JP7263679B2 - 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, various studies have been made on non-aqueous electrolyte solutions for batteries used in batteries such as lithium secondary batteries.
For example, Patent Literature 1 discloses a method for providing a secondary battery with improved safety under overcharge conditions and an electrolytic solution used therein, containing at least one selected from the group consisting of carbonate esters, ethers and lactones. In an electrolytic solution obtained by dissolving a lithium salt in a solvent mainly composed of a non-aqueous solvent, the solvent contains a dicarboxylic acid diester (excluding succinic acid diester) or a derivative thereof and an aromatic compound having a molecular weight of 500 or less. An electrolytic solution characterized by the following is described.
Further, Patent Document 2 discloses a secondary battery having a positive electrode, a negative electrode, and an electrolyte for the purpose of providing a secondary battery that is highly safe and does not require an additional structure. A secondary battery is described which is characterized by containing an overcharge inhibitor which forms a solid salt when it is discharged.
In addition, Patent Document 3 aims to provide an electrolytic solution that can improve both charge and discharge efficiency and load characteristics, and a battery using the same, and is characterized by containing a silane coupling agent and an oxalic acid ester. is disclosed.
Further, Patent Document 4 discloses a lithium secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte solution in which an electrolyte salt is dissolved in a non-aqueous solvent, wherein the positive electrode is a material containing a lithium composite oxide, and the negative electrode is graphite. wherein the nonaqueous electrolyte contains 0.01 to 10% by weight of a dialkyl oxalate having an alkyl group with 1 to 12 carbon atoms relative to the weight of the nonaqueous electrolyte, and 1 , and 3-propanesultone in an amount of 0.01 to 20% by weight. Patent Document 5 discloses excellent cycle performance and resistance increase rate after high-temperature storage test. For the purpose of providing an electrolytic solution that can obtain an electrochemical device or module such as a lithium ion secondary battery with a small , the amine (1) represented by the general formula (1) and the amide represented by the general formula (2) ( 2), and at least one selected from the group consisting of dialkyl oxalate (3) represented by general formula (3), compound (4) represented by general formula (4), and general formula (5) At least one lithium salt (X) selected from the group consisting of the compound (5) represented by the general formula (6), the compound (6) represented by the general formula (6), and the compound (7) represented by the general formula (7) and is disclosed.
In addition, Patent Document 6 provides an electrolytic solution that can obtain an electrochemical device or module such as a lithium ion secondary battery that has excellent storage characteristics at high temperatures and does not increase in resistance even after high temperature storage. For the purpose of, from the group consisting of amine (1) represented by general formula (1), amide (2) represented by general formula (2), and dialkyl oxalate (3) represented by general formula (3) At least one selected and a compound (4) containing a multiple bond between a heteroatom (excluding an oxygen atom) and an adjacent atom in the molecule, and the compound (4) is 0 with respect to the electrolytic solution Electrolyte solutions characterized by 0.001 to 20% by weight are disclosed.
In addition, Patent Document 7 provides an electrolytic solution that can obtain an electrochemical device or module such as a lithium ion secondary battery that has excellent storage characteristics at high temperatures and does not increase in resistance even after high temperature storage. For the purpose of, from the group consisting of amine (1) represented by general formula (1), amide (2) represented by general formula (2), and dialkyl oxalate (3) represented by general formula (3) at least one selected and at least one cyclic dicarbonyl compound selected from the group consisting of compound (4) represented by general formula (4) and compound (5) represented by general formula (5); is disclosed, wherein the cyclic dicarbonyl compound is 0.001 to 10% by mass with respect to the electrolyte.

JP-A-2002-367674 JP 2004-063233 A JP-A-2005-339900 Patent No. 4710609 JP 2017-004692 A JP 2017-004691 A JP 2017-004690 A

By the way, lithium secondary batteries containing a lithium-nickel-manganese-cobalt composite oxide as a positive electrode active material are widely used, for example, as batteries for automobiles.
This lithium-nickel-manganese-cobalt composite oxide contributes to improving the capacity of the lithium secondary battery.
However, in the above lithium secondary battery, the battery resistance may increase during storage.
Therefore, it may be required to reduce the increase in battery resistance during storage of the lithium secondary battery.

An object of one aspect of the present disclosure is to provide a non-aqueous electrolyte for a battery that can reduce an increase in battery resistance due to storage in a lithium secondary battery containing a lithium-nickel-manganese-cobalt composite oxide as a positive electrode active material.
An object of another aspect of the present disclosure is to provide a lithium secondary battery that contains a lithium-nickel-manganese-cobalt composite oxide as a positive electrode active material, and in which an increase in battery resistance due to storage is reduced.

（式（１）中、Ｒ^１１及びＲ^１２は同一であり、かつ、それぞれ炭素数２～４の脂肪族基又は炭素数２～４のフッ化脂肪族基を表す。）
＜２＞
更に、下記式（２）～下記式（９）のいずれかで表される化合物からなる群から選択される少なくとも１種を含有する前記＜１＞に記載の電池用非水電解液。

〔式（２）中、Ｒ^２１～Ｒ^２４は、それぞれ独立に、水素原子、フッ素原子、炭素数１～６の炭化水素基、又は炭素数１～６のフッ化炭化水素基を表す。
式（３）中、Ｒ^３１～Ｒ^３４は、それぞれ独立に、水素原子、炭素数１～６の炭化水素基、式（ａ）で表される基、又は式（ｂ）で表される基を表す。式（ａ）及び式（ｂ）において、＊は、結合位置を表す。
式（４）中、Ｒ^４１～Ｒ^４４は、それぞれ独立に、水素原子、フッ素原子、炭素数１～６の炭化水素基、又は炭素数１～６のフッ化炭化水素基を表す。但し、Ｒ^４１～Ｒ^４４は、同時に水素原子となることはない。
式（５）中、Ｒ^５１及びＲ^５２は、それぞれ独立に、水素原子、フッ素原子、炭素数１～６の炭化水素基、又は炭素数１～６のフッ化炭化水素基を表す。
式（６）中、Ｒ^６１～Ｒ^６３は、それぞれ独立に、フッ素原子又は－ＯＬｉ基を表し、Ｒ^６１～Ｒ^６３の少なくとも１つが－ＯＬｉ基である。
式（７）中、Ｒ^７１～Ｒ^７６は、それぞれ独立に、水素原子、フッ素原子、炭素数１～３の炭化水素基、又は炭素数１～３のフッ化炭化水素基を表す。
式（８）中、Ｒ^８１～Ｒ^８４は、それぞれ独立に、水素原子、フッ素原子、炭素数１～３の炭化水素基、又は炭素数１～３のフッ化炭化水素基を表す。
式（９）中、Ｍは、アルカリ金属を表し、Ｙは、遷移元素、又は周期律表の１３族、１４族もしくは１５族元素を表し、ｂは１～３の整数、ｍは１～４の整数、ｎは０～８の整数、ｑは０又は１を表す。Ｒ^９１は、炭素数１～１０のアルキレン基、炭素数１～１０のハロゲン化アルキレン基、炭素数６～２０のアリーレン基、又は炭素数６～２０のハロゲン化アリーレン基（これらの基は、構造中に置換基、又はヘテロ原子を含んでいてもよく、またｑが１でｍが２～４の場合にはｍ個のＲ^９１はそれぞれが結合していてもよい。）を表し、Ｒ^９２は、ハロゲン原子、炭素数１～１０のアルキル基、炭素数１～１０のハロゲン化アルキル基、炭素数６～２０のアリール基、炭素数６～２０のハロゲン化アリール基（これらの基は、構造中に置換基、又はヘテロ原子を含んでいてもよく、また、ｎが２～８の場合はｎ個のＲ^９２はそれぞれが結合して環を形成していてもよい。）、又は－Ｘ^３Ｒ^９３を表す。Ｘ^１、Ｘ^２及びＸ^３は、それぞれ独立に、Ｏ、ＳまたはＮＲ^９４を表し、Ｒ^９３およびＲ^９４は、それぞれ独立に、水素原子、炭素数１～１０のアルキル基、炭素数１～１０のハロゲン化アルキル基、炭素数６～２０のアリール基、又は炭素数６～２０のハロゲン化アリール基（これらの基は、構造中に置換基、又はヘテロ原子を含んでいてもよく、Ｒ^９３またはＲ^９４が複数個存在する場合はそれぞれが結合して環を形成してもよい。）を表す。〕
＜３＞
前記式（３）で表される化合物を含有する前記＜２＞に記載の電池用非水電解液。
＜４＞
前記式（３）で表される化合物と、前記式（６）で表される化合物と、を含有する前記＜２＞又は＜３＞に記載の電池用非水電解液。
＜５＞
前記式（３）で表される化合物と、前記式（６）で表される化合物と、前記式（５）で表される化合物と、を含有する前記＜２＞～＜４＞のいずれか１つに記載の電池用非水電解液。
＜６＞
前記式（３）で表される化合物の含有質量が、前記式（１）で表される化合物の含有質量よりも大きい前記＜４＞又は＜５＞に記載の電池用非水電解液。
＜７＞
リチウムニッケルマンガンコバルト複合酸化物を正極活物質として含む正極と、
負極と、
前記＜１＞～＜６＞のいずれか１つに記載の電池用非水電解液と、
を備えるリチウム二次電池。
＜８＞
前記＜７＞に記載のリチウム二次電池を充放電させて得られたリチウム二次電池。 Means for solving the above problems include the following aspects.
<1>
Used in a lithium secondary battery containing a lithium nickel manganese cobalt composite oxide as a positive electrode active material,
A non-aqueous electrolyte for a battery containing a compound represented by the following formula (1) in a proportion of 0.05% by mass to 5% by mass with respect to the total amount of the non-aqueous electrolyte.

(In formula (1), R ¹¹ and R ¹² are the same and each represents an aliphatic group having 2 to 4 carbon atoms or a fluoroaliphatic group having 2 to 4 carbon atoms.)
<2>
The non-aqueous electrolyte for a battery according to <1>, further containing at least one compound selected from the group consisting of compounds represented by any one of the following formulas (2) to (9).

[In Formula (2), 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 fluorohydrocarbon group having 1 to 6 carbon atoms.
In formula (3), R ³¹ to R ³⁴ are each independently a hydrogen atom, a hydrocarbon group having 1 to 6 carbon atoms, a group represented by formula (a), or a group represented by formula (b) represents In Formula (a) and Formula (b), * represents a bonding position.
In formula (4), R ⁴¹ to R ⁴⁴ 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 ⁴¹ to R ⁴⁴ are not hydrogen atoms at the same time.
In formula (5), R ⁵¹ and R ⁵² 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 formula (6), R ⁶¹ to R ⁶³ each independently represent a fluorine atom or a —OLi group, and at least one of R ⁶¹ to R ⁶³ is a —OLi group.
In formula (7), R ⁷¹ to R ⁷⁶ 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 formula (8), R ⁸¹ to R ⁸⁴ 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 formula (9), M represents an alkali metal, Y represents a transition element or an element of Group 13, Group 14 or Group 15 of the periodic table, b is an integer of 1 to 3, m is 1 to 4 is an integer of , n is an integer of 0 to 8, and q is 0 or 1. R ⁹¹ is an alkylene group having 1 to 10 carbon atoms, a halogenated alkylene group having 1 to 10 carbon atoms, an arylene group having 6 to 20 carbon atoms, or a halogenated arylene group having 6 to 20 carbon atoms (these groups are The structure may contain a substituent or a heteroatom, and when q is 1 and m is 2 to 4, each of m R ⁹¹ may be bonded.), and R ⁹² is a halogen atom, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms, a halogenated aryl group having 6 to 20 carbon atoms (these groups are , the structure may contain a substituent or a heteroatom, and when n is 2 to 8, each of n R ⁹² may combine to form a ring), or - represents X ³ R ⁹³ ; X ¹ , X ² and X ³ each independently represent O, S or NR ⁹⁴ , and R ⁹³ and R ⁹⁴ each independently represent a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or an alkyl group having 1 to 10 carbon atoms. 10 halogenated alkyl group, aryl group having 6 to 20 carbon atoms, or halogenated aryl group having 6 to 20 carbon atoms (these groups may contain a substituent or a hetero atom in the structure, R When a plurality of ⁹³ or R ⁹⁴ are present, each may combine to form a ring.). ]
<3>
The non-aqueous electrolyte for a battery according to <2> above, containing the compound represented by the formula (3).
<4>
The non-aqueous electrolyte for a battery according to <2> or <3>, containing the compound represented by the formula (3) and the compound represented by the formula (6).
<5>
Any one of <2> to <4> containing the compound represented by the formula (3), the compound represented by the formula (6), and the compound represented by the formula (5) 1. Non-aqueous electrolyte for battery according to one.
<6>
The non-aqueous electrolyte for a battery according to <4> or <5>, wherein the content of the compound represented by the formula (3) is larger than the content of the compound represented by the formula (1).
<7>
a positive electrode containing a lithium-nickel-manganese-cobalt composite oxide as a positive electrode active material;
a negative electrode;
The non-aqueous electrolyte for batteries according to any one of <1> to <6>;
A lithium secondary battery.
<8>
A lithium secondary battery obtained by charging and discharging the lithium secondary battery according to <7>.

According to one aspect of the present disclosure, there is provided a non-aqueous electrolyte for a battery that can reduce an increase in battery resistance due to storage in a lithium secondary battery containing a lithium-nickel-manganese-cobalt composite oxide as a positive electrode active material.
According to another aspect of the present disclosure, there is provided a lithium secondary battery that includes a lithium-nickel-manganese-cobalt composite oxide as a positive electrode active material and in which an increase in battery resistance due to storage is reduced.

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 a lithium secondary battery containing a lithium nickel manganese cobalt composite oxide as a positive electrode active material (for example, the lithium of the present disclosure described later). It is a non-aqueous electrolyte used in secondary batteries) and contains a compound represented by the following formula (1).
The non-aqueous electrolyte solution of the present disclosure contains a compound represented by the following formula (1), thereby preventing an increase in battery resistance during storage in a lithium secondary battery containing a lithium-nickel-manganese-cobalt composite oxide as a positive electrode active material. can be reduced.

<Compound Represented by Formula (1)>

In formula (1), R ¹¹ and R ¹² are the same and each represents an aliphatic group having 2 to 4 carbon atoms or a fluoroaliphatic group having 2 to 4 carbon atoms.

In formula (1), a fluorinated aliphatic group means an aliphatic group substituted with at least one fluorine atom.

In formula (1), the aliphatic group and the fluoroaliphatic group may each contain a branched and/or ring structure.

In formula (1), the aliphatic group is preferably an alkyl group or an alkenyl group, more preferably an alkyl group.
In formula (1), the fluorinated aliphatic group is preferably a fluorinated alkyl group or a fluorinated alkenyl group, more preferably a fluorinated alkyl group.

In formula (1), R ¹¹ and R ¹² are each
It is preferably an alkyl group having 2 to 4 carbon atoms or a fluorinated alkyl group having 2 to 4 carbon atoms,
more preferably an alkyl group having 2 to 4 carbon atoms,
more preferably an ethyl group, a butyl group (that is, a normal butyl group, the same shall apply hereinafter), or a tert-butyl group,
A butyl group is more preferred.

As the compound represented by formula (1),
Dibutyl oxalate (a compound in which both R ¹¹ and R ¹² are butyl groups) is particularly preferred.

The content of the compound represented by the formula (1) is 0.00 to the total amount of the non-aqueous electrolyte. 05% by mass to 5% by mass, preferably 0.1% by mass to 3% by mass, more preferably 0.2% by mass to 1% by mass.

By configuring the non-aqueous battery electrolyte according to the present disclosure as described above, it is possible to reduce an increase in battery resistance due to storage in a lithium secondary battery containing a lithium-nickel-manganese-cobalt composite oxide as a positive electrode active material.
Although the reason is not clear, it is presumed as follows.
When a lithium secondary battery containing a lithium-nickel-manganese-cobalt composite oxide as a positive electrode active material is stored, the volume of the lithium secondary battery may increase due to the generation of gas from the electrolyte, so-called "battery swelling." (See Comparative Example 1 described later). The generation of this gas is considered to be one of the causes of the increase in battery resistance. It is conceivable that the non-aqueous electrolyte solution for a battery in the present disclosure having the above structure can suppress the decomposition of the electrolyte solution on the surface of the electrode, thereby suppressing the generation of gas.

From the viewpoint of obtaining the effect of reducing battery resistance more effectively, the non-aqueous electrolyte solution of the present disclosure further includes at least one compound selected from the group consisting of compounds represented by the following formulas (2) to (9). It may contain seeds.
The compounds represented by formulas (2) to (9) are described below.

<Compound Represented by Formula (2)>
The non-aqueous electrolyte of the present disclosure may contain at least one compound represented by Formula (2).

In formula (2), 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 fluorohydrocarbon group having 1 to 6 carbon atoms.

In formula (2), the hydrocarbon group having 1 to 6 carbon atoms represented by R ²¹ to R ²⁴ may be a linear hydrocarbon group, or a hydrocarbon group having a branched and/or cyclic structure. may be
The hydrocarbon group having 1 to 6 carbon atoms represented by R ²¹ to R ²⁴ is preferably an alkyl group or an aryl group, more preferably an alkyl group.

In formula (2), the number of carbon atoms in the hydrocarbon group having 1 to 6 carbon atoms represented by R ²¹ to R ²⁴ is more preferably 1 to 3, still more preferably 1 or 2, and particularly preferably 1.

In formula (2), the fluorohydrocarbon group having 1 to 6 carbon atoms represented by R ²¹ to R ²⁴ may be a linear fluorohydrocarbon group, or may have a branched and/or cyclic structure. may be a fluorinated hydrocarbon group having
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 aryl group, more preferably a fluorinated alkyl group.

In formula (2), the number of carbon atoms in the fluorohydrocarbon group having 1 to 6 carbon atoms represented by R ²¹ to R ²⁴ is more preferably 1 to 3, more preferably 1 or 2, and particularly preferably 1. .

Specific examples of the compound represented by formula (2) include compounds represented by the following formulas (2-1) to (2-9) (hereinafter referred to as compound (2-1) to compound (2 -9)), but the compound represented by formula (2) is not limited to these specific examples.
Among these, compound (2-1) or compound (2-2) is particularly preferred.

When the non-aqueous electrolyte of the present disclosure contains the compound represented by formula (2), the content of the compound represented by formula (2) with respect to the total amount of the non-aqueous electrolyte is 0.001% by mass to 10 mass % is preferred, 0.005 mass % to 5 mass % is more preferred, 0.01 mass % to 2 mass % is still more preferred, and 0.1 mass % to 1 mass % is particularly preferred.

<Compound Represented by Formula (3)>
The non-aqueous electrolyte of the present disclosure may contain at least one compound represented by Formula (3).

In formula (3), R ³¹ to R ³⁴ are each independently a hydrogen atom, a hydrocarbon group having 1 to 6 carbon atoms, a group represented by formula (a), or a group represented by formula (b) represents In Formula (a) and Formula (b), * represents a bonding position.

A preferred embodiment of the hydrocarbon group having 1 to 6 carbon atoms represented by R ³¹ to R ³⁴ in formula (3) is the C 1 to 6 hydrocarbon group represented by R ²¹ to R ²⁴ in formula (2) It is the same as the preferred embodiment of the hydrocarbon group.
The number of carbon atoms in the hydrocarbon group having 1 to 6 carbon atoms represented by R ³¹ to R ³⁴ is preferably 1 to 3, more preferably 1 or 2, and particularly preferably 1.

A preferred embodiment of formula (3) is
R ³¹ is a hydrocarbon group having 1 to 6 carbon atoms, a group represented by formula (a), or a group represented by formula (b) (more preferably, a group represented by formula (a) or a group represented by formula a group represented by (b)),
R ³² is a hydrogen atom,
R ³³ is a hydrogen atom, a hydrocarbon group having 1 to 6 carbon atoms, a group represented by formula (a), or a group represented by formula (b);
It is an embodiment in which R ³⁴ is a hydrogen atom.

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

When the non-aqueous electrolyte of the present disclosure contains the compound represented by formula (3), the content of the compound represented by formula (3) with respect to the total amount of the non-aqueous electrolyte is 0.001% by mass to 10 mass % is preferable, 0.01 mass % to 5 mass % is more preferable, 0.1 mass % to 3 mass % is still more preferable, and 0.5 mass % to 2 mass % is still more preferable.

When the non-aqueous electrolyte of the present disclosure contains the compound represented by formula (3), the content of the compound represented by formula (3) is higher than the content of the compound represented by formula (1). Large is preferred.
In this case, the ratio of the content mass of the compound represented by formula (3) to the content mass of the compound represented by formula (1) (hereinafter referred to as "content mass ratio [compound represented by formula (3) / formula ( The compound represented by 1)]”) is preferably from 1.1 to 20, more preferably from 1.1 to 10, and even more preferably from 1.1 to 4.

<Compound Represented by Formula (4)>
The non-aqueous electrolyte of the present disclosure may contain at least one compound represented by the following formula (4).

In formula (4), R ⁴¹ to R ⁴⁴ 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 ⁴¹ to R ⁴⁴ are not hydrogen atoms at the same time.

A preferred embodiment of the hydrocarbon group having 1 to 6 carbon atoms represented by R ⁴¹ to R ⁴⁴ in formula (4) is the C 1 to 6 hydrocarbon group represented by R ²¹ to R ²⁴ in formula (2). Similar to hydrocarbon groups.
However, the hydrocarbon groups having 1 to 6 carbon atoms represented by R ⁴¹ to R ⁴⁴ are also preferably alkenyl groups.
The number of carbon atoms in the hydrocarbon group having 1 to 6 carbon atoms represented by R ⁴¹ to R ⁴⁴ is preferably 1 to 3, more preferably 1 or 2, and particularly preferably 1.

Preferred embodiments of the fluorohydrocarbon groups having 1 to 6 carbon atoms represented by R ⁴¹ to R ⁴⁴ in formula (4) are those represented by R ²¹ to R ²⁴ in formula (2) having 1 to 6 carbon atoms. It is the same as the preferred embodiment of the fluorinated hydrocarbon group of 6.
However, the C 1-6 fluorinated hydrocarbon groups represented by R ⁴¹ to R ⁴⁴ are also preferably fluorinated alkenyl groups.
The number of carbon atoms in the fluorohydrocarbon group having 1 to 6 carbon atoms represented by R ⁴¹ to R ⁴⁴ is preferably 1 to 3, more preferably 1 or 2, and particularly preferably 1.

Specific examples of the compound represented by formula (4) include compounds represented by the following formulas (4-1) to (4-5) (hereinafter referred to as compound (4-1) to compound (4 -5)), but the compound represented by formula (4) is not limited to these specific examples.
Among these, compound (4-1) or compound (4-2) is particularly preferred.

When the non-aqueous electrolyte of the present disclosure contains the compound represented by formula (4), the content of the compound represented by formula (4) with respect to the total amount of the non-aqueous electrolyte is 0.001% by mass to 10 mass % is preferred, 0.005 mass % to 5 mass % is more preferred, 0.01 mass % to 2 mass % is still more preferred, and 0.1 mass % to 1 mass % is particularly preferred.

<Compound Represented by Formula (5)>
The non-aqueous electrolyte of the present disclosure may contain at least one compound represented by the following formula (5).

In formula (5), R ⁵¹ and R ⁵² 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.

A preferred embodiment of the hydrocarbon group having ¹ to 6 carbon atoms represented by R ⁵¹ or R ⁵² in formula (5) is ^the It is the same as the preferred embodiment of the hydrocarbon group.
The number of carbon atoms in the hydrocarbon group having 1 to 6 carbon atoms represented by R ⁵¹ or R ⁵² is preferably 1 to 3, more preferably 1 or 2, and particularly preferably 1.

Preferred embodiments of the fluorohydrocarbon group having 1 to 6 carbon atoms represented by R ⁵¹ or R ⁵² in formula (5) are those represented by R ²¹ to R ²⁴ in formula (2) having 1 to 6 carbon atoms. It is the same as the preferred embodiment of the fluorinated hydrocarbon group of 6.
The number of carbon atoms in the fluorohydrocarbon group having 1 to 6 carbon atoms represented by R ⁵¹ or R ⁵² is preferably 1 to 3, more preferably 1 or 2, and particularly preferably 1.

Specific examples of the compound represented by formula (5) include compounds represented by the following formulas (5-1) to (5-11) (hereinafter referred to as compound (5-1) to compound (5 -11)), but the compound represented by formula (5) is not limited to these specific examples.
Among these, compound (5-1) is particularly preferred.

When the non-aqueous electrolyte of the present disclosure contains the compound represented by formula (5), the content of the compound represented by formula (5) with respect to the total amount of the non-aqueous electrolyte is 0.001% by mass to 10% by mass is preferable, 0.005% to 8% by mass is more preferable, 0.01% to 5% by mass is still more preferable, and 0.2% to 2% by mass is particularly preferable.

When the non-aqueous electrolyte of the present disclosure contains the compound represented by formula (5),
The ratio of the content mass of the compound represented by formula (5) to the content mass of the compound represented by formula (1) (hereinafter, “content mass ratio [compound represented by formula (5) / in formula (1) represented compound]”) is preferably 0.01 to 20, more preferably 0.1 to 10, still more preferably 0.1 to 5, still more preferably 0.1 ~3.

<Compound Represented by Formula (6)>
The non-aqueous electrolyte of the present disclosure may contain at least one compound represented by the following formula (6).

In formula (6), R ⁶¹ to R ⁶³ each independently represent a fluorine atom or a —OLi group, and at least one of R ⁶¹ to R ⁶³ is a —OLi group.

Specific examples of the compound represented by formula (6) include compounds represented by the following formulas (6-1) and (6-2) (hereinafter referred to as compound (6-1) and compound (6 -2)), but the compound represented by formula (6) is not limited to these specific examples.

When the non-aqueous electrolyte of the present disclosure contains the compound represented by formula (6), the content of the compound represented by formula (6) with respect to the total amount of the non-aqueous electrolyte is 0.001% by mass to 10 mass % is preferred, 0.005 mass % to 5 mass % is more preferred, 0.01 mass % to 2 mass % is still more preferred, and 0.1 mass % to 1 mass % is particularly preferred.

When the non-aqueous electrolyte of the present disclosure contains the compound represented by formula (6), the ratio of the content mass of the compound represented by formula (6) to the content mass of the compound represented by formula (1) ( Hereinafter, also referred to as "content mass ratio [compound represented by formula (6)/compound represented by formula (1)]") is preferably 0.05 to 10, more preferably 0.3 to 5, more preferably 0.5 to 2, more preferably 0.8 to 1.2.

<Compound Represented by Formula (7)>
The non-aqueous electrolyte of the present disclosure may contain at least one compound represented by the following formula (7).

In formula (7), R ⁷¹ to R ⁷⁶ 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.

Preferred embodiments of the hydrocarbon groups having 1 to 3 carbon atoms represented by R ⁷¹ to R ⁷⁶ in formula (7) are R ²¹ It is the same as the preferred embodiment of the hydrocarbon group having 1 to 6 carbon atoms represented by to R ²⁴ .
The number of carbon atoms in the hydrocarbon group having 1 to 3 carbon atoms represented by R ⁷¹ to R ⁷⁶ is preferably 1 or 2, more preferably 1.

In formula (7), preferred embodiments of the fluorohydrocarbon groups having 1 to 3 carbon atoms represented by R ⁷¹ to R ⁷⁶ are, in formula (2), It is the same as the preferred embodiment of the fluorohydrocarbon group having 1 to 6 carbon atoms represented by R ²¹ to R ²⁴ .
The number of carbon atoms in the fluorohydrocarbon group having 1 to 3 carbon atoms represented by R ⁷¹ to R ⁷⁶ is preferably 1 or 2, more preferably 1.

Specific examples of the compound represented by formula (7) include compounds represented by the following formulas (7-1) to (7-21) (hereinafter referred to as compound (7-1) to compound (7 -21)), but the compound represented by formula (7) is not limited to these specific examples.
Among these, compound (7-1) is particularly preferred.

When the non-aqueous electrolyte of the present disclosure contains the compound represented by formula (7), the content of the compound represented by formula (7) with respect to the total amount of the non-aqueous electrolyte is 0.001% by mass to 10 mass % is preferred, 0.005 mass % to 5 mass % is more preferred, 0.01 mass % to 2 mass % is still more preferred, and 0.1 mass % to 1 mass % is particularly preferred.

<Compound Represented by Formula (8)>
The non-aqueous electrolyte of the present disclosure may contain at least one compound represented by the following formula (8).

In formula (8), R ⁸¹ to R ⁸⁴ 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.

Preferred embodiments of the hydrocarbon groups having 1 to 3 carbon atoms represented by R ⁸¹ to R ⁸⁴ in formula (8) are R ²¹ It is the same as the preferred embodiment of the hydrocarbon group having 1 to 6 carbon atoms represented by to R ²⁴ .
The number of carbon atoms in the hydrocarbon groups having 1 to 3 carbon atoms represented by R ⁸¹ to R ⁸⁴ is preferably 1 or 2, more preferably 1.

In formula (8), preferred embodiments of the fluorohydrocarbon groups having 1 to 3 carbon atoms represented by R ⁸¹ to R ⁸⁴ are, in formula (2), It is the same as the preferred embodiment of the fluorohydrocarbon group having 1 to 6 carbon atoms represented by R ²¹ to R ²⁴ .
The number of carbon atoms in the fluorohydrocarbon groups having 1 to 3 carbon atoms represented by R ⁸¹ to R ⁸⁴ is preferably 1 or 2, more preferably 1.

Specific examples of the compound represented by formula (8) include compounds represented by the following formulas (8-1) to (8-21) (hereinafter referred to as compound (8-1) to compound (8 -21)), but the compound represented by formula (8) is not limited to these specific examples.
Among these, compound (8-1) is particularly preferred.

When the non-aqueous electrolyte of the present disclosure contains the compound represented by formula (8), the content of the compound represented by formula (8) with respect to the total amount of the non-aqueous electrolyte is 0.001% by mass to 10 mass % is preferred, 0.005 mass % to 5 mass % is more preferred, 0.01 mass % to 2 mass % is still more preferred, and 0.1 mass % to 1 mass % is particularly preferred.

<Compound Represented by Formula (9)>
The non-aqueous electrolyte of the present disclosure may contain at least one compound represented by the following formula (9).

In formula (9), M represents an alkali metal, Y represents a transition element or an element of Group 13, Group 14 or Group 15 of the periodic table, b is an integer of 1 to 3, m is 1 to 4 is an integer of , n is an integer of 0 to 8, and q is 0 or 1. R ⁹¹ is an alkylene group having 1 to 10 carbon atoms, a halogenated alkylene group having 1 to 10 carbon atoms, an arylene group having 6 to 20 carbon atoms, or a halogenated arylene group having 6 to 20 carbon atoms (these groups are The structure may contain a substituent or a heteroatom, and when q is 1 and m is 2 to 4, each of m R ⁹¹ may be bonded.), and R ⁹² is a halogen atom, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms, a halogenated aryl group having 6 to 20 carbon atoms (these groups are , the structure may contain a substituent or a heteroatom, and when n is 2 to 8, each of n R ⁹² may combine to form a ring), or - represents X ³ R ⁹³ ; X ¹ , X ² and X ³ each independently represent O, S or NR ⁹⁴ , and R ⁹³ and R ⁹⁴ each independently represent a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or an alkyl group having 1 to 10 carbon atoms. 10 halogenated alkyl group, aryl group having 6 to 20 carbon atoms, or halogenated aryl group having 6 to 20 carbon atoms (these groups may contain a substituent or a hetero atom in the structure, R When a plurality of ⁹³ or R ⁹⁴ are present, each may combine to form a ring.).

In formula (9), M is an alkali metal and Y is a transition metal or an element of Groups 13, 14 or 15 of the Periodic Table. Y is preferably Al, B, V, Ti, Si, Zr, Ge, Sn, Cu, Y, Zn, Ga, Nb, Ta, Bi, P, As, Sc, Hf or Sb. , Al, B or P are more preferred. When Y is Al, B or P, the synthesis of the anion compound becomes relatively easy and the production cost can be suppressed. b representing the valence of the anion and the number of cations is an integer of 1 to 3, preferably 1; If b is larger than 3, the salt of the anion compound tends to be difficult to dissolve in the mixed organic solvent, which is not preferred. The constants m and n are values related to the number of ligands and are determined depending on the type of M, where m is an integer of 1-4 and n is an integer of 0-8. The constant q is 0 or 1. When q is 0, the chelate ring is a five-membered ring, and when q is 1, the chelate ring is a six-membered ring.

R ⁹¹ represents an alkylene group having 1 to 10 carbon atoms, a halogenated alkylene group having 1 to 10 carbon atoms, an arylene group having 6 to 20 carbon atoms or a halogenated arylene group having 6 to 20 carbon atoms. These alkylene groups, halogenated alkylene groups, arylene groups or halogenated arylene groups may contain substituents and heteroatoms in their structures. Specifically, instead of hydrogen atoms of these groups, halogen atoms, chain or cyclic alkyl groups, aryl groups, alkenyl groups, alkoxy groups, aryloxy groups, sulfonyl groups, amino groups, cyano groups, carbonyl groups, It may contain an acyl group, an amide group, or a hydroxyl group as a substituent. Also, a structure in which a nitrogen atom, a sulfur atom, or an oxygen atom is introduced instead of the carbon element of these groups may be used. Further, when q is 1 and m is 2 to 4, each of m R ⁹¹ may be bonded. Examples of such may include ligands such as ethylenediaminetetraacetic acid.

R ⁹² is a halogen atom, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms, a halogenated aryl group having 6 to 20 carbon atoms, or -X ³ represents R ⁹³ (X ³ and R ⁹³ will be described later);
These alkyl groups, halogenated alkyl groups ^{, aryl groups or halogenated aryl groups for R 92 may} contain substituents and heteroatoms in their structures, and n is 2 to When 8, n R ¹² may be combined to form a ring. R ⁹² is preferably an electron-withdrawing group, particularly preferably a fluorine atom.

X ¹ , X ² and X ³ each independently represent O, S or NR ⁹⁴ ; That is, the ligand will be attached to Y through these heteroatoms.

R ⁹³ and R ⁹⁴ are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms, or represents a halogenated aryl group. These alkyl groups, halogenated alkyl groups, aryl groups, or halogenated aryl groups may contain substituents and heteroatoms in their structures, like ^R91 . Also, when a plurality of R ⁹³ and R ⁹⁴ are present, they may combine to form a ring.

Alkali metals represented by M include, for example, lithium, sodium and potassium. Among these, lithium is particularly preferred.
n is preferably an integer of 0 to 4.

Examples of the compound represented by formula (9) include a compound represented by formula (9A) below, a compound represented by formula (9B) below, a compound represented by formula (9C) below, and a compound represented by formula (9D) below. and at least one selected from the group consisting of compounds represented by the following formula (9E) is more preferred.

In Formulas (9A) to (9E), M has the same definition as M in Formula (9), and preferred embodiments are also the same.

The compound represented by formula (9) is particularly preferably a compound represented by formula (9A) in which M is lithium, or a compound represented by formula (9D) in which M is It is a compound that is lithium.

When the non-aqueous electrolyte of the present disclosure contains the compound represented by formula (9), the content of the compound represented by formula (8) with respect to the total amount of the non-aqueous electrolyte is 0.001% by mass to 10 mass % is preferred, 0.005 mass % to 5 mass % is more preferred, 0.01 mass % to 2 mass % is still more preferred, and 0.1 mass % to 1 mass % is particularly preferred.

In the non-aqueous electrolyte solution of the present disclosure, from the viewpoint of obtaining the effect of reducing battery resistance more effectively, among the compounds represented by the above formulas (2) to (9),
It is more preferable to contain a compound represented by formula (3),
It is more preferable to contain a compound represented by formula (3) and a compound represented by formula (6),
It is more preferable to contain a compound represented by formula (3), a compound represented by formula (6), and a compound represented by formula (5).

When the non-aqueous electrolyte of the present disclosure contains the compound represented by formula (3) and the compound represented by formula (6) (further compound represented by formula (5) (including cases where it is contained. The same shall apply hereinafter.),
It is preferable that the mass content of the compound represented by formula (3) is larger than the mass content of the compound represented by formula (1).

When the non-aqueous electrolyte of the present disclosure contains the compound represented by formula (3) and the compound represented by formula (6), the content mass ratio [compound represented by formula (3) / formula ( 1)] is preferably from 1.1 to 20, more preferably from 1.1 to 10, still more preferably from 1.1 to 4.
In this case, the content mass ratio [compound represented by formula (6)/compound represented by formula (1)] is preferably 0.5 to 10, more preferably 0.3 to 5. Yes, more preferably 0.5 to 2, more preferably 0.8 to 1.2.

When the non-aqueous electrolyte of the present disclosure contains the compound represented by formula (3) and the compound represented by formula (6), the content mass of the compound represented by formula (3) is represented by formula ( It is preferably larger than the content mass of the compound represented by 6).
The ratio of the content mass of the compound represented by formula (3) to the content mass of the compound represented by formula (6) (hereinafter, “content mass ratio [compound represented by formula (3) / in formula (6) represented compound]”) is preferably 0.1 to 30, more preferably 0.5 to 20, still more preferably 1.1 to 10, still more preferably 1.1 to 4 .

When the non-aqueous electrolyte of the present disclosure contains a compound represented by formula (3), a compound represented by formula (6), and a compound represented by formula (5), the content mass ratio [Compound represented by formula (5)/compound represented by formula (1)] is preferably 0.01 to 20, more preferably 0.1 to 10, still more preferably 0.1 to 5, more preferably 0.1 to 3.
In this case, the content of the compound represented by formula (3) is preferably larger than the content of the compound represented by formula (5).
The ratio of the content mass of the compound represented by formula (3) to the content mass of the compound represented by formula (5) (hereinafter, “content mass ratio [compound represented by formula (3) / in formula (5) The compound represented]”) is preferably 0.1 to 20, more preferably 0.2 to 15, still more preferably 0.25 to 15, still more preferably 1.5 ~10, more preferably 3-7.

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 non-aqueous electrolytic solution of the present disclosure contains an electrolyte.
The electrolyte 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) (that is, , lithium salts other than LiPF ₆ );
etc.

<Non-aqueous solvent>
The non-aqueous electrolyte of the present disclosure contains a non-aqueous solvent.
The number of non-aqueous solvents contained in the non-aqueous electrolyte 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.

Cyclic carbonate compounds include, for example, 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, 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]
The lithium secondary battery of the present disclosure is
a positive electrode containing a lithium-nickel-manganese-cobalt composite oxide as a positive electrode active material;
a negative electrode;
the non-aqueous electrolytic solution of the present disclosure described above;
Prepare.
The lithium secondary battery of the present disclosure is a lithium secondary battery containing a lithium-nickel-manganese-cobalt composite oxide as a positive electrode active material, yet has reduced battery resistance.
Such effects are brought about by the compound represented by Formula (1) in the non-aqueous electrolyte.

<Positive electrode>
The positive electrode contains a lithium-nickel-manganese-cobalt composite oxide as a positive electrode active material.
As the lithium-nickel-manganese-cobalt composite oxide, a compound represented by the following formula (P1) is preferable.

_{LiNixMnyCozO2 ( P1 )}
[In formula (P1), x, y and z are each independently greater than 0 and less than 1.00, and the sum of x, y and z is 0.99 to 1.00. ]

In formula (P1), x is preferably 0.10 to 0.90, more preferably 0.20 to 0.70, still more preferably 0.30 to 0.60.
In formula (P1), y is preferably 0.10 to 0.90, more preferably 0.10 to 0.50, still more preferably 0.20 to 0.40.
In formula (P1), z is preferably 0.10 to 0.90, more preferably 0.10 to 0.50, still more preferably 0.10 to 0.30.

As the compound represented by formula (P1), LiNi _0.33 Mn _0.33 Co _0.33 O ₂ or LiNi _0.5 Mn _0.3 Co _0.2 O ₂ is preferable.

The positive electrode may contain a component other than the lithium-nickel-manganese-cobalt composite oxide as a positive electrode active material.
Components other than the lithium-nickel-manganese-cobalt composite oxide include;
transition metal oxides or sulfides such as _MoS2 , _TiS2 , _MnO2 , _{V2O5 ;}
Composite oxides composed of lithium and transition metals, such as LiCoO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiNi _X Co _(1−X) O ₂ [0<X<1], LiFePO ₄ , LiMnPO ₄ (However, excluding lithium nickel manganese cobalt composite oxide);
Conductive polymer materials such as polyaniline, polythiophene, polypyrrole, polyacetylene, polyacene, dimercaptothiadiazole, polyaniline complex;
etc.

The proportion of the lithium-nickel-manganese-cobalt composite oxide in the positive electrode active material is preferably 70% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more.
The proportion of the lithium-nickel-manganese-cobalt composite oxide in the positive electrode active material may be 100% by mass or less than 100% by mass.

The positive electrode preferably comprises a positive electrode active material layer containing a positive electrode active material.
The positive electrode active material layer may contain components other than the positive electrode active material.
Components other than the positive electrode active material include conductive aids, binders, and the like.
Conductive aids include carbon materials such as carbon black (eg, acetylene black), amorphous whiskers, and graphite.
Binders include polyvinylidene fluoride and the like.

The positive electrode active material layer can be formed by applying a positive electrode mixture slurry containing a positive electrode active material and a solvent onto a positive electrode current collector described below and drying the slurry.
The positive electrode mixture slurry may contain components other than the positive electrode active material (for example, a conductive aid, a binder, etc.).
Examples of the solvent in the positive electrode mixture slurry include organic solvents such as N-methylpyrrolidone.

The ratio of the positive electrode active material to the total solid content of the positive electrode active material layer is preferably 70% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more.
The ratio of the positive electrode active material to the total solid content of the positive electrode active material layer may be 100% by mass.
Here, when the solvent remains in the positive electrode active material layer, the total solid content of the positive electrode active material layer means the total amount after removing the solvent from the positive electrode active material layer. When it does not remain, it means the total amount of the positive electrode active material layer.

The ratio of the lithium-nickel-manganese-cobalt composite oxide to the total solid content of the positive electrode active material layer is preferably 70% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more.
The ratio of the lithium-nickel-manganese-cobalt composite oxide to the total solid content of the positive electrode active material layer may be 100% by mass or less than 100% by mass.

The positive electrode preferably includes a positive electrode current collector.
The material of the positive electrode current collector 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.

<Negative Electrode>
The negative electrode preferably contains a negative electrode active material.
Examples of negative electrode active materials include metallic lithium, lithium-containing alloys, metals or alloys that can be alloyed with lithium, oxides that can be doped and undoped with lithium ions, and lithium ions that can be doped and undoped. At least one selected from the group consisting of transition metal nitrides and carbon materials capable of doping and dedoping lithium ions 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.
Moreover, lithium titanate is also mentioned as a negative electrode active material.
Among these, a carbon material capable of doping/dedoping lithium ions is preferable.
Examples of such carbon materials include carbon black, activated carbon, graphite materials (artificial graphite, natural graphite), amorphous carbon materials, and the like. The form of the carbon material may be fibrous, spherical, potato-like, or flake-like.

Specific examples of the amorphous carbon material include hard carbon, coke, mesocarbon microbeads (MCMB) 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 proportion of the carbon material (preferably graphite material) in the negative electrode active material is preferably 70% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more.
The ratio of the carbon material (preferably graphite material) in the negative electrode active material may be 100% by mass or less than 100% by mass.

The negative electrode preferably includes a negative electrode active material layer containing a negative electrode active material.
The negative electrode active material layer may contain components other than the negative electrode active material.
A binder is mentioned as components other than a negative electrode active material.
Examples of binders include carboxymethyl cellulose, SBR latex, and the like.

The negative electrode active material layer can be formed by applying a negative electrode mixture slurry containing a negative electrode active material and a solvent onto a negative electrode current collector described below and drying the slurry.
The negative electrode mixture slurry may contain a component (for example, a binder) other than the negative electrode active material.
Examples of the solvent in the negative electrode mixture slurry include water.

The ratio of the negative electrode active material to the total solid content of the negative electrode active material layer is preferably 70% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more.
The ratio of the negative electrode active material to the total solid content of the negative electrode active material layer may be 100% by mass.
Here, when the solvent remains in the negative electrode active material layer, the total solid content of the negative electrode active material layer means the total amount of the negative electrode active material layer excluding the solvent. When it does not remain, it means the total amount of the negative electrode active material layer.

The ratio of the carbon material (preferably graphite material) to the total solid content of the negative electrode active material layer is preferably 70% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more. .
The ratio of the carbon material (preferably graphite material) to the total solid content of the negative electrode active material layer may be 100% by mass.

The negative electrode preferably includes a negative electrode current collector.
The material of the negative electrode current collector 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.

<Separator>
The lithium secondary battery of the present disclosure preferably has 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 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 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. The cathode plate 5 includes a cathode current collector and a cathode active material layer. The negative plate 5 includes a negative current collector and a negative active material layer.
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 cover"). 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 disk-shaped positive electrode 11 includes a positive electrode current collector and a positive electrode active material layer. The disk-shaped negative electrode 12 includes a negative electrode current collector and a negative electrode active material layer.

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

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, the "addition amount" represents the content with respect to the total amount of the finally obtained non-aqueous electrolyte.
Moreover, "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.

<Preparation of positive electrode>
LiNi _0.5 Mn _0.3 Co _0.2 O ₂ (90 parts by mass) as a positive electrode active material, acetylene black (5 parts by mass) as a conductive aid, and polyvinylidene fluoride (5 parts by mass) as a binder Part) was kneaded using N-methylpyrrolidinone as a solvent to prepare a pasty positive electrode mixture slurry.
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 the positive electrode current collector and the positive electrode active material. got At this time, the coating density of the positive electrode active material layer was 22 mg/cm ² and the filling density was 2.5 g/mL.

Here, LiNi _0.5 Mn _0.3 Co _0.2 O ₂ as the positive electrode active material is a specific example of lithium nickel manganese cobalt composite oxide.
LiNi _0.5 Mn _0.3 Co _0.2 O ₂ is hereinafter referred to as NMC532.

<Production of negative electrode>
Amorphous coated natural graphite (97 parts by mass) as a negative electrode active material, carboxymethyl cellulose (1 part by mass) as a binder, and SBR latex (2 parts by mass) as a binder were kneaded with an aqueous solvent to prepare a pasty negative electrode mixture. An agent slurry was prepared.
Next, this negative electrode mixture slurry is applied to a negative electrode current collector made of 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 composed of a negative electrode current collector and a negative electrode active material layer. got At this time, the negative electrode active material layer had a coating density of 12 mg/cm ² and a filling density of 1.5 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 mol/liter.
Dibutyl oxalate (R ¹¹ or R ¹² ), which is a specific example of the compound represented by formula (1) (hereinafter also referred to as “compound of formula (1)”), is added as an additive to the resulting solution. is also a butyl group) is added so that the content with respect to the total weight of the finally prepared non-aqueous electrolyte is 1.0% by mass (i.e., added in an amount of 1.0% by mass) , 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 are stacked in this order in a stainless steel battery can (2032 size). 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 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.

In addition, a laminate-type lithium secondary battery (hereinafter also referred to as “laminate-type battery”) was produced by the following procedure. The configurations of the positive electrode (also referred to as “positive electrode piece”), negative electrode (also referred to as “negative electrode piece”), and non-aqueous electrolyte used are the same as those used in the coin-type battery described above.

(Production of laminated battery)
A laminate 1 having a laminate structure of separator/positive electrode piece/separator was obtained by bending the separator at the center in the longitudinal direction to sandwich the positive electrode piece.
The obtained laminate 1 was sandwiched between two negative electrode pieces to obtain a laminate 2 having a laminated structure of negative electrode piece/separator/positive electrode piece/separator/negative electrode piece.
The obtained laminate 2 was housed in a laminate outer package, and three sides of the laminate outer package were heat-sealed.
Next, 1 g of the non-aqueous electrolyte was injected into the laminated outer packaging from one side of the laminated outer packaging that was not heat-sealed to impregnate the positive electrode piece, the negative electrode piece, and the separator. Then, the non-heat-sealed one side was heat-sealed to seal the laminated exterior body.
As described above, a laminate type battery was obtained.

<Evaluation of battery volume increase>
The obtained laminate-type battery was evaluated for the following increase in battery volume.

(Evaluation of battery volume increase)
The laminate type battery was repeatedly charged and discharged three times between 2.75 V and 4.25 V at 25° C. in a constant temperature bath (hereinafter, this operation is also referred to as “conditioning”). Next, a trickle test was performed on the conditioned laminated battery under conditions of a charging voltage of 4.3 V, 60° C., and 7 days. Before and after the trickle test, the specific gravity of the battery in air and the specific gravity of the laminate type battery in water were each measured by 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, and the difference between the volumes of the batteries after conditioning and after the trickle test was taken as the volume increase.
Table 1 shows the results. It is believed that the increase in battery volume corresponds to gassing.

[Example 2]
The same operation as in Example 1 was performed except that diethyl oxalate was used instead of dibutyl oxalate in the preparation of the non-aqueous electrolyte.
Table 1 shows the results.

[Comparative Example 1]
The same operation as in Example 1 was performed except that the non-aqueous electrolyte did not contain dibutyl oxalate.
Table 1 shows the results.

As can be seen from Table 1, in the examples in which NMC532, which is a lithium-nickel-manganese-cobalt composite oxide, was used as the positive electrode active material, and the compound represented by the formula (1) was contained in the non-aqueous electrolyte, the non-aqueous Compared to Comparative Example 1 in which the electrolytic solution did not contain the compound represented by formula (1), the volume increase of the battery was reduced. In other words, it can be said that the laminated type battery of Example had a suppressed amount of gas generated from the non-aqueous electrolyte as compared with Comparative Example 1.

[Example 101]
In the preparation of the non-aqueous electrolyte, the procedure was the same as in Example 1, except that dibutyl oxalate was added so that the content of the total mass of the finally prepared non-aqueous electrolyte was 0.5% by mass. Thus, a coin-type lithium secondary battery (hereinafter also referred to as a “coin-type battery”) was manufactured.

<Evaluation of battery resistance increase rate of battery>
The obtained coin-type battery was evaluated for battery resistance as follows.

(Measurement of battery resistance (DCIR) before high temperature storage)
The SOC (State of Charge) of the coin-shaped battery after conditioning was adjusted to 80%, and then the DCIR (Direct current internal resistance) of the coin-shaped battery before high-temperature storage was measured by the following method. In addition, the measurement was performed at 25 degreeC.
Using the coin-type battery adjusted to SOC 80% as described above, discharge CC10s at a discharge rate of 0.2C, rest for 300 seconds, discharge CC10s at a discharge rate of 1C, rest for 300 seconds, discharge CC10s 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.
In addition, CC10s discharge means discharging for 10 seconds with a constant current (Constant Current).
The DC resistance is obtained based on the relationship between each discharge rate and the voltage at 10 seconds after the start of discharge at each discharge rate. Ω).

(Measurement of battery resistance (DCIR) after high temperature storage)
The coin-type battery whose battery resistance before high-temperature storage was measured was CC-CV charged to 4.25 V at a charge rate of 0.2 C at 25 ° C. in a constant temperature chamber, and then stored at high temperature (60 ° C., 5 days). The battery resistance (Ω) after high-temperature storage was measured in the same manner as the measurement of the battery resistance before high-temperature storage described above, except that the additional operation was performed.
Here, CC-CV charging means constant current-constant voltage.

(Measurement of increase rate of battery resistance due to high temperature storage)
The rate of increase in battery resistance due to high-temperature storage was calculated by the following formula.
Rate of increase in battery resistance due to high temperature storage (%)
= [(Battery resistance after high temperature storage (Ω))/Battery resistance before high temperature storage (Ω)] × 100
Table 2 shows the results.

[Example 102]
A coin-type battery was produced in the same manner as in Example 101, except that diethyl oxalate was added instead of dibutyl oxalate in the preparation of the non-aqueous electrolyte.
Table 2 shows the results.

[Comparative Example 101]
A coin-type battery was produced in the same manner as in Example 101, except that the non-aqueous electrolyte did not contain dibutyl oxalate.
Table 2 shows the results.

As shown in Table 2, Example 101 and Examples in which NMC532, which is a lithium-nickel-manganese-cobalt composite oxide, was used as the positive electrode active material, and the compound represented by formula (1) was contained in the non-aqueous electrolyte In No. 102, the increase in battery resistance due to storage was reduced compared to Comparative Example 101 in which the non-aqueous electrolyte did not contain the compound represented by Formula (1).

[Example 121]
A compound represented by formula (6-2), which is a specific example of the compound represented by formula (6) (hereinafter also referred to as "compound of formula (6)"), is added to the non-aqueous electrolyte as an additive ( Hereinafter, also referred to as "(6-2)") was added so that the content was 0.5% by mass with respect to the total mass of the finally prepared non-aqueous electrolyte, except that Example 111 and A similar operation was performed.
Table 3 shows the results.

[Comparative Example 121]
The same operation as in Example 121 was performed except that the non-aqueous electrolyte did not contain dibutyl oxalate.
Table 3 shows the results.

As shown in Table 3, in Example 121 in which NMC532, which is a lithium-nickel-manganese-cobalt composite oxide, was used as the positive electrode active material, and the compound represented by formula (1) was contained in the non-aqueous electrolyte, non- Compared to Comparative Example 121 in which the aqueous electrolyte did not contain the compound represented by formula (1), the increase in battery resistance due to storage was reduced.

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)

Used in a lithium secondary battery containing a lithium nickel manganese cobalt composite oxide as a positive electrode active material,
A non-aqueous electrolyte for a battery containing a compound represented by the following formula (1) in a proportion of 0.05% by mass to 5% by mass with respect to the total amount of the non-aqueous electrolyte.

(In formula (1), R ¹¹ and R ¹² are the same and each represents an aliphatic group having 2 to 4 carbon atoms or a fluoroaliphatic group having 2 to 4 carbon atoms.) 2. The non-aqueous electrolyte for a battery according to claim 1, further comprising at least one compound selected from the group consisting of compounds represented by any one of the following formulas (2) to (9).

[In Formula (2), 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 fluorohydrocarbon group having 1 to 6 carbon atoms.
In formula (3), R ³¹ to R ³⁴ are each independently a hydrogen atom, a hydrocarbon group having 1 to 6 carbon atoms, a group represented by formula (a), or a group represented by formula (b) represents In Formula (a) and Formula (b), * represents a bonding position.
In formula (4), R ⁴¹ to R ⁴⁴ 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 ⁴¹ to R ⁴⁴ are not hydrogen atoms at the same time.
In formula (5), R ⁵¹ and R ⁵² 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 formula (6), R ⁶¹ to R ⁶³ each independently represent a fluorine atom or a —OLi group, and at least one of R ⁶¹ to R ⁶³ is a —OLi group.
In formula (7), R ⁷¹ to R ⁷⁶ 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 formula (8), R ⁸¹ to R ⁸⁴ 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 formula (9), M represents an alkali metal, Y represents a transition element or an element of Group 13, Group 14 or Group 15 of the periodic table, b is an integer of 1 to 3, m is 1 to 4 is an integer of , n is an integer of 0 to 8, and q is 0 or 1. R ⁹¹ is an alkylene group having 1 to 10 carbon atoms, a halogenated alkylene group having 1 to 10 carbon atoms, an arylene group having 6 to 20 carbon atoms, or a halogenated arylene group having 6 to 20 carbon atoms (these groups are The structure may contain a substituent or a heteroatom, and when q is 1 and m is 2 to 4, each of m R ⁹¹ may be bonded.), and R ⁹² is a halogen atom, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms, a halogenated aryl group having 6 to 20 carbon atoms (these groups are , the structure may contain a substituent or a heteroatom, and when n is 2 to 8, each of n R ⁹² may combine to form a ring), or - represents X ³ R ⁹³ ; X ¹ , X ² and X ³ each independently represent O, S or NR ⁹⁴ , and R ⁹³ and R ⁹⁴ each independently represent a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or an alkyl group having 1 to 10 carbon atoms. 10 halogenated alkyl group, aryl group having 6 to 20 carbon atoms, or halogenated aryl group having 6 to 20 carbon atoms (these groups may contain a substituent or a hetero atom in the structure, R When a plurality of ⁹³ or R ⁹⁴ are present, each may combine to form a ring.). ] 3. The non-aqueous electrolyte for a battery according to claim 2, containing the compound represented by the formula (3). 4. The non-aqueous electrolyte for a battery according to claim 2, comprising the compound represented by the formula (3) and the compound represented by the formula (6). Any one of claims 2 to 4, containing the compound represented by the formula (3), the compound represented by the formula (6), and the compound represented by the formula (5) The non-aqueous electrolyte for batteries according to the item. 6. The non-aqueous electrolyte for a battery according to claim 4, wherein the content of the compound represented by the formula (3) is larger than the content of the compound represented by the formula (1). a positive electrode containing a lithium-nickel-manganese-cobalt composite oxide as a positive electrode active material;
a negative electrode;
The non-aqueous electrolyte for batteries according to any one of claims 1 to 6,
A lithium secondary battery. A lithium secondary battery obtained by charging and discharging the lithium secondary battery according to claim 7 .

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