JP7395816B2 - Non-aqueous electrolytes for batteries and lithium secondary batteries - Google Patents

Description

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

1,2-dimethoxyethane may be contained in a non-aqueous electrolyte used in batteries (for example, lithium secondary batteries).
For example, Patent Document 1 discloses a non-aqueous electrolyte containing a cyclic carbonate derivative and 1,2-dimethoxyethane.

Japanese Patent Application Publication No. 2010-86722

1,2-dimethoxyethane is effective as a low viscosity solvent.
However, in a battery using a nonaqueous electrolyte containing 1,2-dimethoxyethane, battery resistance may increase.
An object of one embodiment of the present disclosure is to provide a nonaqueous electrolyte for a battery that can reduce battery resistance even though it contains 1,2-dimethoxyethane.
Another object of the present disclosure is to provide a lithium secondary battery that uses a non-aqueous electrolyte containing 1,2-dimethoxyethane and has reduced battery resistance. be.

Means for solving the above problems include the following aspects.
<1> A non-aqueous solvent containing 1,2-dimethoxyethane,
electrolyte and
A compound represented by the following formula (S1), a compound represented by the following formula (S2), a compound represented by the following formula (S3), a compound represented by the following formula (S4), and the following formula (S5) an additive S selected from the group consisting of compounds represented by;
A nonaqueous electrolyte for batteries containing.

In formula (S1), R ¹¹ to R ¹⁴ each independently represent a hydrogen atom, a hydrocarbon group having 1 to 6 carbon atoms, a group represented by formula (1a), or a group represented by formula (1b). represents. In formula (1a) and formula (1b), * represents the bonding position.
In formula (S2), R ²¹ to R ²⁴ each independently represent a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, or a fluorinated hydrocarbon group having 1 to 6 carbon atoms.
In formula (S3), R ³¹ to R ³⁶ each independently represent a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, or a fluorinated hydrocarbon group having 1 to 6 carbon atoms.
In formula (S4), R ⁴¹ represents a fluorine atom, an alkoxy group having 1 to 6 carbon atoms, or a fluorinated hydrocarbon group having 1 to 6 carbon atoms.
In formula (S5), R ⁵¹ represents a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, or a fluorinated hydrocarbon group having 1 to 6 carbon atoms.

<2> The nonaqueous electrolyte for a battery according to <1>, wherein the content of the 1,2-dimethoxyethane is 10% by volume to 40% by volume based on the total amount of the nonaqueous solvent.
<3> The additive S is at least selected from the group consisting of a compound represented by the formula (S1), a compound represented by the formula (S2), and a compound represented by the formula (S3). The non-aqueous electrolyte for batteries according to <1> or <2>, containing one type.
<4> The nonaqueous battery according to any one of <1> to <3>, wherein the additive S contains at least one selected from the group consisting of compounds represented by the formula (S1). Electrolyte.
<5> In the formula (S1), R ¹¹ is a group represented by the formula (1a) or a group represented by the formula (1b), and R ¹² to R ¹⁴ are each independently to any one of <1> to <4>, which is a hydrogen atom, a hydrocarbon group having 1 to 6 carbon atoms, a group represented by formula (1a), or a group represented by formula (1b). Non-aqueous electrolyte for batteries as described.
<6> The battery according to any one of <1> to <5>, wherein the content of the additive S is 0.001% by mass to 10% by mass based on the total amount of the nonaqueous electrolyte for batteries. Non-aqueous electrolyte.
<7> The nonaqueous electrolyte for a battery according to any one of <1> to <6>, wherein the nonaqueous solvent further contains a cyclic carbonate compound and a chain carbonate compound.
<8> 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 nitrides that can be doped and dedoped with lithium ions, and lithium. a negative electrode containing as a negative electrode active material at least one member selected from the group consisting of carbon materials capable of doping and dedoping ions;
The non-aqueous electrolyte for batteries according to any one of <1> to <7>,
Lithium secondary batteries including.
<9> A lithium secondary battery obtained by charging and discharging the lithium secondary battery according to <8>.

According to one aspect of the present disclosure, there is provided a nonaqueous electrolyte for batteries that can reduce battery resistance after storage, even though it contains 1,2-dimethoxyethane.
According to another aspect of the present disclosure, there is provided a lithium secondary battery that uses a non-aqueous electrolyte containing 1,2-dimethoxyethane and has reduced battery resistance after storage. be done.

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. 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. 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. ³ is a graph showing the amount of gas generated (cm 3 ) when each of the non-aqueous electrolytes of Comparative Example 1 and Examples 1 to 4 are used.

In this specification, a numerical range expressed using "~" means a range that includes the numerical values written before and after "~" as lower and upper limits.
In this specification, if there are multiple substances corresponding to each component in the composition, unless otherwise specified, the amount of each component in the composition refers to the total amount of the multiple substances present in the composition. means.

[Non-aqueous electrolyte for batteries]
The non-aqueous electrolyte for batteries (hereinafter also simply referred to as “non-aqueous electrolyte”) of the present disclosure includes:
a non-aqueous solvent containing 1,2-dimethoxyethane;
electrolyte and
A compound represented by the following formula (S1), a compound represented by the following formula (S2), a compound represented by the following formula (S3), a compound represented by the following formula (S4), and the following formula (S5) an additive S selected from the group consisting of compounds represented by;
Contains.

In formula (S1), R ¹¹ to R ¹⁴ each independently represent a hydrogen atom, a hydrocarbon group having 1 to 6 carbon atoms, a group represented by formula (1a), or a group represented by formula (1b). represents. In formula (1a) and formula (1b), * represents the bonding position.
In formula (S2), R ²¹ to R ²⁴ each independently represent a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, or a fluorinated hydrocarbon group having 1 to 6 carbon atoms.
In formula (S3), R ³¹ to R ³⁶ each independently represent a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, or a fluorinated hydrocarbon group having 1 to 6 carbon atoms.
In formula (S4), R ⁴¹ represents a fluorine atom, an alkoxy group having 1 to 6 carbon atoms, or a fluorinated hydrocarbon group having 1 to 6 carbon atoms.
In formula (S5), R ⁵¹ represents a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, or a fluorinated hydrocarbon group having 1 to 6 carbon atoms.

According to the nonaqueous electrolyte of the present disclosure, battery resistance can be reduced even though the nonaqueous electrolyte contains 1,2-dimethoxyethane.
The reason for this effect is presumed to be as follows.

In a battery using a non-aqueous electrolyte containing 1,2-dimethoxyethane (hereinafter also referred to as DME), battery resistance may increase. The reason for the increase in battery resistance is that DME strongly solvates ions (for example, lithium ions in lithium secondary batteries) through bidentate coordination and is co-inserted into the negative electrode with the ions; Possible causes include decomposition at the positive electrode, causing gas generation and/or deposit formation.
In this regard, the non-aqueous electrolyte of the present disclosure contains a non-aqueous solvent containing DME, and also contains additive S. As a result, the additive S forms a high-quality film on the negative electrode and the positive electrode, and these films suppress the above-mentioned co-insertion into the negative electrode, and also prevent gas generation and/or deposit formation on the positive electrode. It is thought that this suppresses the increase in battery resistance caused by DME.

<Non-aqueous solvent>
The non-aqueous electrolyte of the present disclosure contains a non-aqueous solvent.
The non-aqueous solvent includes DME (ie, 1,2-dimethoxyethane).
DME is a low viscosity solvent. Therefore, when the non-aqueous solvent contains DME, the handling properties of the non-aqueous electrolyte are improved.

The content of DME is preferably 10% by mass to 40% by mass based on the total amount of the nonaqueous solvent.
When the content of DME is 10% by mass or more based on the total amount of the nonaqueous solvent, the handling properties of the nonaqueous electrolyte are further improved.
Generally, when the content of DME is 10% by mass or more based on the total amount of non-aqueous solvent, the above-mentioned co-insertion into the negative electrode and the formation of gas or deposits at the positive electrode are generally conducted. becomes more pronounced, and as a result, the battery resistance tends to increase further. However, by containing the additive S, the nonaqueous electrolyte of the present disclosure prevents an increase in battery resistance even when the DME content is 10% by mass or more based on the total amount of the nonaqueous solvent. Can be effectively suppressed. That is, when the content of DME is 10% by mass or more based on the total amount of the nonaqueous solvent, the improvement range (that is, the reduction range of battery resistance) by the additive S becomes larger. When the content of DME is 20% by mass or more based on the total amount of the nonaqueous solvent, the range of improvement by the additive S becomes even larger.
On the other hand, when the content of DME is 40% by mass or less based on the total amount of the nonaqueous solvent, the increase in battery resistance is suppressed due to the small content of DME itself.

The non-aqueous solvent may further include solvent species other than DME.
As the solvent other than DME, various known solvents can be appropriately selected.
As the solvent species other than DME, for example, the solvent species described in paragraphs 0069 to 0087 of JP 2017-45723 A can be used.

It is preferable that the nonaqueous solvent further contains a cyclic carbonate compound and a chain carbonate compound.
In this case, the number of cyclic carbonate compounds and chain carbonate compounds contained in the nonaqueous solvent may be one, or two or more.

Examples of the cyclic carbonate compound include ethylene carbonate (hereinafter also referred to as "EC"), propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, and 2,3-pentylene carbonate. Examples include rencarbonate.
Among these, ethylene carbonate and propylene carbonate, which have a high dielectric constant, are preferred. In the case of a battery using a negative electrode active material containing graphite, the nonaqueous solvent more preferably contains ethylene carbonate.

Examples of chain carbonate compounds include dimethyl carbonate (hereinafter also referred to as "DMC"), ethylmethyl carbonate (hereinafter also referred to as "EMC"), diethyl carbonate, methylpropyl carbonate, methylisopropyl carbonate, ethylpropyl carbonate, and dipropyl carbonate. , methylbutyl carbonate, ethylbutyl carbonate, dibutyl carbonate, methylpentyl carbonate, ethylpentyl carbonate, dipentyl carbonate, methylheptyl carbonate, ethylheptyl carbonate, diheptyl carbonate, methylhexyl carbonate, ethylhexyl carbonate, dihexyl carbonate, methyloctyl carbonate, ethyl Examples include octyl carbonate, dioctyl carbonate, and the like.

Examples of combinations of cyclic carbonate and linear 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, 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, ethylene carbonate, propylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, and the like.

The mixing ratio of the cyclic carbonate compound and the chain carbonate compound, expressed in volume ratio, is, for example, 5:95 to 80:20, preferably 10:90 to 70:30, more preferably 10:90 to 70:30. is from 20:80 to 60:40. By setting such a ratio, it is possible to suppress the increase in viscosity of the non-aqueous electrolyte and increase the degree of dissociation of the electrolyte, thereby increasing the conductivity of the non-aqueous electrolyte, which is related to the charging and discharging characteristics of the battery. . Furthermore, 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 at room temperature or low temperature can be improved.

The non-aqueous solvent may contain other compounds than the cyclic carbonate compound and the chain carbonate compound.
In this case, the number of other compounds contained in the nonaqueous solvent may be one, or two or more.
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 ester compounds, amide compounds, and chain carbamates. compounds, cyclic amide compounds, cyclic urea compounds, boron compounds, polyethylene glycol derivatives, and the like.
Regarding these compounds, the descriptions in paragraphs 0069 to 0087 of JP 2017-45723 A can be appropriately referred to.

The total content of the cyclic carbonate compound and the chain carbonate compound is preferably 60% to 90% by volume, more preferably 60% to 80% by volume, based on the total amount of the nonaqueous solvent.

<Electrolyte>
The non-aqueous electrolyte of the present disclosure contains an electrolyte.
Preferably, the electrolyte includes _LiPF6 .
In this case, the proportion of LiPF ₆ in the electrolyte is preferably 1% by mass to 100% by mass, more preferably 10% by mass to 100% by mass, even more preferably 50% by mass to 100% by mass.

The concentration of electrolyte 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.
Further, 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.

The electrolyte may contain compounds other than _LiPF6 .
As compounds other than LiPF ₆ ;
_{( 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 to 5, k = integer of 1 to 8);
LiBF ₄ , LiClO ₄ , LiAsF ₆ , Li ₂ SiF ₆ , LiOSO ₂ C _k F _(2k+1) (k=integer from 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 ^Lithium _salts ⁽ _i.e. ^{, _} , lithium salt other than LiPF ₆ );
etc.

<Additive S>
The non-aqueous electrolyte of the present disclosure contains additive S.
Additive S includes a compound represented by the following formula (S1), a compound represented by the following formula (S2), a compound represented by the following formula (S3), a compound represented by the following formula (S4), and It is at least one selected from the group consisting of compounds represented by the following formula (S5).

The content of the additive S is preferably 0.001% by mass to 10% by mass, more preferably 0.001% by mass to 5.0% by mass, and 0.001% by mass to 5.0% by mass, based on the total amount of the nonaqueous electrolyte. 3.0% by mass is more preferred, 0.01% by mass to 3.0% by mass is even more preferred, 0.1 to 3.0% by mass is even more preferred, and even more preferably 0.1 to 2.0% by mass. More preferably 0.1 to 1.0% by mass.

(Compound represented by formula (S1))
The compound represented by formula (S1) is as follows.

In formula (S1), R ¹¹ to R ¹⁴ each independently represent a hydrogen atom, a hydrocarbon group having 1 to 6 carbon atoms, a group represented by formula (1a), or a group represented by formula (1b). represents. In formula (1a) and formula (1b), * represents the bonding position.

In formula (S1), the hydrocarbon group having 1 to 6 carbon atoms represented by R ¹¹ to R ¹⁴ may be a straight chain hydrocarbon group or a hydrocarbon group having a branched and/or ring structure. It may be.

In formula (S1), specific examples of the hydrocarbon group having 1 to 6 carbon atoms represented by R ¹¹ to R ¹⁴ 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- Alkyl groups such as hexyl group, isohexyl group, sec-hexyl group, tert-hexyl group; vinyl group, 1-propenyl group, allyl group, 1-butenyl group, 2-butenyl group, 3-butenyl group, pentenyl group, hexenyl group and alkenyl groups such as isopropenyl group, 2-methyl-2-propenyl group, 1-methyl-2-propenyl group, and 2-methyl-1-propenyl group.

In formula (S1), the hydrocarbon group having 1 to 6 carbon atoms represented by R ¹¹ to R ¹⁴ is preferably an alkyl group or an alkenyl group, and more preferably an alkyl group.
In formula (S1), the number of carbon atoms in the hydrocarbon group having 1 to 6 carbon atoms represented by R ¹¹ to R ¹⁴ is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1.

Specific examples of compounds represented by formula (S1) include compounds represented by formulas (S1-1) to (S1-4) below (hereinafter, compound (S1-1) to compound (S1), respectively). -4)), but the compound represented by formula (S1) is not limited to these specific examples.

(Compound represented by formula (S2))
The compound represented by formula (S2) is as follows.

In formula (S2), R ²¹ to R ²⁴ each independently represent a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, or a fluorinated hydrocarbon group having 1 to 6 carbon atoms.

In formula (S2), the hydrocarbon group having 1 to 6 carbon atoms represented by R ²¹ to R ²⁴ may be a straight chain hydrocarbon group or a hydrocarbon group having a branched and/or ring structure. It may be.
Specific examples of the hydrocarbon group having 1 to 6 carbon atoms represented by R ²¹ to R ²⁴ in formula (S2) are the hydrocarbon groups having 1 to 6 carbon atoms represented by R ¹¹ to R ¹⁴ in formula (S1). This is the same as the specific example of the hydrocarbon group.
In formula (S2), the hydrocarbon group having 1 to 6 carbon atoms represented by R ²¹ to R ²⁴ is preferably an alkyl group or an alkenyl group, and more preferably an alkyl group.
In formula (S2), the number of carbon atoms in the hydrocarbon group having 1 to 6 carbon atoms represented by R ²¹ to R ²⁴ is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1.

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

In formula (S2), the fluorinated hydrocarbon group having 1 to 6 carbon atoms represented by R ²¹ to R ²⁴ may be a linear fluorinated hydrocarbon group, or may have a branched and/or ring structure. It may also be a fluorinated hydrocarbon group.
In formula (S2), specific examples of the fluorinated hydrocarbon group having 1 to 6 carbon atoms represented by R ²¹ to R ²⁴ include fluoromethyl group, difluoromethyl group, trifluoromethyl group, 2,2,2 -Trifluoroethyl group, 1,1,2,2-tetrafluoroethyl group, perfluoroethyl group, 2,2,3,3-tetrafluoropropyl group, perfluoropropyl group, perfluorobutyl group, perfluoropentyl 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, perfluoro Examples include fluoroalkenyl groups such as propenyl group and perfluorobutenyl group.

In formula (S2), the fluorinated hydrocarbon group having 1 to 6 carbon atoms represented by R ²¹ to R ²⁴ is preferably a fluorinated alkyl group or a fluorinated alkenyl group, and more preferably a fluorinated alkyl group.
In formula (S2), the number of carbon atoms in the fluorinated hydrocarbon group having 1 to 6 carbon atoms represented by R ²¹ to R ²⁴ is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1.

In formula (S2), R ²¹ to R ²⁴ are each independently preferably a hydrogen atom, a fluorine atom, a methyl group, an ethyl group, a trifluoromethyl group, or a pentafluoroethyl group, and more preferably a hydrogen atom or a methyl group. Preferred is a hydrogen atom, particularly preferred.

Specific examples of compounds represented by formula (S2) include compounds represented by formulas (S2-1) to (S2-21) below (hereinafter, compound (S2-1) to compound (S2), respectively). -21)), but the compound represented by formula (S2) is not limited to these specific examples.
Among these, compound (S2-1) (ie, 1,3-propenesultone; hereinafter also referred to as "PRS") is particularly preferred.

(Compound represented by formula (S3))
The compound represented by formula (S3) is as follows.

In formula (S3), R ³¹ to R ³⁶ each independently represent a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, or a fluorinated hydrocarbon group having 1 to 6 carbon atoms.

In formula (S3), the hydrocarbon group having 1 to 6 carbon atoms represented by R ³¹ to R ³⁶ may be a straight chain hydrocarbon group, or a hydrocarbon group having a branched and/or ring structure. It may be.
Specific examples of the hydrocarbon group having 1 to 6 carbon atoms represented by R ³¹ to R ³⁶ in formula (S3) are the hydrocarbon groups having 1 to 6 carbon atoms represented by R ¹¹ to R ¹⁴ in formula (S1). This is the same as the specific example of the hydrocarbon group.
In formula (S3), the hydrocarbon group having 1 to 6 carbon atoms represented by R ³¹ to R ³⁶ is preferably an alkyl group or an alkenyl group, and more preferably an alkyl group.
In formula (S3), the number of carbon atoms in the hydrocarbon group having 1 to 6 carbon atoms represented by R ³¹ to R ³⁶ is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1.

In formula (S3), the fluorinated hydrocarbon group having 1 to 6 carbon atoms represented by R ³¹ to R ³⁶ may be a straight chain fluorinated hydrocarbon group, or may have a branched and/or ring structure. It may also be a fluorinated hydrocarbon group.
Specific examples of the fluorinated hydrocarbon group having 1 to 6 carbon atoms represented by R ³¹ to R ³⁶ in formula (S3) include 1 to 6 carbon atoms represented by R ²¹ to R ²⁴ in formula (S2); This is the same as the specific example of the fluorinated hydrocarbon group in ~6.
In formula (S3), the fluorinated hydrocarbon group having 1 to 6 carbon atoms represented by R ³¹ to R ³⁶ is preferably a fluorinated alkyl group or a fluorinated alkenyl group, and more preferably a fluorinated alkyl group.
In formula (S3), the number of carbon atoms in the fluorinated hydrocarbon group having 1 to 6 carbon atoms represented by R ³¹ to R ³⁶ is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1.

In formula (S3), R ³¹ to R ³⁶ are each independently preferably a hydrogen atom, a fluorine atom, a methyl group, an ethyl group, a trifluoromethyl group, or a pentafluoroethyl group, and more preferably a hydrogen atom or a methyl group. Preferred is a hydrogen atom, particularly preferred.

Specific examples of compounds represented by formula (S3) include compounds represented by formulas (S3-1) to (S3-21) below (hereinafter, compound (S3-1) to compound (S3), respectively). -21)), but the compound represented by formula (S3) is not limited to these specific examples.
Among these, compound (S3-1) (ie, 1,3-propane sultone; hereinafter also referred to as "PS") is particularly preferred.

(Compound represented by formula (S4))
The compound represented by formula (S4) is as follows.

In formula (S4), R ⁴¹ represents a fluorine atom, an alkoxy group having 1 to 6 carbon atoms, or a fluorinated hydrocarbon group having 1 to 6 carbon atoms.

In formula (S4), the alkoxy group having 1 to 6 carbon atoms represented by R ⁴¹ may be a linear alkoxy group or an alkoxy group having a branched and/or ring structure.
In formula (S4), the number of carbon atoms in the alkoxy group having 1 to 6 carbon atoms represented by R ⁴¹ is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1.

In formula (S4), the fluorinated hydrocarbon group having 1 to 6 carbon atoms represented by R ⁴¹ may be a linear fluorinated hydrocarbon group, or a fluorinated hydrocarbon group having a branched and/or ring structure. It may also be a hydrocarbon group.
Specific examples of the fluorinated hydrocarbon group having 1 to 6 carbon atoms represented by R ⁴¹ in formula (S4) include the fluorinated hydrocarbon group having 1 to 6 carbon atoms represented by R ²¹ to R ²⁴ in formula (S2). This is the same as the specific example of the hydrogenated hydrocarbon group.
In formula (S4), the fluorinated hydrocarbon group having 1 to 6 carbon atoms represented by R ⁴¹ is preferably a fluorinated alkyl group, a fluorinated alkenyl group, or a fluorinated alkynyl group; A fluorinated alkenyl group is more preferred, and a fluorinated alkyl group is particularly preferred.
In formula (S4), the number of carbon atoms in the fluorinated hydrocarbon group having 1 to 6 carbon atoms represented by R ⁴¹ is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1.

In formula (S4), R ⁴¹ is preferably an alkoxy group having 1 to 6 carbon atoms or a fluorinated hydrocarbon group having 1 to 6 carbon atoms, from the viewpoint of further reducing battery resistance. Hydrocarbon groups are particularly preferred.

As the compound represented by formula (S4),
Lithium trifluoromethanesulfonate or lithium pentafluoroethanesulfonate is preferred;
Lithium trifluoromethanesulfonate (hereinafter also referred to as "TFMSLi") is particularly preferred.

(Compound represented by formula (S5))
The compound represented by formula (S5) is as follows.

In formula (S5), R ⁵¹ represents a fluorine atom, a hydrocarbon group having 1 to 6 carbon atoms, or a fluorinated hydrocarbon group having 1 to 6 carbon atoms.

In formula (S5), the hydrocarbon group having 1 to 6 carbon atoms represented by R ⁵¹ may be a straight chain hydrocarbon group or a hydrocarbon group having a branched and/or ring structure. Good too.
In formula (S5), specific examples of the hydrocarbon group having 1 to 6 carbon atoms represented by R ⁵¹ are the hydrocarbon groups having 1 to 6 carbon atoms represented by R ¹¹ to R ¹⁴ in formula (S1). This is the same as the specific example.
In formula (S5), the hydrocarbon group having 1 to 6 carbon atoms represented by R ⁵¹ 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. .
In formula (S5), the number of carbon atoms in the hydrocarbon group having 1 to 6 carbon atoms represented by R ⁵¹ is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1.

In formula (S5), the fluorinated hydrocarbon group having 1 to 6 carbon atoms represented by R ⁵¹ may be a linear fluorinated hydrocarbon group, or a fluorinated hydrocarbon group having a branched and/or ring structure. It may also be a hydrocarbon group.
Specific examples of the fluorinated hydrocarbon group having 1 to 6 carbon atoms represented by R ⁵¹ in formula (S5) include the fluorinated hydrocarbon group having 1 to 6 carbon atoms represented by R ²² to R ²⁴ in formula (S2). This is the same as the specific example of the hydrogenated hydrocarbon group.
In formula (S5), the fluorinated hydrocarbon group having 1 to 6 carbon atoms represented by R ⁵¹ is preferably a fluorinated alkyl group, a fluorinated alkenyl group, or a fluorinated alkynyl group; A fluorinated alkenyl group is more preferred, and a fluorinated alkyl group is particularly preferred.
In formula (S5), the number of carbon atoms in the fluorinated hydrocarbon group having 1 to 6 carbon atoms represented by R ⁵¹ is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1.

In formula (S5), R ⁵¹ is 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 hydrogen Atoms are particularly preferred.

As the compound represented by formula (S5),
Methanesulfonyl fluoride, ethanesulfonyl fluoride, propanesulfonyl fluoride, 2-propanesulfonyl fluoride, butanesulfonyl fluoride, 2-butanesulfonyl fluoride, hexanesulfonyl fluoride, trifluoromethanesulfonyl fluoride, perfluoroethanesulfonyl fluoride Preferred are perfluoropropanesulfonyl fluoride, perfluorobutanesulfonyl fluoride, ethenesulfonyl fluoride, 1-propene-1-sulfonyl fluoride, or 2-propene-1-sulfonyl fluoride,
Methanesulfonyl fluoride, ethanesulfonyl fluoride, propanesulfonyl fluoride, 2-propanesulfonyl fluoride, butanesulfonyl fluoride, 2-butanesulfonyl fluoride, hexanesulfonyl fluoride, trifluoromethanesulfonyl fluoride, perfluoroethanesulfonyl fluoride More preferably, perfluoropropanesulfonyl fluoride or perfluorobutanesulfonyl fluoride,
More preferably, methanesulfonyl fluoride, ethanesulfonyl fluoride, propanesulfonyl fluoride, 2-propanesulfonyl fluoride, butanesulfonyl fluoride, 2-butanesulfonyl fluoride, or hexanesulfonyl fluoride,
More preferably methanesulfonyl fluoride, ethanesulfonyl fluoride, or propanesulfonyl fluoride,
Methanesulfonyl fluoride (hereinafter also referred to as "MSF") is particularly preferred.

As described above, the additive S described above has the effect of reducing battery resistance in a battery using a non-aqueous electrolyte containing DME by forming a high-quality film on the negative electrode and the positive electrode.
Furthermore, the above-described additive S also has the effect of suppressing gas generation (that is, gas generation due to DME being decomposed at the positive electrode) in a battery using a non-aqueous electrolyte containing DME.

From the viewpoint of suppressing gas generation more effectively, the additive S is a group consisting of a compound represented by formula (S1), a compound represented by formula (S2), and a compound represented by formula (S3). It is preferable that at least one type selected from the above is included, and it is more preferable that at least one type selected from the group consisting of compounds represented by formula (S1) is included.

In addition, from the perspective of suppressing gas generation more effectively,
A preferred embodiment of the compound represented by formula (S1) is that in formula (S1), R ¹¹ is a hydrocarbon group having 1 to 6 carbon atoms, a group represented by formula (1a), or a group represented by formula (1b). and R ¹² to R ¹⁴ are each independently a hydrogen atom, a hydrocarbon group having 1 to 6 carbon atoms, a group represented by formula (1a), or a group represented by formula (1b). An embodiment in which the group is;
A more preferable embodiment of the compound represented by formula (S1) is that in formula (S1), R ¹¹ represents a group represented by formula (1a) or a group represented by formula (1b), and R ¹² to R ¹⁴ are each independently a hydrogen atom, a hydrocarbon group having 1 to 6 carbon atoms, a group represented by formula (1a), or a group represented by formula (1b).

The nonaqueous electrolyte of the present disclosure is suitable not only as a nonaqueous electrolyte for lithium secondary batteries, but also as a nonaqueous electrolyte for primary batteries, a nonaqueous electrolyte for electrochemical capacitors, and an electric double layer capacitor. It can also be used as an electrolyte for aluminum electrolytic capacitors.

[Lithium secondary battery]
The lithium secondary battery of the present disclosure includes a positive electrode, a negative electrode, and the nonaqueous 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 materials in the negative electrode include metallic lithium, lithium-containing alloys, metals or alloys that can be alloyed with lithium, oxides that can dope and dedope lithium ions, and oxides that can dope and dedope lithium ions. At least one member selected from the group consisting of a transition metal nitride and a carbon material capable of doping and dedoping lithium ions (it 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. Alternatively, lithium titanate may be used.
Among these, carbon materials that can be doped and dedoped with lithium ions are preferred. Examples of such carbon materials include carbon black, activated carbon, graphite materials (artificial graphite, natural graphite), amorphous carbon materials, and the like. The carbon material may be in any of fibrous, spherical, potato-like, and flake-like forms.

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. As the artificial graphite, graphitized MCMB, graphitized MCF, etc. are used. Further, as the graphite material, one containing boron can also be used. Further, as the graphite material, those coated with metals such as gold, platinum, silver, copper, and tin, those coated with amorphous carbon, and those coated with a mixture of amorphous carbon and graphite can also be used.

These carbon materials may be used alone or in combination of two or more.
The above-mentioned carbon material is particularly preferably 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. Further, as the carbon material, graphite having a true density of 1.70 g/cm ³ or more or a highly crystalline carbon material having properties similar to graphite is also preferable. By using carbon materials such as those described above, it is possible to further increase the energy density of the battery.

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

<Positive electrode>
The positive electrode may include a positive electrode active material and a positive electrode current collector.
As the positive electrode active material in the positive electrode, transition metal oxides or transition metal sulfides such as MoS ₂ , TiS ₂ , MnO ₂ , V ₂ O ₅ , LiCoO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiNi _X Co _{(1-X) O 2 [ 0 <} ≦(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 made of lithium and transition metals such as 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 and LiMnPO ₄ ; Examples include conductive polymer materials such as polyaniline, polythiophene, polypyrrole, polyacetylene, polyacene, dimercaptothiadiazole, and polyaniline composites. Among these, a composite oxide consisting of lithium and a transition metal is particularly preferred. When the negative electrode is lithium metal or lithium alloy, a carbon material can also be used as the positive electrode. Moreover, 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 used in combination. If the positive electrode active material has insufficient electrical conductivity, it can be used together with a conductive additive to form a positive electrode. Examples of the conductive aid 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 includes 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 transmits lithium ions, and examples thereof include a porous membrane 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, and polyester.
Particularly preferred are porous polyolefins, and specific examples include porous polyethylene films, porous polypropylene films, and multilayer films of porous polyethylene films and polypropylene films. Other resins having excellent thermal stability may be coated on the porous polyolefin film.
Examples of the polymer electrolyte include a polymer in which a lithium salt is dissolved, a polymer swollen with an electrolytic solution, and the like.
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 a cylindrical shape, a coin shape, a square shape, a laminate shape, a film shape, and other arbitrary shapes. However, the basic structure of a battery is the same regardless of its shape, and the design can be changed depending on 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 laminated battery that is an example of a lithium secondary battery of the present disclosure, and FIG. 2 is a diagram showing the thickness of a laminated electrode body accommodated in the laminated battery shown in FIG. It is a schematic cross-sectional view of the direction.
The laminated battery shown in FIG. 1 contains a non-aqueous electrolyte (not shown in FIG. 1) and a laminated electrode body (not shown in FIG. 1), and has a sealed peripheral edge. The device includes a laminate exterior body 1 whose interior is hermetically sealed. As the laminate exterior body 1, for example, a laminate exterior body made of aluminum is used.
As shown in FIG. 2, the laminated electrode body housed in the laminate exterior body 1 includes a laminated body in which positive electrode plates 5 and negative electrode plates 6 are alternately laminated with separators 7 in between, and a laminated body of this laminated body. A separator 8 surrounding 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 nonaqueous 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 connected to the laminate exterior body 1. It protrudes outward from the peripheral edge (Figure 1). A portion of the peripheral end of the laminate exterior body 1 from which 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), and a part of the negative electrode terminal 3 is connected to the laminate exterior. It protrudes outward from the peripheral end of the body 1 (Fig. 1). A portion of the peripheral end of the laminate exterior body 1 from which the negative electrode terminal 3 protrudes is sealed with an insulating seal 4.
In addition, in the laminated 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, and the positive electrode plates 5 and the negative electrode plates 6 are connected to the uppermost part of both sides with a separator 7 in between. The outer layers are laminated in such a manner that each of them becomes a negative electrode plate 6. However, it goes without saying that the number of positive electrode plates, the number of negative electrode plates, and their arrangement in the laminate type 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 that is another example of the lithium secondary battery of the present disclosure.
In the coin-type battery shown in FIG. 3, a disc-shaped negative electrode 12, a separator 15 injected with a non-aqueous electrolyte, a disc-shaped positive electrode 11, and spacer plates 17 and 18 made of stainless steel or aluminum, if necessary, are arranged in this order. The stacked state 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 a gasket 16.
In this example, the nonaqueous electrolyte of the present disclosure is used as the nonaqueous electrolyte injected into the separator 15.

Note that the lithium secondary battery of the present disclosure is obtained by charging and discharging a lithium secondary battery (a lithium secondary battery before charging and discharging) that includes a negative electrode, a positive electrode, and the nonaqueous electrolyte of the present disclosure. It may also be a rechargeable lithium battery.
That is, in the lithium secondary battery of the present disclosure, a lithium secondary battery containing a negative electrode, a positive electrode, and the non-aqueous electrolyte of the present disclosure is first prepared before charging and discharging, and then the lithium secondary battery before charging and discharging is prepared. 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).

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, notebook computers, mobile computers, mobile phones, headphone stereos, video movies, LCD TVs, handy cleaners, electronic notebooks, calculators, radios, backup power supplies, motors, automobiles, electric vehicles, motorcycles, electric motorcycles, bicycles, electric It can be widely used in bicycles, lighting equipment, game consoles, watches, power tools, cameras, etc., regardless of whether they are small portable devices or large devices.

Examples of the present disclosure will be shown below, but the present disclosure is not limited to the following examples.
In the following, "addition amount" means the content based on the total amount of the non-aqueous electrolyte finally obtained, and "wt%" means mass %.

[Example 1]
A coin-type battery (test battery), which is a lithium secondary battery, was produced using the following procedure.

<Preparation of negative electrode>
A paste-like negative electrode mixture slurry was prepared by kneading amorphous coated natural graphite (97 parts by mass), carboxymethyl cellulose (1 part by mass), and SBR latex (2 parts by mass) with a water solvent.
Next, this negative electrode mixture slurry is applied to a 10 μm thick strip-shaped copper foil negative electrode current collector, dried, and then compressed with a roll press to form a sheet-like negative electrode consisting of the negative electrode current collector and negative electrode active material layer. I got it. The coating density of the negative electrode active material layer at this time was 12 mg/cm ² and the packing density was 1.5 g/mL.

<Preparation of positive electrode>
LiNi _0.5 Mn _0.3 Co _0.2 O ₂ (90 parts by mass), acetylene black (5 parts by mass) and polyvinylidene fluoride (5 parts by mass) 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 of aluminum foil with a thickness of 20 μm, dried, and then compressed with a roll press to form a sheet-like positive electrode consisting of a positive electrode current collector and a positive electrode active material layer. I got it. The coating density of the positive electrode active material layer at this time was 22 mg/cm ² and the packing density was 2.5 g/mL.

<Preparation of non-aqueous electrolyte>
As the non-aqueous solvent, ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and 1,2-dimethoxyethane (DME) were used in a ratio of 30:10:30:30 (vol%), respectively. to obtain a mixed solvent.
LiPF ₆ as an electrolyte was dissolved in the obtained mixed solvent so that the concentration of LiPF ₆ in the finally obtained non-aqueous electrolyte was 1.0 mol/L.
To the solution obtained above, the following compound (S1-1) (specific example of the compound represented by formula (S1)) (addition amount 0.5% by mass) was added as additive S, and non-aqueous electrolysis I got the liquid.

<Production of coin-type battery>
The above-mentioned negative electrode was punched out into a disk shape with a diameter of 14 mm, and the above-mentioned positive electrode was punched out into a disk shape with a diameter of 13 mm to obtain a coin-shaped negative electrode and a coin-shaped positive electrode, respectively. Further, a 20 μm thick microporous polyethylene film was punched out into a disc 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 stainless steel battery can (2032 size), and then 20 μL of non-aqueous electrolyte was injected into the battery can. The separator, positive electrode, and negative electrode were impregnated.
Next, an aluminum plate (thickness: 1.2 mm, diameter: 16 mm) and a spring were placed on the positive electrode, and a battery can lid was caulked through a polypropylene gasket to seal the battery.
As a result, a coin-shaped battery (ie, 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 of battery resistance>
The obtained coin-shaped battery was subjected to conditioning and aging in this order, and the battery resistance of the aged coin-shaped battery before and after high-temperature storage was evaluated.
Here, "conditioning" refers to charging and discharging the coin-type battery three times between 2.75V and 4.2V at 25° C. in a constant temperature bath.
Furthermore, "aging" refers to an operation in which the conditioned coin-type battery is stored at 60° C. for 72 hours at 100% SOC (State of Charge).
The 100% SOC state in this embodiment corresponds to the state charged at a charging voltage of 4.25V.
Moreover, "high temperature storage" means an operation in which the aged coin-type battery is stored at 60° C. for 72 hours at 100% SOC.
Hereinafter, battery resistance was measured under two temperature conditions, 25°C and -20°C.

(Measurement of battery resistance before high temperature storage)
The SOC (State of Charge) of the coin-type battery after aging was adjusted to 80%, and then, the battery resistance (DC resistance) of the coin-type battery before high temperature storage was measured by the following method.
Using the above coin-type battery adjusted to SOC 80%, CC10s discharge at a discharge rate of 0.2C, pause for 300 seconds, CC10s discharge at a discharge rate of 1C, pause for 300 seconds, CC10s discharge at a discharge rate of 2C, A pause of 300 seconds and CC10s discharge at a discharge rate of 5C were performed in this order.
Note that CC10s discharge means discharging at a constant current for 10 seconds.
The DC resistance is calculated based on the relationship between each discharge rate and the voltage 10 seconds after the start of discharge at each discharge rate, and the obtained DC resistance (Ω) is calculated as the battery resistance of the coin-type battery before high temperature storage ( Ω).
The results are shown in Table 1.

(Measurement of battery resistance after high temperature storage)
The coin type battery whose battery resistance was measured before high temperature storage was CC-CV charged to 4.25V at a charging rate of 0.2C at 25°C to reach a SOC of 100%, and in this state it was stored at high temperature (i.e. 60°C). storage for 72 hours). Here, CC-CV charging means constant current-constant voltage.
The SOC of the coin-type battery after high-temperature storage was adjusted to 80%, and then the battery resistance (Ω) of the coin-type battery after high-temperature storage was measured by the same method as the measurement of battery resistance before high-temperature storage.
The results are shown in Table 1.

[Examples 2 to 7]
The same operation as in Example 1 was performed except that the type of additive S was changed as shown in Table 1.
The results are shown in Table 1.
The additives S used in Examples 2 to 7 are as follows.

[Comparative example 1]
The same operation as in Example 1 was performed except that the non-aqueous electrolyte did not contain additive S. The results are shown in Table 1.
In Table 1, "-" means that no additive was contained.

As shown in Table 1, Examples 1 to 7 containing a non-aqueous solvent containing DME and additive S were compared with Comparative Example 1 containing a non-aqueous solvent containing DME and not containing additive S. As a result, the battery resistance before high-temperature storage and after high-temperature storage were reduced.

<Evaluation of gas generation>
A laminate type battery was produced using the non-aqueous electrolyte in each of Comparative Example 1 and Examples 1 to 4, and gas generation was evaluated using the obtained laminate type battery.
Details are shown below.

(Preparation of negative electrode piece)
The negative electrode mixture slurry prepared in Example 1 was applied to one side of a 10 μm thick negative electrode current collector made of strip-shaped copper foil, dried, and then compressed with a roll press to separate the negative electrode current collector from the negative electrode active material layer. A sheet-like negative electrode was obtained.
Two 40 mm x 60 mm negative electrode pieces were cut out from the obtained sheet-like negative electrode.
A nickel tab was ultrasonically welded to each negative electrode piece.

(Preparation of positive electrode piece)
The positive electrode mixture slurry prepared in Example 1 was applied to both sides of a positive electrode current collector made of strip-shaped aluminum foil with a thickness of 20 μm, and after drying, the positive electrode mixture slurry was compressed with a roll press to form a positive electrode current collector and a positive electrode active material layer. A sheet-like positive electrode was obtained.
One 40 mm x 40 mm positive electrode piece was cut out from the obtained sheet-like positive electrode.
An aluminum tab was ultrasonically welded to the positive electrode piece.

(Separator)
A separator with a size of 60 mm x 110 mm was cut out from a microporous polyethylene film with a thickness of 20 μm.

(Preparation of laminate battery)
The separator was bent at its longitudinal center to sandwich the positive electrode piece, thereby obtaining a laminate 1 having a laminated structure of separator/positive electrode piece/separator.
The obtained laminate 1 was sandwiched between two negative electrode pieces to obtain a laminate 2 having a laminate structure of negative electrode piece/separator/positive electrode piece/separator/negative electrode piece.
The obtained laminate 2 was housed in a laminate exterior body, and three sides of the laminate exterior body were heat-sealed.
Next, 1 g of the nonaqueous electrolyte in either Comparative Example 1 or Examples 1 to 4 was injected into the laminate exterior from one side of the laminate exterior that was not heat-sealed, and the positive electrode piece, the negative electrode piece, and impregnated the separator. Next, the laminate exterior body was sealed by heat-sealing the one side that was not heat-sealed.
Through the above steps, a laminate type battery was obtained.

(Measurement of gas generation amount)
The specific gravity of the laminated battery in the atmosphere and the specific gravity of the laminated battery in water were each measured using a specific gravity measuring device (manufactured by Shimadzu Corporation, SGM-300P).
Based on the obtained results, the amount of gas generated (cm ³ ) was determined using Archimedes' principle.

FIG. 4 is a graph showing the amount of gas generated (cm ³ ) when each of the nonaqueous electrolytes of Comparative Example 1 and Examples 1 to 4 was used.
As shown in FIG. 4, when the non-aqueous electrolytes of Examples 1 to 4 were used, the amount of gas generated was significantly reduced compared to when the non-aqueous electrolyte of Comparative Example 1 was used. Ta.
As a result, as the additive S in the non-aqueous electrolyte, the compound represented by the formula (S1) (Examples 1 and 2), the compound represented by the formula (S2) (Example 3), and the formula (S4 ) It was found that when the compound represented by (Example 4) was used, gas generation caused by DME was significantly suppressed.

1 Laminate 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 Gasket 17, 18 Spacer plate

Claims (8)

a non-aqueous solvent containing 1,2-dimethoxyethane;
electrolyte and
an additive S selected from the group consisting of a compound represented by the following formula (S1) and a compound represented by the following formula (S5);
A nonaqueous electrolyte for batteries containing.

[In formula (S1), R ¹¹ represents a hydrocarbon group having 1 to 6 carbon atoms, a group represented by formula (1a), or a group represented by formula (1b), and R ¹² to R ¹⁴ are , each independently represents a hydrogen atom, a hydrocarbon group having 1 to 6 carbon atoms, a group represented by formula (1a), or a group represented by formula (1b). In formula (1a) and formula (1b), * represents the bonding position .
In formula (S5), R ⁵¹ is a fluorine atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 1 to 6 carbon atoms, an alkynyl group having 1 to 6 carbon atoms, or a fluorinated alkyl group having 1 to 6 carbon atoms. , represents a fluorinated alkenyl group having 1 to 6 carbon atoms, or a fluorinated alkynyl group having 1 to 6 carbon atoms . ] The nonaqueous electrolyte for a battery according to claim 1, wherein the content of the 1,2-dimethoxyethane is 10% by volume to 40% by volume based on the total amount of the nonaqueous solvent. The non-aqueous electrolyte for a battery according to claim 1 or 2, wherein the additive S contains at least one selected from the group consisting of compounds represented by the formula (S1). In formula (S1), R ¹¹ is a group represented by formula (1a) or formula (1b), and R ¹² to R ¹⁴ each independently represent hydrogen. The battery according to any one of claims 1 to 3, which is an atom, a hydrocarbon group having 1 to 6 carbon atoms, a group represented by formula ( 1a ), or a group represented by formula (1b). Non-aqueous electrolyte. The non-aqueous battery according to any one of claims 1 to 4 , wherein the content of the additive S is 0.001% by mass to 10% by mass based on the total amount of the non-aqueous electrolyte for batteries. Electrolyte. The nonaqueous electrolyte for a battery according to any one of claims 1 to 5 , wherein the nonaqueous solvent further contains a cyclic carbonate compound and a chain carbonate compound. a 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 nitrides that can be doped and dedoped with lithium ions, and lithium. a negative electrode containing as a negative electrode active material at least one member selected from the group consisting of carbon materials capable of doping and dedoping ions;
The non-aqueous electrolyte for batteries according to any one of claims 1 to 6 ,
Lithium secondary batteries including. A lithium secondary battery obtained by charging and discharging the lithium secondary battery according to claim 7 .

Images