JPWO2015046173A1 - Lithium ion secondary battery - Google Patents

Abstract

Provided is a lithium ion secondary battery in which reactivity between a non-aqueous electrolyte and an electrode is small, a calorific value is reduced, and thermal runaway is unlikely to occur. An electrode (at least one of a positive electrode and a negative electrode) produced by using an electrode mixture comprising an active material, a medium, a resin (A) soluble in the medium, and a resin (B) dispersed or emulsified in the medium; A non-aqueous electrolyte containing an electrolyte and a liquid composition, wherein the electrolyte is a lithium salt, and the liquid composition comprises a fluorine-containing ether compound, a fluorine-containing chain carboxylic acid ester compound, and a fluorine-containing chain carbonate A lithium ion secondary battery comprising at least one fluorine-containing solvent (α) selected from the group consisting of compounds and a cyclic carboxylic acid ester compound.

Description

  The present invention relates to a highly safe lithium ion secondary battery.

  2. Description of the Related Art Lithium ion secondary batteries having 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. As a solvent for a non-aqueous electrolyte solution of a lithium ion secondary battery, a carbonate-based solvent (ethylene carbonate, dimethyl carbonate) is used because it can exhibit high ionic conductivity by dissolving lithium salt well and has a wide potential window. Etc.) are widely used. However, since the carbonate-based solvent is flammable, there is a risk of ignition due to heat generation of the battery.

Then, the lithium ion secondary battery which has the non-aqueous electrolyte using a fluorine-containing solvent as a lithium ion secondary battery excellent in the flame retardance is proposed.
For example, a non-aqueous electrolyte containing a fluorinated solvent, a non-fluorinated cyclic carbonate, a non-fluorinated cyclic ester, and a lithium salt as a flame retardant and having good battery characteristics (cycle characteristics, discharge capacity), and an electrode There is known a lithium ion secondary battery having the following (Patent Document 1). The positive electrode of the lithium ion secondary battery includes an electrode containing LiCoO _{2 as} a positive electrode active material, carbon black as a conductivity-imparting agent, polyvinylidene fluoride as a binder, and N-methyl-2-pyrrolidone as a medium. A positive electrode or the like produced using a mixture is used. Moreover, the negative electrode etc. which were produced using the electrode mixture containing artificial graphite powder which is a negative electrode active material, the styrene-butadiene rubber which is a binder, and distilled water which is a medium are used for the negative electrode.

  By the way, in general, the battery temperature of a secondary battery rises due to Joule heat during use or external heating, but if the battery temperature reaches a high temperature exceeding 150 ° C., a thermal runaway occurs and the battery is damaged. Sometimes. As a cause of thermal runaway, heat generation due to a reaction between a component in the electrolytic solution and an electrode and decomposition of the component in the electrolytic solution is known. Therefore, in a lithium ion secondary battery, it is important to reduce the calorific value by reducing the reactivity between the non-aqueous electrolyte and the electrode.

JP 2008-192504 A

  When the present inventors examined about a lithium ion secondary battery like patent document 1, when the application to the vehicle-mounted power supply etc. of an electric vehicle which requires a bigger energy is considered, reaction of a non-aqueous electrolyte and an electrode The amount of heat generated by the heat was still insufficient.

  The present invention provides a lithium ion secondary battery that has low reactivity between a non-aqueous electrolyte and an electrode, reduces the amount of heat generated by the reaction, hardly causes thermal runaway, and has high safety.

（但し、式中、Ｒ^７〜Ｒ^１２はそれぞれ独立に水素原子、フッ素原子、塩素原子、炭素数１〜２のアルキル基、炭素数１〜２のフッ素化アルキル基、又は１個以上のエーテル性酸素原子を有する炭素数２〜３のアルキル基である。ｎは１〜３の整数である。）
[２０]前記リチウム塩がＬｉＰＦ_６を含む、前記[１]〜[１９]のいずれか一項に記載のリチウムイオン二次電池。
[２１]前記非水電解液中の前記リチウム塩の含有量が０．１〜３．０ｍｏｌ／Ｌであり、前記非水電解液の総質量に対する前記環状カルボン酸エステル化合物の質量の割合が４〜７０質量％である、前記[１]〜[２０]のいずれか一項に記載のリチウムイオン二次電池。The present invention is for achieving the above-mentioned problems, and the gist thereof is as follows.
[1] At least one of a positive electrode and a negative electrode was prepared using an electrode mixture containing an active material, a medium, a resin (A) soluble in the medium, and a resin (B) dispersed or emulsified in the medium. Electrodes,
The non-aqueous electrolyte includes an electrolyte and a liquid composition,
The electrolyte is a lithium salt;
The liquid composition comprises at least one fluorine-containing solvent (α) 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 cyclic carboxylic acid ester compound, A lithium ion secondary battery comprising:
[2] A lithium ion secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte,
At least one of the positive electrode and the negative electrode contains an active material, a resin (AI) that is soluble in an aqueous medium, and a resin (BI) that is dispersed or emulsified in an aqueous medium,
The non-aqueous electrolyte includes an electrolyte and a liquid composition,
The electrolyte is a lithium salt;
The liquid composition comprises at least one fluorine-containing solvent (α) 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 cyclic carboxylic acid ester compound, Lithium ion secondary battery.
[3] The resin (AI) soluble in the aqueous medium is a resin having a solubility in water of 0.5% by mass or more, and the resin (BI) dispersed or emulsified in the aqueous medium is water. The lithium ion secondary battery according to the above [1] or [2], which is a resin having a solubility of less than 0.5% by mass.
[4] Any one of [1] to [3], wherein the negative electrode includes an active material, a resin (AI) soluble in an aqueous medium, and a resin (BI) dispersed or emulsified in an aqueous medium. The lithium ion secondary battery according to one item.
[5] Any of the above [1] to [3], wherein the positive electrode contains an active material, a resin (AI) soluble in an aqueous medium, and a resin (BI) dispersed or emulsified in an aqueous medium The lithium ion secondary battery according to one item.
[6] A lithium ion secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte,
At least one of the positive electrode and the negative electrode includes an active material, a resin (A-II) soluble in an organic solvent, and a resin (B-II) dispersed or emulsified in an organic solvent,
The non-aqueous electrolyte includes an electrolyte and a liquid composition,
The electrolyte is a lithium salt;
The liquid composition comprises at least one fluorine-containing solvent (α) 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 cyclic carboxylic acid ester compound, Lithium ion secondary battery.
[7] The resin (A-II) soluble in the organic solvent is a resin having a solubility in N-methyl-2-pyrrolidone of 0.5% by mass or more, and is a resin (B that is dispersed or emulsified in the aqueous medium) The lithium ion secondary battery according to [1] or [6], wherein -II) is a resin having a solubility in N-methyl-2-pyrrolidone of less than 0.5% by mass.
[8] The lithium ion secondary battery according to [1], wherein the medium is an aqueous medium.
[9] The above [1] to [5], wherein the resin (AI) is a resin containing at least one selected from the group consisting of Li ⁺ , Na ⁺ , Ca ²⁺ , Mg ²⁺ and NH ₄ ⁺ . Or the lithium ion secondary battery as described in any one of [8].
[10] The lithium ion according to any one of [1] to [5], [8], or [9], wherein the resin (AI) is carboxymethyl cellulose, polyacrylic acid, or a salt thereof. Secondary battery.
[11] The lithium ion secondary battery according to any one of [1] to [10], wherein the resin (B) is a soft polymer.
[12] The lithium ion secondary battery according to any one of [1] to [11], wherein the resin (B) has an average particle size of 10 to 1000 nm.
[13] The lithium ion according to any one of [1] to [12], wherein the positive electrode is a positive electrode that can occlude and release lithium ions and uses a positive electrode active material containing a transition metal as the active material. Secondary battery.
[14] The lithium ion according to any one of [1] to [13], wherein the negative electrode is a negative electrode having a negative electrode active material containing a carbon-based material capable of occluding and releasing lithium ions as the active material. Secondary battery.
[15] N _A / N _Li which is a ratio of the total number of moles (N _A ) of the cyclic carboxylic acid ester compound to the total number of moles (N _Li ) of lithium atoms derived from the lithium salt is 1 to 10, [1 to is the lithium ion secondary battery according to any one of [14].
[16] The lithium ion secondary battery according to any one of [1] to [15], wherein the fluorine-containing solvent (α) includes a fluorine-containing ether compound.
[17] The lithium ion secondary battery according to [16], wherein the fluorine-containing ether compound is at least one selected from the group consisting of compounds represented by the following formula (1).
R ¹ —O—R ² (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.)
[18] The compound represented by the formula (1) is CF ₃ CH ₂ OCF ₂ CHF ₂ , CHF ₂ CF ₂ CH ₂ OCF ₂ CHF ₂ , CF ₃ CF ₂ CH ₂ OCF ₂ CHF ₂ , or CF ₃ CH _2. OCF ₂ CHFCF _3, and _CHF 2 _CF containing at least one selected from the group consisting of 2 _CH 2 _OCF 2 CHFCF _3, lithium ion secondary battery according to [17].
[19] The lithium according to any one of [1] to [18], wherein the cyclic carboxylic acid ester compound is at least one selected from the group consisting of compounds represented by the following formula (5): Ion secondary battery.

(In the formula, 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 ethers. An alkyl group having 2 to 3 carbon atoms having a reactive oxygen atom, n is an integer of 1 to 3)
[20] The lithium salt includes LiPF _6, wherein [1] The lithium ion secondary battery according to any one of - [19].
[21] The content of the lithium salt in the non-aqueous electrolyte is 0.1 to 3.0 mol / L, and the ratio of the mass of the cyclic carboxylic acid ester compound to the total mass of the non-aqueous electrolyte is 4 Lithium ion secondary battery as described in any one of said [1]-[20] which is -70 mass%.

  The lithium ion secondary battery of the present invention has a low reactivity between the non-aqueous electrolyte and the electrode, the amount of heat generated by the reaction is reduced, and thermal runaway is unlikely to occur.

Graph showing the relationship between the _N A _{/ N Li} and total amount of heat generation in Example 12 and Example 13. Graph showing the relationship between the concentration of LiPF ₆ and the total amount of heat generation in Example 14 and Example 15. The graph which showed the relationship between the AE3000 ratio and the total calorific value in Example 16 and Example 17. Graph showing the relationship between the _N A _{/ N Li} and total amount of heat generation in Example 18 and Example 19. Graph showing the relationship between the concentration of LiPF ₆ and the total amount of heat generated at Example 20 and Example 21. The graph which showed the relationship between the AE3000 ratio and the total calorific value in Example 22 and Example 23.

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.
“Soft polymer” means a polymer having a glass transition temperature of 30 ° C. or less as measured by differential scanning calorimetry. The glass transition temperature of the soft polymer is preferably 15 ° C. or less, and particularly preferably 5 ° C. or less.
“Fluorine-containing soft polymer” means a soft polymer having a fluorine atom in the molecule.
“Weight average molecular weight” means a value determined in terms of polystyrene by gel permeation chromatography (GPC).
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.
Other compounds (other solvents, additives, etc.) other than lithium salt, fluorine-containing solvent (α), cyclic carboxylic acid ester compound and compound (β) are defined as “other components”, and lithium salt and liquid composition Differentiated from things.
The “fluorinated ether compound” means a chain or cyclic compound having an ether bond and having a fluorine atom.
“Fluorine-containing chain carboxylic acid ester compound” means a chain compound having an ester bond in a chain structure, no ring structure containing 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 containing 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.
The “saturated cyclic carbonate compound” is a ring skeleton composed of a carbon atom and an oxygen atom, having a carbonate bond represented by —O—C (═O) —O— as a part of the ring skeleton, It means a cyclic compound having no carbon unsaturated bond.
The “saturated chain carbonate compound having no fluorine atom” has a carbonate bond represented by —O—C (═O) —O— in the chain structure and has a ring structure including the carbonate bond. It means a chain compound having no fluorine atom and no carbon-carbon unsaturated bond.
“Fluorinated” and “fluorinated” mean that some or all of the hydrogen atoms bonded to the carbon atom are replaced by 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.
“Carbon-carbon unsaturated bond” means a carbon-carbon double bond or a carbon-carbon triple bond.

  The lithium ion secondary battery of the present invention includes a positive electrode, a negative electrode, and a non-aqueous electrolyte.

≪Electrode≫
In the lithium ion secondary battery of the present invention, at least one of the positive electrode and the negative electrode comprises an active material, a medium, a resin (A) soluble in the medium, and a resin (B) dispersed or emulsified in the medium. It is an electrode produced by using an agent. That is, at least one of the positive electrode and the negative electrode of the lithium ion secondary battery of the present invention is an electrode using the resin (A) and the resin (B) as a binder. By combining the electrode with a specific non-aqueous electrolyte described later, the reactivity between the electrode and the non-aqueous electrolyte is reduced, the amount of heat generated by the reaction is reduced, and thermal runaway is less likely to occur.

  In the present invention, either the positive electrode or the negative electrode may be an electrode produced using the electrode mixture, or both the positive electrode and the negative electrode may be electrodes produced using the electrode mixture. Good. Among them, since the amount of heat generated by the reaction between the electrode and the non-aqueous electrolyte is further reduced and thermal runaway is less likely to occur, both the positive electrode and the negative electrode are electrodes prepared using the electrode mixture. preferable.

<Positive electrode>
When the positive electrode of the lithium ion secondary battery of the present invention is an electrode produced using the electrode mixture, the positive electrode is classified into the following positive electrode (I) or positive electrode (II) depending on the type of medium used. .
(I) A positive electrode produced using an aqueous medium.
(II) A positive electrode produced using an organic solvent.

[Positive electrode (I)]
The positive electrode (I) uses an electrode mixture comprising a positive electrode active material, an aqueous medium, a resin (AI) soluble in the aqueous medium, and a resin (BI) dispersed or emulsified in the aqueous medium. It is the produced positive electrode.
The positive electrode (I) includes a positive electrode active material, a resin (AI), and a resin (BI). Examples of the positive electrode (I) include a positive electrode in which a positive electrode layer containing a positive electrode active material, a conductivity-imparting agent, a resin (AI), and a resin (BI) is formed on a current collector.

(Aqueous medium)
The aqueous medium is water alone or a mixture of water and a water-soluble organic solvent. As the water-soluble organic solvent, known compounds that can be mixed with water at an arbitrary ratio can be appropriately used.
Examples of the water-soluble organic solvent include ketones such as acetone and methyl ethyl ketone; amines such as triethylamine and aniline; amides such as N-methyl-2-pyrrolidone and dimethylformamide; methanol, ethanol, propanol, isopropanol, n- Examples include alcohols such as butanol and t-butanol. Among these, as the water-soluble organic solvent, alcohols and amides are preferable, alcohols are more preferable, methanol, isopropanol, and t-butanol are further preferable, and t-butanol is particularly preferable. A water-soluble organic solvent may be used individually by 1 type, and may use 2 or more types together.

The content of the water-soluble organic solvent in the aqueous medium is preferably small.
Specifically, the content of the water-soluble organic solvent in the aqueous medium is preferably 5 parts by mass or less, more preferably 1 part by mass or less, and further preferably 0.5 parts by mass or less with respect to 100 parts by mass of water. Preferably, 0.1 mass part or less is especially preferable. If the content of the water-soluble organic solvent is not more than the upper limit value, the environmental burden at the time of preparing the electrode mixture or drying the electrode is likely to be reduced.

(Resin (A))
Examples of the resin (AI) soluble in an aqueous medium used for the positive electrode (I) include resins having a solubility in water of 0.5% by mass or more. In addition, "the solubility with respect to water is 0.5 mass% or more" means that it dissolves at a concentration of 0.5 mass% or more with respect to water at 25 ° C.
The solubility of the resin (A) in water is preferably 1% by mass or more, more preferably 1.5% by mass or more, and further preferably 2% by mass or more.

  Examples of the resin (AI) in the positive electrode (I) include anionic water-soluble polymers such as carboxymethyl cellulose (hereinafter referred to as “CMC”), polyacrylic acid, polyvinyl alcohol, and polymethacrylic acid. Among these, CMC or polyacrylic acid is preferable as the resin (A) in the positive electrode (I) from the viewpoint of the stability of the electrode mixture.

The resin (AI) in the positive electrode (I) preferably forms a salt with at least one selected from the group consisting of Li ⁺ , Na ⁺ , Ca ²⁺ , Mg ²⁺ and NH ₄ ⁺ , and Na ⁺ and Li It is more preferable to form a salt with at least one selected from the group consisting of ⁺ . That is, the resin (AI) in the positive electrode (I) is preferably at least one selected from the group consisting of lithium salt, sodium salt, calcium salt, magnesium salt and ammonium salt of the anionic water-soluble polymer. More preferred is at least one selected from the group consisting of sodium salts and lithium salts of the anionic water-soluble polymers. Thereby, it becomes easy to suppress the capacity | capacitance reduction by cation exchange with electrolyte solution.

The weight average molecular weight of the resin (AI) in the positive electrode (I) is preferably 1,000 to 1,000,000, more preferably 10,000 to 500,000, and still more preferably 50,000 to 200,000. . When the weight average molecular weight of the resin (A) is at least the lower limit value, the stability of the electrode mixture is enhanced and it is easy to use for a long period of time. If the weight average molecular weight of the resin (A) is not more than the upper limit value, the stability of the electrode mixture is easily obtained, and therefore an electrode mixture without aggregates is easily obtained.
The weight average molecular weight of the resin (AI) can be adjusted by a known method such as addition of a chain transfer agent during polymerization, control of a polymerization temperature, or a polymerization pressure.
The resin (AI) in the positive electrode (I) may be one type or two or more types.

The method for producing the anionic water-soluble polymer is not particularly limited, and a known polymerization method can be employed.
For example, CMC is obtained by a method of reacting cellulose with a base such as sodium hydroxide and then etherifying by reacting monochloroacetic acid or the like. Polyacrylic acid can be obtained by a known radical polymerization method or the like.

(Resin (B))
Examples of the resin (BI) used for the positive electrode (I) that is dispersed or emulsified in an aqueous medium include resins having a solubility in water of less than 0.5% by mass. Note that “the solubility in water is less than 0.5% by mass” means that it cannot be dissolved in water at 25 ° C. at a concentration of 0.5% by mass or more.
The solubility of the resin (BI) in water is preferably less than 0.3% by mass, more preferably less than 0.2% by mass, and still more preferably less than 0.1% by mass.
Further, the difference between the solubility of the resin (AI) in water and the solubility of the resin (BI) in water is preferably 1% by mass or more, more preferably 1.5% by mass or more, and 2% by mass or more. Is more preferable.

  As the resin (BI) used for the positive electrode (I), a soft polymer is preferable because the active material is less likely to drop off from the current collector and variation in battery characteristics is reduced. The soft polymer may have a cross-linked structure or may have a functional group introduced by modification.

Examples of the resin (BI) that is a soft polymer include the following resins (B1-I) to (B5-I).
(B1-I): A homopolymer of the monomer (b1).
(B2-I): A copolymer of the monomer (b1) and the monomer (b2) copolymerizable with the monomer (b1).
(B3-I): a fluorine-containing soft polymer.
(B4-I): A homopolymer of any of monomers (b41) to (b46).
(B5-I): a copolymer using two or more selected from the group consisting of monomers (b41) to (b46).

Hereinafter, the resins (B1-I) to (B5-I) will be described in order.
Resin (B1-I):
The monomer (b1) is a diene compound having no fluorine atom.
Examples of the monomer (b1) include 1,3-butadiene, 1,3-pentadiene, 2,3-pentadiene, isoprene, 1,3-hexadiene, 2,3-dimethyl-1,3-butadiene, 2 -Ethyl-1,3-butadiene, 1,3-heptadiene and the like.

Specific examples of the resin (B1-I) include polybutadiene and polyisoprene.
The resin (B1-I) used for the positive electrode (I) may be one type or two or more types.

Resin (B2-I):
The monomer (b2) is a monomer having no fluorine atom and copolymerizable with the monomer (b1).
Examples of the monomer (b2) include α-olefins such as ethylene, 1-butene, and isobutene; vinyl ether compounds such as ethyl vinyl ether, butyl vinyl ether, hydroxybutyl vinyl ether, and cyclohexyl vinyl ether; vinyl acetate, vinyl benzoate, and crotonic acid. Vinyl ester compounds such as vinyl; aromatic vinyl compounds such as styrene, α-methylstyrene, 2,4-dimethylstyrene, ethylstyrene, and vinylnaphthalene; cyano group-containing vinyl compounds such as acrylonitrile and methacrylonitrile.
The number of repeating units based on the monomer (b2) in the resin (B2-I) may be one, or two or more.

As resin (B2-I), the following resin (B21-I) is preferable.
(B21-I) A copolymer having a repeating unit based on butadiene and a repeating unit based on styrene.

  The resin (B21-I) has a repeating unit based on a monomer (b2) other than styrene, in addition to the repeating unit based on styrene and the repeating unit based on butadiene, as long as the effects of the present invention are not impaired. You may do it.

  Specific examples of the resin (B21-I) include, for example, a butadiene / styrene copolymer (meaning a copolymer composed of a butadiene-based repeating unit and a styrene-based repeating unit; the same applies hereinafter), acrylonitrile / butadiene. / Styrene copolymer and the like. Examples of the butadiene / styrene copolymer include a butadiene / styrene random copolymer, a butadiene / styrene block copolymer, and a styrene / butadiene / styrene block copolymer.

The total ratio of the repeating unit based on styrene and the repeating unit based on butadiene is preferably 75 mol% or more, and more preferably 90 mol% or more with respect to all the repeating units of the resin (B21-I). When the total ratio is equal to or higher than the lower limit, the flexibility of the resin is increased, and good binding properties are easily obtained.
The upper limit of the total ratio of the repeating unit based on styrene and the repeating unit based on butadiene is 100 mol%.

  The ratio (molar ratio) of the repeating unit based on styrene / the repeating unit based on butadiene in the resin (B21-I) is preferably 0.3 / 0.45 to 0.45 / 0.3, and 0.35 / 0. .45 to 0.45 / 0.35 is more preferable, and 0.4 / 0.5 to 0.5 / 0.4 is still more preferable. When the ratio is within the above range, the flexibility of the resin is increased, and good binding properties are easily obtained.

The weight average molecular weight of the resin (B21-I) is preferably 10,000 to 1,000,000, more preferably 50,000 to 500,000, and still more preferably 100,000 to 200,000. When the weight average molecular weight of the resin (B1-I) is equal to or higher than the lower limit, the binding force is increased and the sliding of the active material is easily suppressed. When the weight average molecular weight of the resin (B1-I) is not more than the upper limit value, it is easy to uniformly disperse in the electrode mixture and it is easy to reduce the resistance.
The weight average molecular weight of the resin (B21-I) can be adjusted by known methods such as addition of a chain transfer agent during polymerization, control of the polymerization temperature, and polymerization pressure.

Examples of the resin (B2-I) other than the resin (B21-I) include, for example, isoprene / styrene random copolymer, acrylonitrile / butadiene copolymer, isoprene / styrene block copolymer, and styrene / isoprene / styrene block copolymer. Examples include coalescence.
The resin (B2-I) used for the positive electrode (I) may be one type or two or more types.

Resin (B3-I):
Examples of the fluorine-containing soft polymer include fluorine-containing rubbers such as vinylidene fluoride rubber and tetrafluoroethylene-propylene rubber.
As the resin (B3-I), the following resin (B31-I) is preferable.
(B31-I) At least one selected from the group consisting of tetrafluoroethylene (hereinafter also referred to as TFE), hexafluoropropylene (hereinafter also referred to as HFP), and vinylidene fluoride (hereinafter also referred to as VdF). A fluorine-containing rubber comprising a copolymer having a repeating unit based on the monomer (b31) and having a fluorine content of 50 to 76% by mass.
In addition, fluorine content shows the ratio of the total mass of a fluorine atom with respect to the total mass of all the atoms which comprise resin.

  The resin (B31-I) is a copolymer composed of two or more types of repeating units, of which at least one type of repeating unit is a repeating unit based on the monomer (b31). The resin (B31) may be a copolymer composed of repeating units based on two or three types of monomers (b31), and may be a repeating unit based on one or more types of monomers (b31); The copolymer which consists of a repeating unit based on 1 or more types of the monomer (b31) copolymerizable with a monomer (b31) may be sufficient.

As the monomer (b32), propylene (hereinafter also referred to as P), ethylene (hereinafter also referred to as E), or perfluoro (alkyl vinyl ether) (hereinafter also referred to as PAVE) is preferable.
Examples of PAVE include perfluoro (methyl vinyl ether) and perfluoro (propyl vinyl ether).
When the resin (B31-I) has a repeating unit based on the monomer (b32), the repeating unit may be one type or two or more types.

  50-74 mass% is preferable and, as for fluorine content of resin (B31-I), 53-70 mass% is more preferable. When the fluorine content is less than 50% by mass, the alkali resistance and voltage resistance tend to be insufficient.

  Specific examples of the resin (B31-I) include, for example, a TFE / P copolymer, a TFE / P / VdF copolymer, a VdF / HFP copolymer, a VdF / TFE copolymer, and a TFE / VdF / HFP copolymer. Polymer, TFE / PAVE copolymer, E / PAVE copolymer, E / P / PAVE copolymer, E / HFP copolymer, TFE / P / E copolymer, TFE / P / PAVE copolymer , TFE / P / VdF / PAVE copolymer, VdF / PAVE copolymer, VdF / TFE / PAVE copolymer, VdF / TFE / HFP / PAVE copolymer, and the like.

  Among them, as the resin (B31-I), TFE / P copolymer, TFE / P / VdF copolymer, VdF / HFP copolymer, VdF / TFE copolymer, TFE / VdF / HFP copolymer are used. , TFE / PAVE copolymer, TFE / P / PAVE copolymer, or TFE / P / VdF / PAVE copolymer are preferable, and TFE / P copolymer or TFE / P / VdF copolymer is particularly preferable. .

  Hereinafter, a more preferable copolymer composition of the resin (B31-I) will be described. When the copolymer composition of the resin (B31-I) is in the following range, the adhesiveness to the current collector is excellent, and excellent alkali resistance and voltage resistance are easily obtained.

  In the TFE / P copolymer, the ratio (molar ratio) of the repeating unit based on TFE / the repeating unit based on P is 30 to 80/70 to 20 (however, the repeating unit based on TFE and the repeating unit based on P are 100 mol% in total. The same shall apply hereinafter.), Preferably 40 to 70/60 to 30, more preferably 60 to 50/40 to 50.

  In the TFE / P / VdF copolymer, the ratio of the repeating unit based on TFE / the repeating unit based on P / the repeating unit based on VdF (molar ratio) is preferably 30 to 80/15 to 70 / 0.01 to 50. 30-70 / 20-60 / 1-40 are more preferable.

  The ratio (molar ratio) of repeating units based on VdF / repeating units based on HFP in the VdF / HFP copolymer is preferably 45 to 90/55 to 10, more preferably 50 to 80/50 to 20.

  The ratio (molar ratio) of the repeating unit based on VdF / the repeating unit based on HFP in the VdF / TFE copolymer is preferably 50 to 90 / 50-10.

  The ratio (molar ratio) of repeating units based on TFE / repeating units based on VdF / repeating units based on HFP in the TFE / VdF / HFP copolymer is preferably 2 to 50/30 to 90/1 to 35.

  The ratio (molar ratio) of repeating units based on TFE / repeating units based on PAVE in the TFE / PAVE copolymer is preferably 50 to 90/50 to 10, more preferably 50 to 80/50 to 20.

  In the TFE / P / PAVE copolymer, the ratio (molar ratio) of the repeating unit based on TFE / the repeating unit based on P / the repeating unit based on PAVE is preferably 25-80 / 15-70 / 0.1-40. 39-70 / 20-60 / 1-30 are more preferable.

The weight average molecular weight of the resin (B3-I) is preferably 10,000 to 300,000, more preferably 20,000 to 250,000, still more preferably 20,000 to 200,000, and 30,000 to 190, 000 is particularly preferred. When the weight average molecular weight of the resin (B3) is at least the lower limit value, a lithium secondary battery having good charge / discharge characteristics is easily obtained. If the weight average molecular weight of the resin (B3-I) is not more than the upper limit value, good adhesion (binding property) can be easily obtained.
The weight average molecular weight of the resin (B3-I) can be adjusted by a known method such as addition of a chain transfer agent during polymerization, control of the polymerization temperature and polymerization pressure.
The resin (B3-I) used for the positive electrode (I) may be one type or two or more types.

Resin (B4-I):
The resin (B4-I) is a homopolymer of any of the following monomers (b41) to (b46).
(B41) Ethylenically unsaturated carboxylic acid ester.
(B42) An aromatic vinyl compound.
(B43) A cyano group-containing vinyl compound.
(B44) Vinyl ester compound.
(B45) Vinyl ether compound.
(B46) Amide group-containing vinyl compound.

Examples of the monomer (b41) include ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, ethoxyethyl acrylate, methyl methacrylate, butyl methacrylate, and 2-ethylhexyl methacrylate. N-decyl methacrylate, 2-hydroxyethyl methacrylate, isoamyl crotonic acid, n-hexyl crotonic acid, dimethylaminoethyl methacrylate, monomethyl maleate and the like.
Examples of the monomer (b42) include styrene, α-methylstyrene, 2,4-dimethylstyrene, ethylstyrene, vinylnaphthalene and the like.
Examples of the monomer (b43) include acrylonitrile and methacrylonitrile.
Examples of the monomer (b44) include vinyl acetate and vinyl propionate.
Examples of the monomer (b45) include ethyl vinyl ether, cetyl vinyl ether, hydroxybutyl vinyl ether, and the like.
Examples of the monomer (b46) include acrylamide and N-methylacrylamide.

Specific examples of the resin (B4-I) include, for example, polybutyl acrylate, polybutyl methacrylate, polyhydroxyethyl methacrylate, polyacrylamide, polyacrylonitrile and the like.
The resin (B4-I) used for the positive electrode (I) may be one type or two or more types.

Resin (B5-I):
The resin (B5-I) is a copolymer using two or more selected from the group consisting of the monomers (b41) to (b46). The resin (B5-I) is preferably the following resin (B51-I) from the viewpoint that it is difficult to dissolve in a medium or an electrolytic solution at the time of manufacturing an electrode because a crosslinked structure is imparted to the resin (B5-I).
(B51-I) A copolymer obtained by copolymerization by adding a small amount of a crosslinkable monomer to two or more selected from the group consisting of monomers (b41) to (b46).

Examples of the crosslinkable monomer include divinyl compounds such as divinylbenzene; polyfunctional dimethacrylates such as diethylene glycol dimethacrylate and ethylene glycol dimethacrylate; polyfunctional trimethacrylic acids such as trimethylolpropane trimethacrylate. Ester; Polyfunctional diacrylate such as polyethylene glycol diacrylate and 1,3-butylene glycol diacrylate; Multifunctional triacrylate such as trimethylolpropane triacrylate and the like.
0.1-20 mass% is preferable and, as for the ratio of the repeating unit based on the said crosslinkable monomer with respect to all the repeating units in resin (B51), 0.5-15 mass% is more preferable.

In the positive electrode (I), only one of the resins (B1-I) to (B5-I) may be used, and two or more selected from the group consisting of the resins (B1-I) to (B5-I) May be used in combination.
The resin (BI) used for the positive electrode (I) is preferably at least one selected from the group consisting of the resins B3-I) to (B5-I). Further, the resin (BI) used for the positive electrode (I) may be a resin other than the resins (B1-I) to (B5-I) described above.
Examples of the resin (BI) other than the resins (B1-I) to (B5-I) include polytetrafluoroethylene (hereinafter referred to as “PTFE”).

10-1000 nm is preferable and, as for the average particle diameter of resin (BI), 15-700 nm is more preferable. If the average particle diameter of the resin (BI) is equal to or greater than the lower limit value, it is easy to suppress covering the active material surface excessively densely, and thus it is easy to reduce the internal resistance. If the average particle size of the resin (BI) is not more than the upper limit value, good adhesion (binding property) can be easily obtained.
The average particle diameter of the resin (BI) can be adjusted by a known method such as the type of emulsifier and the amount used.
The average particle diameter of the resin (BI) can be measured by a dynamic light scattering method using a laser zeta electrometer ELS-8000 manufactured by Otsuka Electronics Co., Ltd.

  For the production of the resin (BI) used for the positive electrode (I), a known polymerization method can be employed, and among these, a radical copolymerization method is preferable. The radical polymerization method is not particularly limited, and a method of starting a radical polymerization reaction by light, heat, ionizing radiation or the like using an organic or inorganic radical polymerization initiator is preferable. As the polymerization form, known polymerization forms such as bulk polymerization, suspension polymerization, emulsion polymerization, and solution polymerization can be adopted, and emulsion polymerization is particularly preferable.

The dispersion of the resin (BI) obtained by emulsion polymerization, suspension polymerization or the like is preferably adjusted to pH 5 to 13, and preferably adjusted to pH 6 to 12. This makes it easy to obtain excellent binding between the current collector and the positive electrode layer.
Examples of pH adjusters include aqueous solutions of ammonia, alkali metals (lithium, sodium, potassium, rubidium, cesium, etc.) hydroxide, inorganic ammonium compounds (ammonium chloride, etc.), organic amine compounds (ethanolamine, diethylamine, etc.), etc. Etc. Of these, an aqueous solution of ammonia or an alkali metal hydroxide is preferable.

(Positive electrode active material)
The positive electrode active material may be any material that can occlude and release lithium ions, and known positive electrode active materials for lithium ion secondary batteries can be employed.
Specific examples of the positive electrode active material include, for example, a lithium-containing transition metal oxide, a lithium-containing transition metal composite oxide using one or more transition metals, a transition metal oxide, a transition metal sulfide, a metal oxide, and an olivine. Type metal lithium salt.
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 (LiMnO ₂ , LiMn ₂ O ₄ , Li ₂ MnO _{3 and the} like). Can be 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 the lithium-containing transition metal composite oxide include lithium ternary composite oxide (Li (Ni _a Co _b Mn _c ) O ₂ (where a, b, c ≧ 0, a + b + c = 1), etc.), 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.

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 adhering substances include oxides (aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, etc.), sulfates (lithium sulfate, sodium sulfate, potassium sulfate, Magnesium sulfate, 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.

From the viewpoint of charge / discharge characteristics, the positive electrode active material is preferably a positive electrode active material that can occlude and release lithium ions and contains a transition metal. In addition, since the discharge voltage is high and the electrochemical stability is high, as the positive electrode active material, a lithium-containing transition metal composite oxide (LiCoO ₂ , LiNiO ₂ , LiMnO _2, etc.) based on an α-NaCrO ₂ structure is used. ), Lithium-containing transition metal composite oxide (LiMn ₂ O ₄ or the like) having a spinel structure as a base is more preferable.

(Conductivity imparting agent)
The conductivity-imparting agent is not particularly limited, and carbon materials (acetylene black, ketjen black, carbon black, vapor-grown carbon fiber, carbon nanotube, etc.), metal substances (Al, etc.), conductive oxide powders, etc. Can be mentioned.

(Current collector)
The current collector is not particularly limited, and examples thereof include metal foils such as Al, Ni, and Cu, metal nets, and metal porous bodies. As the current collector for the positive electrode, an Al foil is preferable.

  The thickness of the current collector is preferably 1 to 100 μm. If the thickness of the current collector is 1 μm or more, a lithium ion secondary battery having sufficient durability and excellent reliability can be easily obtained. If the thickness of the current collector is 100 μm or less, the lithium ion secondary battery can be easily reduced in weight.

  1-100 micrometers is preferable, as for the thickness of a positive electrode layer, 5-100 micrometers is more preferable, and 10-100 micrometers is especially preferable. If the thickness of the positive electrode layer is not less than the lower limit, problems such as peeling and cracking of the positive electrode layer are unlikely to occur. If the thickness of the positive electrode layer is not more than the upper limit value, good battery characteristics can be easily obtained.

(Ratio of each component in positive electrode (I))
80-99.8 mass% is preferable, as for content of the positive electrode active material in a positive electrode layer (100 mass%), 90-99.8 mass% is more preferable, and 95-99.8 mass% is still more preferable. If the proportion of the positive electrode active material is equal to or higher than the lower limit value, good battery characteristics are easily obtained. When the proportion of the positive electrode active material is not more than the upper limit value, an electrode having a high capacity density is easily obtained.

  0.1-20 mass parts is preferable with respect to 100 mass parts of positive electrode active materials, and, as for content of resin (AI) in a positive electrode layer, 0.1-10 mass parts is more preferable, 0.5- 5 mass parts is still more preferable, and 0.5-3 mass parts is especially preferable. If the ratio of the resin (AI) is not less than the lower limit value, good binding properties are easily obtained. If the ratio of the resin (AI) is not more than the upper limit value, good battery characteristics can be easily obtained.

  The content of the resin (BI) in the positive electrode layer is preferably 0.1 to 20 parts by mass, more preferably 0.1 to 10 parts by mass, with respect to 100 parts by mass of the positive electrode active material. 5 mass parts is still more preferable, and 0.5-3 mass parts is especially preferable. When the ratio of the resin (BI) is at least the lower limit value, good binding properties are easily obtained. If the ratio of the resin (BI) is not more than the upper limit value, good battery characteristics can be easily obtained.

  The mass ratio (AI / BI) between the resin (AI) and the resin (BI) in the positive electrode layer is preferably 0.3 to 3, more preferably 0.5 to 2, and 7 to 1.4 are more preferable, and 0.8 to 1.2 are particularly preferable. When the mass ratio (AI / BI) is equal to or higher than the lower limit value, the binding property with the current collector is easily improved. If the mass ratio (A-I / B-I) is not more than the upper limit value, it is easy to improve the safety of the battery.

  When the positive electrode layer of the positive electrode (I) contains a conductivity-imparting agent, the proportion of the conductivity-imparting agent in the positive electrode layer is preferably 0.01 to 10% by mass, and more preferably 0.1 to 3% by mass. If the ratio of the conductivity-imparting agent is at least the lower limit value, it is easy to ensure good conductivity. When the ratio of the conductivity-imparting agent is not more than the upper limit value, an electrode having a high capacity density is easily obtained.

(Method for producing positive electrode (I))
The manufacturing method of positive electrode (I) employs a well-known method except for using a positive electrode active material, an aqueous medium, and an electrode mixture containing resin (AI) and resin (BI) as a binder. it can. For example, there is a method in which the electrode mixture is applied to at least one surface, preferably both surfaces of the current collector, the aqueous medium in the electrode mixture is removed by drying, and the positive electrode layer is formed. If necessary, the positive electrode layer after drying may be pressed to have a desired thickness.

Examples of the method of applying the electrode mixture to the current collector include a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, and a brush coating method.
Examples of the drying method include drying with warm air, hot air, low-humidity air, and vacuum drying.

  20-70 mass% is preferable, as for content of the aqueous medium in the electrode mixture (100 mass%) used for manufacture of positive electrode (I), 25-65 mass% is more preferable, and 30-60 mass% is still more preferable. 35-55 mass% is especially preferable. If content of an aqueous medium is more than a lower limit, it will be easy to improve the dispersibility of an electrode mixture. If content of an aqueous medium is below an upper limit, it will be easy to obtain the electrode mixture excellent in coatability.

  25-75 mass% is preferable, as for content of the positive electrode active material in the electrode mixture (100 mass%) used for positive electrode (I), 30-70 mass% is more preferable, and 35-65 mass% is still more preferable.

  The content of the resin (AI) in the electrode mixture (100% by mass) used for the positive electrode (I) is preferably 0.2 to 3% by mass, more preferably 0.5 to 2.5% by mass, 0.7-2 mass% is still more preferable, and 1-2 mass% is especially preferable.

  The content of the resin (BI) in the electrode mixture (100% by mass) used for the production of the positive electrode (I) is preferably 0.2 to 3% by mass, more preferably 0.5 to 2.5% by mass. Preferably, 0.7-2 mass% is further more preferable, and 1-2 mass% is especially preferable.

  When the electrode mixture used for production of the positive electrode (I) includes a conductivity-imparting agent, the content of the conductivity-imparting agent in the electrode mixture (100 mass%) is preferably 0.01 to 10 mass%, and 0.1 -3 mass% is more preferable.

[Positive electrode (II)]
The positive electrode (II) uses an electrode mixture composed of a positive electrode active material, an organic solvent, a resin (A-II) soluble in the organic solvent, and a resin (B-II) dispersed or emulsified in the organic solvent. It is the produced electrode.
The positive electrode (II) includes a positive electrode active material, a resin (A-II), and a resin (B-II). Examples of the positive electrode (II) include an electrode in which a positive electrode layer containing a positive electrode active material, a conductivity imparting agent, a resin (A-II), and a resin (B-II) is formed on a current collector.

(Organic solvent)
As an organic solvent, the well-known organic solvent used for preparation of an electrode can be used. Specific examples of the organic solvent include, for example, ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, hexane, octane, toluene, xylene, naphtha, acetonitrile, N-methyl-2-pyrrolidone, acetylpyridine, cyclopentanone. Dimethylformamide, dimethylsulfoxide, methylformamide, methanol, ethanol and the like. Among these, as the organic solvent, N-methyl-2-pyrrolidone or butyl acetate is preferable, and N-methyl-2-pyrrolidone is particularly preferable.
An organic solvent may be used individually by 1 type, and may use 2 or more types together.

  The electrode mixture used for the production of the positive electrode (II) is preferably an organic solvent having a low water content from the viewpoint of easily suppressing the viscosity from becoming too high. Specifically, the water content of the organic solvent is preferably less than 1,000 ppm by mass, and more preferably less than 100 ppm by mass.

(Resin (A-II))
Examples of the resin (A-II) soluble in an organic solvent used for the positive electrode (II) include resins having a solubility in N-methyl-2-pyrrolidone of 0.5% by mass or more. “The solubility in N-methyl-2-pyrrolidone is 0.5% by mass or more” means that the compound is dissolved in N-methyl-2-pyrrolidone at 25 ° C. at a concentration of 0.5% by mass or more. To do.
The solubility of the resin (A-II) in N-methyl-2-pyrrolidone is preferably 1% by mass or more, more preferably 5% by mass or more, and still more preferably 8% by mass or more.

  Examples of the resin (A-II) in the positive electrode (II) include polyvinylidene fluoride (hereinafter referred to as “PVDF”).

The weight average molecular weight of the resin (A-II) in the positive electrode (II) is preferably 1,000 to 1,000,000, more preferably 10,000 to 500,000, and still more preferably 50,000 to 300,000. . If the weight average molecular weight of the resin (A-II) is not less than the lower limit, it is easy to improve the adhesion of the electrode. When the weight average molecular weight of the resin (A-II) is not more than the upper limit value, a low resistance electrode is easily obtained.
The weight average molecular weight of the resin (A-II) can be adjusted by a known method such as addition of a chain transfer agent during polymerization, control of the polymerization temperature and polymerization pressure. The resin (A-II) in the positive electrode (II) may be one type or two or more types.

  For the production of the resin (A-II) used for the positive electrode (II), a known polymerization method can be adopted, and among these, a radical copolymerization method is preferable. The radical polymerization method is not particularly limited, and a method of starting a radical polymerization reaction by light, heat, ionizing radiation or the like using an organic or inorganic radical polymerization initiator is preferable. As the polymerization form, known polymerization forms such as bulk polymerization, suspension polymerization, emulsion polymerization, and solution polymerization can be adopted, and emulsion polymerization is particularly preferable.

(Resin (B))
Examples of the resin (B-II) used for the positive electrode (II) that is dispersed or emulsified in an organic solvent include resins having a solubility in N-methyl-2-pyrrolidone of less than 0.5% by mass. “The solubility in N-methyl-2-pyrrolidone is less than 0.5% by mass” means that it cannot be dissolved in N-methyl-2-pyrrolidone at 25 ° C. at a concentration of 0.5% by mass or more. To do.
The solubility of the resin (B-II) in N-methyl-2-pyrrolidone is preferably less than 0.5% by mass, more preferably less than 0.4% by mass, and still more preferably less than 0.3% by mass.
The difference between the solubility of the resin (A-II) in N-methyl-2-pyrrolidone and the solubility of the resin (B-II) in N-methyl-2-pyrrolidone is preferably 2% by mass or more, and 5% by mass. % Or more is more preferable, and 8 mass% or more is still more preferable.

As resin (B-II) used for positive electrode (II), the said resin (B3-I) and PTFE are preferable, for example. The preferable aspect of resin (B3-I) used for positive electrode (II) is the same as the preferable aspect of resin (B3-I) in the case of using for positive electrode (I).
The resin (B-II) used for the positive electrode (II) may be one type or two or more types.

(Positive electrode active material, conductivity-imparting agent, current collector)
Examples of the positive electrode active material, the conductivity-imparting agent, and the current collector include the same materials as those mentioned for the positive electrode (I).

(Ratio of each component in positive electrode (II))
The ratio of the positive electrode active material in the positive electrode layer in the positive electrode (II), the ratio of the resin (A-II), the ratio of the resin (B-II), the mass ratio of the resin (A-II) and the resin (B-II), And the preferable range of the ratio of a conductive provision agent is the same as the preferable range in positive electrode (I).

(Production method of positive electrode (II))
The manufacturing method of positive electrode (II) employs a known method except that an electrode mixture containing a positive electrode active material, an organic solvent, and a resin (A-II) and a resin (B-II) as a binder is used. it can. For example, the electrode mixture is applied to at least one surface, preferably both surfaces of the current collector, and the organic solvent in the electrode mixture is removed by drying to form a positive electrode layer. If necessary, the positive electrode layer after drying may be pressed to have a desired thickness.
Examples of the method for applying the electrode mixture and the method for drying include the same as those mentioned in the method for the positive electrode (I).

  15-55 mass% is preferable, as for content of the organic solvent in the electrode mixture (100 mass%) used for manufacture of positive electrode (II), 20-50 mass% is more preferable, and 25-45 mass% is still more preferable. 30 to 40% by mass is particularly preferable. If content of an organic solvent is more than a lower limit, it will be easy to improve the dispersibility of an electrode mixture. If the content of the solvent is not more than the upper limit value, an electrode mixture having excellent coating properties is easily obtained.

  The preferred range of the content of the positive electrode active material, the content of the resin (A-II), the content of the resin (B-II), and the content of the conductivity-imparting agent in the electrode mixture used for the positive electrode (II) is: It is the same as the preferable range in the electrode mixture used for positive electrode (I).

<Negative electrode>
When the negative electrode of the lithium ion secondary battery of the present invention is an electrode produced using the electrode mixture, the negative electrode is classified into the following negative electrode (III) or negative electrode (IV) depending on the type of medium used. .
(III) A negative electrode produced using an aqueous medium.
(IV) A negative electrode produced using an organic solvent.

[Negative electrode (III)]
The negative electrode (III) uses an electrode mixture comprising a negative electrode active material, an aqueous medium, a resin (AI) soluble in the aqueous medium, and a resin (BI) dispersed or emulsified in the aqueous medium. It is the produced negative electrode.
The negative electrode (III) includes a negative electrode active material, a resin (AI), and a resin (BI). Examples of the negative electrode (III) include a negative electrode in which a negative electrode layer containing a negative electrode active material, a conductivity-imparting agent, a resin (AI), and a resin (BI) is formed on a current collector.
The negative electrode (III) is the same as the positive electrode (I) except that a negative electrode active material is used instead of the positive electrode active material.

(Aqueous medium)
As an aqueous medium, the same thing as the aqueous medium quoted by positive electrode (I) is mentioned, A preferable aspect is also the same.

(Resin (A), Resin (B))
Examples of the resin (AI) and the resin (BI) used for the negative electrode (III) are the same as the resin (AI) and the resin (BI) mentioned for the positive electrode (I).
The resin (BI) used for the negative electrode (III) is preferably at least one selected from the group consisting of the resins (B1-I) to (B3-I), and (B2-I) and (B3-I). Is particularly preferred.

(Negative electrode active material)
As the negative electrode active material, known negative electrode active materials for lithium ion secondary batteries can be employed. Examples of the negative electrode active material include one or more selected from the group consisting of lithium metal, a lithium alloy, and a carbon-based material capable of inserting and extracting lithium ions.
Examples of the lithium alloy include a Li—Al alloy, a Li—Pb alloy, and a Li—Sn alloy. Examples of the carbon-based material include graphite, coke, and hard carbon. From the viewpoint of life characteristics, the negative electrode active material is preferably a carbon-based material that can occlude and release lithium ions.

(Conductivity imparting agent, current collector)
Examples of the conductivity-imparting agent include the same ones as mentioned for the positive electrode (I).
Examples of the current collector for the negative electrode include the same ones as those cited for the current collector for the positive electrode, and Cu foil is preferred.

(Ratio of each component in the negative electrode (III))
The ratio of the negative electrode active material in the negative electrode layer (100% by mass) is preferably 80 to 99.8% by mass, more preferably 90 to 99.8% by mass, and still more preferably 95 to 99.8% by mass. If the ratio of the negative electrode active material is equal to or higher than the lower limit value, the capacity density is easily increased. If the ratio of the negative electrode active material is not more than the upper limit value, it is easy to obtain good battery characteristics.

  The preferred range of the ratio of the resin (AI) in the negative electrode layer in the negative electrode (III), the ratio of the resin (BI), and the mass ratio of the resin (AI) and the resin (BI) is the positive electrode ( The same as the preferred range in I).

(Production method of negative electrode (III))
The manufacturing method of the negative electrode (III) employs a known method except that an electrode mixture containing a negative electrode active material, an aqueous medium, and a resin (AI) and a resin (BI) as a binder is used. it can. For example, the same method as that described for the positive electrode (I) can be used except that the negative electrode active material is used instead of the positive electrode active material.

  The content of the negative electrode active material in the electrode mixture (100% by mass) used for the negative electrode (III) is preferably 25 to 75% by mass, more preferably 30 to 70% by mass, and still more preferably 35 to 65% by mass.

  The preferred range of the content of the aqueous medium, the content of the resin (AI), the content of the resin (BI), and the content of the conductivity-imparting agent in the electrode mixture used for the negative electrode (III) is positive electrode It is the same as the preferable range in the electrode mixture used for (I).

[Negative electrode (IV)]
The negative electrode (IV) uses an electrode mixture composed of a negative electrode active material, an organic solvent, a resin (A-II) soluble in the organic solvent, and a resin (B-II) dispersed or emulsified in the organic solvent. It is the produced negative electrode.
The negative electrode (IV) includes a negative electrode active material, a resin (A-II), and a resin (B-II). Examples of the negative electrode (IV) include a negative electrode in which a negative electrode layer containing a negative electrode active material, a conductivity-imparting agent, a resin (A-II), and a resin (B-II) is formed on a current collector.
The negative electrode (IV) is the same as the positive electrode (II) except that a negative electrode active material is used instead of the positive electrode active material.

(Organic solvent)
As an organic solvent, the same thing as the organic solvent quoted by positive electrode (II) is mentioned, A preferable aspect is also the same.

(Resin (A-II), Resin (B-II))
Preferred examples of the resin (A-II) and the resin (B-II) used for the negative electrode (IV) are the same as the resin (A-II) and the resin (B-II) mentioned in the positive electrode (II). Is the same.

(Negative electrode active material, conductivity-imparting agent, current collector)
As a negative electrode active material, the same thing as what was mentioned by negative electrode (III) is mentioned, A preferable aspect is also the same.
Examples of the conductivity-imparting agent include the same ones as mentioned for the positive electrode (I).
Examples of the current collector for the negative electrode include the same ones as those cited for the current collector for the positive electrode, and Cu foil is preferred.

(Ratio of each component in the negative electrode (IV))
The preferable range of the ratio of the negative electrode active material in the negative electrode layer of the negative electrode (IV) is the same as the preferable range in the negative electrode (III).
The ratio of the resin (A-II) in the negative electrode layer in the negative electrode (IV), the ratio of the resin (B-II), the mass ratio of the resin (A-II) and the resin (B-II), and the ratio of the conductivity-imparting agent. The preferred range is the same as the preferred range for the positive electrode (I).

(Production method of negative electrode (IV))
The manufacturing method of the negative electrode (IV) employs a known method except that an electrode mixture containing a negative electrode active material, an organic solvent, and a resin (A-II) and a resin (B-II) as a binder is used. it can. For example, the same method as that described for the positive electrode (I) can be used except that the negative electrode active material is used instead of the positive electrode active material.

The content of the organic solvent and the content of the negative electrode active material in the electrode mixture used for the production of the negative electrode (IV) are the same as the preferred range in the electrode mixture used for the negative electrode (III).
The preferred range of the content of the resin (A-II), the content of the resin (B-II), and the content of the conductivity-imparting agent in the electrode mixture used for the negative electrode (IV) is the electrode used for the positive electrode (I). It is the same as the preferable range in the mixture.

<Combination of electrodes>
Examples of the positive electrode and the negative electrode in the lithium ion secondary battery of the present invention include the following combinations.
(I) a combination of positive electrode (I) and negative electrode (III),
(Ii) combination of positive electrode (I) and negative electrode (IV),
(Iii) combination of positive electrode (II) and negative electrode (III),
(Iv) combination of positive electrode (II) and negative electrode (IV),
(V) a combination of the positive electrode (I) and a negative electrode other than the negative electrode (III) and the negative electrode (IV),
(Vi) a combination of the positive electrode (II) and the negative electrode other than the negative electrode (III) and the negative electrode (IV),
(Vii) a combination of a positive electrode other than the positive electrode (I) and the positive electrode (II) and the negative electrode (III),
(Viii) A combination of a positive electrode other than the positive electrode (I) and the positive electrode (II) and the negative electrode (IV).

As said other positive electrode, well-known positive electrodes other than positive electrode (I) and positive electrode (II) can be used.
As said other negative electrode, well-known negative electrodes other than negative electrode (III) and negative electrode (IV) can be used. As the other negative electrode, for example, when the negative electrode active material can keep its shape by itself (for example, when it is a lithium metal thin film), a negative electrode formed only of the negative electrode active material may be used.

  In the present invention, as the combination of the positive electrode and the negative electrode, combinations (i) to (iv) are preferable because the amount of heat generated by the reaction between the electrode and the non-aqueous electrolyte can be further reduced and thermal runaway is less likely to occur. Moreover, it is preferable to use an aqueous medium as a medium from the point of the uniform coverage of resin (A) and resin (B). From the viewpoint of battery characteristics, it is preferable to use an organic solvent as a medium for the positive electrode. The combination can be selected as appropriate. For example, in consideration of safety, battery characteristics, and environmental load, combination (iii) is preferable. In view of the above performance and ease of production, the combination (vii) is also preferable.

≪Nonaqueous electrolyte≫
The non-aqueous electrolyte includes a lithium salt 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 0.4 S / m. A secondary battery using a non-aqueous electrolyte having an ionic conductivity at 25 ° C. of less than 0.4 S / m has poor output characteristics and poor practicality. If the non-aqueous electrolyte has an ionic conductivity at 25 ° C. of 0.4 S / m or more, the secondary battery has good output characteristics.

<Lithium salt>
Lithium salt is an electrolyte that dissociates in a non-aqueous electrolyte and supplies lithium ions. Examples of the lithium salt include Li ₂ PO ₃ F, LiPO ₂ F ₂ , LiPF ₆ , the following compound (C) (where k is an integer of 1 to 5), FSO ₂ N (Li) SO ₂ F, CF ₃ 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 , the following compound (D ) To Compound (G), LiBF _{4 and the} like.

The lithium salt contained in the non-aqueous electrolyte preferably contains LiPF ₆ and more preferably LiPF ₆ only.
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. It is difficult to dissolve in a fluorine-containing solvent. However, the combined use with a cyclic carboxylic acid ester compound improves the solubility of LiPF _{6 in} a fluorine-containing solvent. When LiPF ₆ is uniformly dissolved in the fluorine-containing solvent, it becomes easy to obtain a nonaqueous electrolytic solution having practically sufficient ionic conductivity. In addition, LiPF ₆ is easily decomposed easily and lowers the thermal stability of the battery. However, by combining a nonaqueous electrolytic solution containing a cyclic carboxylic acid ester compound with the above electrode, a lithium ion secondary using LiPF ₆ is used. Thermal runaway is less likely to occur even with batteries.

  Examples of the compound (C) include the following compound (C-1) to compound (C-4). From the viewpoint of easily obtaining a nonaqueous electrolytic solution having high ionic conductivity, the compound (C) preferably includes a compound (C-2) in which k is 2, and only a compound (C-2) in which k is 2 More preferably, it consists of.

<Liquid composition>
The liquid composition contains a fluorine-containing solvent (α) and a cyclic carboxylic acid ester compound, and may contain a compound (β) as necessary. That is, the liquid composition in the present invention comprises only the fluorinated solvent (α) and the cyclic carboxylic acid ester compound, or comprises the fluorinated solvent (α), the cyclic carboxylic acid ester compound and the compound (β), One of them.
By combining a non-aqueous electrolyte solution containing a lithium salt, a liquid composition containing a fluorine-containing solvent (α) and a cyclic carboxylic acid ester compound, and the electrode described above, heat is generated by the reaction between the electrode and the non-aqueous electrolyte solution. The amount of the lithium ion secondary battery is reduced and the thermal runaway hardly occurs, and the thermal stability is excellent.

[Fluorine-containing solvent (α)]
The fluorine-containing solvent (α) contains 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, and other fluorine-containing solvents (if necessary) However, the fluorine-containing cyclic carbonate compound may be excluded). Fluorine-containing ether compounds, fluorine-containing chain carboxylic acid ester compounds, and fluorine-containing chain carbonate compounds have similar characteristics in terms of chemical stability due to introduction of fluorine atoms, compatibility with other compounds, and the like. Yes, it can be treated as an equivalent compound.
The fluorine-containing solvent (α) is a solvent having a fluorine atom in the molecule and is excellent in flame retardancy. A fluorine-containing solvent ((alpha)) may be used individually by 1 type, and may use 2 or more types together. When the number of fluorine-containing solvents (α) is two or more, the ratio can be arbitrarily determined.

(Fluorine-containing ether compound)
The fluorine-containing solvent (α) 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 nonaqueous electrolytic solution.
Examples of the fluorine-containing ether compound include at least one selected from the group consisting of the following compound (1) and the following compound (2).
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} each independently represent 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, fluorinated C3-10 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.
X is 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 2 to 5 carbon atoms having an etheric oxygen atom. A fluorinated alkylene group;

  As the fluorine-containing ether compound, the compound (1) is preferable from the viewpoints of excellent cycle characteristics, lithium salt solubility, withstand voltage characteristics, flame retardancy, and ionic conductivity of the nonaqueous electrolytic solution. When the compound (1) is included, the compound (1) may be used alone or in combination of two or more.

Compound (1):
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 is a fluorinated alkyl group having 1 to 10 carbon atoms, a fluorinated cycloalkyl group 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 are excellent. R ¹ and R ² may be the same or different.

As compound (1), R ¹ and R ² are both fluorinated alkyl groups having 1 to 10 carbon atoms, R ¹ and R ² because R ¹ is excellent in solubility in a liquid composition; ¹ is a fluorinated alkyl group having 2 to 10 carbon atoms having one or more ether oxygen atoms, ^{and R 2} is a fluorinated alkyl group having 1 to 10 carbon atoms and (1-B), ^{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, and the compound (1-A) and the compound (1-C) are preferably More preferred is compound (1-A).

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.
When the compound (1) has an etheric oxygen atom, the number of etheric oxygen atoms in the compound (1) is preferably 1 to 4, more preferably 1 or 2, and still more preferably 1. The number of etheric oxygen atoms in the compound (4) affects flammability.
50 mass% or more is preferable and, as for the fluorine content in a compound (1), 60 mass% or more is 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 a part 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 compound (1-A) and compound (1-B), and specific examples of fluorine-containing ether compounds other than compound (1-A) and compound (1-B) include, for example, International Publication No. 2009 / And the compounds described in No. 133899.

Compound (1) has excellent cycle characteristics, excellent solubility of lithium salt in a liquid composition, high withstand voltage characteristics, excellent flame retardancy, low viscosity, and low boiling point. ₃ CH ₂ OCF ₂ CHF ₂ , CHF ₂ CF ₂ CH ₂ OCF ₂ CHF ₂ , CF ₃ CF ₂ CH ₂ OCF ₂ CHF ₂ , CF ₃ CH ₂ OCF ₂ CHFCF ₃ , and CHF ₂ CF ₂ CH ₂ OCF ₂ CHFCF ₃ Preferably, at least one selected from the group consisting of 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 OCF ₂ CHFCF ₃ is selected. Species are particularly preferred.

Compound (2):
In the compound (2), X may be a linear structure or a branched structure. X 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 X 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 at least one of the compound wherein X is —CH ₂ CH ₂ — and the compound where X is —CH (CH ₃ ) CH ₂ — is more preferred, and X is —CH ₂ CH _2. - those compounds, or X is -CH _(CH 3) CH ₂ - and more preferably any one compound is.

(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 compound (3) is included, the compound (3) may be used alone or in combination of two or more. When the number of fluorine-containing chain carboxylic acid ester compounds is two or more, the ratio can be arbitrarily determined.

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 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 preferred, a methyl group, an ethyl group, or a 2,2,2-trifluoroethyl group is more preferred, and a methyl group or an ethyl group is still more preferred.

When the total carbon number 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 7, 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.
The fluorine content in the compound (3) is preferably 25% by mass or more, and more preferably 30% by mass or more from the viewpoint of improving flame retardancy.

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

(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 compound (4) is included, the compound (4) may be used alone or in combination of two or more. When the number of fluorine-containing chain carbonate compounds is two or more, the ratio can be arbitrarily determined.

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 compound (4) is excellent in the solubility and flame retardancy of the lithium salt. 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. The R ⁵ and _{^{R 6, CF 3 CH 2 -}} , CHF 2 CF 2 CH 2 - is preferred.

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 number of carbon atoms is preferably 4 to 7.
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 improving 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 (α) may contain a fluorine-containing alkane compound as another fluorine-containing solvent. 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]
The liquid composition contains a cyclic carboxylic acid ester compound. By including the cyclic carboxylic acid ester compound, the lithium salt is uniformly dissolved in the fluorine-containing solvent (α). In addition, the inclusion of the cyclic carboxylic acid ester compound makes it difficult for the non-aqueous electrolyte, the positive electrode, and the negative electrode to react with each other, making it difficult for thermal runaway in the secondary battery to occur. The cyclic carboxylic acid ester compound may be one kind or two or more kinds.

As the cyclic carboxylic acid ester compound, a saturated cyclic carboxylic acid ester compound having no carbon-carbon unsaturated bond in the molecule is preferable from the viewpoint of stability to the redox reaction.
The ring structure in the cyclic carboxylic acid ester compound is preferably a 4- to 10-membered ring and more preferably a 4- to 7-membered ring from the viewpoints of structural stability and viscosity. From the viewpoint of easy availability, a 5- to 6-membered ring is more preferable and a 5-membered ring is particularly preferable. Moreover, 4-8 are preferable and, as for the total carbon number of a cyclic carboxylic acid ester compound, 4-6 are more preferable from an easy point. The cyclic carboxylic acid ester is preferably composed of only a carbon atom, a hydrogen atom and an oxygen atom, and the portion other than the ester bond represented by the —C (═O) —O— bond contained in the ring structure is carbon. More preferably, it consists only of atoms and hydrogen atoms.

The ring structure of the cyclic carboxylic acid ester compound is preferably a ring structure having one ester bond from the viewpoint of viscosity.
The cyclic carboxylic acid ester compound is preferably a compound composed of only carbon atoms, hydrogen atoms and oxygen atoms.
The cyclic carboxylic acid ester compound 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.

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. n is an integer of 1 to 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, an ethyl group, or a fluorine atom, more preferably a hydrogen atom, a methyl group, or an ethyl group, from the viewpoint of stability to redox reaction, viscosity, and availability of the compound. preferable.
n is preferably 1 to 3, and more preferably 1 from the viewpoint of viscosity and availability of the compound.

  Examples of the compound (5) include cyclic ester compounds such as γ-butyrolactone, γ-valerolactone, γ-hexanolactone, δ-valerolactone, and ε-caprolactone, and carbon atoms forming the ring of the cyclic ester compound. 1 or more of the hydrogen atoms bonded to the carbon atom have 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 Examples thereof include compounds substituted with 2 to 3 alkyl groups. The compound (5) is preferably at least one selected from the group consisting of γ-butyrolactone, γ-valerolactone and ε-caprolactone from the viewpoint of easy availability and high thermal runaway suppression effect, and γ-butyrolactone is preferable. Is more preferable.

[Compound (β)]
The liquid composition is also referred to as a saturated cyclic carbonate compound or a saturated chain carbonate compound having no fluorine atom (hereinafter referred to as “non-fluorinated saturated chain carbonate compound”), from the viewpoint of excellent lithium salt solubility and ionic conductivity. ), A saturated cyclic sulfone compound (however, excluding lithium salt) and at least one compound (β) selected from the group consisting of phosphate ester compounds.

Examples of the saturated cyclic carbonate compound include propylene carbonate (PC), ethylene carbonate (EC), 4-fluoro-1,3-dioxolan-2-one (FEC) and the like.
Examples of the non-fluorinated saturated chain carbonate compound include dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and the like.
Examples of the saturated cyclic sulfone compound include sulfolane and 3-methylsulfolane.
Examples of the phosphate 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 non-aqueous electrolyte is a compound other than the lithium salt, the fluorine-containing solvent (α), the cyclic carboxylic acid ester compound, and the compound (β) as necessary, as long as the effects of the present invention are not impaired. , Additives, etc.).

[Other solvents]
The nonaqueous electrolytic solution may contain a solvent other than the fluorine-containing solvent (α), the cyclic carboxylic acid ester compound and the compound (β).

[Additive]
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)
Examples of the overcharge inhibitor include aromatic compounds (biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, dibenzofuran, etc.), aromatic Partially fluorinated compounds (2-fluorobiphenyl, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene, etc.), fluorine-containing anisole compounds (2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole) All). 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.

(Characteristic improvement aid)
The characteristic improving aid is for improving capacity maintenance characteristics and cycle characteristics after high temperature storage. Examples of the property improving aid include unsaturated carbonate compounds (vinylene carbonate (VC), vinyl ethylene carbonate (VEC), 4-ethynyl-1,3-dioxolan-2-one, etc.), sulfur-containing compounds (ethylene sulfite). 1,3-propane sultone, 1,4-butane sultone, methyl methanesulfonate, busulfan, sulfolene, dimethyl sulfone, diphenyl sulfone, methyl phenyl sulfone, dibutyl disulfide, dicyclohexyl disulfide, tetramethyl thiuram monosulfide, N, N-dimethyl Methanesulfonamide, N, N-diethylmethanesulfonamide, etc.), hydrocarbon compounds (heptane, octane, cycloheptane, etc.), fluorine-containing aromatic compounds (fluorobenzene, difluorobenzene, hexafur) Robenzen, etc.) 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 electrode mixture or the separator with the nonaqueous electrolytic solution. 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>
[Rate of lithium salt]
Although the upper limit of content of lithium salt in a non-aqueous electrolyte is not specifically limited, 3.0 mol / L is preferable, 2.0 mol / L is more preferable, 1.4 mol / L is still more preferable. Although the lower limit of content of lithium salt in a non-aqueous electrolyte is not specifically limited, 0.1 mol / L is preferable, 0.5 mol / L is preferable and 0.8 mol / L is more preferable.
In terms of mass standard, the ratio of the mass of the lithium salt to the total mass of the non-aqueous electrolyte is preferably 1 to 30% by mass, more preferably 5 to 20% by mass, and still more preferably 8 to 15% by mass.
If the ratio of lithium salt is more than the said lower limit, the ionic conductivity of a non-aqueous electrolyte will become high. If the proportion of the lithium salt is not more than the above upper limit value, the lithium salt is easily dissolved uniformly in the liquid composition, and the lithium salt does not precipitate even under low temperature conditions. Further, lithium ions are easily diffused into the non-aqueous electrolyte, and the lithium ion diffusion coefficient is increased.

The nonaqueous electrolytic solution of the present invention preferably contains at least LiPF ₆ as a lithium salt. The molar ratio of LiPF ₆ to the total number of moles of lithium salt contained in the non-aqueous electrolyte is preferably 40 to 100 mol%, more preferably 50 to 100 mol%, still more preferably 65 to 100 mol%, and more preferably 80 to 100 mol%. Particularly preferred. When the molar ratio of LiPF ₆ with respect to the total number of moles of lithium salt is equal to or more than the lower limit value, a nonaqueous electrolytic solution having excellent ion conductivity and high practicality is obtained.

Non If aqueous electrolyte solution containing LiPF _6, the mass ratio of the LiPF ₆ with respect to the total mass of the nonaqueous electrolytic solution of the present invention is preferably from 1 to 30 wt%, more preferably from 5 to 20 wt%, 8-15 More preferred is mass%. When the proportion of LiPF ₆ is more than the above lower limit, it is easy to obtain a high ion conductivity non-aqueous electrolyte. If the ratio of LiPF ₆ is not more than the above upper limit value, the lithium salt is likely to be uniformly dissolved in the liquid composition.

[Ratio of fluorinated solvent (α)]
The ratio of the mass of the fluorine-containing solvent (α) to the total mass of the nonaqueous electrolytic solution is not particularly limited. The lower limit of the ratio of the mass of the fluorinated solvent (α) to the total mass of the nonaqueous electrolytic solution is preferably 20% by mass, more preferably 30% by mass, still more preferably 40% by mass, particularly preferably 50% by mass, 55% by mass is most preferred. The upper limit of the proportion of the fluorinated solvent (α) is preferably 80% by mass, more preferably 70% by mass, still more preferably 60% by mass, and particularly preferably 55% by mass.
When the proportion of the fluorinated solvent (α) is at least the lower limit, a lithium ion secondary battery having excellent cycle characteristics can be easily obtained. In addition, it is easy to obtain a lithium ion secondary battery that is excellent in flame retardancy, has low reactivity between the electrode and the non-aqueous electrolyte, hardly causes thermal runaway, and has excellent high voltage resistance. When the proportion of the fluorinated solvent (α) is not more than the above upper limit value, the lithium salt is uniformly dissolved and the lithium salt is unlikely to precipitate at a low temperature.

20-90 mass% is preferable, as for the ratio of the mass of a fluorine-containing solvent ((alpha)) with respect to the total mass of a liquid composition, 40-85 mass% is more preferable, 55-80 mass% is still more preferable, 60-75 mass%. Is particularly preferred.
When the proportion of the fluorinated solvent (α) is at least the lower limit, a lithium ion secondary battery having excellent cycle characteristics can be easily obtained. In addition, it is easy to obtain a lithium ion secondary battery that is excellent in flame retardancy, has low reactivity between the electrode and the non-aqueous electrolyte, hardly causes thermal runaway, and has excellent high voltage resistance. When the proportion of the fluorinated solvent (α) is not more than the above upper limit value, the lithium salt is uniformly dissolved and the lithium salt is unlikely to precipitate at a low temperature.

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

  The ratio of the mass of the fluorinated ether compound to the total mass of the non-aqueous electrolyte is preferably 10 to 80% by mass. The lower limit of the proportion of the fluorine-containing ether compound is more preferably 20% by mass, further preferably 30% by mass, particularly preferably 45% by mass, and most preferably 50% by mass. Further, the upper limit of the ratio of the fluorine-containing ether compound is more preferably 75% by mass, still more preferably 73% by mass, and particularly preferably 70% by mass.

  When the fluorine-containing solvent (α) contains a fluorine-containing chain carboxylic acid ester compound, the ratio of the mass of the fluorine-containing chain carboxylic acid ester compound to the total mass of the fluorine-containing solvent (α) is 0.01 to 50% by mass. Is preferable, 0.01-40 mass% is more preferable, 0.01-30 mass% is still more preferable, 0.01-20 mass% is especially preferable.

  When the fluorine-containing solvent (α) contains a fluorine-containing chain carbonate compound, the ratio of the mass of the fluorine-containing chain carbonate compound to the total mass of the fluorine-containing solvent (α) is preferably 0.01 to 50% by mass, 0 0.01-40 mass% is more preferable, 0.01-30 mass% is still more preferable, and 0.01-20 mass% is especially preferable.

When the fluorinated solvent (α) 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%.
If the ratio of a fluorine-containing alkane compound is 0.01 mass% or more, it will be excellent in the flame retardance of a non-aqueous electrolyte. When the proportion of the fluorinated alkane is 5% by mass or less, the solubility of the lithium salt is easily maintained.

  When the fluorine-containing solvent (α) is used in combination with one or more fluorine-containing ether compounds and one or more fluorine-containing chain carboxylic acid esters, fluorine-containing chain carbonate compounds, and fluorine-containing alkane compounds, the ratio thereof is arbitrary. I can decide.

[Ratio of cyclic carboxylic acid ester compound]
The ratio of the mass of the cyclic carboxylic acid ester compound to the total mass of the nonaqueous electrolytic solution is preferably 4 to 70 mass%, more preferably 7 to 45 mass%, still more preferably 10 to 40 mass%, and more preferably 15 to 35 mass%. Is particularly preferred.
If the ratio of the cyclic carboxylic acid ester compound is equal to or higher than the lower limit, the non-aqueous electrolyte uniformly dissolves the lithium salt, the reactivity between the non-aqueous electrolyte and the electrode is small, and thermal runaway hardly occurs. If the ratio of the cyclic carboxylic acid ester compound is not more than the above upper limit value, the non-aqueous electrolyte is excellent in flame retardancy.
The ratio of the mass of the cyclic carboxylic acid ester to the total mass of the liquid composition is preferably 4 to 80% by mass, more preferably 4 to 55% by mass, still more preferably 10 to 50% by mass, and particularly preferably 15 to 45% by mass. preferable.
When the ratio of the cyclic carboxylic acid ester is not less than the lower limit, the liquid composition has excellent solubility, small positive electrode reactivity and negative electrode reactivity, hardly causes thermal runaway, and has high voltage resistance. If the ratio of cyclic carboxylic acid ester is below the said upper limit, a liquid composition will be excellent in a flame retardance.

Contained in the nonaqueous electrolytic solution, the ratio N _{A /} N _Li of the total number of moles N _A cyclic carboxylic acid ester compound to the total number of moles N _Li of lithium atoms from the lithium salt is not particularly limited, 1 to 10 preferable. The lower limit value of the N _A / N _Li is more preferably 2, more preferably 2.5, and particularly preferably 3. The upper limit of the _N A _{/ N Li} is 7, still more preferably 6, particularly preferably 5.5, 5 being most preferred.
If NA / NLi is within the above range, the reactivity between the non-aqueous electrolyte, the positive electrode and the negative electrode can be reduced while the lithium salt is uniformly dissolved to obtain sufficient ionic conductivity for the following reasons. It is possible to suppress thermal runaway of the secondary battery.

When the non-aqueous electrolyte is used in a lithium ion secondary battery, the cyclic carboxylic acid ester compound forms a stable coating on the electrode layer, and the coating suppresses the reaction between the electrode and the non-aqueous electrolyte. Along with this, it is estimated that thermal runaway is suppressed. If N _A / N _Li is equal to or greater than the lower limit, the non-aqueous electrolyte contains a sufficient amount of the cyclic carboxylic acid ester compound, so that the coating is sufficiently formed and the reaction between the electrode and the non-aqueous electrolyte is suppressed. It is considered that a sufficient effect of suppressing thermal runaway can be obtained by sufficiently exhibiting the effect. In addition, the cyclic carboxylic acid ester compound has a high affinity with the lithium salt, and is considered to promote the dissolution of the lithium salt in a solvent. When N _A / N _Li is equal to or higher than the lower limit, the lithium salt is sufficiently dissolved in the solvent, and an electrolytic solution having practically sufficient ionic conductivity is easily obtained. Note that fluorine-containing compounds such as fluorine-containing ether compounds, fluorine-containing chain carboxylic acid ester compounds, and fluorine-containing chain carbonate compounds are considered to have low affinity with lithium salts, and promote dissolution of lithium salts in solvents. The effect of doing this tends to be very small.

The film formed on the electrode layer is considered to be easily dissolved in a highly polar solvent, and it is estimated that the film formation is likely to be insufficient due to dissolution even if the film is formed in a highly polar solvent. Is done. If N _A / N _Li is not more than the above upper limit, the content of the cyclic carboxylic acid ester compound in the non-aqueous electrolyte does not become excessive, and the polarity of the entire non-aqueous electrolyte is within an appropriate range, It is considered that dissolution of the film formed on the electrode layer hardly occurs. By maintaining a sufficient film on the electrode layer, an exothermic reaction between the electrode and the non-aqueous electrolyte is unlikely to occur, and thermal runaway is unlikely to occur. Note that fluorine-containing compounds such as a fluorine-containing ether compound, a fluorine-containing chain carboxylic acid ester compound, and a fluorine-containing chain carbonate compound are low in polarity, and thus the effect of dissolving the coating is considered to be very low. Moreover, the flame retardance of a non-aqueous electrolyte improves also by reducing content of the highly flammable cyclic carboxylic acid ester compound.

[Ratio of compound (β)]
When the liquid composition contains the compound (β), the ratio of the mass of the compound (β) to the total mass of the non-aqueous electrolyte is preferably 0.01 to 40% by mass, more preferably 0.1 to 30% by mass. 0.1 to 20% by mass is more preferable.
If the ratio of a compound ((beta)) is below the said upper limit, it will be easy to suppress reaction with a compound ((beta)) and an electrode, and the nonaqueous electrolyte solution excellent in stability will be obtained. Moreover, since content of a fluorine-containing solvent ((alpha)) 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 40% by mass, more preferably 0.01 to 30% by mass. 0.01% by mass or more and less than 20% by mass is more preferable, and 0.01 to 5% by mass is particularly preferable.
If the ratio of a cyclic carbonate compound is below the said upper limit, a cyclic carbonate compound and an electrode will be hard to react, a nonaqueous electrolyte solution is excellent in stability, and is excellent in a flame retardance.

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, and 0.01-15 mass% is still more preferable.
If the proportion of the non-fluorinated saturated chain carbonate compound is less than or equal to the above upper limit, the non-fluorinated saturated chain carbonate compound and the electrode are less likely 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 and 0.01-20 mass% is more preferable.
If the ratio of the total mass is equal to or less than the upper limit, even when a saturated cyclic carbonate compound and a non-fluorinated saturated chain carbonate compound are used, The dissolution of the coating can be suppressed, the reactivity between them and the electrode can be kept low, and it is easy to obtain a non-aqueous electrolyte 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 saturated cyclic sulfone compound, the ratio of the mass of the saturated cyclic sulfone compound to the total mass of the non-aqueous electrolyte is preferably 0.01 to 20% by mass, more preferably 0.01 to 15% by mass. 0.01 to 10% by mass is more preferable, and 0.01 to 5% by mass is particularly preferable.
If the ratio of the saturated cyclic sulfone compound is not more than the above upper limit value, the saturated cyclic sulfone compound and the electrode are unlikely to react with each other, and the non-aqueous electrolyte is excellent in stability and flame retardancy.

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 equal to or less than the upper limit, the phosphate ester compound and the electrode are difficult 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 to the total mass of the cyclic carboxylic acid ester compound and the compound (β) is preferably 40 to 100% by mass, more preferably 50 to 100% by mass, and still more preferably 60 to 100% by mass. 70 to 100% by mass is more preferable, and 80 to 100% by mass is particularly preferable.
When the ratio of the cyclic carboxylic acid ester compound is within the above range, the reactivity between the non-aqueous electrolyte, the positive electrode, and the negative electrode can be reduced, and thermal runaway of the secondary battery can be suppressed.

When the liquid composition contains the compound (β), the sum of the total mole number NA of the cyclic carboxylic acid ester compound and the total mole number NB of the compound (β) with respect to the total mole number N _Li of lithium atoms derived from the lithium salt The ratio (N _A + N _B ) / N _Li is preferably 3.0 to 9.0. The lower limit of the _{(N A + N B) /} N Li is more preferably 3.2, 3.5 is more preferable. Furthermore, the _{(N A + N B) /} N upper limit of _Li is more preferably 8.0, more preferably 7.0, particularly preferably 6.0, 5.0 is most preferred.

The compound (β) has a high affinity with the lithium salt similarly to the cyclic carboxylic acid ester compound, and is considered to have an effect of promoting dissolution of the lithium salt in a solvent. (N _A + N _B ) / N _Li is not less than the above lower limit value, that is, the total amount of the cyclic carboxylic acid ester compound and the compound (β) considered to have a high lithium salt dissolution promoting effect is a certain amount or more with respect to the amount of the lithium salt. If the lithium salt solubility in the fluorine-containing solvent (α) is improved, the ionic conductivity of the nonaqueous electrolytic solution is improved, and in particular, when a lithium salt such as LiPF ₆ that is difficult to dissolve in the fluorine-based solvent is used. Can be dissolved in a fluorine-based solvent, and practically sufficient ionic conductivity is easily obtained.

When the polarity of the solvent is high, the film of the cyclic carboxylic acid ester compound formed on the electrode active material is dissolved, and the film formation tends to be insufficient. Since the compound (β) is also highly polar, it is considered that it exhibits an action of dissolving the film. _{(N A + N B) /} N Li is less than the upper limit, that is, if constant less is the lithium salt total amount of the compound cyclic carboxylic acid ester compound showing the effect of dissolving the coating (beta), the coating It is considered that the solubility is low, and the film formation is difficult to be insufficient. As a result, it is estimated that the reactivity between the non-aqueous electrolyte and the electrode becomes smaller, and the thermal runaway of the secondary battery is less likely to occur. Moreover, the flame retardance of a non-aqueous electrolyte is also improved by reducing the content of a highly flammable cyclic carboxylic acid ester compound or compound (β) in the non-aqueous electrolyte.

In particular, by using a lithium salt containing LiPF ₆ and controlling N _A / N _Li and (N _A + N _B ) / N _Li within the above ranges, practically sufficient ion conductivity and thermal runaway can be achieved. It is easy to obtain a non-aqueous electrolyte that has excellent stability that does not easily occur.

[Ratio of other ingredients]
When the nonaqueous electrolytic solution contains another solvent, the ratio of the total mass of the other solvent and the compound (β) to the total mass of the nonaqueous electrolytic solution is preferably 0.01 to 30 mass, and preferably 0.1 to 20 The mass% is more preferable. If the ratio of the total mass of the other solvent and the compound (β) is less than or equal to the above upper limit value, it is easy to suppress the reaction between the other solvent and the compound (β) and the electrode, and the nonaqueous electrolyte solution is excellent in stability. Is obtained. Moreover, since content of a fluorine-containing solvent ((alpha)) can be increased, the nonaqueous electrolyte solution excellent in the flame retardance is easy to be obtained.

  When the non-aqueous electrolyte contains a nitrile compound as the other solvent, the ratio of the mass of the nitrile compound to the total mass of the non-aqueous electrolyte is less reactive with the electrode, and the non-aqueous electrolyte does not easily cause thermal runaway. From the point which becomes easy to obtain, 10 mass% or less is preferable, 5 mass% or less is more preferable, and 3 mass% or less is still more preferable.

  When the non-aqueous electrolyte contains an ether compound having no fluorine atom as the other solvent, the ratio of the mass of the ether compound having no fluorine atom to the total mass of the non-aqueous electrolyte is less reactive with the electrode, 10 mass% or less is preferable from the point which becomes easy to obtain the nonaqueous electrolyte solution which does not raise | generate a thermal runaway easily, 5 mass% or less is more preferable, 3 mass% or less is further more preferable, and 1 mass% or less is especially preferable.

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.
When the ratio of the overcharge preventing agent is within the above range, it becomes easier to suppress the rupture and ignition of the secondary battery due to overcharge, and the lithium ion 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 ratio of the mass of the surfactant to the total mass of the non-aqueous electrolyte is preferably 0.05 to 5% by mass, more preferably 0.05 to 3% by mass, 0.05-2 mass% is still more preferable.

<Separator>
A separator is interposed between the positive electrode and the negative electrode to prevent a short circuit. An example of the separator is a porous film. A non-aqueous electrolyte is used by impregnating the porous membrane. Moreover, you may use as a gel electrolyte what impregnated the porous film with the nonaqueous electrolyte solution, and was made to gelatinize.

As the porous film, one that is stable with respect to the non-aqueous electrolyte and excellent in liquid retention can be used. As a porous film, a porous sheet or a nonwoven fabric is preferable.
Examples of porous membrane materials include fluororesins (polyvinylidene fluoride, polytetrafluoroethylene, copolymers of ethylene and tetrafluoroethylene, etc.), polyimides, polyolefins (polyethylene, polypropylene, etc.), oxidation resistance, air permeability From the viewpoint of availability, polyolefin is preferred.

<Battery exterior>
Examples of the material for the battery outer package include nickel-plated iron, stainless steel, aluminum or an alloy thereof, nickel, titanium, a resin material, and a film material.

<Shape>
The shape of the lithium ion secondary battery may be selected according to the application, and may be any shape such as a coin shape, a cylindrical shape, a square shape, and a laminate shape. Moreover, the shape of a positive electrode and a negative electrode can be suitably selected according to the shape of a secondary battery.

<Charging voltage>
The charging voltage of the lithium ion secondary battery of the present invention is preferably 4.0 V or higher, more preferably 4.2 V or higher, and still more preferably 4.3 V or higher. When the positive electrode active material is a lithium-containing transition metal oxide, a lithium-containing transition metal composite oxide, a transition metal oxide, a transition metal sulfide, or a metal oxide, the charging voltage is preferably 4.2 V or more, and 4.3 V The above is more preferable. When the positive electrode active material is an olivine type lithium metal salt, the charging voltage is preferably 3.2 V or more, and more preferably 3.4 V or more.

<Effect>
In the lithium ion secondary battery of the present invention described above, the reactivity between the non-aqueous electrolyte and the electrode is reduced by combining the specific electrode and the specific non-aqueous electrolyte. Thermal runaway is unlikely to occur because the amount of heat generated by the reaction is reduced. The mechanism by which the above effect is obtained by the combination of the electrode and the non-aqueous electrolyte is not necessarily clear, but is estimated as follows.
The resin (A) that is soluble in the medium and the resin (B) that is dispersed or emulsified in the medium have different adsorption characteristics for the active material. It is considered that the adsorption amount of the resin (B) is different. Further, it is considered that a stable film is formed on the electrode layer by the cyclic carboxylic acid ester compound in the non-aqueous electrolyte. In this way, the coating is formed by the cyclic carboxylic acid ester compound on the electrode layer formed by adsorbing the resin (A) and the resin (B) in a biased manner on the basal surface and the edge surface of the active material. It is considered that the reactivity between the electrode and the non-aqueous electrolyte is kept low due to the synergistic effect thereof.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by the following description. Examples 1 to 11 are production examples, and Examples 12 to 23 are experimental examples. The abbreviations below are as follows.
[Lithium salt]
LPF: LiPF ₆ .

[Fluorine-containing solvent (α)]
_{AE3000: CF 3 CH 2 OCF 2} CHF 2 ( trade name: AE3000, manufactured by Asahi Glass Co., Ltd.).

[Cyclic carboxylic acid ester compound]
GBL: γ-butyrolactone.

[Compound (β)]
DMC: dimethyl carbonate.

<Copolymerization composition>
The resin (B) was dissolved in deuterated tetrahydrofuran, and ¹³ C-NMR was measured to analyze the copolymer composition of the resin (B).

<Solubility>
The solubility of the resin (A) and the resin (B) in water is such that the resin (A) or the resin (B) is dissolved in water at 25 ° C. until saturation, and the resin (A) or resin in the saturated solution is dissolved. The mass ratio of (B) was measured and evaluated.

<Manufacture of resin (B)>
[Example 1]
According to the manufacture example 1 of international publication 2011/055760, the water dispersion of the soft polymer (resin (B31-1-I)) which consists of a TFE / P copolymer was obtained. The weight average molecular weight of the resin (B31-1-I) was 180,000, and the copolymer composition was (repeat unit based on TFE) / (repeat unit based on P) = 56/44 (molar ratio).

<Preparation of non-aqueous electrolyte>
[Example 2]
LPF (1.52 g), which is a lithium salt, is diffused into AE3000 (10.24 g), which is a fluorine-containing solvent (α), and then mixed with GBL (3.44 g), which is a cyclic carboxylic acid ester compound. Water electrolyte-1 was prepared.

[Examples 3 to 11]
Except having changed composition as shown in Table 1, it carried out similarly to Example 1, and prepared non-aqueous electrolyte-2-nonaqueous electrolyte-10.

In addition, in Table 1, the usage-amount (mass (g), molar amount (mmol)) about LPF, and content (mol / L, mass%) in nonaqueous electrolyte solution were shown. About AE3000, GBL, and DMC, the usage-amount (mass (g)) and those content (mass%) in a non-aqueous electrolyte were shown. Further, "N _{A /} N _Li" in Table 1, the total number of moles N _Li of lithium atoms from the lithium salt, the ratio of the total mole number N _A of the cyclic carboxylic acid ester compound. _{"(N A + N B) /} N Li ", the to the total number of moles _{N Li,} is the ratio of the sum of the total number of moles _{N B} of the total number of moles _{N A} and the compound (beta).

<Evaluation of negative electrode reactivity>
[Test method]
The negative electrode for evaluation obtained in the following example was obtained by punching a lithium metal foil into a circle having a diameter of 19 mm as a counter electrode. Between these electrodes, a polyolefin microporous membrane was present as a separator. Furthermore, 0 of a carbonate-based non-aqueous electrolyte (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. manufactured by Kishida Chemical Co., Ltd.) A nonaqueous electrolytic solution in which vinylene carbonate was added to 2% by mass in 5 mL was injected to prepare a single electrode cell made of graphite electrode-lithium metal foil.
The following charging / discharging cycle was implemented about the obtained monopolar cell. In cycle 1, at 25 ° C., constant current charging to 0.2 V (negative electrode) with a current corresponding to 0.04 C, further constant current charging to 0.05 V with a current corresponding to 0.2 C, and the lower charging limit Constant voltage charging was performed until the current value corresponding to 0.02C in voltage was reached. Thereafter, constant current discharge was performed to 1.0 V at a current corresponding to 0.2C. In cycles 2 to 4, constant current charging was performed at a current corresponding to 0.2 C up to 0.05 V, and further, constant voltage charging was performed until the current value reached a current corresponding to 0.02 C at the charging lower limit voltage. Thereafter, constant current discharge was performed to 1.0 V at a current corresponding to 0.2C. In cycle 5, constant current charging was performed up to 0.05V with a current corresponding to 0.2C.
Thereafter, the obtained charged single electrode cell was decomposed in an argon atmosphere to obtain a charged negative electrode. The obtained negative electrode was washed three times with DMC (2 mL), vacuum-dried, then punched into a circle with a diameter of 5 mm, placed in a stainless steel (SUS) sealed container, and 2 μL of the non-aqueous electrolyte of each example was added. And sealed to obtain an evaluation sample.
About each obtained evaluation sample, the total calorific value was measured on the conditions of the temperature range of 50-350 degreeC, and the temperature increase rate of 5 degree-C / min with the differential scanning calorimeter (SII nanotechnology company make DSC-6000).

[Example 12 (Negative electrode (III))]
Artificial graphite (9.1 g) and acetylene black (0.32 g), which is a conductivity-imparting agent, are mixed, and the number of rotations is determined using a rotating and rotating stirrer (Shinky Co., Ltd., Awatori Nerita AR-E310). The step of stirring at 2000 rpm for 1 minute was performed 3 times. Next, an aqueous CMC solution (9 g) in which CMC (sodium salt, manufactured by Nippon Paper Chemical Co., Ltd., solubility in water: 4% by mass, the same applies hereinafter) as resin (AI) was dissolved to 2% by mass was added. Further, the step of stirring for 1 minute at a rotational speed of 2000 rpm using the agitator was performed once. Distilled water (5 g) was further added, and the mixture was stirred for 1 minute at a rotational speed of 2000 rpm using the stirrer. Thereafter, SBR latex (0.8 g) in which styrene-butadiene rubber (solubility in water of 0.3% by mass) as resin (BI) is dispersed at a solid content concentration of 40% by mass is added, and the agitator is used. The mixture was stirred for 5 minutes at a rotational speed of 2000 rpm to obtain an electrode mixture.
The electrode mixture was applied on a Cu foil having a thickness of 20 μm to a thickness of 80 μm, dried, and then punched into a circle having a diameter of 19 mm to obtain a negative electrode (III-1).

A single electrode cell was prepared using the negative electrode (III-1) as a negative electrode for evaluation, and the total calorific value was measured by the test method. The total calorific value was measured for single electrode cells using the nonaqueous electrolytic solution-1 to nonaqueous electrolytic solution-5 obtained in Examples 2 to 6, respectively, as the nonaqueous electrolytic solution.
The relationship of the measurement result of the total calorific value with respect to N _A / N _Li is shown in FIG.

[Example 13 (negative electrode for comparison)]
Artificial graphite (9.1 g) and acetylene black (0.32 g), which is a conductivity-imparting agent, are mixed, and the number of rotations is determined using a rotating and rotating stirrer (Shinky Co., Ltd., Awatori Nerita AR-E310). The step of stirring at 2000 rpm for 1 minute was performed 3 times. Next, a step of adding N-methyl-2-pyrrolidone (8 g) and stirring for 10 minutes at a rotational speed of 2000 rpm using the stirrer was performed once. Next, a step of adding N-methyl-2-pyrrolidone (2 g) and stirring for 10 minutes at a rotational speed of 2000 rpm using the stirrer was performed once. Further, an N-methyl-2-pyrrolidone solution of PVDF (12% by mass, 8 g) was added and stirred for 1 minute at a rotational speed of 2000 rpm using the stirrer to obtain an electrode mixture.
The electrode mixture was applied on a Cu foil having a thickness of 20 μm to a thickness of 80 μm, dried, and then punched into a circle having a diameter of 19 mm to obtain a comparative negative electrode.

A single electrode cell was prepared using the comparative negative electrode as an evaluation negative electrode, and the total calorific value was measured by the test method. The total calorific value was measured for a single electrode cell using nonaqueous electrolyte-1, nonaqueous electrolyte-3, and nonaqueous electrolyte-5 as the nonaqueous electrolyte.
The relationship of the measurement result of the total calorific value with respect to N _A / N _Li is shown in FIG.

[Example 14 (Negative electrode (III))]
A negative electrode (III-1) was produced in the same manner as in Example 12, and the total calorific value was measured by the test method. The total calorific value was measured for single electrode cells using nonaqueous electrolyte-1, nonaqueous electrolyte-6 to nonaqueous electrolyte-9, respectively, as nonaqueous electrolytes.
The relationship of the measurement result of the total calorific value with respect to the LiPF ₆ concentration is shown in FIG.

[Example 15 (negative electrode for comparison)]
A comparative negative electrode was prepared in the same manner as in Example 13, and the total calorific value was measured by the test method. The total calorific value was measured for single electrode cells using nonaqueous electrolyte-1, nonaqueous electrolyte-6 to nonaqueous electrolyte-9, respectively, as nonaqueous electrolytes.
The relationship of the measurement result of the total calorific value with respect to the LiPF ₆ concentration is shown in FIG.

[Example 16 (Negative electrode (III))]
A negative electrode (III-1) was produced in the same manner as in Example 12, and the total calorific value was measured by the test method. The total calorific value was measured for a single electrode cell using Nonaqueous Electrolytic Solution-1 and Nonaqueous Electrolytic Solution-10 as the nonaqueous electrolytic solution.
The relationship of the total calorific value measurement result with respect to the AE3000 ratio is shown in FIG.

[Example 17 (negative electrode for comparison)]
A comparative negative electrode was prepared in the same manner as in Example 13, and the total calorific value was measured by the test method. The total calorific value was measured for a single electrode cell using non-aqueous electrolyte-1 as the non-aqueous electrolyte.
The relationship of the total calorific value measurement result with respect to the AE3000 ratio is shown in FIG.

As shown in FIG. 1, in Example 12 using the negative electrode (III-1) produced using both the resin (AI) and the resin (BI), the resin (BI) was not used. Compared with Example 13 using the produced comparative negative electrode, the calorific value was small.
Further, as shown in FIG. 2, the calorific value was smaller in Example 14 using the negative electrode (III-1) than in Example 15 using the comparative negative electrode. Further, in Example 14, the smaller the content of LiPF _6, the heating value is small.
Moreover, as shown in FIG. 3, the negative electrode (III-1) was combined with a non-aqueous electrolyte solution containing a fluorinated solvent (α) and a cyclic carboxylic acid ester compound and having a different ratio of AE3000 and DMC. Then, the calorific value was small compared with Example 17 using the comparative negative electrode.

<Evaluation of positive electrode reactivity>
[Test method]
For the evaluation positive electrode obtained in the following example, a lithium metal foil punched into a circle having a diameter of 19 mm was used as a counter electrode. Between these electrodes, a polyolefin microporous membrane was present as a separator. Furthermore, 0 of a carbonate-based non-aqueous electrolyte (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. manufactured by Kishida Chemical Co., Ltd.) .5 mL was injected to prepare a single electrode cell made of LiCoO ₂ electrode-lithium metal foil.
The following charging / discharging cycle was implemented about the obtained monopolar cell. In cycles 1 to 4, constant current charging was performed up to 4.5 V with a current corresponding to 0.5 C, and further constant voltage charging was performed until the current value reached a current corresponding to 0.02 C at the charging lower limit voltage. Then, constant current discharge was performed to 3.0V with the electric current equivalent to 0.2C. In cycle 5, constant current charging was performed up to 4.5V at a current corresponding to 0.5C, and further constant voltage charging was performed until the current value reached a current corresponding to 0.02C at the charging lower limit voltage.
Thereafter, the obtained single electrode cell in a charged state was decomposed in an argon atmosphere to obtain a charged positive electrode. The obtained positive electrode was washed three times with dimethyl carbonate (2 mL), vacuum-dried and then punched out to a diameter of 5 mm, placed in a sealed container made of SUS, and further sealed with 2 μL of the nonaqueous electrolyte of each example, An evaluation sample was used.
About each obtained evaluation sample, the total calorific value was measured on the conditions of a temperature range of 50-350 degreeC, and the temperature increase rate of 5 degree-C / min with the differential scanning calorimeter (SII nanotechnology company make DSC-6000).

[Example 18 (positive electrode (I))]
LiCoO ₂ (manufactured by AGC Seimi Chemical Co., Ltd., trade name “Selion C”, 32 g) and carbon black (manufactured by Denki Kagaku Kogyo Co., Ltd., trade name “Denka Black”, 0.8 g) are mixed and the agitator is used. The step of stirring for 30 seconds at a rotational speed of 2000 rpm was performed three times. Next, a step of adding a CMC aqueous solution (5.3 g) in which CMC as the resin (AI) was dissolved to 2% by mass and further stirring for 5 minutes at a rotational speed of 2000 rpm using the stirrer 4 I went twice. Further, a 2% by mass CMC aqueous solution (3.4 g) was added, and the mixture was stirred for 10 minutes at a rotational speed of 2000 rpm using the agitator. Thereafter, binder composition-1 (2.4 g) containing the resin (B31-1-I) obtained in Example 1 was added, and the mixture was stirred for 1 minute at a rotational speed of 2000 rpm using the agitator. Got.
The electrode mixture was applied to an Al foil having a thickness of 20 μm to a thickness of 100 μm, dried, and then punched into a circle having a diameter of 18 mm to obtain a positive electrode (I-1).

A single electrode cell was prepared using the positive electrode (I-1) as a positive electrode for evaluation, and the total calorific value was measured by the test method. The total calorific value was measured for a single electrode cell using nonaqueous electrolyte-1 to nonaqueous electrolyte-5 as the nonaqueous electrolyte.
The relationship of the measurement result of the total calorific value with respect to N _A / N _Li is shown in FIG.

[Example 19 (positive electrode for comparison)]
LiCoO ₂ (manufactured by AGC Seimi Chemical Co., Ltd., trade name “Selion C”, 32 g) and carbon black (manufactured by Denki Kagaku Kogyo Co., Ltd., trade name “Denka Black”, 0.8 g) are mixed and the agitator is used. The step of stirring for 1 minute at a rotational speed of 2000 rpm was performed three times. Next, a step of adding N-methyl-2-pyrrolidone (6 g) and stirring for 3 minutes at 2000 rpm using the stirrer was performed three times. Next, the step of adding N-methyl-2-pyrrolidone (0.8 g) and stirring for 3 minutes at 2000 rpm using the stirrer was performed three times. Further, an N-methyl-2-pyrrolidone solution of PVDF (12% by mass, 7.45 g) was added, and the mixture was stirred for 1 minute at a rotational speed of 2000 rpm using the stirrer to obtain an electrode mixture.
The electrode mixture was applied to a thickness of 100 μm on an Al foil having a thickness of 20 μm, dried, and then punched into a circle having a diameter of 18 mm to obtain a comparative positive electrode.

A single electrode cell was prepared using the comparative positive electrode as an evaluation positive electrode, and the total calorific value was measured by the test method. The total calorific value was measured for a single electrode cell using nonaqueous electrolyte-1, nonaqueous electrolyte-3, and nonaqueous electrolyte-5 as the nonaqueous electrolyte.
The relationship of the measurement result of the total calorific value with respect to N _A / N _Li is shown in FIG.

[Example 20 (positive electrode (I))]
A positive electrode (I-1) was produced in the same manner as in Example 18, and the total calorific value was measured by the test method. The total calorific value was measured for single electrode cells using nonaqueous electrolyte-1, nonaqueous electrolyte-6 to nonaqueous electrolyte-9 as the nonaqueous electrolyte.
The relationship of the measurement result of the total calorific value with respect to the LiPF ₆ concentration is shown in FIG.

[Example 21 (positive electrode for comparison)]
A comparative positive electrode was produced in the same manner as in Example 19, and the total calorific value was measured by the above test method. The total calorific value was measured for single electrode cells using nonaqueous electrolyte-1, nonaqueous electrolyte-6 to nonaqueous electrolyte-9, respectively, as nonaqueous electrolytes.
The relationship of the measurement result of the total calorific value with respect to the LiPF ₆ concentration is shown in FIG.

[Example 22 (positive electrode (I))]
A positive electrode (I-1) was produced in the same manner as in Example 18, and the total calorific value was measured by the test method. The total calorific value was measured for a single electrode cell using Nonaqueous Electrolytic Solution-1 and Nonaqueous Electrolytic Solution-10 as the nonaqueous electrolytic solution.
The relationship of the total calorific value measurement result with respect to the AE3000 ratio is shown in FIG.

[Example 23 (positive electrode for comparison)]
A comparative positive electrode was produced in the same manner as in Example 19, and the total calorific value was measured by the above test method. The total calorific value was measured for a single electrode cell using Nonaqueous Electrolytic Solution-1 and Nonaqueous Electrolytic Solution-10 as the nonaqueous electrolytic solution.
The relationship of the total calorific value measurement result with respect to the AE3000 ratio is shown in FIG.

As shown in FIG. 4, in Example 18 using the positive electrode (I-1) produced using both the resin (AI) and the resin (BI), the resin (BI) was not used. The calorific value was smaller than that of Example 19 using the produced comparative negative electrode.
Similarly, as shown in FIG. 5, in Example 20 using the positive electrode (I-1), the calorific value was smaller than in Example 21 using the comparative negative electrode.
Further, as shown in FIG. 6, the calorific value in Example 22 using the positive electrode (I-1) was smaller than that in Example 23 using the negative electrode for comparison.
As a result, in the evaluation of the positive electrode and the non-aqueous electrolyte, and in the evaluation of the negative electrode and the non-aqueous electrolyte, a decrease in the calorific value was observed, and in the secondary battery equipped with the positive electrode, the negative electrode and the non-aqueous electrolyte, the heat was generated similarly. A decrease in the amount can be estimated.

The lithium ion 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, an aircraft, an artificial It can be applied to various uses such as satellites, submarines, ships, uninterruptible power supplies, robots, and power storage systems. The lithium ion secondary battery of the present invention is particularly useful as a large secondary battery for electric vehicles, hybrid vehicles, trains, aircraft, satellites, submarines, ships, uninterruptible power supplies, robots, power storage systems, and the like. is there.
It should be noted that the entire contents of the specification, claims, drawings and abstract of Japanese Patent Application No. 2013-197590 filed on September 24, 2013 are incorporated herein as the disclosure of the present invention. .

Claims (21)

A lithium ion secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte,
At least one of the positive electrode and the negative electrode is an electrode produced by using an electrode mixture containing an active material, a medium, a resin (A) soluble in the medium, and a resin (B) dispersed or emulsified in the medium ,
The non-aqueous electrolyte includes an electrolyte and a liquid composition,
The electrolyte is a lithium salt;
The liquid composition comprises at least one fluorine-containing solvent (α) 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 cyclic carboxylic acid ester compound, A lithium ion secondary battery comprising: A lithium ion secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte,
At least one of the positive electrode and the negative electrode contains an active material, a resin (AI) that is soluble in an aqueous medium, and a resin (BI) that is dispersed or emulsified in an aqueous medium,
The non-aqueous electrolyte includes an electrolyte and a liquid composition,
The electrolyte is a lithium salt;
The liquid composition comprises at least one fluorine-containing solvent (α) 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 cyclic carboxylic acid ester compound, Lithium ion secondary battery.   The resin (AI) soluble in the aqueous medium is a resin having a solubility in water of 0.5% by mass or more, and the resin (BI) dispersed or emulsified in the aqueous medium has a solubility in water. The lithium ion secondary battery of Claim 1 or 2 which is resin less than 0.5 mass%.   The lithium according to any one of claims 1 to 3, wherein the negative electrode includes an active material, a resin (AI) soluble in an aqueous medium, and a resin (BI) dispersed or emulsified in an aqueous medium. Ion secondary battery.   The lithium according to any one of claims 1 to 3, wherein the positive electrode includes an active material, a resin (AI) soluble in an aqueous medium, and a resin (BI) dispersed or emulsified in an aqueous medium. Ion secondary battery. A lithium ion secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte,
At least one of the positive electrode and the negative electrode includes an active material, a resin (A-II) soluble in an organic solvent, and a resin (B-II) dispersed or emulsified in an organic solvent,
The non-aqueous electrolyte includes an electrolyte and a liquid composition,
The electrolyte is a lithium salt;
The liquid composition comprises at least one fluorine-containing solvent (α) 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 cyclic carboxylic acid ester compound, Lithium ion secondary battery.   Resin (A-II) soluble in the organic solvent is a resin having a solubility in N-methyl-2-pyrrolidone of 0.5% by mass or more, and resin (B-II) dispersed or emulsified in the aqueous medium Is a resin having a solubility in N-methyl-2-pyrrolidone of less than 0.5% by mass, according to claim 1 or 6.   The lithium ion secondary battery according to any one of claims 1 to 5, wherein the medium is an aqueous medium. 9. The resin according to claim 1, wherein the resin (AI) is a resin containing at least one selected from the group consisting of Li ⁺ , Na ⁺ , Ca ²⁺ , Mg ²⁺ and NH ₄ ^+. The lithium ion secondary battery according to item.   The lithium ion secondary battery according to any one of claims 1 to 5, 8, or 9, wherein the resin (AI) is carboxymethylcellulose, polyacrylic acid, or a salt thereof.   The lithium ion secondary battery according to any one of claims 1 to 10, wherein the resin (B) is a soft polymer.   The lithium ion secondary battery as described in any one of Claims 1-11 whose average particle diameters of the said resin (B) are 10-1000 nm.   The lithium ion secondary battery according to any one of claims 1 to 12, wherein the positive electrode is a positive electrode that can occlude and release lithium ions and uses a positive electrode active material containing a transition metal as the active material.   The lithium ion secondary battery as described in any one of Claims 1-13 whose said negative electrode is a negative electrode which uses the negative electrode active material containing the carbonaceous material which can occlude and discharge | release lithium ion as said active material. N _A / N _Li which is a ratio of the total number of moles (N _A ) of the cyclic carboxylic acid ester compound to the total number of moles (N _Li ) of lithium atoms derived from the lithium salt is 1 to 10. The lithium ion secondary battery according to any one of 14.   The lithium ion secondary battery according to any one of claims 1 to 15, wherein the fluorine-containing solvent (α) contains a fluorine-containing ether compound. The lithium ion secondary battery according to claim 16, wherein the fluorine-containing ether compound is at least one selected from the group consisting of compounds represented by the following formula (1).
R ¹ —O—R ² (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 , CHF ₂ CF ₂ CH ₂ OCF ₂ CHF ₂ , CF ₃ CF ₂ CH ₂ OCF ₂ CHF ₂ , CF ₃ CH ₂ OCF ₂ CHFCF _3, and _CHF 2 _CF containing at least one selected from the group consisting of 2 _CH 2 _OCF 2 CHFCF _3, lithium ion secondary battery according to claim 17. The lithium ion secondary battery according to any one of claims 1 to 18, wherein the cyclic carboxylic acid ester compound is at least one selected from the group consisting of compounds represented by the following formula (5).

(In the formula, 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 ethers. An alkyl group having 2 to 3 carbon atoms having a reactive oxygen atom, n is an integer of 1 to 3) The lithium salt includes LiPF _6, lithium-ion secondary battery according to any one of claims 1 to 19.   Content of the said lithium salt in the said non-aqueous electrolyte is 0.1-3.0 mol / L, and the ratio of the mass of the said cyclic carboxylic acid ester compound with respect to the total mass of the said non-aqueous electrolyte is 4-70 mass. The lithium ion secondary battery according to any one of claims 1 to 20, which is%.

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