JP2016038997A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery which enables the suppression of short circuit of positive and negative electrodes, and which is hard to cause thermorunaway and superior in safety.SOLUTION: A nonaqueous electrolyte secondary battery comprises: a nonaqueous electrolytic solution; a positive electrode; a negative electrode; a separator provided between the positive and negative electrodes, and composed of a micro porous film including a thermoplastic resin as a main constituent; and a filler layer provided between the positive and negative electrodes, and including an inorganic filler as a main constituent. The nonaqueous electrolytic solution includes an electrolyte and a liquid composition. At least one kind of the electrolyte is a lithium salt. The liquid composition includes: at least one kind of fluorine-containing solvent (A) selected from a group consisting of a fluorine-containing ether compound, a fluorine-containing chain carboxylic acid ester compound and a fluorine-containing chain carbonate compound; and a cyclic carboxylic acid ester compound (B).SELECTED DRAWING: None

Description

  The present invention relates to a non-aqueous electrolyte secondary battery.

  Non-aqueous electrolyte secondary batteries including a positive electrode, a negative electrode, and a non-aqueous electrolyte are widely used in portable electronic devices such as mobile phones and notebook computers. For example, a non-aqueous electrolyte secondary battery using a non-aqueous electrolyte mainly composed of a carbonate solvent such as ethylene carbonate or dimethyl carbonate is known as the non-aqueous electrolyte.

  As a non-aqueous electrolyte secondary battery having a non-aqueous electrolyte mainly composed of a carbonate-based solvent, for example, a non-aqueous electrolyte 2 having a separator that can prevent a short circuit due to thermal contraction of the separator and has excellent heat resistance is used. As a secondary battery, a battery having a separator in which an insulating layer containing insulating fine particles and a microporous film are integrated between a positive electrode and a negative electrode has been proposed (Patent Document 1).

JP 2014-56843 A

  However, in a non-aqueous electrolyte secondary battery using a non-aqueous electrolyte mainly composed of a carbonate-based solvent as in Patent Document 1, the temperature rises due to the reaction between the electrolyte and the electrode, and finally the heat There is a risk of runaway.

  An object of the present invention is to provide a non-aqueous electrolyte secondary battery excellent in safety that can suppress a short circuit between a positive electrode and a negative electrode and hardly cause thermal runaway.

The present invention has the following configuration.
[1] A non-aqueous electrolyte, a positive electrode, a negative electrode, a separator made of a microporous film mainly composed of a thermoplastic resin provided between the positive electrode and the negative electrode, and between the positive electrode and the negative electrode A non-aqueous electrolyte secondary battery comprising a filler layer mainly composed of an inorganic filler, wherein the non-aqueous electrolyte comprises an electrolyte and a liquid composition, and at least one of the electrolytes is lithium. A salt, and the liquid composition comprises at least one fluorine-containing solvent (A) selected from the group consisting of a fluorine-containing ether compound, a fluorine-containing chain carboxylic acid ester compound and a fluorine-containing chain carbonate compound; A non-aqueous electrolyte secondary battery containing an acid ester compound (B).
[2] The nonaqueous electrolyte secondary battery according to [1], wherein the negative electrode contains a non-carbon active material as a negative electrode active material.
[3] A separator with a filler layer in which the filler layer is provided on the surface of one or both of the positive electrode side and the negative electrode side of the separator, between the positive electrode and the negative electrode. 2] non-aqueous electrolyte secondary battery.
[4] The non-carbon-based active material is a simple substance of at least one metal selected from the group consisting of Si, Sn, Al, and Ti, or an alloy of Li, Li, and one of oxides and sulfides thereof. The nonaqueous electrolyte secondary battery according to [2] or [3], which is a seed or more.
[5] The nonaqueous electrolyte secondary battery according to any one of [1] to [4], wherein the mass of the fluorine-containing solvent (A) is 30 to 80% by mass relative to the total mass of the nonaqueous electrolyte.
[6] The liquid composition further includes at least one compound (C) selected from the group consisting of a saturated cyclic carbonate compound, a chain carbonate compound having no fluorine atom, a saturated cyclic sulfone compound, and a phosphate ester compound. , [1] to [5] The nonaqueous electrolyte secondary battery.
[7] The nonaqueous electrolyte secondary battery according to [6], wherein the ratio of the mass of the chain carbonate compound having no fluorine atom to the total mass of the nonaqueous electrolyte is 30% by mass or less.
[8] The ratio of the total mass of the mass of the saturated cyclic carbonate compound not having fluorine atoms and the mass of the chain carbonate compound not having fluorine atoms to the total mass of the non-aqueous electrolyte is 30% by mass or less. [6] or [7] non-aqueous electrolyte secondary battery.
[9] The lithium salt includes LiPF _6, [1] one of the non-aqueous electrolyte secondary battery to [8].
[10] The nonaqueous electrolyte secondary battery according to any one of [1] to [9], wherein the fluorine-containing solvent (A) contains the fluorine-containing ether compound.
[11] The nonaqueous electrolyte secondary battery according to [10], wherein the fluorine-containing ether compound is at least one selected from the group consisting of compounds represented by the following formula (1).

(In the formula, R ¹ and R ² are each independently an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, a fluorinated alkyl group having 1 to 10 carbon atoms, or 3 to 10 carbon atoms. A fluorinated cycloalkyl group, an alkyl group having 2 to 10 carbon atoms having one or more etheric oxygen atoms, or a fluorinated alkyl group having 2 to 10 carbon atoms having one or more etheric oxygen atoms. , One or both of R ¹ and R ² is a fluorinated alkyl group having 1 to 10 carbon atoms, a fluorinated cycloalkyl group having 3 to 10 carbon atoms, or 2 to 2 carbon atoms having one or more etheric oxygen atoms. 10 fluorinated alkyl groups.)
[12] The compound represented by the formula (1) is CF ₃ CH ₂ OCF ₂ CHF ₂ , CF ₃ CH ₂ OCF ₂ CHFCF ₃ , CHF ₂ CF ₂ CH ₂ OCF ₂ CHF ₂ , or CH ₃ CH ₂ OCF _2. CHF _2, and a _CHF 2 _CF 2 _CH 2, at least one selected from the group consisting of _OCF 2 CHFCF _3, non-aqueous electrolyte secondary battery of [11].
[13] The nonaqueous electrolysis according to any one of [1] to [12], wherein the cyclic carboxylic acid ester compound (B) is one or more selected from the group consisting of compounds represented by the following formula (5): Liquid secondary battery.

(However, R ^{7 to} R ¹² are each independently a hydrogen atom, a fluorine atom, a chlorine atom, an alkyl group having 1 to 2 carbon atoms, a fluorinated alkyl group having 1 to 2 carbon atoms, or a carbon having an etheric oxygen atom. (It is an alkyl group having a number of 2 to 3. q is an integer of 0 to 3.)
[14] The nonaqueous electrolyte secondary battery according to any one of [1] to [13], wherein the content of the cyclic carboxylic acid ester compound (B) in the nonaqueous electrolyte is 4 to 50% by mass.
[15] The nonaqueous electrolyte secondary battery according to any one of [1] to [14], wherein the content of the lithium salt in the nonaqueous electrolyte is 0.1 to 3.0 mol / L.

  The nonaqueous electrolyte secondary battery of the present invention can suppress a short circuit between the positive electrode and the negative electrode, hardly cause thermal runaway, and is excellent in safety.

In the present specification, a compound represented by the formula (1) is referred to as a compound (1). The same applies to compounds represented by other formulas.
The following definitions of terms apply throughout this specification and the claims.
The “non-aqueous electrolyte” is an electrolyte that does not substantially contain water, and even if water is included, the water content of the secondary battery using the non-aqueous electrolyte does not deteriorate in performance. It means an electrolyte solution in a range of amounts. The amount of water that can be contained in the non-aqueous electrolyte is preferably 500 ppm by mass or less, more preferably 100 ppm by mass or less, and particularly preferably 50 ppm by mass or less with respect to the total mass of the non-aqueous electrolyte. The lower limit of the moisture content is 0 mass ppm.
The “liquid composition” contains the fluorine-containing solvent (A) and the cyclic carboxylic acid ester compound (B) as essential components, and optionally contains the compound (C).
Other compounds (other solvents, additives, etc.) other than the electrolyte, the fluorine-containing solvent (A), the cyclic carboxylic acid ester compound (B) and the compound (C) are defined as “other components”, and are electrolytes and liquids. Differentiated from the composition.
The “fluorinated ether compound” means a chain or cyclic compound having an ether bond and having a fluorine atom.
The “fluorinated chain carboxylic acid ester compound” means a chain compound having an ester bond in a chain structure and not having a ring structure having an ester bond and having a fluorine atom.
The “fluorine-containing chain carbonate compound” is a fluorine atom having a carbonate bond represented by —O—C (═O) —O— in the chain structure, having no ring structure having a carbonate bond. Means a chain-like compound having
The “fluorinated alkane compound” means a compound in which one or more hydrogen atoms of an alkane are substituted with fluorine atoms, and hydrogen atoms remain.
The “cyclic carboxylic acid ester compound” means a cyclic compound having an ester bond as a part of the ring skeleton.
“Saturated cyclic carbonate compound” is a ring skeleton composed of carbon atoms and oxygen atoms, and has a carbonate bond represented by —O—C (═O) —O— as a part of the ring skeleton, Means a cyclic compound having no carbon-carbon unsaturated bond.
“Fluorinated” and “fluorinated” mean that some or all of the hydrogen atoms bonded to the carbon atom are replaced with fluorine atoms.
The “fluorinated alkyl group” means a group in which part or all of the hydrogen atoms of the alkyl group are substituted with fluorine atoms. Among the partially fluorinated groups are hydrogen atoms and fluorine atoms.
The “perfluoroalkyl group” means a group in which all hydrogen atoms of an alkyl group are substituted with fluorine atoms.
“Carbon-carbon unsaturated bond” means a carbon-carbon double bond or a carbon-carbon triple bond.
The “non-carbon-based active material” means a negative electrode active material that can occlude and release lithium ions, and does not have a carbon atom as a main component in the active material. “Having no carbon atom as a main component in the active material” means that the proportion of carbon atoms in the active material is 10% by mass or less. The non-carbon active material is preferably an active material having no carbon atom.

[Nonaqueous electrolyte secondary battery]
The non-aqueous electrolyte secondary battery of the present invention is a separator comprising a non-aqueous electrolyte, a positive electrode, a negative electrode, and a microporous film mainly composed of a thermoplastic resin provided between the positive electrode and the negative electrode. And a non-aqueous electrolyte secondary battery comprising a filler layer mainly comprising an inorganic filler provided between the positive electrode and the negative electrode.

(Nonaqueous electrolyte)
The nonaqueous electrolytic solution includes an electrolyte and a liquid composition, and includes other components as necessary.
The lower limit of the ionic conductivity at 25 ° C. of the nonaqueous electrolytic solution is preferably 0.30 S / m. If the ionic conductivity at 25 ° C. of the non-aqueous electrolyte is 0.30 S / m or more, the battery characteristics of the secondary battery are further improved.

<Electrolyte>
At least one of the electrolytes is a lithium salt.
The electrolyte may be a lithium salt alone or a combination of a lithium salt and an electrolyte other than the lithium salt. Examples of the electrolyte other than the lithium salt include sodium salt or potassium salt of monofluorophosphoric acid or difluorophosphoric acid, NaPF _{6 and the} like.

≪Lithium salt≫
The lithium salt dissociates in the non-aqueous electrolyte and supplies lithium ions.
Lithium salt preferably includes a LiPF _6.
LiPF ₆ can exhibit high ionic conductivity when dissolved in a solvent having a high solubility, but compared to other lithium salts such as CF ₃ CF ₂ SO ₂ N (Li) SO ₂ CF ₂ CF _3. Therefore, it is difficult to dissolve in the fluorinated solvent (A). However, by using together with the cyclic carboxylic acid ester compound (B), the solubility of LiPF _{6 in} the fluorine-containing solvent (A) is improved. When LiPF ₆ is uniformly dissolved in the fluorine-containing solvent (A), it becomes easy to obtain a nonaqueous electrolytic solution having practically sufficient ionic conductivity. In addition, LiPF ₆ is likely to be thermally decomposed and easily reduce the thermal stability of the battery, but by including the cyclic carboxylic acid ester compound (B), thermal runaway occurs even in a non-aqueous electrolyte secondary battery using LiPF _6. It becomes difficult to get up.

Examples of lithium salts other than LiPF ₆ include the following compound (L1).

  However, M is a boron atom or a phosphorus atom, R is a C1-C10 alkylene group which may have a substituent, X is a halogen atom, n is 0-4. , M is 0 or 1, and p is 1 or 2.

When M is a boron atom and p is 1, n is 2.
When M is a boron atom and p is 2, n is 0.
When M is a phosphorus atom and p is 1, n is 4.
When M is a phosphorus atom and p is 2, n is 2.
When p is 2, both m may be 0, both may be 1, one may be 0 and the other may be 1.
When p is 2 and two m's are both 1, the two R ¹ groups may be different from each other or the same group.

Examples of the substituent for R include a halogen atom, a chain or cyclic alkyl group, an aryl group, a sulfonyl group, a cyano group, a hydroxyl group, and an alkoxy group.
X is preferably a fluorine atom or a chlorine atom, particularly preferably a fluorine atom.
As the compound (L1), one type may be used alone, or two or more types may be used in combination.

When the non-aqueous electrolyte contains the compound (L1) as a lithium salt, the non-aqueous electrolyte is excellent in battery characteristics such as cycle characteristics and rate characteristics. This is considered as follows.
It is considered that the compound (L1) decomposes on the negative electrode during charging of the secondary battery and forms a lithium ion conductive film (SEI) having a low interface resistance on the negative electrode surface. Conventionally, vinylene carbonate etc. are known as a film formation agent which forms such SEI. Since the compound (L1) can form a good SEI having a lower interface resistance than conventional film forming agents such as vinylene carbonate, it is considered to be a non-aqueous electrolyte excellent in battery characteristics such as cycle characteristics and rate characteristics. It is done.

  The compound (L1) is selected from the group consisting of the following compounds (L1-1) to (L1-5) from the viewpoint of easily obtaining a nonaqueous electrolytic solution excellent in battery characteristics such as cycle characteristics and rate characteristics. It is preferable to include at least one kind.

As the lithium _{salt, Li 2 PO 3 F, LiPO} 2 F 2, the following compound (L2) (however, k is an integer of 1 to _{5.), FSO 2 N (Li} ) SO 2 F, CF 3 with _{SO 2 N (Li) SO 2} CF 3, CF 3 CF 2 SO 2 N (Li) SO 2 CF 2 CF 3, CF 3 CFHSO 2 N (Li) SO 2 CFHCF 3, LiClO 4, LiBF 4 , etc. Also good.

<Liquid composition>
The liquid composition contains the fluorine-containing solvent (A) and the cyclic carboxylic acid ester compound (B) as essential components, and optionally contains the compound (C).

≪Fluorine-containing solvent (A) ≫
The fluorine-containing solvent (A) is a fluorine-containing solvent containing at least one selected from the group consisting of fluorine-containing ether compounds, fluorine-containing chain carboxylic acid ester compounds and fluorine-containing chain carbonate compounds.
The fluorine-containing solvent (A) is a solvent having a fluorine atom in the molecule and is excellent in flame retardancy. A fluorine-containing solvent (A) may be used individually by 1 type, and may use 2 or more types together. When the number of fluorine-containing solvents (A) is two or more, the ratio can be arbitrarily determined.

Fluorine-containing ether compound:
The fluorine-containing solvent (A) preferably contains a fluorine-containing ether compound from the viewpoint of the solubility of the lithium salt, the flame retardancy, and the ionic conductivity of the non-aqueous electrolyte. The fluorine-containing ether compound is at least one selected from the group consisting of the following compound (1) and the following compound (2) from the viewpoint of the solubility of the lithium salt, flame retardancy, and the ionic conductivity of the non-aqueous electrolyte. Species are preferred.
A fluorine-containing ether compound may be used individually by 1 type, and may use 2 or more types together. When the number of fluorine-containing ether compounds is two or more, the ratio can be arbitrarily determined.

However, R ¹ and R ² are each independently an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, a fluorinated alkyl group having 1 to 10 carbon atoms, or a fluorinated group having 3 to 10 carbon atoms. A cycloalkyl group, an alkyl group having 2 to 10 carbon atoms having one or more etheric oxygen atoms, or a fluorinated alkyl group having 2 to 10 carbon atoms having one or more etheric oxygen atoms, R ¹ And one or both of R ² are fluorinated alkyl groups having 1 to 10 carbon atoms, fluorinated cycloalkyl groups having 3 to 10 carbon atoms, or fluorine having 2 to 10 carbon atoms having one or more etheric oxygen atoms. Alkyl group.
In Formula (3), Y represents an alkylene group having 1 to 5 carbon atoms, a fluorinated alkylene group having 1 to 5 carbon atoms, an alkylene group having 2 to 5 carbon atoms having an etheric oxygen atom, or etheric oxygen. It is a C2-C5 fluorinated alkylene group having an atom.

Examples of the alkyl group and the alkyl group having an etheric oxygen atom in the compound (1) include a linear structure, a branched structure, or a group having a partial cyclic structure (for example, a cycloalkylalkyl group).
One or both of R ¹ and R ² are fluorinated alkyl groups having 1 to 10 carbon atoms, fluorinated cycloalkyl groups having 3 to 10 carbon atoms, or 2 to 10 carbon atoms having one or more etheric oxygen atoms. Of the fluorinated alkyl group. When one or both of R ¹ and R ² are these groups, the solubility of the lithium salt in the non-aqueous electrolyte and the flame retardancy of the non-aqueous electrolyte are excellent. R ¹ and R ² in the compound (1) may be the same or different.

As the compound (1), R ¹ and R ² are both fluorinated alkyl groups having 1 to 10 carbon atoms because lithium salt solubility, flame retardancy, and ionic conductivity of the non-aqueous electrolyte are increased. Compound (1-A), R ¹ is a fluorinated alkyl group having 2 to 10 carbon atoms having one or more etheric oxygen atoms, and R ² is a fluorinated alkyl group having 1 to 10 carbon atoms (1-B) and a compound (1-C) in which R ¹ is a fluorinated alkyl group having 1 to 10 carbon atoms and R ² is an alkyl group having 1 to 10 carbon atoms are preferred. ) And compound (1-C) are more preferable, and compound (1-A) is particularly preferable.

When the total carbon number of the compound (1) is too small, the boiling point is too low, and when it is too large, 4 to 10 is preferable, and 4 to 8 is more preferable.
When the molecular weight of the compound (1) is too small, the boiling point is too low, and when it is too large, the viscosity is preferably 150 to 800, more preferably 150 to 500, and particularly preferably 200 to 500.
1-4 are preferable, as for the number of etheric oxygen atoms in a compound (1), 1 or 2 is more preferable, and 1 is further more preferable. The number of etheric oxygen atoms in the compound (1) affects flammability.
40 mass% or more is preferable, as for the fluorine content in a compound (1), 50 mass% or more is more preferable, and 60 mass% or more is further more preferable. When the fluorine content in the compound (1) is high, the flame retardancy is excellent. The fluorine content is the ratio of the total mass of fluorine atoms to the molecular weight.

The compound (1) is preferably a compound in which both R ¹ and R ² are alkyl groups in which some of the hydrogen atoms of the alkyl group are fluorinated from the viewpoint of excellent solubility in a lithium salt liquid composition, A compound in which one or both ends of R ¹ and R ² are —CF ₂ H is more preferable.

  Specific examples of the compound (1-A) and the compound (1-B), and specific examples of the fluorinated ether compound other than the compound (1-A) and the compound (1-B) include International Publication No. 2009/133899. And the like.

As the compound (1), the solubility of the lithium salt is excellent, the flame retardancy is excellent, the viscosity is low, and the boiling point is not too low. Therefore, CF ₃ CH ₂ OCF ₂ CHF ₂ , CF ₃ CH ₂ OCF ₂ CHFCF ₃ CHF ₂ CF ₂ CH ₂ OCF ₂ CHF ₂ , CH ₃ CH ₂ CH ₂ OCF ₂ CHF ₂ , CH ₃ CH ₂ OCF ₂ CHF ₂ , and CHF ₂ CF ₂ CH ₂ OCF ₂ CHFCF ₃ preferably _{one, CF 3 CH 2 OCF 2 CHF} 2, CHF 2 CF 2 CH 2 OCF 2 CHF 2 and _CHF 2 _CF 2 _CH 2 at least one selected from the group consisting of _OCF 2 CHFCF ₃ is particularly preferred.

  Y in the compound (2) may have a linear structure or a branched structure. Y is preferably an alkylene group having 1 to 5 carbon atoms, more preferably an alkylene group having 2 to 4 carbon atoms. The alkylene group preferably has a linear structure or a branched structure. When the alkylene group in Y has a branched structure, the side chain is preferably an alkyl group having 1 to 3 carbon atoms or an alkyl group having 1 to 3 carbon atoms having an etheric oxygen atom.

The compound (2) is selected from the group consisting of —CH ₂ —, —CH ₂ CH ₂ —, —CH (CH ₃ ) CH ₂ — and —CH ₂ CH ₂ CH ₂ — in the formula (2). And one or both of the compound in which Y is —CH ₂ CH ₂ — and the compound in which Y is —CH (CH ₃ ) CH ₂ — is more preferable, and Y is —CH _2. CH ₂ -, compound and Y is -CH _(CH 3) CH ₂ - is still more preferably one of a compound.
Specific examples of the compound (2) include a compound represented by the following formula.

  As the fluorine-containing ether compound, compound (1) alone, compound (2) alone, or a mixture of compound (1) and compound (2) is preferred, and compound (1) alone is more preferred. As the compound (1), one type may be used alone, or two or more types may be used in combination. A compound (2) may be used individually by 1 type, and may be used in combination of 2 or more type.

Fluorine-containing chain carboxylic acid ester compound:
The fluorine-containing chain carboxylic acid ester compound preferably includes the following compound (3) from the viewpoint of viscosity, boiling point, and the like, and more preferably includes only the compound (3). A fluorine-containing chain carboxylic acid ester compound may be used individually by 1 type, and may use 2 or more types together. When the number of fluorine-containing chain carboxylic acid ester compounds is two or more, the ratio can be arbitrarily determined. When the compound (3) is included, the compound (3) may be used alone or in combination of two or more.

However, ^{R 3} and ^{R 4} are each independently an alkyl group having 1 to 3 carbon atoms or a fluorinated alkyl group having 1 to 3 carbon atoms, one or both of ^{R 3} and ^{R 4,} 1 carbon atoms 3 is a fluorinated alkyl group.

Examples of the alkyl group and the fluorinated alkyl group in the compound (3) include a linear structure and a branched structure, respectively.
One or both of R ³ and R ⁴ is a fluorinated alkyl group having 1 to 3 carbon atoms. By making one or both of R ³ and R ⁴ a fluorinated alkyl group having 1 to 3 carbon atoms, the compound (3) is excellent in oxidation resistance and flame retardancy. R ³ and R ⁴ in the compound (3) may be the same or different.

R ³ is preferably a methyl group, an ethyl group, a difluoromethyl group, a trifluoromethyl group, a tetrafluoroethyl group, or a pentafluoroethyl group from the viewpoints of viscosity, boiling point, or availability of the compound. A fluoromethyl group is more preferred.
R ⁴ is methyl, ethyl, trifluoromethyl, 2-fluoroethyl, 2,2-difluoroethyl, 2,2,2-trimethyl from the viewpoint of viscosity, boiling point, or availability of the compound. A fluoroethyl group is preferable, a methyl group, an ethyl group, and a 2,2,2-trifluoroethyl group are more preferable, and a methyl group and an ethyl group are more preferable.

When the total number of carbon atoms of the compound (3) is too small, the boiling point is too low, and when it is too large, the viscosity is increased, preferably 3 to 8, more preferably 3 to 6, and further preferably 3 to 5.
When the molecular weight of the compound (3) is too small, the boiling point is too low, and when it is too large, the viscosity is preferably 100 to 300, more preferably 100 to 250, and particularly preferably 100 to 200.
From the point which is excellent in a flame retardance, 25 mass% or more is preferable and, as for the fluorine content in a compound (3), 30 mass% or more is more preferable.

  Specific examples of the compound (3) include acetic acid (2,2,2-trifluoroethyl), methyl difluoroacetate, ethyl difluoroacetate, ethyl trifluoroacetate and the like. From the viewpoint of availability and battery performance such as cycle characteristics, methyl difluoroacetate and ethyl trifluoroacetate are preferable.

Fluorine-containing chain carbonate compound:
The fluorine-containing chain carbonate compound preferably contains the following compound (4), more preferably only the compound (4), from the viewpoints of viscosity and boiling point. A fluorine-containing chain carbonate compound may be used individually by 1 type, and may use 2 or more types together. When the number of fluorine-containing chain carbonate compounds is two or more, the ratio can be arbitrarily determined. When the compound (4) is included, the compound (4) may be used alone or in combination of two or more.

However, R < ⁵ > and R < ⁶ > is respectively independently a C1-C3 alkyl group or a C1-C3 fluorinated alkyl group, and one or both of R < ⁵ > and R < ⁶ > are C1-C1 3 is a fluorinated alkyl group.

Examples of the alkyl group and the fluorinated alkyl group in the compound (4) include a linear structure and a branched structure, respectively.
One or both of R ⁵ and R ⁶ is a fluorinated alkyl group having 1 to 3 carbon atoms. By making one or both of R ⁵ and R ⁶ a fluorinated alkyl group having 1 to 3 carbon atoms, the solubility and flame retardancy of the lithium salt are excellent. R ⁵ and R ⁶ may be the same or different.

The compound (4) is preferably a compound in which both R ⁵ and R ⁶ are fluorinated alkyl groups having 1 to 3 carbon atoms from the viewpoint of viscosity, boiling point, or availability of the compound. R ⁵ and R ⁶ are preferably CF ₃ CH ₂ — or CHF ₂ CF ₂ CH ₂ —.

When the total number of carbon atoms of the compound (4) is too small, the boiling point is too low, and when it is too large, the viscosity is increased to 4 to 10, and 4 to 7 is more preferable.
When the molecular weight of the compound (4) is too small, the boiling point is too low, and when it is too large, the viscosity is preferably 180 to 400, more preferably 200 to 350, and particularly preferably 210 to 300.
The fluorine content in the compound (4) is preferably 25% by mass or more and more preferably 30% by mass or more from the viewpoint of excellent flame retardancy.

  Specific examples of the compound (4) include bis (2,2,2-trifluoroethyl) carbonate, bis (2,2,3,3-tetrafluoropropyl) carbonate, and the like. Bis (2,2,2-trifluoroethyl) carbonate is preferred from the viewpoint of battery performance such as viscosity, availability, and output characteristics.

Other fluorine-containing solvents:
The fluorine-containing solvent (A) may contain a fluorine-containing alkane compound as a fluorine-containing solvent other than the fluorine-containing ether compound, the fluorine-containing chain carboxylic acid ester compound, and the fluorine-containing chain carbonate compound. When the fluorine-containing alkane compound is contained, the vapor pressure of the non-aqueous electrolyte is suppressed and the flame retardancy is further improved.

As the fluorine-containing alkane compound, a fluorine-containing alkane compound having 4 to 12 carbon atoms is preferable. If the fluorine-containing alkane compound has 4 or more carbon atoms, the vapor pressure of the non-aqueous electrolyte is lowered. When the fluorine-containing alkane compound has 12 or less carbon atoms, the lithium salt has good solubility.
The fluorine content in the fluorine-containing alkane compound is preferably 50 to 80% by mass. If the fluorine content in the fluorine-containing alkane compound is 50% by mass or more, the flame retardancy is excellent. If the fluorine content in the fluorine-containing alkane compound is 80% by mass or less, the solubility of the lithium salt is easily maintained.

The fluorinated alkane compounds, compounds of the linear structure is preferable, for _{example, n-C 4 F 9 CH} 2 CH 3, n-C 6 F 13 CH 2 CH 3, n-C 6 F 13 H, n-C ₈ F ₁₇ H and the like. A fluorine-containing alkane compound may be used individually by 1 type, and may use 2 or more types together.

≪Cyclic carboxylic acid ester compound (B) ≫
When the liquid composition contains the cyclic carboxylic acid ester compound (B), the lithium salt is uniformly dissolved in the fluorine-containing solvent (A). Further, by including the cyclic carboxylic acid ester compound (B), the non-aqueous electrolyte and the electrode are less likely to react and thermal runaway is less likely to occur. The cyclic carboxylic acid ester compound (B) may be only one type or two or more types.

As the cyclic carboxylic acid ester compound (B), a saturated cyclic carboxylic acid ester compound having no carbon-carbon unsaturated bond in the molecule is preferable from the viewpoint of stability to redox reaction.
The ring structure in the cyclic carboxylic acid ester compound (B) is preferably a 4- to 10-membered ring, more preferably a 4- to 7-membered ring, more preferably a 5- to 6-membered ring, particularly preferably a 5-membered ring from the viewpoint of availability. preferable.

The ring structure of the cyclic carboxylic acid ester compound (B) is preferably a ring structure having one ester bond from the viewpoint of viscosity and stability to redox reaction.
The cyclic carboxylic acid ester compound (B) may be a compound in which one or more hydrogen atoms of the alkylene group are substituted with a substituent. Examples of the substituent include a fluorine atom, a chlorine atom, an alkyl group, and a fluorinated alkyl group. The alkyl group preferably has 1 to 2 carbon atoms, and the fluorinated alkyl group has preferably 1 to 2 carbon atoms.

  The cyclic carboxylic acid ester compound preferably contains the following compound (5), and more preferably consists only of the compound (5), from the viewpoints of stability to redox reaction, structural stability, and viscosity. A compound (5) may be used individually by 1 type, and may use 2 or more types together.

Provided that R ^{7 to} R ¹² are each independently a hydrogen atom, a fluorine atom, a chlorine atom, an alkyl group having 1 to 2 carbon atoms, a fluorinated alkyl group having 1 to 2 carbon atoms, or one or more etheric oxygen atoms And an alkyl group having 2 to 3 carbon atoms. q is an integer of 0-3.

R ^{7 to} R ¹² may be the same or different.
R ^{7 to} R ¹² are preferably a hydrogen atom, a methyl group, or a fluorine atom, more preferably a hydrogen atom or a methyl group, from the viewpoints of stability to redox reaction, viscosity, and availability of the compound.
q is preferably 1 to 2 and more preferably 1 from the viewpoint of viscosity and availability of the compound.

  Compound (5) is a cyclic ester compound such as γ-butyrolactone, γ-valerolactone, γ-hexanolactone, δ-valerolactone, ε-caprolactone, and the carbon atom forming the ring of the cyclic ester compound. One or more hydrogen atoms to be bonded are fluorine atoms, chlorine atoms, alkyl groups having 1 to 2 carbon atoms, fluorinated alkyl groups having 1 to 2 carbon atoms, or alkyl groups having 2 to 3 carbon atoms having etheric oxygen atoms The compound substituted by is mentioned. At least one selected from the group consisting of γ-butyrolactone and γ-valerolactone is preferable, and γ-butyrolactone is particularly preferable because it is easily available and has a high effect of suppressing thermal runaway.

≪Compound (C) ≫
Since the liquid composition has excellent lithium salt solubility and ionic conductivity, a saturated cyclic carbonate compound, a saturated chain carbonate compound having no fluorine atom (hereinafter also referred to as a non-fluorine-based saturated chain carbonate compound), It is preferable to further include at least one compound (C) selected from the group consisting of saturated cyclic sulfone compounds (excluding electrolytes) and phosphate ester compounds.

As saturated cyclic carbonate compounds, propylene carbonate (PC), ethylene carbonate (EC), 4-fluoro-1,3-dioxolan-2-one (FEC), 4-trifluoromethyl-1,3-dioxolane-2- ON etc. are mentioned.
Examples of the non-fluorinated saturated chain carbonate compound include dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC).
Examples of the saturated cyclic sulfone compound include sulfolane and 3-methylsulfolane.
Examples of the phosphoric acid ester compound include trimethyl phosphate, triethyl phosphate, and tris phosphate (2,2,2-trifluoroethyl).

  The liquid composition preferably contains a non-fluorinated saturated chain carbonate compound. When the non-fluorinated saturated chain carbonate compound is included, the viscosity of the non-aqueous electrolyte can be lowered, and the lithium ion diffusion coefficient in the non-aqueous electrolyte and the ionic conductivity of the non-aqueous electrolyte are easily increased.

<Other ingredients>
The nonaqueous electrolytic solution is a compound other than the lithium salt, the fluorine-containing solvent (A), the cyclic carboxylic acid ester compound (B), and the compound (C) as necessary, as long as the effects of the present invention are not impaired. Other solvents, additives, etc.) may be included.

≪Other solvents≫
The nonaqueous electrolytic solution may contain a solvent other than the fluorine-containing solvent (A), the cyclic carboxylic acid ester compound (B), and the compound (C).

≪Additives≫
In order to improve the function of the non-aqueous electrolyte, the non-aqueous electrolyte may contain conventionally known additives as necessary. Examples of the additive include an overcharge inhibitor, a dehydrating agent, a deoxidizing agent, a property improving aid, and a surfactant.

Overcharge prevention agent:
As an overcharge inhibitor, aromatic compounds (biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, dibenzofuran, etc.), aromatic compounds Partially fluorinated products (2-fluorobiphenyl, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene, etc.), fluorine-containing anisole compounds (2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroaniol, etc.) ). An overcharge inhibitor may be used individually by 1 type, and may use 2 or more types together.

Dehydrating agent:
Examples of the dehydrating agent include molecular sieves, mirabilite, magnesium sulfate, calcium hydride, sodium hydride, potassium hydride, lithium aluminum hydride and the like. As the liquid composition or other solvent used for the non-aqueous electrolyte, those obtained by rectification after dehydration with a dehydrating agent are preferable. Moreover, what performed only the dehydration by the said dehydrating agent without performing rectification may be used.

Property improvement aids:
The characteristic improving aid is for improving capacity maintenance characteristics and cycle characteristics after high temperature storage. As the property improvement aid, unsaturated cyclic carbonate compounds (dimethyl vinylene carbonate, vinylene carbonate, vinyl ethylene carbonate, 4-acetylin-1,3-dioxolan-2-one, 3-methyl-4-vinylethylene carbonate, 4, 5-divinylethylene carbonate, 4,5-bis (2-methylvinyl) ethylene carbonate, etc.), sulfur-containing compounds (ethylene sulfite, 1,3-propane sultone, 1,4-butane sultone, methyl methanesulfonate, busulfan, Sulfolene, dimethylsulfone, diphenylsulfone, methylphenylsulfone, dibutyldisulfide, dicyclohexyldisulfide, tetramethylthiuram monosulfide, N, N-dimethylmethanesulfonamide, N, N-diethylmethane Ruhon'amido etc.), hydrocarbon compounds (heptane, octane, cycloheptane and the like), a fluorine-containing aromatic compound (fluorobenzene, difluorobenzene, hexafluorobenzene and the like). A characteristic improvement adjuvant may be used individually by 1 type, and may use 2 or more types together.

Surfactant:
The surfactant assists the impregnation of the non-aqueous electrolyte into the electrode mixture or separator. As the surfactant, any of cationic surfactants, anionic surfactants, nonionic surfactants and amphoteric surfactants may be used. Anionic surfactants are easily available and have a high surfactant effect. Agents are preferred. As the surfactant, a fluorine-containing surfactant is preferable from the viewpoint of high oxidation resistance and good cycle characteristics and rate characteristics. Only one surfactant may be used, or two or more surfactants may be used.

<Ratio of each component>
≪Lithium salt ratio≫
The content of the lithium salt in the non-aqueous electrolyte is preferably 0.1 to 3.0 mol / L. The lower limit value of the lithium salt content is more preferably 0.3 mol / L, further preferably 0.5 mol / L. The upper limit value of the lithium salt content is more preferably 2.5 mol / L, further preferably 2 mol / L.
0.9-57 mass% is preferable, as for the ratio of the mass of lithium salt with respect to the total mass of nonaqueous electrolyte, 2.5-48 mass% is more preferable, and 4.5-40 mass% is further more preferable.
If the ratio of lithium salt is more than a lower limit, the ionic conductivity of a non-aqueous electrolyte will become high. When the proportion of the lithium salt is not more than the upper limit, the lithium salt is easily dissolved uniformly in the liquid composition, and the lithium salt does not precipitate even under low temperature conditions.

The nonaqueous electrolytic solution of the present invention preferably contains LiPF ₆ as a lithium salt. The lower limit of the molar ratio of LiPF ₆ with respect to the total number of moles of lithium salt contained in the nonaqueous electrolytic solution is preferably 40 mol%, more preferably 50 mol%, still more preferably 65 mol%, and particularly preferably 80 mol%. The upper limit of the molar ratio of LiPF ₆ with respect to the total number of moles of lithium salt contained in the nonaqueous electrolytic solution is 100 mol%. If the molar ratio of LiPF ₆ with respect to the total number of moles of lithium salt is equal to or higher than the lower limit value, the non-aqueous electrolyte solution is excellent in ionic conductivity and highly practical.

≪Ratio of fluorine-containing solvent (A) ≫
The ratio of the mass of the fluorinated solvent (A) to the total mass of the non-aqueous electrolyte is preferably 30 to 80% by mass. The lower limit of the mass ratio of the fluorinated solvent (A) is more preferably 35 mass%, further preferably 40 mass%, particularly preferably 45 mass%. The upper limit of the proportion of the fluorinated solvent (A) is more preferably 75% by mass, further preferably 73% by mass, and particularly preferably 70% by mass.
If the proportion of the fluorinated solvent (A) is at least the lower limit value, the non-aqueous electrolyte is excellent in flame retardancy, small in positive electrode reactivity and negative electrode reactivity, hardly causes thermal runaway, and has high voltage resistance. . If the ratio of the fluorine-containing solvent (A) is not more than the upper limit value, the lithium salt is uniformly dissolved, and the lithium salt does not easily precipitate at a low temperature, so that the ionic conductivity is hardly lowered.

30-90 mass% is preferable, as for the ratio of the mass of a fluorine-containing solvent (A) with respect to the total mass of a liquid composition, 35-85 mass% is more preferable, 40-80 mass% is further more preferable, 45-75 mass%. Is particularly preferred.
If the proportion of the fluorinated solvent (A) is at least the lower limit value, the non-aqueous electrolyte is excellent in flame retardancy, small in positive electrode reactivity and negative electrode reactivity, hardly causes thermal runaway, and has high voltage resistance. . If the ratio of the fluorine-containing solvent (A) is not more than the upper limit value, the lithium salt is uniformly dissolved, and the lithium salt does not easily precipitate at a low temperature, so that the ionic conductivity is hardly lowered.

When the fluorine-containing solvent (A) contains a fluorine-containing ether compound, the ratio of the mass of the fluorine-containing ether compound to the total mass of the fluorine-containing solvent (A) is preferably 25% by mass, more preferably 30% by mass, and 50% by mass. % Is more preferable, 60% by mass is more preferable, and 70% by mass is particularly preferable. The upper limit of the ratio of the mass of the fluorinated ether compound to the total mass of the fluorinated solvent (A) is 100% by mass.
The fluorine-containing solvent (A) is particularly preferably composed only of a fluorine-containing ether compound from the viewpoints of the solubility of the lithium salt, the flame retardance of the non-aqueous electrolyte, and the ionic conductivity.

  When the fluorine-containing solvent (A) of the non-aqueous electrolyte contains a fluorine-containing ether compound, the lower limit of the ratio of the mass of the fluorine-containing ether compound to the total mass of the non-aqueous electrolyte is preferably 10% by mass, and 20% by mass. Is more preferable, 30% by mass is further preferable, 45% by mass is further preferable, and 50% by mass is particularly preferable. The upper limit of the ratio of the mass of the fluorine-containing ether compound to the total mass of the nonaqueous electrolytic solution is preferably 80% by mass, more preferably 75% by mass, further preferably 73% by mass, and particularly preferably 70% by mass.

  When the fluorinated solvent (A) contains a fluorinated chain carboxylic acid ester compound, the lower limit of the ratio of the mass of the fluorinated chain carboxylic acid ester compound to the total mass of the fluorinated solvent (A) is 0.01 mass. % Is preferred. The upper limit of the ratio of the mass of the fluorinated chain carboxylic acid ester compound to the total mass of the fluorinated solvent (A) is preferably 50 mass%, more preferably 40 mass%, further preferably 30 mass%, more preferably 20 mass%. Is particularly preferred.

  When the fluorine-containing solvent (A) contains a fluorine-containing chain carbonate compound, the lower limit of the ratio of the mass of the fluorine-containing chain carbonate compound to the total mass of the fluorine-containing solvent (A) is preferably 0.01% by mass. The upper limit of the ratio of the mass of the fluorinated chain carbonate compound to the total mass of the fluorinated solvent (A) is preferably 50 mass%, more preferably 40 mass%, further preferably 30 mass%, particularly preferably 20 mass%. preferable.

  When the fluorinated solvent (A) contains a fluorinated alkane compound, the ratio of the mass of the fluorinated alkane compound to the total mass of the nonaqueous electrolytic solution is preferably from 0.01 to 5 mass%. When the ratio of the fluorine-containing alkane compound is 0.01% by mass or more, the vapor pressure is low and the flame retardancy is excellent. When the proportion of the fluorine-containing alkane compound is 5% by mass or less, the solubility of the lithium salt is easily maintained.

  When the fluorine-containing solvent (A) is used in combination with a fluorine-containing ether compound and at least one selected from a fluorine-containing chain carboxylic acid ester, a fluorine-containing chain carbonate compound and a fluorine-containing alkane compound, the ratio thereof is arbitrary. Can be decided.

<< Ratio of cyclic carboxylic acid ester compound (B) >>
The ratio of the mass of the cyclic carboxylic acid ester compound (B) to the total mass of the nonaqueous electrolytic solution is preferably 4 to 50 mass%. The lower limit of the mass ratio of the cyclic carboxylic acid ester compound (B) is more preferably 7% by mass, further preferably 10% by mass, and particularly preferably 15% by mass. The upper limit of the mass ratio of the cyclic carboxylic acid ester compound (B) is more preferably 45% by mass, further preferably 40% by mass, and particularly preferably 35% by mass.
If the ratio of the cyclic carboxylic acid ester compound (B) is at least the lower limit value, the non-aqueous electrolyte uniformly dissolves the lithium salt and the reactivity between the non-aqueous electrolyte and the electrode is small. Therefore, the thermal runaway of the secondary battery is less likely to occur. If the ratio of the cyclic carboxylic acid ester compound (B) is not more than the upper limit value, the non-aqueous electrolyte is excellent in flame retardancy.

The ratio N _B / N _Li of the total number of moles N _B of the cyclic carboxylic acid ester compound (B) to the total number of moles N _Li of lithium atoms derived from the lithium salt contained in the non-aqueous electrolyte is not particularly limited, but 1 .5 to 7.0 is preferable. The lower limit of the _N B _{/ N Li} is 2, still more preferably 2.5, most preferably 3. The upper limit of the _N B _{/ N Li} is preferably 6.5, more preferably 6, more preferably 5, particularly preferably 4.5, 4.2 is most preferred.
If N _B / N _Li is equal to or greater than the lower limit, the non-aqueous electrolyte uniformly dissolves the lithium salt, and the reactivity between the non-aqueous electrolyte and the electrode is reduced. Therefore, the thermal runaway of the secondary battery is less likely to occur. If N _B / N _Li is not more than the upper limit value, the non-aqueous electrolyte is excellent in flame retardancy.

<< Ratio of Compound (C) >>
When the liquid composition contains the compound (C), the upper limit of the ratio of the mass of the compound (C) to the total mass of the non-aqueous electrolyte is preferably 30% by mass, more preferably 25% by mass, and 20% by mass. Further preferred. The lower limit of the ratio of the mass of the compound (C) to the total mass of the non-aqueous electrolyte is 0% by mass.
If the ratio of a compound (C) is below an upper limit, it will be easy to suppress reaction with a compound (C) and an electrode, and the nonaqueous electrolyte solution excellent in stability will be obtained. Moreover, since content of a fluorine-containing solvent (A) can be increased, the nonaqueous electrolyte solution excellent in the flame retardance is easy to be obtained.

When the liquid composition contains a saturated cyclic carbonate compound, the ratio of the mass of the saturated cyclic carbonate compound to the total mass of the non-aqueous electrolyte is preferably 0.01 to 30% by mass, more preferably 0.01 to 20% by mass. 0.01 to 15 mass% is more preferable, 0.1 to 15 mass% is particularly preferable, and 1 to 15 mass% is most preferable.
When the ratio of the saturated cyclic carbonate compound is not more than the upper limit value, the saturated cyclic carbonate compound and the electrode are difficult to react, and the nonaqueous electrolytic solution is excellent in stability and flame retardancy.

When the liquid composition contains a non-fluorinated saturated chain carbonate compound, the ratio of the mass of the non-fluorinated saturated chain carbonate compound to the total mass of the non-aqueous electrolyte is preferably 0.01 to 30% by mass, and 01-20 mass% is more preferable, 0.01-15 mass% is further more preferable, 0.1-15 mass% is especially preferable, and 1-15 mass% is the most preferable.
When the ratio of the non-fluorinated saturated chain carbonate compound is less than or equal to the upper limit, the non-fluorinated saturated chain carbonate compound and the electrode are unlikely to react, and the non-aqueous electrolyte is excellent in stability and flame retardancy.

When the liquid composition contains a saturated cyclic carbonate compound and a non-fluorinated saturated chain carbonate compound, the ratio of the total mass of the saturated cyclic carbonate compound and the non-fluorinated saturated chain carbonate compound to the total mass of the non-aqueous electrolyte is: 0.01-30 mass% is preferable, 0.01-20 mass% is more preferable, 0.01-15 mass% is further more preferable, and 1-15 mass% is especially preferable.
If the ratio of the total mass is less than or equal to the upper limit, even when a saturated cyclic carbonate compound and a non-fluorinated saturated chain carbonate compound are used, the coating of the cyclic carboxylic acid ester compound due to an increase in the polarity of the solvent described above It is easy to obtain a non-aqueous electrolyte solution with excellent stability. Moreover, it is easy to set it as the non-aqueous electrolyte which has the outstanding flame retardance by restraining content of a combustible compound low.

When the liquid composition contains a phosphate ester compound, the mass ratio of the phosphate ester compound to the total mass of the non-aqueous electrolyte is preferably 0.01 to 5 mass%.
When the proportion of the phosphate ester compound is less than or equal to the upper limit, the phosphate ester compound and the electrode are unlikely to react, and the non-aqueous electrolyte is excellent in stability and flame retardancy.

The ratio of the mass of the cyclic carboxylic acid ester compound (B) to the total mass of the cyclic carboxylic acid ester compound (B) and the compound (C) in the liquid composition is preferably 30 to 100% by mass, and 35 to 100% by mass. More preferably, 40-100 mass% is further more preferable, 45-100 mass% is further more preferable, and 50-100 mass% is especially preferable.
When the ratio of the cyclic carboxylic acid ester compound (B) is within the above range, the reactivity between the non-aqueous electrolyte and the electrode can be reduced, and the thermal runaway of the secondary battery can be suppressed.

When the liquid composition contains the compound (C), the total mole number N _B of the cyclic carboxylic acid ester compound (B) and the total mole number N of the compound (C) with respect to the total mole number N _Li of lithium atoms derived from the lithium salt. The ratio of the sum to _C (N _B + N _C ) / N _Li is preferably 3.0 to 7.0. The lower limit value of (N _B + N _C ) / N _Li is more preferably 3.2, and even more preferably 3.5. In addition, the upper limit of the (N _B + N _C ) / N _Li is more preferably 6.5, still more preferably 6, more preferably 5.5, and most preferably 4.5.
If (N _B + N _C ) / N _Li is equal to or higher than the lower limit, the solubility of the lithium salt in the fluorinated solvent (A) is excellent, so that the ionic conductivity increases. If (N _B + N _C ) / N _Li is not more than the upper limit value, it is considered that the solubility of the coating is low and the formation of the coating is unlikely to be insufficient. As a result, the reactivity between the non-aqueous electrolyte and the electrode is further reduced, and the thermal runaway of the secondary battery can be suppressed.

≪Ratio of other ingredients≫
When the non-aqueous electrolyte contains an overcharge inhibitor, the mass ratio of the overcharge inhibitor to the total mass of the non-aqueous electrolyte is preferably 0.01 to 5% by mass.
If the ratio of the non-aqueous electrolyte is equal to or more than the lower limit value, it becomes easier to suppress the rupture and ignition of the secondary battery due to overcharging, and the secondary battery can be used more stably.

  When the non-aqueous electrolyte contains a property improving aid, the ratio of the mass of the property improving aid to the total mass of the non-aqueous electrolyte is preferably 0.01 to 5% by mass.

  When the non-aqueous electrolyte contains a surfactant, the upper limit of the ratio of the mass of the surfactant to the total mass of the non-aqueous electrolyte is preferably 5% by mass, more preferably 3% by mass, and further 2% by mass preferable. The lower limit of the ratio of the mass of the surfactant to the total mass of the non-aqueous electrolyte is preferably 0.05% by mass.

(Positive electrode)
Examples of the positive electrode include an electrode in which a positive electrode layer including a positive electrode active material, a conductivity-imparting agent, and a binder is formed on a current collector.

<Positive electrode active material>
The positive electrode active material may be any material that can occlude and release lithium ions. Examples of positive electrode active materials include lithium-containing transition metal oxides, lithium-containing transition metal composite oxides using two or more transition metals, transition metal oxides, transition metal sulfides, metal oxides, olivine-type metal lithium salts, etc. Is mentioned. A positive electrode active material may be used individually by 1 type, and may use 2 or more types together.

Examples of the lithium-containing transition metal oxide include lithium cobalt oxide (LiCoO _{2 and the} like), lithium nickel oxide (LiNiO _{2 and the} like), lithium manganese oxide and the like (LiMnO ₂ , LiMn ₂ O ₄ , Li ₂ MnO _{3 and the} like). Is mentioned.

As the metal contained in the lithium-containing transition metal composite oxide, Al, V, Ti, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, Yb and the like are preferable. Examples of lithium-containing transition metal composite oxides include lithium ternary composite oxides (Li (Ni _a Co _b Mn _c ) O ₂ (where a, b, c ≧ 0, a + b + c = 1), and the like). Some of the transition metal atoms that are the main components of these lithium transition metal composite oxides are Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, and Yb. And the like substituted with other metals.
Specific examples of the lithium-containing transition metal composite oxide include the following.
LiMn _0.5 Ni _0.5 O ₂ ,
LiMn _1.8 Al _0.2 O ₄ ,
LiNi _0.85 Co _0.10 Al _0.05 O ₂ ,
LiMn _1.5 Ni _0.5 O ₄ ,
LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ,
LiMn _1.8 Al _0.2 O ₄ etc.

Examples of the transition metal oxide include TiO ₂ , MnO ₂ , MoO ₃ , V ₂ O ₅ , V ₆ O _{13 and the} like.
Examples of the transition metal sulfide include TiS ₂ , FeS, and MoS ₂ .
Examples of the metal oxide include SnO ₂ and SiO ₂ .

The olivine-type metallic lithium salt is Li _L M ¹ _x M ² _y O _z F _g (where M ¹ is Fe (II), Co (II), Mn (II), Ni (II), V (II) or Cu (II), M ² is P or Si, and 0 ≦ L ≦ 3, 1 ≦ x ≦ 2, 1 ≦ y ≦ 3, 4 ≦ z ≦ 12, 0 ≦ g ≦ 1. Or a complex thereof.
Specific examples of the olivine-type metal lithium salt include the following.
LiFePO ₄ ,
Li ₃ Fe ₂ (PO ₄ ) ₃ ,
LiFeP ₂ O ₇ ,
LiMnPO ₄ ,
LiNiPO ₄ ,
LiCoPO ₄ ,
Li ₂ FePO ₄ F,
Li ₂ MnPO ₄ F,
Li ₂ NiPO ₄ F,
Li ₂ CoPO ₄ F,
Li ₂ FeSiO ₄ ,
Li ₂ MnSiO ₄ ,
Li ₂ NiSiO ₄ ,
Li ₂ CoSiO ₄ etc.

The positive electrode active material is preferably a compound containing Li, at least one element selected from the group consisting of Co, Ni, Mn, and Fe, and O from the viewpoint of high energy density, and includes the above-described lithium-containing material. Among transition metal oxides, lithium-containing transition metal composite oxides, and olivine-type metal lithium salts, compounds containing the above elements are more preferable.
As the positive electrode active material, a lithium-containing composite oxide (LiCoO ₂ , LiNiO ₂ , LiMnO _2, etc.) based on an α-NaCrO ₂ structure, a spinel type, because it has a high discharge voltage and high electrochemical stability. A lithium-containing composite oxide (LiMn ₂ O ₄ or the like) having a structure as a base is more preferable.

A material in which a substance having a composition different from that of the main constituent of the positive electrode active material is attached to the surface of the positive electrode active material can also be used. Surface adhesion substances include oxides (aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide), sulfate (lithium sulfate, sodium sulfate, potassium sulfate, sulfuric acid) Magnesium, calcium sulfate, aluminum sulfate, etc.), carbonates (lithium carbonate, calcium carbonate, magnesium carbonate, etc.) and the like.
The amount of the surface adhesion substance with respect to the positive electrode active material is preferably 0.1 mass ppm or more and 20 mass% or less, more preferably 1 mass ppm or more and 10 mass% or less, and particularly preferably 10 massppm or more and 5 mass% or less. The surface adhering substance can suppress the oxidation reaction of the nonaqueous electrolytic solution on the surface of the positive electrode active material, and can improve the battery life.

<Conductivity imparting agent>
Examples of the conductivity-imparting agent include carbon materials, metal substances (such as Al), and conductive oxide powders.

<Binder>
Examples of the binder include resin binders (such as polyvinylidene fluoride) and rubber binders (hydrocarbon rubber, fluororubber, etc.).

<Current collector>
Examples of the current collector include a metal thin film mainly composed of Al or the like.

(Negative electrode)
Examples of the negative electrode include an electrode in which a negative electrode layer containing a powdered negative electrode active material, a conductivity-imparting agent, and a binder is formed on a current collector. In addition, when a negative electrode active material can maintain a shape by itself (for example, when it is a lithium metal thin film), a negative electrode can be formed only with a negative electrode active material.

<Negative electrode active material>
Examples of the negative electrode active material include at least one selected from the group consisting of a carbon material that can occlude and release lithium ions and a non-carbon active material that can occlude and release lithium ions. Especially, as a negative electrode active material, it is preferable to contain a non-carbon-type active material from the point which is easy to make high capacity | capacitance.

  Examples of the carbon material include graphite, coke, and hard carbon.

Li can be used as the non-carbon-based active material. Moreover, the simple substance of the metal which can form an alloy with Li, the alloy of this metal and Li, those oxides, sulfides, etc. are mentioned. Examples of the metal capable of forming an alloy with Li include Si, Sn, Al, and Ti. Specific examples of the oxide include SiO and SiO _r (where 0 <r <2).
Further, as the non-carbon-based active material, SiC, SiAg, Mg ₂ Si, or the like may be used.
As the negative electrode active material, only a carbon material may be used, only a non-carbon active material may be used, or a combination of a carbon material and a non-carbon active material may be used.

<Conductivity imparting agent, binder>
As the binder for the negative electrode and the conductivity-imparting agent, the same as those for the positive electrode can be used.

<Current collector>
Examples of the current collector include a metal thin film mainly composed of Cu or the like.

(Separator)
In the nonaqueous electrolyte secondary battery of the present invention, a separator made of a microporous film is provided between the positive electrode and the negative electrode.
The microporous membrane constituting the separator is preferably a microporous membrane that has been made porous by the stretch-opening method from the viewpoint of production cost and the degree of thermal shrinkage. The stretch opening method melts a polymer crystal having a lamellar (layered) structure, extrudes it from a die, forms a sheet, heat-treats it for crystallization, peels the crystal interface by uniaxial stretching, and opens the lamella. It is a technique to make a hole.

The microporous film is a film mainly composed of a thermoplastic resin. The microporous membrane is not particularly limited as long as it has electrical insulating properties, is electrochemically stable, and is stable with respect to the non-aqueous electrolyte described above.
The phrase “mainly comprising a thermoplastic resin” means that the ratio of the thermoplastic resin in the separator is 50% by volume or more. The ratio of the thermoplastic resin is preferably 70% by volume or more. Moreover, the upper limit of the ratio of this thermoplastic resin is 100 volume%.

Examples of the thermoplastic resin include polyolefin (polyethylene (PE), polypropylene (PP), ethylene-propylene copolymer, etc.), polyester (polyethylene terephthalate, copolymerized polyester, etc.) and the like. Among these, polyolefin is preferable because it is inexpensive and has excellent processability.
When a microporous film containing PE as a main component is used as the separator, a shutdown function (a property of closing the pores of the separator) of 80 ° C. or more and 150 ° C. or less can be secured in the separator. Further, when a microporous film containing PP as a main component is used as the separator, the separator does not easily shrink by heat.

  The microporous membrane may have a single layer structure or a multilayer structure. Examples of the microporous film having a multilayer structure include a PE layer / PP layer two-layer structure, a PE layer / PP layer / PE layer, a three-layer structure such as a PP layer / PE layer / PP layer, etc. Is mentioned.

The lower limit of the thickness of the separator is preferably 6 μm and more preferably 10 μm from the viewpoint of easily preventing a short circuit between the positive electrode and the negative electrode. The upper limit of the thickness of the separator is preferably 25 μm and more preferably 20 μm from the viewpoint of easily increasing the energy density of the battery and easily obtaining excellent battery characteristics.
When the separator is a microporous film having a multilayer structure, the thickness is the entire thickness of the microporous film.

(Filler layer)
In the nonaqueous electrolyte secondary battery of the present invention, a filler layer mainly composed of an inorganic filler is provided between a positive electrode and a negative electrode. By having the filler layer in the nonaqueous electrolyte secondary battery of the present invention, it is possible to suppress a short circuit between the positive electrode and the negative electrode even if the separator melts when the nonaqueous electrolyte secondary battery becomes high temperature.
The filler layer may be provided on the positive electrode side of the separator, may be provided on the negative electrode side of the separator, or may be provided on both the positive electrode side and the negative electrode side of the separator. Further, the filler layer may be formed on the surface of the separator or may be formed separately from the separator.

  The filler layer is a layer mainly composed of an inorganic filler. The phrase “mainly composed of inorganic filler” means that the proportion of the inorganic filler in the filler layer is 50% by volume or more. The proportion of the inorganic filler is preferably 70% by volume or more, more preferably 80% by volume or more, and still more preferably 90% by volume or more.

As the inorganic filler, an electrochemically stable one that is stable with respect to the non-aqueous electrolyte and is not easily oxidized and reduced in the operating voltage range of the secondary battery is preferable. If the inorganic filler is electrochemically stable, deterioration of the separator due to oxidation can be suppressed, for example, by facing the filler layer to a positive electrode that is frequently exposed to a high voltage.
As the inorganic filler, inorganic fine particles having a heat resistant temperature of 150 ° C. or higher are more preferable. Even when a microporous film mainly composed of PE is used as the separator, thermal contraction of the separator can be suppressed.

Specific examples of the inorganic filler include alumina, boehmite, silica, titania and the like. The inorganic filler is preferably fine particles. As the particle shape of the inorganic filler, a plate shape, a granular shape, and a fiber shape are preferable, and a plate shape is more preferable because the dendrite hardly reaches the positive electrode from the negative electrode.
An inorganic filler may be used individually by 1 type, and may use 2 or more types together.

The lower limit of the average particle diameter of the inorganic filler is preferably 0.01 μm, and more preferably 0.1 μm. The upper limit of the average particle diameter of the inorganic filler is preferably 10 μm and more preferably 2 μm.
The average particle diameter is, for example, D ₅₀ (volume-based measurement) measured by dispersing an inorganic filler in a medium that does not dissolve the inorganic filler using a laser scattering particle size distribution meter (for example, “LA-920” manufactured by Horiba, Ltd.). Particle diameter at 50% cumulative fraction).

When the inorganic filler is plate-like, the lower limit value of the average thickness of the inorganic filler is preferably 0.02 μm and more preferably 0.05 μm from the viewpoint of being hard to break. The upper limit value of the average thickness of the inorganic filler is preferably 0.7 μm and more preferably 0.5 μm from the viewpoint that a high discharge capacity is easily obtained and the filler layer is not easily broken during battery production.
The average thickness of the plate-like inorganic filler can be determined as an average value (number average value) of the thicknesses of 100 inorganic fillers by observing a cross section of the inorganic filler with an SEM.

More preferably, the filler layer contains a binder from the viewpoint of easily forming the filler layer on the separator surface and ensuring the shape stability of the filler layer.
As the binder, ethylene-vinyl acetate copolymer (EVA, vinyl acetate-derived unit having 20 to 35 mol%), ethylene-acrylic acid copolymer such as ethylene-ethyl acrylate copolymer, fluorine-based rubber, Styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyvinyl pyrrolidone (PVP), cross-linked acrylic resin, polyurethane, epoxy resin, silane coupling agent Etc. Among these, highly flexible binders such as EVA, ethylene-acrylic acid copolymer, fluorine-based rubber, and SBR are preferable.
A binder may be used individually by 1 type and may use 2 or more types together.

  The lower limit of the ratio of the binder in the filler layer is preferably 0.3% by volume, and 0.5% by volume from the viewpoint that the filler layer is easily formed on the separator surface and the shape stability of the filler layer is easily secured. More preferred. The upper limit of the ratio of the binder in the filler layer is preferably 15% by volume from the viewpoint that the pores in the filler layer are not blocked, sufficient ion conductivity can be secured, and the charge / discharge characteristics as a battery are excellent. Volume% is more preferable.

  The lower limit value of the thickness of the filler layer is preferably 1 μm from the viewpoint that the effect of the filler layer can be more effectively exhibited. The upper limit value of the thickness of the filler layer is preferably 10 μm from the viewpoint of easily increasing the energy density of the battery.

  In this invention, it is preferable to provide the separator with a filler layer which formed the filler layer in the surface of either the positive electrode side of a separator, the negative electrode side, or both between a positive electrode and a negative electrode. As a method for forming the separator with a filler layer, for example, a composition in which an inorganic filler and a binder to be used are dispersed in a medium is applied to one surface of a microporous membrane forming the separator. And a method of drying. The binder can be dissolved in the medium.

  Any medium can be used as long as it can uniformly disperse the inorganic filler and can evenly dissolve or disperse the binder. Specific examples of the medium are preferably organic solvents such as aromatic hydrocarbons (such as toluene), furans (such as tetrahydrofuran), and ketones (such as methyl ethyl ketone and methyl isobutyl ketone). Moreover, when a binder is water-soluble, it is good also as an emulsion using water. In order to control the interfacial tension, alcohol (ethylene glycol, propylene glycol, etc.), propylene oxide glycol ether (monomethyl acetate, etc.), etc. may be appropriately added to these media.

[Charging voltage]
The charging voltage of the non-aqueous electrolyte secondary battery of the present invention is preferably 4.25 V or more, more preferably 4.30 V or more, further preferably 4.35 V or more, and particularly preferably 4.40 V or more in terms of the potential with respect to lithium.

(Mechanism of action)
In the non-aqueous electrolyte secondary battery of the present invention, since the non-aqueous electrolyte contains the cyclic carboxylic acid ester compound (B) together with the fluorine-containing solvent (A), the non-aqueous electrolyte mainly contains a conventional carbonate solvent. Compared to the aqueous electrolyte, the non-aqueous electrolyte and the electrode are less likely to react. Therefore, thermal runaway is unlikely to occur. In the nonaqueous electrolyte secondary battery of the present invention, since the filler layer is provided between the positive electrode and the negative electrode in addition to the separator, even if the separator melts at a high temperature, the filler layer causes the positive electrode and the negative electrode to Short circuit is prevented.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by the following description.
[Compound]
The compounds and abbreviations used in the examples are as follows.
(Lithium salt)
LPF: LiPF ₆ .

(Fluorine-containing solvent (A))
AE3000: CF ₃ CH ₂ OCF ₂ CHF ₂ (trade name: AE-3000, manufactured by Asahi Glass Co., Ltd.).

(Cyclic carboxylic acid ester compound (B))
GBL: γ-butyrolactone.

(Compound (C))
DMC: dimethyl carbonate.

(Other ingredients)
VC: vinylene carbonate.

[Example 1]
(Preparation of negative electrode)
Artificial graphite (9.1 g) was stirred for 1 minute at a rotational speed of 2000 rpm using a rotation and revolution type stirrer (manufactured by Shinky Co., Ltd., Awatori Nertaro AR-E310). Subsequently, 2 mass% carboxymethylcellulose aqueous solution (9.0g) was added, and the process stirred for 1 minute at the rotation speed of 2000 rpm using the said stirrer was performed twice. Thereafter, distilled water (4.7 g) was added, and the step of stirring for 1 minute at a rotational speed of 2000 rpm was performed twice using the stirrer. Thereafter, a tetrafluoroethylene-propylene rubber aqueous dispersion latex binder (0.26 g) adjusted to a solid content concentration of 34% by mass was added, and the mixture was stirred for 1 minute at a rotational speed of 2000 rpm using the agitator. A slurry was obtained.
The slurry was applied to a thickness of 210 μm on a copper foil having a thickness of 20 μm, dried, and then punched into a circle having a diameter of 16 mm to obtain a negative electrode.

(Preparation of positive electrode)
LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (manufactured by AGC Seimi Chemical Co., Ltd., 32.0 g) and carbon black (manufactured by Denki Kagaku Kogyo Co., Ltd., 1.78 g) are mixed, and a rotating and rotating stirrer The step of stirring for 60 seconds at a rotational speed of 2000 rpm was performed three times using (Akinori Nertaro AR-E310, manufactured by Shinky Corporation). Next, it was mixed with a 2% by weight aqueous carboxymethyl cellulose solution (7.0 g), and stirred for 10 powders with the agitator. Further, a 2% by weight aqueous carboxymethyl cellulose solution (3.0 g) and distilled water (0.35 g) were added. Added and stirred for 10 minutes. Next, a tetrafluoroethylene-propylene rubber aqueous dispersion latex binder (2.4 g) adjusted to a solid content concentration of 34% by mass was added and stirred for 30 seconds at a rotation speed of 500 rpm using the stirrer to obtain a slurry. The slurry was applied to an aluminum foil having a thickness of 20 μm with a thickness of 180 μm, dried, and then punched into a circle having a diameter of 15 mm to form a positive electrode.

(Preparation of non-aqueous electrolyte)
After diffusing LPF (0.15 g) as a lithium salt into AE3000 (0.71 g) as a fluorine-containing ether compound, GBL (0.34 g) as a cyclic carboxylic acid ester compound (B) and a compound (C DMC (0.22 g) was mixed, and VC (0.03 g) was further added as a characteristic improving aid to obtain a non-aqueous electrolyte solution 1.

The positive electrode and the negative electrode were laminated so as to alternately face each other, and a polyolefin microporous film (hereinafter referred to as separator (I)) was present as a separator between the electrodes to produce a battery element. Further, a non-aqueous electrolyte (1.0 mL) was added to prepare a cell composed of LiNi _0.5 Co _0.2 Mn _0.3 O ₂ electrode-graphite electrode.

[Example 2]
A cell was fabricated in the same manner as in Example 1 except that silicon oxide was used as the negative electrode active material and a negative electrode coated with a thickness of 50 μm was used.

[Example 3]
(Preparation of separator)
On one side of the separator (I), alumina particles (20.0 g) and tetrafluoroethylene-propylene rubber aqueous dispersion latex binder (2.0 g) adjusted to a solid content concentration of 34% by mass were added to 0.5% by mass of carboxy. An aqueous solution uniformly dispersed in an aqueous methylcellulose solution (31.8 g) was applied using a bar coater, and then dried at 60 ° C. to remove water, and a filler layer was formed on one surface of the separator. A separator with a filler layer (hereinafter referred to as separator (II)) was produced.
A cell was produced in the same manner as in Example 1 except that the separator (II) obtained by the above method was used. When arranging this separator (II), it arrange | positioned so that a filler layer might become a positive electrode side.

[Example 4]
A cell was prepared in the same manner as in Example 1 except that the separator (II) obtained in the same manner as in Example 3 was used, silicon oxide was used as the negative electrode active material, and a negative electrode coated with a thickness of 50 μm was used. When arranging the separator (II), the filler layer was arranged on the positive electrode side.

[Example 5]
As the non-aqueous electrolyte, except that a carbonate-based solvent (a non-aqueous electrolyte in which ethylene carbonate and ethyl methyl carbonate are mixed at a mass ratio of 3: 7 and dissolved so that LiPF ₆ is 1.0 M) is used. A cell was produced in the same manner as in Example 1.

[Example 6]
A cell was prepared in the same manner as in Example 1 except that silicon oxide was used as the negative electrode active material, a negative electrode coated with a thickness of 50 μm was used, and a carbonate-based solvent similar to Example 5 was used as the non-aqueous electrolyte.

[Example 7]
A cell was prepared in the same manner as in Example 1 except that the separator (II) obtained in the same manner as in Example 3 was used and the same carbonate-based solvent as in Example 5 was used as the non-aqueous electrolyte. When arranging the separator (II), the filler layer was arranged on the positive electrode side.

[Example 8]
Using the separator (II) obtained in the same manner as in Example 3, using silicon oxide as the negative electrode active material, using a negative electrode coated with a thickness of 50 μm, and using the same carbonate solvent as in Example 5 as the non-aqueous electrolyte A cell was produced in the same manner as in Example 1 except that. When arranging the separator (II), the filler layer was arranged on the positive electrode side.

[Evaluation method]
The following charging / discharging cycle was implemented about the obtained cell. In cycle 1, at 25 ° C., constant current charging is performed up to 3.4 V with a current corresponding to 0.05 C, and further constant current charging is performed up to 4.3 V with a current corresponding to 0.2 C. Constant voltage charging was performed until the value reached a current corresponding to 0.02C. Then, constant current discharge was performed to 3.0V with the electric current equivalent to 0.2C. In cycles 2 to 4, constant current charging was performed up to 4.3 V with a current corresponding to 0.2 C, and further constant voltage charging was performed until the current value reached a current corresponding to 0.02 C at 4.3 V. Then, constant current discharge was performed to 3.0V with the electric current equivalent to 0.2C. The discharge capacity of cycle 4 was evaluated as the discharge capacity of each cell. In cycle 5, constant current charging was performed up to 4.3V with a current corresponding to 0.2C. Then, a thermocouple was attached to the obtained charged cell, and the temperature was increased from 25 ° C. to 160 ° C. at a rate of 5 ° C./min. Thereafter, 160 ° C. was maintained for 5 hours. State change was evaluated.
(Discharge capacity)
The discharge capacity was evaluated by dividing the obtained discharge capacity value by the sum of the positive and negative electrode volumes as Ah / L, with 230 Ah / L or more being “◎”, 150 Ah / L or more and less than 230 Ah / L. Is “◯”, 120 Ah / L or more and less than 150 Ah / L is “Δ”, and less than 120 Ah / L is “x”.
(Exothermic temperature)
The exothermic temperature was evaluated using the “exothermic peak temperature”. The exothermic peak temperature was the peak top temperature of the exothermic peak that appears at the lowest temperature among the exothermic peaks whose calorific value exceeds 5 ° C. from the external environment temperature in the measurement. The temperature of the exothermic peak was evaluated as “◎” when 150 ° C. or higher, “◯” when 120 ° C. or higher and lower than 150 ° C., “Δ” when 110 ° C. or higher and lower than 120 ° C. Moreover, it was set as "x" without evaluating temperature about the thing in which ignition, smoke, etc. were observed.

  The evaluation results in each example are shown in Table 1.

As shown in Table 1, Example 1, which is a nonaqueous electrolyte secondary battery of the present invention, has a smaller calorific value than that of Example 5 having a similar configuration except that a carbonate-based solvent is used, and thermal runaway is unlikely to occur. It was a thing.
Example 2, which is a nonaqueous electrolyte secondary battery of the present invention, had a smaller calorific value than that of Example 6 having a similar configuration except that a carbonate-based solvent was used, and thermal runaway hardly occurred. In Example 2, since a lithium alloy was used for the negative electrode, the discharge capacity was higher than that in Example 1 in which a carbon material was used for the negative electrode.
Example 3 which is a non-aqueous electrolyte secondary battery of the present invention had a smaller calorific value than that of Example 7 having the same configuration except that a carbonate-based solvent was used, and thermal runaway was difficult to occur.
Example 4, which is a nonaqueous electrolyte secondary battery of the present invention, had a smaller amount of heat generation than that of Example 8 having a similar configuration except that a carbonate-based solvent was used, and thermal runaway was difficult to occur. In Example 4, since a lithium alloy was used for the negative electrode, the discharge capacity was higher than that in Example 3 in which a carbon material was used for the negative electrode.

  The non-aqueous electrolyte secondary battery of the present invention includes a mobile phone, a portable game machine, a digital camera, a digital video camera, an electric tool, a notebook computer, a portable information terminal, a portable music player, an electric vehicle, a hybrid vehicle, a train, and an aircraft. It can be applied to various uses such as satellites, submarines, ships, uninterruptible power supplies, robots, and power storage systems. The non-aqueous electrolyte secondary battery of the present invention is particularly a large-sized secondary battery for electric vehicles, hybrid vehicles, trains, airplanes, artificial satellites, submarines, ships, uninterruptible power supply devices, robots, power storage systems, etc. Useful.

Claims (15)

A non-aqueous electrolyte, a positive electrode, a negative electrode, a separator formed between the positive electrode and the negative electrode and made of a microporous film mainly composed of a thermoplastic resin, and provided between the positive electrode and the negative electrode. A non-aqueous electrolyte secondary battery comprising a filler layer mainly containing an inorganic filler,
The non-aqueous electrolyte is composed of an electrolyte and a liquid composition;
At least one of the electrolytes is a lithium salt;
The liquid composition comprises at least one fluorine-containing solvent (A) selected from the group consisting of a fluorine-containing ether compound, a fluorine-containing chain carboxylic acid ester compound and a fluorine-containing chain carbonate compound, and a cyclic carboxylic acid ester compound ( A non-aqueous electrolyte secondary battery including B).   The non-aqueous electrolyte secondary battery according to claim 1, wherein the negative electrode contains a non-carbon active material as a negative electrode active material.   The separator of Claim 1 or 2 provided with the separator with a filler layer in which the said filler layer was provided in the surface of any one or both of the said positive electrode side of the said separator, and the said negative electrode side between the said positive electrode and the said negative electrode. Non-aqueous electrolyte secondary battery.   The non-carbon-based active material is a single metal selected from the group consisting of Si, Sn, Al and Ti, or at least one of an alloy of Li and Li, and one or more of oxides and sulfides thereof. The non-aqueous electrolyte secondary battery according to claim 2 or 3.   The nonaqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein a mass of the fluorine-containing solvent (A) is 30 to 80 mass% with respect to a total mass of the nonaqueous electrolyte solution.   The liquid composition further includes at least one compound (C) selected from the group consisting of a saturated cyclic carbonate compound, a chain carbonate compound having no fluorine atom, a saturated cyclic sulfone compound, and a phosphate ester compound. The nonaqueous electrolyte secondary battery according to any one of 1 to 5.   The nonaqueous electrolyte secondary battery according to claim 6, wherein a ratio of the mass of the chain carbonate compound having no fluorine atom to the total mass of the nonaqueous electrolyte is 30% by mass or less.   The ratio of the total mass of the mass of the saturated cyclic carbonate compound having no fluorine atom and the mass of the chain carbonate compound having no fluorine atom with respect to the total mass of the nonaqueous electrolytic solution is 30% by mass or less. The nonaqueous electrolyte secondary battery according to 6 or 7. The non-aqueous electrolyte secondary battery according to claim 1, wherein the lithium salt includes LiPF ₆ .   The non-aqueous electrolyte secondary battery according to any one of claims 1 to 9, wherein the fluorine-containing solvent (A) contains the fluorine-containing ether compound. The nonaqueous electrolyte secondary battery according to claim 10, wherein the fluorine-containing ether compound is at least one selected from the group consisting of compounds represented by the following formula (1).

(In the formula, R ¹ and R ² are each independently an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, a fluorinated alkyl group having 1 to 10 carbon atoms, or 3 to 10 carbon atoms. A fluorinated cycloalkyl group, an alkyl group having 2 to 10 carbon atoms having one or more etheric oxygen atoms, or a fluorinated alkyl group having 2 to 10 carbon atoms having one or more etheric oxygen atoms. , One or both of R ¹ and R ² is a fluorinated alkyl group having 1 to 10 carbon atoms, a fluorinated cycloalkyl group having 3 to 10 carbon atoms, or 2 to 2 carbon atoms having one or more etheric oxygen atoms. 10 fluorinated alkyl groups.) The compound represented by the formula (1) is CF ₃ CH ₂ OCF ₂ CHF ₂ , CF ₃ CH ₂ OCF ₂ CHFCF ₃ , CHF ₂ CF ₂ CH ₂ OCF ₂ CHF ₂ , CH ₃ CH ₂ CH ₂ OCF ₂ CHF The nonaqueous electrolyte secondary battery according to claim 11, which is at least one selected from the group consisting of ₂ , CH ₃ CH ₂ OCF ₂ CHF ₂ , and CHF ₂ CF ₂ CH ₂ OCF ₂ CHFCF ₃ . The non-aqueous electrolyte according to any one of claims 1 to 12, wherein the cyclic carboxylic acid ester compound (B) is one or more selected from the group consisting of compounds represented by the following formula (5). Secondary battery.

(However, R ^{7 to} R ¹² are each independently a hydrogen atom, a fluorine atom, a chlorine atom, an alkyl group having 1 to 2 carbon atoms, a fluorinated alkyl group having 1 to 2 carbon atoms, or a carbon having an etheric oxygen atom. (It is an alkyl group having a number of 2 to 3. q is an integer of 0 to 3.)   The non-aqueous electrolyte secondary battery according to any one of claims 1 to 13, wherein the content of the cyclic carboxylic acid ester compound (B) in the non-aqueous electrolyte is 4 to 50% by mass.   The nonaqueous electrolyte secondary battery according to any one of claims 1 to 14, wherein a content of the lithium salt in the nonaqueous electrolyte is 0.1 to 3.0 mol / L.