JP7341957B2 - Non-aqueous secondary battery - Google Patents

Description

The present disclosure relates to non-aqueous secondary batteries.

In non-aqueous secondary batteries, an insulating layer or a separator is used to insulate a positive electrode and a negative electrode.
For example, Patent Document 1 or Patent Document 2 describes an active material layer containing a positive electrode active material or a negative electrode active material, and a heat-resistant porous layer containing a heat-resistant polymer and an inorganic filler laminated on the active material layer. An electrode sheet for a non-aqueous electrolyte battery is disclosed.
For example, Patent Document 3 describes a battery element including a positive electrode, a negative electrode, a ceramic separator layer containing a fluororesin and insulating inorganic particles, a lithium ion conductive nonaqueous electrolyte, and an exterior body housing the battery element. A lithium ion secondary battery is disclosed.
For example, Patent Document 4 describes a step of coating an electrode with a composition for forming a separator layer containing two or more types of resin particles having different average particle sizes, and a step of coating the composition for forming a separator layer on an electrode. A process of drying the object from the coated end to form a separator layer on the electrode that is integrated with the electrode, and constructing a secondary battery using the electrode with the separator layer formed, a counter electrode, and an electrolyte. A method for manufacturing a secondary battery is disclosed, which includes the steps of:
For example, Patent Document 5 discloses a separator-electrode integrated power storage for lithium ion secondary batteries, which is formed by bonding and integrating a separator, which is a porous layer containing magnesium hydroxide with an average particle size of 0.5 μm to 3.0 μm, and an electrode. A device is disclosed.
For example, Patent Document 6 discloses a battery including a positive electrode, a negative electrode, and an adhesive resin layer disposed between the positive electrode and the negative electrode and bonding at least one of the positive electrode and the negative electrode, the adhesive resin layer being A battery containing a resin and a filler having an average diameter of 0.01 μm to 1 μm is disclosed.
For example, U.S. Pat. No. 5,002,300 describes the steps of disposing a separator precursor solution containing a solid particulate material and a polymeric binder onto an electrode by screen printing, and converting the separator precursor solution into a porous separator in the form of a thin film. A method of manufacturing a porous separator having the following is disclosed.
For example, Patent Document 8 discloses a nonaqueous secondary battery using a separator including a porous base material and an adhesive porous layer containing a polyvinylidene fluoride resin and having a crystal size of 1 nm to 13 nm. ing.
For example, Patent Document 9 discloses a method comprising a porous base material and an adhesive porous layer containing a polyvinylidene fluoride resin having a weight average molecular weight of 600,000 to 3,000,000 and having a porosity of 30% to 60%. A non-aqueous secondary battery using a separator has been disclosed.
For example, Patent Document 10 discloses an electricity storage device using a separator made of a composite material containing inorganic particles and an organic binder and having a ratio of pigment volume concentration to critical pigment volume concentration of 0.7 to 1.15. There is.
For example, Patent Document 11 describes a current collector, an electrode active material layer formed on one surface of the current collector, and an inorganic and inorganic porous layer formed on the electrode active material layer and containing inorganic particles and a binder polymer. , a porous first support layer formed on an inorganic porous layer, and a sheet-type secondary battery electrode is disclosed.
For example, Patent Document 12 describes a porous base material, a binder resin, and an average primary particle size of 0.01 μm or more. A non-aqueous secondary battery using a separator comprising a heat-resistant porous layer containing barium sulfate particles having a diameter of less than 30 μm and having a volume proportion of barium sulfate particles of 50% to 90% by volume is disclosed.
For example, Patent Document 13 describes a positive electrode having a positive electrode active material layer, a negative electrode having a negative electrode active material layer, a separator, an electrolytic solution, and a positive electrode disposed between the positive electrode active material layer or the negative electrode active material layer and the separator. A lithium ion secondary battery is disclosed that includes an inorganic particle layer containing Al ₂ O ₃ and polyvinylidene fluoride.
For example, Patent Document 14 describes a porous base material, an adhesive porous layer containing a polyvinylidene fluoride resin containing vinylidene fluoride and an acrylic monomer as monomer components and having a melting point of 130° C. to 148° C.; A non-aqueous secondary battery using a separator comprising:

Japanese Patent Application Publication No. 2010-056037 JP2011-108516A Japanese Patent Application Publication No. 2015-191710 Japanese Patent Application Publication No. 2016-177962 Japanese Patent Application Publication No. 2017-123269 Patent No. 4077045 Patent No. 4790880 Patent No. 4988972 Patent No. 5129895 Patent No. 5880555 Patent No. 5938523 Patent No. 6526359 Patent No. 6597267 International Publication No. 2018/212252

Nonaqueous secondary batteries are desired to have excellent discharge characteristics, coulombic efficiency, and cell strength, that is, to have high reliability. The insulating layer, which is one of the components of non-aqueous secondary batteries, is required to have electrical insulation properties, ion permeability, adhesion to electrodes, etc. in order to increase the reliability of non-aqueous secondary batteries. .

The embodiments of the present disclosure were made under the above circumstances.
Embodiments of the present disclosure aim to provide a highly reliable non-aqueous secondary battery, and aim to achieve this.

Specific means for solving the above problem include the following aspects.

<1> A single layer consisting of a positive electrode and a negative electrode, one surface of which is in contact with the positive electrode and the other surface of which is in contact with the negative electrode, in which vinylidene fluoride and a monomer represented by the following general formula (1) are polymerized. A non-aqueous secondary battery comprising an insulating layer containing a polyvinylidene fluoride resin and inorganic particles as components, and an electrolyte.

In general formula (1), R ¹ , R ² and R ³ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, a carboxy group, or a derivative of a carboxy group, and X is a single represents a bond, an alkylene group having 1 to 5 carbon atoms, or an alkylene group having 1 to 5 carbon atoms having a substituent, and Y is substituted with a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or at least one hydroxy group. an alkyl group having 1 to 5 carbon atoms substituted with at least one carboxy group, or -R-O-C(=O)-(CH ₂ ) _n -C(=O )-OH (R represents an alkylene group having 1 to 5 carbon atoms, and n represents an integer of 0 or more).

<2> The non-aqueous secondary battery according to <1>, wherein the inorganic particles include at least one selected from the group consisting of metal hydroxide particles and metal sulfate particles.
<3> The non-aqueous secondary battery according to <1> or <2>, wherein the inorganic particles included in the insulating layer have an average primary particle size of 0.01 μm or more and less than 1.00 μm.
<4> The non-aqueous secondary battery according to any one of <1> to <3>, wherein a mass proportion of the inorganic particles in the insulating layer is 50% by mass or more and less than 90% by mass.
<5> The nonaqueous secondary battery according to any one of <1> to <4>, wherein the insulating layer has a thickness of 5 μm or more and 30 μm or less.
<6> The non-aqueous secondary battery according to any one of <1> to <5>, wherein the insulating layer has a porosity of 40% or more and less than 80%.
<7> The non-aqueous secondary battery according to any one of <1> to <6>, wherein the insulating layer has a mass per unit area of 4 g/m ² or more and less than 40 g/m ² .
<8> The non-aqueous secondary battery according to any one of <1> to <7>, which obtains an electromotive force by doping and dedoping lithium ions.

According to the present disclosure, a highly reliable non-aqueous secondary battery is provided.

FIG. 1 is a schematic diagram showing an embodiment of a non-aqueous secondary battery of the present disclosure.

Embodiments of the present disclosure will be described below. These descriptions and examples are illustrative of the embodiments and do not limit the scope of the embodiments.

In the present disclosure, "A and/or B" is synonymous with "at least one of A and B." That is, "A and/or B" means that it may be only A, only B, or a combination of A and B.

In the present disclosure, a numerical range indicated using "~" indicates a range that includes the numerical values written before and after "~" as the minimum and maximum values, respectively.
In the numerical ranges described step by step in this disclosure, the upper limit or lower limit described in one numerical range may be replaced with the upper limit or lower limit of another numerical range described step by step. . Furthermore, in the numerical ranges described in this disclosure, the upper limit or lower limit of the numerical range may be replaced with the values shown in the Examples.

In the present disclosure, the term "step" is included not only in an independent step but also in the case where the intended purpose of the step is achieved even if the step cannot be clearly distinguished from other steps.

In the present disclosure, when embodiments are described with reference to drawings, the configuration of the embodiments is not limited to the configuration shown in the drawings. Furthermore, the sizes of the members in each figure are conceptual, and the relative size relationships between the members are not limited thereto.

When referring to the amount of each component in the composition in this disclosure, if there are multiple types of substances corresponding to each component in the composition, unless otherwise specified, the amount of each component in the composition is means the total amount of substance.

In the present disclosure, each component may include a plurality of types of particles. When a plurality of types of particles corresponding to each component are present in the composition, the particle size of each component means a value for a mixture of the plurality of types of particles present in the composition, unless otherwise specified.

<Nonaqueous secondary battery>
The technology of the present disclosure relates to a secondary battery whose electrolyte does not contain water, that is, a non-aqueous secondary battery. An example of an embodiment of the nonaqueous secondary battery of the present disclosure is a lithium ion secondary battery that obtains an electromotive force by doping and dedoping lithium ions.

The non-aqueous secondary battery of the present disclosure includes a positive electrode, a negative electrode, an insulating layer, and an electrolyte. The insulating layer is a single layer with one side in contact with the positive electrode and the other side in contact with the negative electrode. The insulating layer contains a polyvinylidene fluoride resin containing vinylidene fluoride and a monomer represented by the following general formula (1) as polymerization components, and inorganic particles. Hereinafter, a polyvinylidene fluoride resin containing vinylidene fluoride and a monomer represented by the following general formula (1) as polymerization components will be referred to as "PVDF resin (1)."

In general formula (1), R ¹ , R ² and R ³ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, a carboxy group, or a derivative of a carboxy group, and X is a single represents a bond, an alkylene group having 1 to 5 carbon atoms, or an alkylene group having 1 to 5 carbon atoms having a substituent, and Y is substituted with a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or at least one hydroxy group. an alkyl group having 1 to 5 carbon atoms substituted with at least one carboxy group, or -R-O-C(=O)-(CH ₂ ) _n -C(=O )-OH (R represents an alkylene group having 1 to 5 carbon atoms, and n represents an integer of 0 or more).

Hereinafter, the "positive electrode" and the "negative electrode" will be collectively referred to as "electrodes." In addition, a "non-aqueous secondary battery" is also simply referred to as a "battery."

Since the insulating layer in the battery of the present disclosure is a single layer, (1) there is no boundary between layers inside the insulating layer, so the discharge characteristics and coulombic efficiency of the battery can be improved; and (2) the inside of the insulating layer Since no delamination occurs between the layers, the electrical resistance of the insulating layer can be kept low, and the Coulombic efficiency and cell strength of the battery can be increased.

In the battery of the present disclosure, the insulating layer includes PVDF-based resin (1). Polyvinylidene fluoride resin, styrene-butadiene copolymer, etc. are used as a binder resin for the electrode active material layer, but PVDF resin (1) is a polyvinylidene fluoride resin, so it can be used as a binder resin for the electrode active material layer. Shows affinity for vinylidene chloride resin, and has affinity for the styrene-butadiene copolymer of the electrode active material layer by having a monomer-derived moiety represented by general formula (1) . An insulating layer containing a resin that has a high affinity for the binder resin of the electrode active material layer adheres well to the electrode and increases the coulombic efficiency and cell strength of the battery.
In addition, when heat pressing is performed on a laminate of electrodes and insulating layers during battery manufacture, the insulating layer containing the resin that has a high affinity for the binder resin of the electrode active material layer is Adheres well to electrodes even under relatively mild pressure conditions. Therefore, an insulating layer containing a resin that has a high affinity for the binder resin of the electrode active material layer maintains ion permeability without blocking the pores of the insulating layer during battery manufacturing, and as a result, the battery Enhances the discharge characteristics of.

The effects of each of the above configurations are synergistic, and the non-aqueous secondary battery of the present disclosure has excellent discharge characteristics, Coulombic efficiency, and cell strength, and therefore has high reliability.

Hereinafter, the configuration of the non-aqueous secondary battery of the present disclosure will be described in detail.

[Positive electrode]
The positive electrode includes, for example, a current collector and a positive electrode active material layer disposed on one or both sides of the current collector.

Examples of the current collector of the positive electrode include metal foil. Examples of the metal foil include aluminum foil, titanium foil, stainless steel foil, and the like. The thickness of the current collector of the positive electrode is preferably 5 μm to 20 μm.

The positive electrode active material layer preferably contains a positive electrode active material and a resin. The positive electrode active material layer may further contain a conductive additive.

Examples of the positive electrode active material include lithium-containing transition metal oxides. Examples of lithium-containing transition metal oxides include LiCoO ₂ , LiNiO ₂ , LiMn _1/2 Ni _1/2 O ₂ , LiCo _1/3 Mn _1/3 Ni _1/3 O ₂ , LiMn ₂ O ₄ , LiFePO ₄ , LiCo _1/2 Ni _1/2 O ₂ , LiAl _1/4 Ni _3/4 O ₂ and the like.

Examples of the resin include polyvinylidene fluoride resin, alginate, and the like.

Examples of the conductive aid include carbon materials. Examples of the carbon material include acetylene black, Ketjen black, and carbon fiber.

[Negative electrode]
The negative electrode includes, for example, a current collector and a negative electrode active material layer disposed on one or both sides of the current collector.

Examples of the negative electrode current collector include metal foil. Examples of the metal foil include copper foil, nickel foil, stainless steel foil, and the like. The thickness of the current collector of the negative electrode is preferably 5 μm to 20 μm.

The negative electrode active material layer preferably contains a negative electrode active material and a resin. The negative electrode active material layer may further contain a conductive additive.

Examples of the negative electrode active material include materials that can electrochemically occlude lithium ions. Examples of the material include carbon materials; alloys of lithium with silicon, silicon compounds, tin, aluminum, etc.; wood alloys; and the like.

Examples of the resin include polyvinylidene fluoride resin, styrene-butadiene copolymer, and carboxymethyl cellulose.

Examples of the conductive aid include carbon materials. Examples of the carbon material include acetylene black, Ketjen black, and carbon fiber.

[Insulating layer]
The insulating layer is a single layer that has many micropores inside and has a porous structure in which these micropores are connected, allowing gas or liquid to pass from one surface to the other. be.

In one embodiment of the insulating layer, one surface is in contact with the positive electrode active material layer, and the other surface is in contact with the negative electrode active material layer.

The insulating layer contains a PVDF resin (1) and inorganic particles. The insulating layer may contain other resins other than the PVDF resin (1), organic fillers, and the like.

-PVDF resin (1)-
The insulating layer contains PVDF resin (1). The PVDF resin (1) contains at least vinylidene fluoride (also referred to as VDF) and a monomer represented by the following general formula (1) as polymerization components.

In general formula (1), R ¹ , R ² and R ³ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, a carboxy group, or a derivative of a carboxy group, and X is a single represents a bond, an alkylene group having 1 to 5 carbon atoms, or an alkylene group having 1 to 5 carbon atoms having a substituent, and Y is substituted with a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or at least one hydroxy group. an alkyl group having 1 to 5 carbon atoms substituted with at least one carboxy group, or -R-O-C(=O)-(CH ₂ ) _n -C(=O )-OH (R represents an alkylene group having 1 to 5 carbon atoms, and n represents an integer of 0 or more).

In general formula (1), the halogen atom represented by R ¹ , R ² and R ³ may be any of a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, with a fluorine atom being preferred.

In the general formula (1), the alkyl group having 1 to 5 carbon atoms represented by R ¹ , R ² and R ³ includes, for example, a linear alkyl group such as a methyl group, an ethyl group, an n-propyl group, n-butyl group, n-pentyl group; branched alkyl groups such as isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, isopentyl group, neopentyl group, and tert-pentyl group; The alkyl group having 1 to 5 carbon atoms in R ¹ , R ² and R ³ is preferably an alkyl group having 1 to 4 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms.

In general formula (1), examples of derivatives of the carboxy group represented by R ¹ , R ² and R ³ include -C(=O)-OR ⁴ (R ⁴ represents an alkyl group). Examples of R ⁴ include linear alkyl groups such as methyl, ethyl, n-propyl, n-butyl, and n-pentyl; branched alkyl groups such as isopropyl and isobutyl. , sec-butyl group, tert-butyl group, isopentyl group, neopentyl group, tert-pentyl group; R ⁴ is preferably an alkyl group having 1 to 5 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, and even more preferably an alkyl group having 1 to 3 carbon atoms.

In general formula (1), examples of the alkylene group having 1 to 5 carbon atoms represented by X include linear alkylene groups such as methylene group, ethylene group, n-propylene group, n-butylene group, n- Pentylene group: branched alkylene groups such as isopropylene group, isobutylene group, sec-butylene group, tert-butylene group, isopentylene group, neopentylene group, and tert-pentylene group; The alkylene group having 1 to 5 carbon atoms in X is preferably an alkylene group having 1 to 4 carbon atoms, more preferably an alkylene group having 1 to 3 carbon atoms.

In the general formula (1), the substituent in the alkylene group having 1 to 5 carbon atoms and having a substituent represented by good. Examples of the substituted alkylene group having 1 to 5 carbon atoms in X include linear alkylene groups such as methylene group, ethylene group, n-propylene group, n-butylene group, and n-pentylene group; Examples of alkylene groups include isopropylene group, isobutylene group, sec-butylene group, tert-butylene group, isopentylene group, neopentylene group, and tert-pentylene group. The substituted alkylene group having 1 to 5 carbon atoms in X is preferably an alkylene group having 1 to 4 carbon atoms, more preferably an alkylene group having 1 to 3 carbon atoms.

In general formula (1), examples of the alkyl group having 1 to 5 carbon atoms represented by Y include linear alkyl groups such as methyl group, ethyl group, n-propyl group, n-butyl group, n- Pentyl group: Branched alkyl groups such as isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, isopentyl group, neopentyl group, and tert-pentyl group. The alkyl group having 1 to 5 carbon atoms in Y is preferably an alkyl group having 1 to 4 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms.

In the general formula (1), the substituted alkyl group having 1 to 5 carbon atoms in the alkyl group having 1 to 5 carbon atoms substituted with at least one hydroxy group represented by Y is, for example, a linear Alkyl groups such as methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group; branched alkyl groups such as isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, Examples include isopentyl group, neopentyl group, and tert-pentyl group. The substituted alkyl group having 1 to 5 carbon atoms in Y is preferably an alkyl group having 1 to 4 carbon atoms, and more preferably an alkyl group having 1 to 3 carbon atoms. The number of hydroxyl group substitutions is preferably one or two, more preferably one.

In general formula (1), examples of the alkyl group having 1 to 5 carbon atoms substituted with at least one hydroxy group represented by Y include 2-hydroxyethyl group, 2-hydroxypropyl group, and 4-hydroxybutyl group. Can be mentioned.

In the general formula (1), the substituted alkyl group having 1 to 5 carbon atoms in the alkyl group having 1 to 5 carbon atoms substituted with at least one carboxy group represented by Y is, for example, a linear Alkyl groups such as methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group; branched alkyl groups such as isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, Examples include isopentyl group, neopentyl group, and tert-pentyl group. The substituted alkyl group having 1 to 5 carbon atoms in Y is preferably an alkyl group having 1 to 4 carbon atoms, and more preferably an alkyl group having 1 to 3 carbon atoms. The number of carboxyl group substitutions is preferably one or two, more preferably one.

In general formula (1), examples of the alkyl group having 1 to 5 carbon atoms substituted with at least one carboxy group represented by Y include 2-carboxyethyl group, 2-carboxypropyl group, and 4-carboxybutyl group. Can be mentioned.

In the general formula (1), in -R-O-C(=O)-(CH ₂ ) _n -C(=O)-OH represented by Y, R represents an alkylene group having 1 to 5 carbon atoms, and n represents an integer greater than or equal to 0.
R is, for example, a linear alkylene group such as a methylene group, ethylene group, n-propylene group, n-butylene group, or n-pentylene group; a branched alkylene group such as an isopropylene group or an isobutylene group. , sec-butylene group, tert-butylene group, isopentylene group, neopentylene group, tert-pentylene group; R is preferably an alkylene group having 1 to 4 carbon atoms, more preferably an alkylene group having 1 to 3 carbon atoms.
n is preferably an integer of 0 to 5, more preferably 1 to 4, and even more preferably 2 or 3.
Specific examples of the group include -(CH ₂ ) ₂ -OC(=O)-(CH ₂ ) ₂ -C(=O)-OH.

In the monomer represented by general formula (1), for example, R ¹ , R ² and R ³ are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and X is a single bond. , Y is an alkyl group having 1 to 4 carbon atoms or an alkyl group having 1 to 3 carbon atoms substituted with at least one hydroxy group.

Examples of the monomer represented by general formula (1) include acrylic monomers, unsaturated dibasic acids, and monoesters of unsaturated dibasic acids.

Examples of acrylic monomers include (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, and (meth)acrylate. isobutyl acid, tert-butyl (meth)acrylate, pentyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, ( Examples include 2-carboxyethyl meth)acrylate, 2-carboxypropyl (meth)acrylate, 4-carboxybutyl (meth)acrylate, butenoic acid, pentenoic acid, hexenoic acid, (meth)acryloyloxyethylsuccinic acid, etc. . In the present disclosure, the expression "(meth)acrylic" means either "acrylic" or "methacrylic".

Examples of unsaturated dibasic acids include unsaturated dicarboxylic acids, more specifically maleic acid, maleic anhydride, citraconic acid, itaconic acid, and the like.

Examples of monoesters of unsaturated dibasic acids include maleic acid monomethyl ester, maleic acid monoethyl ester, citraconic acid monomethyl ester, citraconic acid monoethyl ester, itaconic acid monomethyl ester, itaconic acid monoethyl ester, etc. Among these, maleic acid monomethyl ester and citraconic acid monomethyl ester are preferred.

In the PVDF resin (1), the proportion of the monomer represented by general formula (1) in the total polymerization components is 0.1 mol% or more from the viewpoint of affinity for the resin contained in the electrode active material layer. is preferable, 0.2 mol% or more is more preferable, and even more preferably 0.5 mol% or more.
In the PVDF resin (1), the proportion of the monomer represented by the general formula (1) in the total polymerization components is preferably 5.0 mol% or less from the viewpoint of low influence on the electrode active material. The content is more preferably 4.0 mol% or less, and even more preferably 3.0 mol% or less.

The PVDF resin (1) may contain VDF and other monomers other than the monomer represented by the general formula (1) as a polymerization component. Other monomers include halogen-containing monomers such as hexafluoropropylene, tetrafluoroethylene, trifluoroethylene, chlorotrifluoroethylene, vinyl fluoride, and trichloroethylene.

As the PVDF resin (1), a resin containing hexafluoropropylene (also referred to as HFP) as a polymerization component is preferable. The crystallinity of the PVDF resin (1), the adhesion to the electrode active material layer, the dissolution resistance to the electrolytic solution, etc. can be controlled within appropriate ranges by increasing or decreasing the proportion of HFP in the total polymerization component. .
In the PVDF resin (1), the proportion of HFP in the total polymerization components is preferably more than 2.0 mol%, more preferably more than 3.5 mol%, even more preferably 4.0 mol% or more, and 4.5 It is more preferably mol% or more, preferably 7.0 mol% or less, more preferably 6.5 mol% or less, even more preferably 6.0 mol% or less.

In the PVDF resin (1), the proportion of VDF in the total polymerization components is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, preferably 99 mol% or less, and 98 mol%. % or less is more preferable.

As the PVDF resin (1), a terpolymer consisting of VDF, HFP, and a monomer represented by the general formula (1) is preferable. In the terpolymer, the proportion of the monomer represented by general formula (1) in the total polymerization components is preferably 0.1 mol% or more, more preferably 0.2 mol% or more, and 0.1 mol% or more. It is more preferably 5 mol% or more, preferably 5.0 mol% or less, more preferably 4.0 mol% or less, even more preferably 3.0 mol% or less, and the proportion of HFP in the total polymerization components is 2. More than .0 mol% is preferable, more than 3.5 mol% is more preferable, 4.0 mol% or more is even more preferable, 4.5 mol% or more is still more preferable, 7.0 mol% or less is preferable, 6.5 The content is more preferably mol % or less, and even more preferably 6.0 mol % or less.

As the terpolymer consisting of VDF, HFP, and the monomer represented by general formula (1), a VDF-HFP-acrylic acid terpolymer is preferred. In the acrylic acid terpolymer, the proportion of acrylic acid in the total polymerization components is preferably 0.1 mol% or more, more preferably 0.2 mol% or more, even more preferably 0.5 mol% or more, and 5 0 mol% or less is preferable, 4.0 mol% or less is more preferable, 3.0 mol% or less is still more preferable, and the proportion of HFP in the total polymerization components is preferably more than 2.0 mol%, More preferably more than .5 mol%, still more preferably 4.0 mol% or more, even more preferably 4.5 mol% or more, preferably 7.0 mol% or less, more preferably 6.5 mol% or less, 6. More preferably, it is 0 mol% or less.

The weight average molecular weight (Mw) of the PVDF resin (1) is preferably 300,000 or more, and 500,000 or more, from the viewpoint that pores in the insulating layer are less likely to be clogged when heat is applied to the insulating layer during battery manufacturing. The number is more preferably 1,000,000 or more, and even more preferably 1,000,000 or more.
The weight average molecular weight (Mw) of the PVDF resin (1) is determined from the viewpoint that the resin moderately softens when heat is applied to the insulating layer during battery manufacturing, and the insulating layer and the electrodes adhere well. It is preferably 3,000,000 or less, more preferably 2,500,000 or less, and even more preferably 2,300,000 or less.

The mass proportion of the PVDF resin (1) in the insulating layer is preferably 10% by mass to 50% by mass, more preferably 15% by mass to 50% by mass, and even more preferably 20% by mass to 50% by mass.

The content of the PVDF resin (1) contained in the insulating layer is preferably 85% by mass to 100% by mass, more preferably 90% by mass to 100% by mass, based on the total amount of all resins contained in the insulating layer. More preferably 95% by mass to 100% by mass.

-Other resins-
The insulating layer may contain other resins than the PVDF resin (1). Other resins include, for example, polyvinylidene fluoride resins that do not have ester bonds in the molecule (a homopolymer of VDF (i.e., polyvinylidene fluoride); VDF, hexafluoropropylene, tetrafluoroethylene, trifluoroethylene, chloro Copolymers with halogen-containing monomers such as trifluoroethylene, vinyl fluoride, and trichloroethylene; mixtures thereof), acrylic resins, fluorine rubber, styrene-butadiene copolymers, vinyl nitrile compounds (acrylonitrile, methacrylic nitrile, etc.), carboxymethylcellulose, hydroxyalkylcellulose, polyvinyl alcohol, polyvinyl butyral, polyvinylpyrrolidone, polyether (polyethylene oxide, polypropylene oxide, etc.), polyamide, wholly aromatic polyamide (also called aramid). ), polyimide, polyamideimide, polysulfone, polyketone, polyetherketone, polyethersulfone, polyetherimide, and mixtures thereof.

The content of other resins other than the PVDF resin (1) contained in the insulating layer is preferably 0% by mass to 15% by mass, and 0% by mass to 10% by mass, based on the total amount of all resins contained in the insulating layer. % is more preferable, and 0% to 5% by weight is even more preferable.

-Inorganic particles-
The particle shape of the inorganic particles is not limited, and may be spherical, plate-like, acicular, or irregularly shaped. The inorganic particles are preferably spherical or plate-shaped particles from the viewpoint of suppressing short circuits in the battery or from the viewpoint of being easily packed densely into the insulating layer.

The material of the inorganic particles is not limited. Examples of the inorganic particles include metal hydroxide particles, metal sulfate particles, metal oxide particles, metal carbonate particles, metal nitride particles, metal fluoride particles, clay mineral particles, and the like. One type of inorganic particles may be used alone, or two or more types of different materials may be used in combination.

Examples of metal hydroxide particles include magnesium hydroxide (Mg(OH) ₂ ), aluminum hydroxide (Al(OH) ₃ ), calcium hydroxide (Ca(OH) ₂ ), and nickel hydroxide (Ni(OH) ) ₂ ). As the metal hydroxide particles, magnesium hydroxide particles are preferred.

Examples of metal sulfate particles include barium sulfate (BaSO ₄ ), strontium sulfate (SrSO ₄ ), calcium sulfate (CaSO ₄ ), calcium sulfate dihydrate (CaSO ₄ .2H ₂ O), alumite (KAl ₃ Examples include particles such as (SO ₄ ) ₂ (OH) ₆ ) and jarosite (KFe ₃ (SO ₄ ) ₂ (OH) ₆ ). As the metal sulfate particles, barium sulfate particles are preferred.

Examples of metal oxide particles include magnesium oxide, alumina (Al ₂ O ₃ ), boehmite (AlOOH, alumina monohydrate), titania (TiO ₂ ), silica (SiO ₂ ), zirconia (ZrO ₂ ), and titanium. Examples include particles of barium acid (BaTiO ₃ ), zinc oxide, and the like.

Examples of metal carbonate particles include particles of magnesium carbonate, calcium carbonate, and the like.

Examples of metal nitride particles include particles of magnesium nitride, aluminum nitride, calcium nitride, titanium nitride, and the like.

Examples of metal fluoride particles include particles of magnesium fluoride, calcium fluoride, and the like.

Examples of clay mineral particles include particles of calcium silicate, calcium phosphate, apatite, and talc.

As the inorganic particles, metal hydroxide particles are preferred from the viewpoint of flame retardancy, and metal sulfate particles are preferred from the viewpoint of being stable in the electrolytic solution and suppressing gas generation. Preferably, the inorganic particles include at least one selected from the group consisting of metal hydroxide particles and metal sulfate particles.

The average primary particle size of the inorganic particles contained in the insulating layer is preferably 0.01 μm or more, more preferably 0.02 μm or more, and still more preferably 0.03 μm or more, from the viewpoint of making the insulating layer porous and increasing ion permeability. preferable.
The average primary particle size of the inorganic particles contained in the insulating layer is preferably less than 1.00 μm, more preferably less than 0.95 μm, and still more preferably less than 0.90 μm, from the viewpoint of making the insulating layer thinner and increasing the energy density of the battery. preferable.

Two or more types of inorganic particles having different average primary particle sizes may be used in combination as the inorganic particles, and in that case, it is preferable that the average primary particle size of each is within the above range, and the overall average primary particle size is within the above range. It is preferable that

The average primary particle size of the inorganic particles is determined by measuring the major diameters of 100 randomly selected primary particles during observation using a scanning electron microscope (SEM), and averaging the 100 major diameters. If the primary particle diameter of the inorganic particles is small and it is difficult to measure the major axis of the primary particles by SEM, and/or if the aggregation of the inorganic particles is significant and it is difficult to measure the major axis of the primary particles by SEM, the BET specific surface area of the inorganic particles ( m ² /g), and assuming that the inorganic particles are true spheres, the average primary particle diameter is determined according to the following formula.
Average primary particle size (μm) = 6÷[specific gravity (g/cm ³ )×BET specific surface area (m ² /g)]
The BET specific surface area (m ² /g) is determined by the BET multi-point method, which is a gas adsorption method using nitrogen gas. When measuring by gas adsorption method, nitrogen gas is adsorbed onto inorganic particles at the boiling point of liquid nitrogen (-196°C).

The sample subjected to SEM observation or BET specific surface area measurement is an inorganic particle that is a material forming an insulating layer, or an inorganic particle taken out from an insulating layer. There are no restrictions on the method of taking out inorganic particles from the insulating layer, for example, heating the insulating layer to about 800°C to eliminate the binder resin and taking out the inorganic particles, immersing the insulating layer in an organic solvent and removing the binder resin with the organic solvent. Examples include a method of dissolving inorganic particles and extracting inorganic particles.

The mass proportion of inorganic particles in the insulating layer is set at 50% from the viewpoint of increasing the electrical insulation of the insulating layer, and from the viewpoint of increasing the porosity of the insulating layer to improve ion permeability and improve the discharge characteristics of the battery. It is preferably at least 55% by mass, more preferably at least 60% by mass.
The mass proportion of the inorganic particles in the insulating layer is preferably less than 90 mass% from the viewpoint of increasing the mechanical strength of the insulating layer, improving the adhesion between the insulating layer and the electrode, and increasing the Coulombic efficiency and cell strength of the battery. It is more preferably less than 88% by mass, and even more preferably less than 85% by mass.

-Organic filler-
Examples of organic fillers include crosslinked poly(meth)acrylic acid, crosslinked poly(meth)acrylic acid ester, crosslinked polysilicone, crosslinked polystyrene, crosslinked polydivinylbenzene, crosslinked styrene-divinylbenzene copolymer, melamine resin, and phenol. Examples include particles made of crosslinked polymers such as resins and benzoguanamine-formaldehyde condensates; particles made of heat-resistant polymers such as polysulfone, polyacrylonitrile, aramid, and polyacetal. These organic fillers may be used alone or in combination of two or more.

-Other ingredients-
The insulating layer may contain additives such as a dispersant such as a surfactant, a wetting agent, an antifoaming agent, and a pH adjuster. These may be added to a coating liquid for forming an insulating layer.

[Characteristics of insulating layer]
The thickness of the insulating layer is preferably 5 μm or more from the viewpoint of electrical insulation and mechanical strength of the insulating layer, and preferably 30 μm or less and more preferably 25 μm or less from the viewpoint of ion permeability and battery energy density. More preferably, the thickness is 20 μm or less.

The mass per unit area of the insulating layer is preferably 4 g/m ² or more, more preferably 8 g/m ² or more, and even more preferably 10 g/m ² or more, from the viewpoint of electrical insulation and mechanical strength of the insulating layer. From the viewpoints of ion permeability and battery energy density, it is preferably less than 40 g/m ² , more preferably less than 35 g/m ² , and even more preferably less than 30 g/m ² .

The porosity of the insulating layer is preferably 40% or more, more preferably 45% or more, even more preferably 50% or more, from the viewpoint of ion permeability, and from the viewpoint of electrical insulation and mechanical strength of the insulating layer, It is preferably less than 80%, more preferably less than 75%, even more preferably less than 70%.

The porosity ε (%) of the insulating layer is determined by the following method.
The bulk density d1 of the insulating layer is determined by dividing the mass per unit area of the insulating layer by the thickness of the insulating layer. The true density d0 of the insulating layer is calculated from the following equation (1). Then, the porosity ε (%) of the insulating layer is calculated from the following equation (2).
Formula (1)...d0=100/(resin solid content ratio of insulating layer/density of resin + inorganic particle solid content ratio of insulating layer/density of inorganic particles)
Formula (2)...ε=(1-d1/d0)×100

[Electrolyte]
Examples of the electrolytic solution include a solution in which a lithium salt is dissolved in a non-aqueous solvent.
Examples of the lithium salt include LiPF ₆ , LiBF ₄ , LiClO ₄ , and the like.
Examples of non-aqueous solvents include cyclic carbonates such as ethylene carbonate, propylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, and vinylene carbonate; chain carbonates such as dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, and fluorine-substituted products thereof; Examples include cyclic esters such as γ-butyrolactone and γ-valerolactone. These may be used alone or in combination.

As an electrolyte for a lithium ion secondary battery, a cyclic carbonate and a chain carbonate are mixed at a ratio of cyclic carbonate:chain carbonate=20:80 to 40:60 (mass ratio), and a lithium salt is mixed at a ratio of 0.5 mol/L to 0.5 mol/L. A solution having a concentration of 1.5 mol/L is suitable.

FIG. 1 is an example of an embodiment of a non-aqueous secondary battery of the present disclosure. FIG. 1 is a diagram schematically showing a cross section of a battery. FIG. 1 is an illustration of an embodiment of a non-aqueous secondary battery, and is not intended to limit the embodiment.

A non-aqueous secondary battery 100 shown in FIG. 1 includes a battery element 10, an electrolyte 50, and an exterior material 90. Battery element 10 and electrolyte 50 are housed inside exterior material 90 .

The battery element 10 includes a positive electrode 20, an insulating layer 30, and a negative electrode 40. The battery element 10 has a structure in which at least one layer of a positive electrode 20, an insulating layer 30, and a negative electrode 40 are laminated in this order.

The positive electrode 20 includes a positive electrode current collector 22 and positive electrode active material layers 24 disposed on both sides of the positive electrode current collector 22. The positive electrode active material layer 24 is not disposed at one end of the positive electrode current collector 22, and the positive electrode current collector 22 has, for example, a tab shape.

The negative electrode 40 includes a negative electrode current collector 42 and negative electrode active material layers 44 disposed on both sides of the negative electrode current collector 42. One end of the negative electrode current collector 42 is not provided with the negative electrode active material layer 44 and has, for example, a tab shape.

The insulating layer 30 has one surface in contact with the positive electrode active material layer 24 and the other surface in contact with the negative electrode active material layer 44. The insulating layer 30 is a porous layer, and the insulating layer 30 is impregnated with an electrolytic solution 50.

Examples of the exterior material 90 include metal cans, aluminum laminate film packs, and the like.

The non-aqueous secondary battery 100 includes a positive electrode terminal (not shown) and a negative electrode terminal (not shown) outside the exterior casing 90. A plurality of positive electrode current collectors 22 are connected to the positive electrode terminal, and a plurality of negative electrode current collectors 42 are connected to the negative electrode terminal. A lead tab may be interposed between the positive electrode terminal and the positive electrode current collector 22 (or between the negative electrode terminal and the negative electrode current collector 42).

Examples of the shape of the nonaqueous secondary battery 100 include a square shape, a cylindrical shape, and a coin shape.

[Method for manufacturing non-aqueous secondary battery]
The nonaqueous secondary battery of the present disclosure can be manufactured, for example, by the following manufacturing method. That is,
Step A of forming an insulating layer on the support by a wet coating method or a dry coating method;
Step B of manufacturing a laminate in which an insulating layer is arranged between a positive electrode and a negative electrode;
Step C of performing wet heat press and/or dry heat press on the laminate;
This is a manufacturing method including.

-Process A-
The support means a sheet-like material to which a coating liquid for forming an insulating layer is applied. Examples of the support include a positive electrode, a negative electrode, and a release sheet.

The wet coating method refers to a method in which a coating layer is solidified in a coagulating liquid, and the dry coating method refers to a method in which a coating layer is dried and solidified.

As an embodiment of step A, a step of forming an insulating layer on the active material layer of the positive electrode by a wet coating method or a dry coating method; forming an insulating layer on the active material layer of the negative electrode by a wet coating method or a dry coating method. Step: A step of forming an insulating layer on a release sheet by a wet coating method or a dry coating method.

Hereinafter, an embodiment in which an insulating layer is formed on a support by a wet coating method will be described.

As an embodiment of the wet coating method, a coating liquid containing a resin and inorganic particles is applied onto a support, immersed in a coagulation liquid to solidify the coating layer, and then removed from the coagulation liquid and washed with water and dried. One example is the form.

A coating liquid for forming an insulating layer is prepared by dissolving or dispersing a resin and inorganic particles in a solvent. Components other than the resin and the inorganic particles are dissolved or dispersed in the coating liquid, if necessary.

The solvent used to prepare the coating liquid includes a solvent that dissolves the resin (hereinafter also referred to as a "good solvent"). Examples of good solvents include polar amide solvents such as N-methylpyrrolidone, dimethylacetamide, and dimethylformamide.

The solvent used for preparing the coating liquid preferably contains a phase separation agent that induces phase separation, from the viewpoint of forming an insulating layer having a good porous structure. Therefore, the solvent used for preparing the coating liquid is preferably a mixed solvent of a good solvent and a phase separation agent. It is preferable that the phase separating agent is mixed with a good solvent in an amount that can ensure a viscosity suitable for coating. Examples of the phase separation agent include water, methanol, ethanol, propyl alcohol, butyl alcohol, butanediol, ethylene glycol, propylene glycol, tripropylene glycol, and the like.

From the viewpoint of forming an insulating layer with a good porous structure, the solvent used for preparing the coating liquid is a mixed solvent of a good solvent and a phase separation agent, containing 60% by mass or more of a good solvent, and a phase separation agent. A mixed solvent containing 5% to 40% by weight of the agent is preferred.

The resin concentration of the coating liquid is preferably 3% by mass to 10% by mass from the viewpoint of forming an insulating layer having a good porous structure. The concentration of inorganic particles in the coating liquid is preferably 2% by mass to 50% by mass from the viewpoint of forming an insulating layer having a good porous structure.

The coating liquid may contain a dispersant such as a surfactant, a wetting agent, an antifoaming agent, a pH adjuster, and the like. These additives may remain in the insulating layer as long as they are electrochemically stable within the range of use of the non-aqueous secondary battery and do not inhibit reactions within the battery.

Examples of the means for applying the coating liquid to the support include a Mayer bar, a die coater, a reverse roll coater, a roll coater, a gravure coater, a knife coater, and the like.

Solidification of the coating layer is performed by immersing the support on which the coating layer is formed in a coagulating liquid, and solidifying the resin while inducing phase separation in the coating layer. This yields a composite in which the insulating layer is disposed on the support.

The coagulating liquid generally contains water and the good solvent and phase separation agent used in preparing the coating liquid. The mixing ratio of the good solvent and the phase separating agent is preferably adjusted to the mixing ratio of the mixed solvent used for preparing the coating liquid in terms of production. The content of water in the coagulation liquid is preferably 40% by mass to 90% by mass from the viewpoint of forming the porous structure of the insulating layer and productivity. The temperature of the coagulating liquid is, for example, 20°C to 50°C.

After the coating layer is solidified in the coagulation liquid, the composite is lifted from the coagulation liquid and washed with water. The coagulation liquid is removed from the composite by washing with water. Furthermore, water is removed from the composite by drying. Water washing is performed, for example, by transporting the composite in a water bath. Drying is performed, for example, by transporting the composite in a high-temperature environment, by blowing air on the composite, by bringing the composite into contact with a heat roll, or the like. The drying temperature is preferably 40°C to 80°C. In order to prevent the water in the insulating layer from coming into contact with the electrolyte, it is preferable to perform vacuum drying at a high temperature (for example, 80° C. to 110° C.) from the viewpoint of removing as much water as possible from the insulating layer.

The insulating layer can also be formed by a dry coating method. As an embodiment of the dry coating method, an insulating layer is formed on the support by applying a coating liquid to the support, drying the coating layer, and removing the solvent by volatilization.

-Process B-
Examples of embodiments of step B include an embodiment in which a positive electrode and a negative electrode in which an insulating layer is formed on a negative electrode active material layer are stacked together; an embodiment in which a negative electrode and a positive electrode in which an insulating layer is formed on a positive electrode active material layer are stacked; Examples include an embodiment in which a positive electrode, an insulating layer peeled off from a release sheet, and a negative electrode are stacked.

The method of arranging the insulating layer between the positive electrode and the negative electrode may be a method of laminating at least one layer of the positive electrode, the insulating layer, and the negative electrode in this order (so-called stacking method). It may also be a method of stacking them in order and winding them in the length direction.

-Process C-
Wet heat press means that the insulating layer is impregnated with electrolyte and heat press is performed, and dry heat press is that heat press is performed without impregnating the coating layer with electrolyte. do.

Examples of embodiments of step C include the following (1) to (3).

(1) Place the laminate in an exterior material (for example, an aluminum laminate film pack; the same applies hereinafter), inject electrolyte into it, create a vacuum inside the exterior material, and wet the laminate from above the exterior material. Heat press to bond the electrode and insulating layer and seal the exterior material.

(2) After dry heat pressing the laminate to bond the electrode and insulating layer, place it in an exterior material, inject an electrolyte into it, create a vacuum inside the exterior material, and then seal the exterior material. I do.

(3) After dry heat pressing the laminate to bond the electrode and insulating layer, place it in an exterior material, inject an electrolyte into it, create a vacuum inside the exterior material, and then press the top of the exterior material. Furthermore, the laminate is subjected to wet heat pressing to bond the electrodes and the insulating layer and to seal the exterior material.

As for the hot press conditions in the manufacturing methods (1) to (3) above, the press pressure is preferably 0.1 MPa to 10.0 MPa and the temperature is preferably 60°C to 100°C for dry heat press and wet heat press, respectively. .

The non-aqueous secondary battery of the present disclosure will be described in more detail with reference to Examples below. The materials, amounts used, proportions, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present disclosure. Therefore, the scope of the non-aqueous secondary battery of the present disclosure should not be interpreted to be limited by the specific examples shown below.

<Measurement method, evaluation method>
The measurement methods and evaluation methods applied to the Examples and Comparative Examples are as follows.

[Ratio of monomers constituting polyvinylidene fluoride resin]
10 mg of polyvinylidene fluoride resin was dissolved in 0.6 mL of heavy dimethyl sulfoxide at 100°C, and ^{the 19} F-NMR spectrum was measured at 100°C, and ^{the 1} H-NMR spectrum was measured at room temperature. The proportion of monomers constituting the polyvinylidene fluoride resin was determined from the ratio of the peak intensities derived from the monomers in the NMR spectrum.

[Thickness of insulation layer]
The thickness of the electrode (μm) and the thickness (μm) of the composite with an insulating layer placed on the electrode are measured using a contact thickness meter (LITEMATIC VL-50, Mitutoyo Co., Ltd.) of 5 cm x 3 cm. It was determined by measuring 20 points within a rectangle and averaging them. A cylindrical terminal with a diameter of 5 mm was used as the measurement terminal, and adjustments were made so that a load of 0.01 N was applied during the measurement. Then, the value obtained by subtracting the thickness of the electrode from the thickness of the composite was defined as the thickness (μm) of the insulating layer.

[Mass per unit area of insulating layer]
The electrode and the composite body with an insulating layer arranged on the electrode are each cut into a rectangle of 5 cm x 3 cm, the mass (g) of each is measured, and the mass is divided by the area (0.0015 m ² ) to obtain the unit. The mass per area (g/m ² ) was determined. Then, the value obtained by subtracting the mass per unit area of the electrode from the mass per unit area of the composite was defined as the mass per unit area of the insulating layer (g/m ² ).

[Porosity of insulating layer]
The porosity ε (%) of the insulating layer was determined by the method described above.

[Average primary particle size of inorganic particles]
The average primary particle size of the inorganic particles is determined by using the inorganic particles as a sample before being added to the coating solution for forming an insulating layer, and observing 100 randomly selected primary particles using a scanning electron microscope (SEM). It was determined by measuring the major axis and averaging the 100 major axes.

[Discharge characteristics]
The battery was subjected to 5 cycles of charging and discharging as described in (a) below, and then 1 cycle of charging and discharging as described in (b) below.
(a) Constant current constant voltage charging at 4 mA/4.2V for 15 hours and constant current discharging at 4 mA/2.5V cutoff (b) Constant current constant voltage charging at 8 mA/4.2V for 8 hours, and , constant current discharge at 200 mA/2.5 V cutoff The discharge capacity in (b) above was divided by the discharge capacity at the 5th cycle in (a) above, and the obtained value was taken as the discharge characteristic of the battery. Using the discharge characteristics of Reference Example 1 as a reference value, the percentages of the discharge characteristics of Examples and Comparative Examples relative to Reference Example 1 were calculated and classified as follows.
A: 95% or more B: 85% or more and less than 95% C: 70% or more and less than 85% D: Less than 70%

[Coulombic efficiency]
The discharge capacity at the first cycle in (a) above was divided by the charge capacity, and the obtained value was taken as the coulombic efficiency of the battery. Using the coulombic efficiency of Reference Example 1 as a reference value, the percentages of the coulombic efficiencies of Examples and Comparative Examples with respect to Reference Example 1 were calculated and classified as follows.
A: 95% or more B: 85% or more and less than 95% C: 70% or more and less than 85% D: Less than 70%

[Cell strength]
The battery was subjected to a three-point bending test according to ISO 178, and the maximum load (N) at which the battery broke was determined. Using the maximum load of Reference Example 1 as a reference value, the percentage of each of the maximum loads of Examples and Comparative Examples with respect to Reference Example 1 was calculated and classified as follows.
A: 90% or more B: Less than 90%

<Manufacture of non-aqueous secondary batteries>
[Example 1]
-Preparation of positive electrode-
A slurry was prepared by kneading 94 parts by mass of lithium cobalt oxide powder, 3 parts by mass of acetylene black, 3 parts by mass of polyvinylidene fluoride resin, and an appropriate amount of N-methyl-2-pyrrolidone. The slurry was applied onto a 20 μm thick aluminum foil, dried and then pressed to obtain a positive electrode (single-sided coating, basis weight 20.5 mg/cm ² , density 2.95 g/cm ³ ).

-Preparation of negative electrode-
A slurry was prepared by kneading 96.2 parts by mass of graphite powder, 2.8 parts by mass of a modified styrene-butadiene copolymer, 1.0 parts by mass of carboxymethyl cellulose, and an appropriate amount of water. The slurry was applied onto a 15 μm thick copper foil, dried and then pressed to obtain a negative electrode (single-sided coating, basis weight 10.0 mg/cm ² , density 1.60 g/cm ³ ).

-Preparation of insulating layer-
A VDF-HFP-acrylic acid terpolymer was prepared in which the proportion of HFP in the total polymerization components was 2.4 mol% and the proportion of acrylic acid in the total polymerization components was 0.5 mol%. This resin is called PVDF resin (A).

After dissolving the PVDF resin (A) in a mixed solvent of dimethylacetamide (DMAc) and tripropylene glycol (TPG) (DMAc:TPG=80:20 [mass ratio]) so that the concentration is 5% by mass. , magnesium hydroxide particles (average primary particle size 0.88 μm) were added and mixed with stirring to obtain a coating liquid (A). The mass ratio of the PVDF resin (A) to the magnesium hydroxide particles (PVDF resin (A):magnesium hydroxide particles) was 20:80.

The coating liquid (A) was applied onto the active material layer of the negative electrode using a knife coater. This was immersed in a coagulation solution (DMAc:water = 50:50 (mass ratio), liquid temperature 25°C) for 5 minutes to solidify the coating layer, and then washed for 1 minute in a washing tank with a water temperature of 25°C. This was taken out of the washing tank, placed in a constant temperature bath at 70°C, dried for 15 minutes, and then dried under reduced pressure at 110°C for 3 hours. In this way, a composite body in which an insulating layer was disposed on the negative electrode was obtained.

-Battery production-
The positive electrode was cut out to a size of 5.0 cm x 3.0 cm, and the composite body in which an insulating layer was arranged on the negative electrode was cut out to a size of 5.2 cm x 3.2 cm, and lead tabs were welded to each piece. The positive electrode and the composite were stacked so that the positive electrode active material layer and the insulating layer were in contact with each other to obtain a laminate. The laminate was impregnated with an electrolyte and enclosed in an aluminum laminate film exterior material. Heat pressing (85° C., 0.5 MPa, 2 minutes) was performed on the exterior material to bond the electrode and the insulating layer, and a battery was obtained. 1 mol/L LiPF ₆ -ethylene carbonate:ethyl methyl carbonate (mass ratio 3:7) was used as the electrolyte. The set capacity of the battery was 40 mAh (range 4.2V-2.5V).

[Examples 2 to 9, Comparative Examples 1 to 3]
Each battery was produced in the same manner as in Example 1, except that the material, composition, and thickness of the insulating layer were set to the specifications listed in Table 1.
The PVDF resin (B) used in Example 6 etc. was a VDF in which the proportion of HFP in the total polymerization components was 5.7 mol%, and the proportion of acrylic acid in the total polymerization components was 0.8 mol%. -HFP-acrylic acid terpolymer.
The PVDF resin (C) used in Comparative Example 3 is a VDF-HFP binary copolymer in which the proportion of HFP in the total polymerization component is 2.5 mol%.
In Examples 5 and 9, magnesium hydroxide particles and barium sulfate particles were used together in a ratio of magnesium hydroxide particles to barium sulfate particles of 50:50 (mass ratio).

[Reference example 1]
-Production of separator consisting of three layers-
An equal amount of the coating liquid (A) was applied to both sides of a polyethylene microporous membrane (thickness: 7 μm, porosity: 36%, Gurley value: 120 seconds/100 mL) using a reverse roll coater. This was immersed in a coagulation solution (DMAc:water = 50:50 (mass ratio), liquid temperature: 40°C) to solidify the coating layer, then washed in a washing tank with a water temperature of 40°C, and dried. In this way, a separator was obtained in which coating layers were formed on both sides of the polyethylene microporous membrane.

-Battery production-
A positive electrode and a negative electrode in Example 1 were prepared. The positive electrode was cut into a size of 5.0 cm x 3.0 cm, and the negative electrode was cut into a size of 5.2 cm x 3.2 cm, and a lead tab was welded to each piece. The separator was cut into a size of 5.4 cm x 3.4 cm.
A laminate was obtained by stacking the positive electrode, separator, and negative electrode in this order so that the electrode active material layer and the separator were in contact with each other. The laminate was impregnated with an electrolytic solution (the same electrolytic solution used in Example 1), and the laminate was enclosed in an aluminum laminate film exterior material. Heat pressing (85° C., 0.5 MPa, 2 minutes) was performed on the exterior material to bond the electrode and separator, and a battery was obtained.

Table 1 shows the composition, physical properties, and evaluation results of each battery of Examples 1 to 9, Comparative Examples 1 to 3, and Reference Example 1.

100 Nonaqueous secondary battery 10 Battery element 20 Positive electrode 22 Positive electrode current collector 24 Positive electrode active material layer 30 Insulating layer 40 Negative electrode 42 Negative electrode current collector 44 Negative electrode active material layer 50 Electrolyte 90 Exterior material

Claims (8)

a positive electrode;
a negative electrode;
A polyvinylidene fluoride resin which is a single layer with one surface in contact with the positive electrode and the other surface in contact with the negative electrode, and which contains vinylidene fluoride and a monomer represented by the following general formula (1) as polymerization components; an insulating layer containing inorganic particles;
electrolyte and
A non-aqueous secondary battery comprising:

In general formula (1), R ¹ , R ² and R ³ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, a carboxy group, or a derivative of a carboxy group, and X is a single represents a bond, an alkylene group having 1 to 5 carbon atoms, or an alkylene group having 1 to 5 carbon atoms having a substituent, and Y is substituted with a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or at least one hydroxy group. an alkyl group having 1 to 5 carbon atoms substituted with at least one carboxy group, or -R-O-C(=O)-(CH ₂ ) _n -C(=O )-OH (R represents an alkylene group having 1 to 5 carbon atoms, and n represents an integer of 0 or more). The non-aqueous secondary battery according to claim 1, wherein the inorganic particles include at least one selected from the group consisting of metal hydroxide particles and metal sulfate particles. The nonaqueous secondary battery according to claim 1 or 2, wherein the inorganic particles contained in the insulating layer have an average primary particle size of 0.01 μm or more and less than 1.00 μm. The nonaqueous secondary battery according to any one of claims 1 to 3, wherein a mass proportion of the inorganic particles in the insulating layer is 50% by mass or more and less than 90% by mass. The nonaqueous secondary battery according to any one of claims 1 to 4, wherein the insulating layer has a thickness of 5 μm or more and 30 μm or less. The nonaqueous secondary battery according to any one of claims 1 to 5, wherein the insulating layer has a porosity of 40% or more and less than 80%. The nonaqueous secondary battery according to any one of claims 1 to 6, wherein the insulating layer has a mass per unit area of 4 g/m ² or more and less than 40 g/m ² . The nonaqueous secondary battery according to any one of claims 1 to 7, wherein the electromotive force is obtained by doping and dedoping with lithium ions.