (C7) are carbon atoms represented by R ³¹ to R ³³ in the compound (3) It is the same as the specific examples and preferred embodiments of the fluorinated hydrocarbon groups of numbers 1 to 6.

R ^c71 and R ^c72 are each independently particularly preferably a fluorine atom, a trifluoromethyl group, or a pentafluoroethyl group.

Specific examples of the compound (C7) are shown below, but the compound (C7) is not limited to the following specific examples.
Among the specific examples below, the compound (C7-1) is lithium bis(fluorosulfonyl)imide (hereinafter also referred to as "LiFSI"),
Compound (C7-2) is lithium bis(trifluoromethanesulfonyl)imide (hereinafter also referred to as “LiTFSI”).

The content of the additive (C) described above is preferably 0.001% by mass to 10% by mass, more preferably 0.003% by mass to 5% by mass, and 0.001% by mass to 10% by mass, more preferably 0.003% by mass to 5% by mass. 003% by mass to 3% by mass, more preferably 0.03% by mass to 3% by mass, still more preferably 0.1% by mass to 3% by mass, and 0.1% by mass % to 2 mass %.

These ranges of the content of the additive (C) are also applicable as the ranges of the content of each of the compounds (C1) to (C7).

When the non-aqueous electrolytic solution of the present disclosure contains the additive (C), the ratio of the content mass of the additive (C) to the total content mass of the sultone compound (A) and the boron compound (B) (i.e., content mass ratio [Additive (C)/sultone compound (A) + boron compound (B)]) is preferably 0.1 to 3.0, preferably 0.2 to 2.5, more preferably 0 .3 to 2.0.

The additive (C) preferably contains the compound (C1).
In other words, the additive (C) is
consisting only of the compound (C1), or
It is preferably composed of compound (C1) and at least one selected from the group consisting of compounds (C2) to (C7).

It is particularly preferred that the additive (C) consists of the compound (C1) and at least one selected from the group consisting of the compounds (C2) to (C7).
When the additive (C) consists of the compound (C1) and at least one selected from the group consisting of the compounds (C2) to (C7), the additive (C) is the compound (C1) As compared with the case where the battery is composed of only one, it is possible to further suppress the resistance increase during storage of the battery, and further reduce the resistance of the battery after storage.

When the additive (C) consists of the compound (C1) and at least one selected from the group consisting of the compounds (C2) to (C7), the compound (C2) relative to the content mass of the compound (C1) to the ratio of the total content mass of the compound (C7) (that is, the content mass ratio [(compound (C2) to compound (C7))/compound (C1)]) is preferably 0.1 to 15.0, It is more preferably 0.2 to 10.0, still more preferably 0.3 to 5.0, still more preferably 0.5 to 3.0.

Next, other components of the non-aqueous electrolyte will be described. A non-aqueous electrolyte generally contains an electrolyte and a non-aqueous solvent.

<Electrolyte>
The electrolyte in the non-aqueous electrolyte of the present disclosure preferably contains a lithium salt, more preferably _LiPF6 .
When the electrolyte contains LiPF ₆ , the ratio of LiPF ₆ in the electrolyte is preferably 10% by mass to 100% by mass, more preferably 50% by mass to 100% by mass, and still more preferably 70% by mass to 100% by mass. be.

The electrolyte concentration in the non-aqueous electrolytic solution of the present disclosure is preferably 0.1 mol/L to 3 mol/L, more preferably 0.5 mol/L to 2 mol/L.
Also, the concentration of LiPF ₆ in the non-aqueous electrolyte of the present disclosure is preferably 0.1 mol/L to 3 mol/L, more preferably 0.5 mol/L to 2 mol/L.

When the electrolyte contains LiPF ₆ , the electrolyte may contain compounds other than LiPF ₆ .
Compounds other than LiPF ₆ include:
( _{C2H5 ) 4NPF6 ,} ( _{C2H5 ) 4NBF4 , ( C2H5 ) 4NClO4 ,} ( _{C2H5 ) 4NAsF6 , ( C2H5} ) _{4N2SiF 6} , (C ₂ H ₅ ) ₄ NOSO ₂ C _k F _(2k+1) (k = integer from 1 to 8), (C ₂ H ₅ ) ₄ NPF _n [C _k F _(2k+1) ] _(6-n) ( tetraalkylammonium salts such as n = 1-5, k = an integer of 1-8;
LiBF ₄ , LiClO ₄ , LiAsF ₆ , Li ₂ SiF ₆ , LiOSO ₂ C _k F _(2k+1) (k=integer of 1 to 8), LiPF _n [C _k F _(2k+1) ] _(6−n) (n= 1 to 5, k=an integer of 1 to 8), LiC(SO ₂ R ⁷ )(SO ₂ R ⁸ )(SO ₂ R ⁹ ), LiN(SO ₂ OR ¹⁰ )(SO ₂ OR ¹¹ ), LiN(SO ₂ R ¹² ) (SO ₂ R ¹³ ) (wherein R ⁷ to R ¹³ may be the same or different and are a fluorine atom or a perfluoroalkyl group having 1 to 8 carbon atoms) or the like lithium salt (that is, , lithium salts other than LiPF ₆ );
etc.

<Non-aqueous solvent>
The number of non-aqueous solvents in the non-aqueous electrolyte of the present disclosure may be one, or two or more.
As the non-aqueous solvent, various known solvents can be appropriately selected.
As the non-aqueous solvent, for example, non-aqueous solvents described in paragraphs 0069 to 0087 of JP-A-2017-45723 can be used.

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

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

Examples of chain carbonate compounds 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, ethyl pentyl carbonate, dipentyl carbonate, methylheptyl carbonate, ethylheptyl carbonate, diheptyl carbonate, methylhexyl carbonate, ethylhexyl carbonate, dihexyl carbonate, methyloctyl carbonate, ethyloctyl carbonate, dioctyl carbonate, and the like.

Specific examples of combinations of cyclic carbonate and chain carbonate include ethylene carbonate and dimethyl carbonate, ethylene carbonate and methylethyl carbonate, ethylene carbonate and diethyl carbonate, propylene carbonate and dimethyl carbonate, propylene carbonate and methylethyl 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 and diethyl carbonate , ethylene carbonate and dimethyl carbonate and methyl ethyl carbonate and diethyl carbonate, ethylene carbonate and propylene carbonate and dimethyl carbonate and methyl ethyl carbonate, ethylene carbonate and propylene carbonate and dimethyl carbonate and diethyl carbonate, ethylene carbonate and propylene carbonate and methyl ethyl carbonate and diethyl carbonate Carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate, methylethyl carbonate, diethyl carbonate and the like.

The mixing ratio of the cyclic carbonate compound and the linear carbonate compound is expressed by mass ratio, and the cyclic carbonate compound: linear carbonate compound is, for example, 5:95 to 80:20, preferably 10:90 to 70:30, more preferably 10:90 to 70:30. is 15:85 to 55:45. By setting such a ratio, it is possible to suppress the viscosity increase of the non-aqueous electrolyte and increase the degree of dissociation of the electrolyte, so that the conductivity of the non-aqueous electrolyte, which is related to the charge and discharge characteristics of the battery, can be increased. . Also, the solubility of the electrolyte can be further increased. Therefore, a non-aqueous electrolyte having excellent electrical conductivity at room temperature or low temperature can be obtained, so that the load characteristics of the battery can be improved from room temperature to low temperature.

The non-aqueous solvent may contain compounds other than the cyclic carbonate compound and the chain carbonate compound.
In this case, the other compound contained in the non-aqueous solvent may be of only one type, or may be of two or more types.
Other compounds include cyclic carboxylic acid ester compounds (e.g., γ-butyrolactone), cyclic sulfone compounds, cyclic ether compounds, chain carboxylic acid ester compounds, chain ether compounds, chain phosphate compounds, amide compounds, and chain carbamates. compounds, cyclic amide compounds, cyclic urea compounds, boron compounds, polyethylene glycol derivatives, and the like.
For these compounds, the description in paragraphs 0069 to 0087 of JP-A-2017-45723 can be referred to as appropriate.

The proportion of the cyclic carbonate compound and the chain carbonate compound in the non-aqueous solvent is preferably 80% by mass or more, more preferably 90% by mass or more, and still more preferably 95% by mass or more.
The ratio of the cyclic carbonate compound and the chain carbonate compound in the non-aqueous solvent may be 100% by mass.

The proportion of the non-aqueous solvent in the non-aqueous electrolyte is preferably 60% by mass or more, more preferably 70% by mass or more.
The upper limit of the ratio of the non-aqueous solvent in the non-aqueous electrolyte depends on the content of other components (electrolytes, additives, etc.), but the upper limit is, for example, 99% by mass, preferably 97% by mass. Yes, more preferably 90% by mass.

[Lithium secondary battery]
A lithium secondary battery of the present disclosure includes a positive electrode, a negative electrode, and a non-aqueous electrolyte 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 includes metal 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 nitrides 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 metals or alloys that can be alloyed with lithium (or lithium ions) include silicon, silicon alloys, tin, and tin alloys. Lithium titanate may also be used.
Among these, a carbon material capable of doping/dedoping lithium ions is preferable from the viewpoint of further improving the formability of the film on the negative electrode and further reducing the resistance of the battery at the initial stage and/or after storage. 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) fired at 1500° C. or lower, and mesophase pitch carbon fiber (MCF).
Examples of the graphite material include natural graphite and artificial graphite. Graphitized MCMB, graphitized MCF, and the like are used as artificial graphite. As the graphite material, one containing boron can also be used. As the graphite material, those coated with metals such as gold, platinum, silver, copper, and tin, those coated with amorphous carbon, and those in which amorphous carbon and graphite are mixed can be used.

These carbon materials may be used singly or in combination of two or more.
As the above-mentioned carbon material, a carbon material in which the interplanar spacing d(002) of the (002) plane measured by X-ray analysis is 0.340 nm or less is particularly preferable. As the carbon material, graphite having a true density of 1.70 g/cm ³ or more or a highly crystalline carbon material having properties close thereto is also preferable. The energy density of the battery can be increased by using the above carbon materials.

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

The negative electrode may include a negative electrode current collector and a negative electrode active material layer provided on at least part of the surface of the negative electrode current collector.
The negative electrode active material layer contains at least one negative electrode active material. The negative electrode active material in the negative electrode active material layer preferably contains the carbon material described above.
The content of the carbon material in the negative electrode active material layer is the total amount of the negative electrode active material layer from the viewpoint of further improving the formation of a film on the negative electrode and further reducing the resistance of the battery at the initial stage and/or after storage. On the other hand, it is preferably 70% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more.
The negative electrode active material layer may further contain at least one binder.
Binders include styrene-butadiene (SBR) rubber (e.g., SBR latex), acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, carboxymethylcellulose (CMC), hydroxypropylmethylcellulose, polyvinyl alcohol, hydroxypropylcellulose, and diacetylcellulose. At least one selected from the group consisting of is preferred. Preferably, the binder comprises SBR latex and carboxymethylcellulose.
The content of the binder in the negative electrode active material layer is preferably 1% by mass to 20% by mass, more preferably 1% by mass to 10% by mass, still more preferably 1% by mass, based on the total amount of the negative electrode active material layer. % to 5% by mass.

The content of Si in the entire negative electrode is preferably 5% by mass or less.
When the Si content in the entire negative electrode is 5% by mass or less, the ability to form a film on the negative electrode is further improved, and the resistance of the battery at the initial stage and/or after storage is further reduced.

<Positive electrode>
The positive electrode may include a positive electrode active material and a positive electrode current collector.
Examples of positive electrode active materials for the positive electrode include transition metal oxides or sulfides such as MoS ₂ , TiS ₂ , MnO ₂ and V ₂ O ₅ , LiCoO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , _{LiNiXCo (1−X)} O ₂ [0<X<1], α-NaFeO Li _1+α Me _1-α O ₂ having a _2- type crystal structure (Me is a transition metal element including 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, composite oxides composed of _lithium and _{a transition} metal _{such as LiNi0.33Co0.33Mn0.33O2} , _{LiNi0.5Co0.2Mn0.3O2} , _{LiFePO4 , LiMnPO4} ; Examples thereof include conductive polymer materials such as polyaniline, polythiophene, polypyrrole, polyacetylene, polyacene, dimercaptothiadiazole, and polyaniline complexes. Among these, a composite oxide composed of lithium and a transition metal is particularly preferred. Carbon materials can also be used as the positive electrode when the negative electrode is lithium metal or a lithium alloy. A mixture of a composite oxide of lithium and a transition metal and a carbon material can also be used as the positive electrode.
One type of positive electrode active material may be used, or two or more types may be mixed and used. If the positive electrode active material has insufficient conductivity, it can be used together with a conductive aid to form the positive electrode. Examples of conductive aids 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 alloys, stainless steel, nickel, titanium, and tantalum; carbon materials such as carbon cloth and carbon paper; and the like.

The positive electrode may include a positive electrode current collector and a positive electrode active material layer provided on at least part of the surface of the positive electrode current collector.
The positive electrode active material layer contains at least one positive electrode active material. The negative electrode active material in the positive electrode active material layer preferably contains a composite oxide composed of lithium and a transition metal.
The content of the composite oxide in the positive electrode active material layer is preferably 70% by mass or more, more preferably 80% by mass or more, relative to the total amount of the positive electrode active material layer.
The positive electrode active material layer may further contain at least one conductive aid.
The positive electrode active material layer may further contain at least one binder.
Binders include, for example, polyvinyl acetate, polymethyl methacrylate, nitrocellulose, fluororesin, and rubber particles. Examples of fluororesins include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), vinylidene fluoride-hexafluoropropylene copolymer, and the like. Examples of rubber particles include styrene-butadiene rubber particles and acrylonitrile rubber particles. Among these, fluororesins are preferable from the viewpoint of improving the oxidation resistance of the positive electrode active material layer.
The content of the binder in the positive electrode active material layer is preferably 1% by mass to 20% by mass, more preferably 1% by mass to 10% by mass, relative to the total amount of the positive electrode active material layer.

<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 allows lithium ions to pass through, and is exemplified by a porous film and a polymer electrolyte.
A microporous polymer film is preferably used as the porous membrane, and examples of the material include polyolefin, polyimide, polyvinylidene fluoride, polyester, and the like.
In particular, porous polyolefin is preferable, and specific examples include porous polyethylene film, porous polypropylene film, or multilayer film of porous polyethylene film and polypropylene film. Other resins having excellent thermal stability may be coated on the porous polyolefin film.
Examples of polymer electrolytes include polymers in which lithium salts are dissolved and polymers swollen with an electrolytic solution.
The non-aqueous electrolyte 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, such as cylindrical, coin, square, laminate, film, and other arbitrary shapes. 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 of the present disclosure is a laminate type battery.
FIG. 1 is a schematic perspective view showing an example of a laminate type battery, which is an example of the lithium secondary battery of the present disclosure, and FIG. 2 shows the thickness of the laminated electrode body housed in the laminate type battery shown in FIG. 1 is a schematic sectional view in a direction; FIG.
The laminated battery shown in FIG. 1 contains a non-aqueous electrolyte (not shown in FIG. 1) and a laminated electrode assembly (not shown in FIG. 1), and the peripheral portion is sealed. It has a laminated exterior body 1 whose inside is sealed by. 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 outer package 1 is composed of a laminated body in which a positive electrode plate 5 and a negative electrode plate 6 are alternately laminated with separators 7 interposed therebetween, and this laminated body. a surrounding separator 8; The positive electrode plate 5, the negative electrode plate 6, the separator 7, and the separator 8 are impregnated with the non-aqueous electrolyte of the present disclosure.
Each of the plurality of positive electrode plates 5 in the laminated electrode body is 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 the laminated outer body 1. It protrudes outward from the peripheral edge (Fig. 1). A portion of the peripheral end portion of the laminate package 1 where the positive electrode terminal 2 protrudes 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 via a negative electrode tab (not shown). It protrudes outward from the peripheral edge of the body 1 (Fig. 1). A portion of the peripheral end portion of the laminate package 1 where the negative electrode terminal 3 protrudes is sealed with an insulating seal 4 .
In the laminate type battery according to the above example, the number of positive electrode plates 5 is five and the number of negative electrode plates 6 is six. The outer layers are laminated in such a manner that all of them serve as the negative electrode plate 6 . However, the number of positive plates and the number and arrangement of negative plates in the laminate type battery are not limited to this example, and it goes without saying that various modifications 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 filled with a non-aqueous electrolyte, a disk-shaped positive electrode 11, and optionally spacer plates 17 and 18 made of stainless steel or aluminum are arranged in this order. In a stacked state, they are accommodated 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 with a gasket 16 interposed therebetween.
In this example, the non-aqueous electrolytic solution of the present disclosure is used as the non-aqueous electrolytic solution injected into the separator 15 .

The lithium secondary battery of the present disclosure is obtained by charging and discharging a lithium secondary battery (lithium secondary battery before charging and discharging) containing the negative electrode, the positive electrode, and the non-aqueous electrolyte of the present disclosure. It may be a lithium secondary battery.
That is, in the lithium secondary battery of the present disclosure, first, a lithium secondary battery before charging and discharging including the negative electrode, the positive electrode, and the non-aqueous electrolyte of the present disclosure is produced, and then the lithium secondary battery before charging and discharging is produced. It may be a lithium secondary battery produced by charging and discharging a lithium secondary battery one or more times (charged and discharged lithium secondary battery).

Applications of the lithium secondary battery of the present disclosure are not particularly limited, and can be used for various known applications. For example, notebook computers, mobile computers, mobile phones, headphone stereos, video movies, liquid crystal televisions, handy cleaners, electronic notebooks, calculators, radios, backup power supply applications, motors, automobiles, electric vehicles, motorcycles, electric motorcycles, bicycles, electric It can be widely used in small mobile devices and large devices such as bicycles, lighting equipment, game machines, clocks, power tools, and cameras.

Examples of the present disclosure are shown below, but the present disclosure is not limited to the following examples.
In the following examples, "addition amount" means the content with respect to the total amount of the finally obtained non-aqueous electrolytic solution, and "wt%" means mass%.

[Example 1]
A coin-type lithium secondary battery (hereinafter, also referred to as a “coin-type battery”) having the configuration shown in FIG. 3 was manufactured by the following procedure.

<Production of negative electrode>
Amorphous coated natural graphite-based graphite (97 parts by mass), carboxymethyl cellulose (1 part by mass) and SBR latex (2 parts by mass) were kneaded with a water solvent to prepare a pasty 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 with a thickness of 10 μm, dried, and then compressed by a roll press to form a sheet-like negative electrode current collector and a negative electrode active material layer. A negative electrode was obtained. At this time, the negative electrode active material layer had a coating density of 10 mg/cm ² and a filling density of 1.5 g/ml.

<Preparation of positive electrode>
LiNi _0.5 Mn _0.3 Co _0.2 O ₂ (90 parts by mass), acetylene black (5 parts by mass) and polyvinylidene fluoride (5 parts by mass) were kneaded using N-methylpyrrolidinone as a solvent to form a paste. A 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 At this time, the coating density of the positive electrode active material layer was 30 mg/cm ² and the filling density was 2.5 g/ml.

<Preparation of non-aqueous electrolyte>
As non-aqueous solvents, ethylene carbonate (EC), dimethyl carbonate (DMC), and methyl ethyl carbonate (EMC) were mixed at a ratio of 30:35:35 (mass ratio), respectively, to obtain a mixed solvent.
In the obtained mixed solvent, LiPF ₆ as an electrolyte was dissolved so that the concentration of the electrolyte in the finally prepared non-aqueous electrolyte was 1.2 mol/liter.
PRS and the boron compound (B), which are specific examples of the sultone compound (A), were added to and dissolved in the respective amounts shown in Table 1 to the resulting solution to obtain a non-aqueous electrolyte.

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

<Evaluation>
The obtained coin-type battery was evaluated as follows.
Table 1 shows the evaluation results.
Table 1 shows the initial resistance, the resistance after storage, and the resistance increase rate during storage in each example as relative values when the value in Comparative Example 1 described later is set to 100.

In the following
"Conditioning" means that the coin-type battery is charged and discharged three times between 2.75 V and 4.25 V at 25 ° C. in a constant temperature bath,
“Storage” means an operation of storing the coin-type battery in a constant temperature bath at 60° C. for 10 days.
Below, the DC resistance was measured under the temperature condition of -10°C.

(Measurement of initial resistance)
The SOC (State of Charge) of the coin cell after conditioning was adjusted to 50%, and then the initial (i.e., before storage) DCIR (Direct current internal resistance (direct current resistance) was measured.
CC10s discharge was performed at a discharge rate of 0.2C using the coin-type battery adjusted to SOC 50%.
Here, CC10s discharge means discharging for 10 seconds at a constant current.
In the above "CC10s discharge at a discharge rate of 0.2C", the current value (that is, the current value corresponding to the discharge rate of 0.2C) and the amount of voltage drop (= voltage before the start of discharge - 10 seconds after the start of discharge The DC resistance (Ω) was obtained based on the voltage), and the obtained DC resistance (Ω) was taken as the initial resistance (that is, the resistance before storage) (Ω).

Table 1 shows the relative value of the initial resistance of Example 1 when the initial resistance of Comparative Example 1, which will be described later, is set to 100, as the "initial resistance (relative value)" of Example 1.

(Measurement of resistance after storage)
After conditioning and before adjusting the SOC to 50%, the coin-type battery was CC-CV charged to 4.25 V at a charge rate of 0.2 C in a constant temperature bath at 25 ° C. The resistance (Ω) after storage was measured in the same manner as the measurement of the initial resistance described above, except that the operation of applying "" was added.
Here, CC-CV charging means constant current-constant voltage.

Table 1 shows the relative value of the resistance after storage of Example 1 when the resistance after storage of Comparative Example 1 described later is set to 100 as "resistance after storage (relative value)" of Example 1.

(Calculation of resistance increase rate during storage)
The resistance increase rate during storage was calculated by the following formula.
Resistance increase rate during storage = ((resistance after storage (relative value) / initial resistance (relative value)) x 100) - 100

Table 1 shows the resistance increase rate during storage.
The fact that the rate of increase in resistance during storage is a negative value means that compared to Comparative Example 1, the increase in resistance during storage is suppressed.
The resistance increase rate of Comparative Example 1 is zero.

[Comparative Example 1]
In the preparation of the non-aqueous electrolyte, the same operation as in Example 1 was performed except that PRS and LiFOB were not added.
Table 1 shows the results.

[Comparative Example 2]
In the preparation of the non-aqueous electrolyte, the same operation as in Example 1 was performed except that LiFOB was not added.
Table 1 shows the results.

[Comparative Example 3]
In the preparation of the non-aqueous electrolyte, the same operation as in Example 1 was performed except that PRS was not added.
Table 1 shows the results.

[Example 2]
In the preparation of the non-aqueous electrolyte, the amount of PRS added was changed as shown in Table 1, and vinylene carbonate (VC), which is a specific example of the additive (C), was added in the amount shown in Table 1. The same operation as in Example 1 was performed, except that the solution was dissolved with the
Table 1 shows the results.

[Comparative Example 4]
In the preparation of the non-aqueous electrolyte, the same operation as in Example 2 was performed except that LiFOB was not added.
Table 1 shows the results.

[Comparative Example 5]
In the preparation of the non-aqueous electrolyte, the same operation as in Example 2 was performed except that PRS was not added.
Table 1 shows the results.

[Examples 3 to 6]
In the preparation of the non-aqueous electrolyte, the type of additive (C) shown in Table 1 (that is, LiDFP, compound (C6-1), compound (C5-3), or compound (C4A-1); The structure of the compound is as described above) was added in the amount shown in Table 1 and dissolved in the same manner as in Example 2.
Table 1 shows the results.

As shown in Table 1, in the battery of Example 1 using the non-aqueous electrolyte containing the sultone compound (A) and the boron compound (B), compared with the batteries of Comparative Examples 1 to 3, the resistance was reduced.

More specifically, compared with the battery of Comparative Example 1 using a non-aqueous electrolyte containing neither the sultone compound (A) nor the boron compound (B), the sultone compound (A) was contained but the boron compound (B) was In the battery of Comparative Example 2 using the non-aqueous electrolyte containing no, the initial resistance (resistance before storage) increased.
Compared to the battery of Comparative Example 1, the battery of Comparative Example 3 using the non-aqueous electrolyte solution containing the boron compound (B) but not the sultone compound (A) caused an increase in resistance during storage.
In the battery of Example 1 using the non-aqueous electrolyte containing the sultone compound (A) and the boron compound (B), the initial resistance (resistance before storage) was reduced compared to the battery of Comparative Example 2, and Compared to the battery of Comparative Example 3, an increase in resistance during storage was suppressed. In the battery of Example 1, compared with the battery of Comparative Example 1, the initial resistance (resistance before storage) was maintained at the same level, and the increase in resistance during storage was suppressed.

Compared to the battery of Example 1, in Example 2 using the non-aqueous electrolyte containing the sultone compound (A), the boron compound (B) and the additive (C) (VC), the initial resistance was further reduced. Ta.
Compared to the battery of Example 2, the batteries of Examples 3 to 6 using a non-aqueous electrolyte containing the sultone compound (A), the boron compound (B), and the additive (C) (VC + others) are resistance and resistance increase during storage were further improved.

1 Laminated exterior body 2 Positive electrode terminal 3 Negative electrode terminal 4 Insulating seal 5 Positive electrode plate 6 Negative electrode plates 7, 8 Separator 11 Positive electrode 12 Negative electrode 13 Positive electrode can 14 Sealing plate 15 Separator 16 Gaskets 17, 18 Spacer plate

Claims (8)

the following sultone compound (A),
a boron compound (B) which is at least one selected from the group consisting of the following compounds (1) to (6);
an additive (C) that is at least one selected from the group consisting of the following compound (C2), the following compound (C4), the following compound (C5), the following compound (C6), and the following compound (C7);
contains
The content of the sultone compound (A) is 0.001% by mass to 10% by mass with respect to the total amount of the battery non-aqueous electrolyte,
The content of the boron compound (B) is 0.001% by mass to 10% by mass with respect to the total amount of the battery non-aqueous electrolyte,
A non-aqueous electrolyte for batteries, 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 for batteries.


[In compound (A), R ^a1 to R ^a4 each independently represent a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 3 carbon atoms, or a fluorohydrocarbon group having 1 to 3 carbon atoms.
Among compounds (1) to (6),
R ³¹ to R ³³ each independently represent a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, or a fluorohydrocarbon group having 1 to 6 carbon atoms,
R ⁴¹ to R ⁴³ each independently represents a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, or a fluorohydrocarbon group having 1 to 6 carbon atoms,
R ⁵¹ represents a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, or a fluorohydrocarbon group having 1 to 6 carbon atoms,
R ⁵² represents a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, or a fluorohydrocarbon group having 1 to 6 carbon atoms,
n represents an integer of 1 to 3; ]



[In the compound (C2), R ^c21 to R ^c24 each independently represent a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, or a fluorohydrocarbon group having 1 to 6 carbon atoms. However, R ^c21 to R ^c24 are not hydrogen atoms at the same time.
In the compound (C4), R ^c41 to R ^c43 each independently represent a hydrocarbon group having 1 to 6 carbon atoms, a fluorohydrocarbon group having 1 to 6 carbon atoms, or a group (s), and n is Represents 0 or 1.
In group (s), R ^c44 to R ^c46 each independently represent a hydrocarbon group having 1 to 6 carbon atoms, and * represents a bonding position.
In compound (C5), R ^c51 to R ^c54 each independently represent a hydrogen atom, group (a), or group (b). However, R ^c51 to R ^c54 are not hydrogen atoms at the same time. In group (a) and group (b), * represents a bonding position.
In compound (C6), R ^c61 represents a fluorine atom or a fluorohydrocarbon group having 1 to 6 carbon atoms.
In compound (C7), R ^c71 and R ^c72 each independently represent a fluorine atom or a fluorohydrocarbon group having 1 to 6 carbon atoms. ]
The non-aqueous electrolyte for a battery according to claim 1, wherein the boron compound (B) contains the compound (1). the following sultone compound (A),
A boron compound (B) that is the following compound (1),
an additive (C) which is the following compound (C1) or the following compound (C3);
contains
The content of the sultone compound (A) is 0.001% by mass to 10% by mass with respect to the total amount of the battery non-aqueous electrolyte,
The content of the boron compound (B) is 0.001% by mass to 10% by mass with respect to the total amount of the battery non-aqueous electrolyte,
A non-aqueous electrolyte for batteries, 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 for batteries.



[In compound (A), R ^a1 to R ^a4 each independently represent a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 3 carbon atoms, or a fluorohydrocarbon group having 1 to 3 carbon atoms. ]


[In the compound (C1), R ^c11 and R ^c12 each independently represent a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, or a fluorohydrocarbon group having 1 to 6 carbon atoms.
In the compound (C3), R ^c31 to R ^c33 each independently represent a fluorine atom or a —OLi group, and at least one of R ^c31 to R ^c33 is a —OLi group. ]
the following sultone compound (A),
A boron compound (B) that is the following compound (1),
an additive (C) consisting of the following compound (C1) and at least one selected from the group consisting of the following compound (C2) to the following compound (C7);
contains
The content of the sultone compound (A) is 0.001% by mass to 10% by mass with respect to the total amount of the battery non-aqueous electrolyte,
The content of the boron compound (B) is 0.001% by mass to 10% by mass with respect to the total amount of the battery non-aqueous electrolyte,
A non-aqueous electrolyte for batteries, 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 for batteries.


[In compound (A), R ^a1 to R ^a4 each independently represent a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 3 carbon atoms, or a fluorohydrocarbon group having 1 to 3 carbon atoms. ]



[In the compound (C1), R ^c11 and R ^c12 each independently represent a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, or a fluorohydrocarbon group having 1 to 6 carbon atoms.
In compound (C2), R ^c21 to R ^c24 each independently represent a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, or a fluorohydrocarbon group having 1 to 6 carbon atoms. However, R ^c21 to R ^c24 are not hydrogen atoms at the same time.
In the compound (C3), R ^c31 to R ^c33 each independently represent a fluorine atom or a —OLi group, and at least one of R ^c31 to R ^c33 is a —OLi group.
In the compound (C4), R ^c41 to R ^c43 each independently represent a hydrocarbon group having 1 to 6 carbon atoms, a fluorohydrocarbon group having 1 to 6 carbon atoms, or a group (s), and n is Represents 0 or 1.
In group (s), R ^c44 to R ^c46 each independently represent a hydrocarbon group having 1 to 6 carbon atoms, and * represents a bonding position.
In compound (C5), R ^c51 to R ^c54 each independently represent a hydrogen atom, a hydrocarbon group having 1 to 6 carbon atoms, group (a), or group (b). In group (a) and group (b), * represents a bonding position.
In compound (C6), R ^c61 represents a fluorine atom or a fluorohydrocarbon group having 1 to 6 carbon atoms.
In compound (C7), R ^c71 and R ^c72 each independently represent a fluorine atom or a fluorohydrocarbon group having 1 to 6 carbon atoms. ]
5. The non-aqueous electrolyte for a battery according to claim 4 , wherein the additive (C) is the compound (C1) and the compound (C3 ) . a positive electrode;
Metallic lithium, lithium-containing alloys, metals or alloys that can be alloyed with lithium, oxides that can be doped/dedoped with lithium ions, transition metal nitrides that can be doped/dedoped 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 batteries according to any one of claims 1 to 5 ,
Lithium secondary battery including. 7. The lithium secondary battery according to claim 6 , wherein the content of Si in the negative electrode is 5% by mass or less with respect to the entire negative electrode. A lithium secondary battery obtained by charging and discharging the lithium secondary battery according to claim 6 or 7 .