WO2024071057A1

WO2024071057A1 - Member for electrochemical element electrode, and electrochemical element

Info

Publication number: WO2024071057A1
Application number: PCT/JP2023/034795
Authority: WO
Inventors: 明彦宮崎; 健彦片山
Original assignee: 日本ゼオン株式会社
Priority date: 2022-09-30
Filing date: 2023-09-25
Publication date: 2024-04-04

Abstract

One purpose of the present invention is to provide a member for an electrochemical element electrode, said member being able to impart superior cycle characteristics to the electrochemical element while ensuring that the electrochemical element is highly safe. The present invention is a member for an electrochemical element electrode, said member comprising a current collector and a conductive thermal expansion material-including section that is located on the current collector, wherein the percentage of coverage by the conductive thermal expansion material of a current collector-side positioning surface of the conductive thermal expansion material-including section is 20% to 98%, and the product of this percentage of coverage and the average particle size of the conductive thermal expansion material is 500 to 15000.

Description

Electrode member for electrochemical element and electrochemical element

The present invention relates to an electrochemical element electrode member and an electrochemical element.

Electrochemical elements such as lithium ion secondary batteries, electric double layer capacitors, and lithium ion capacitors are small, lightweight, have high energy density, and can be repeatedly charged and discharged, and are used in a wide range of applications. Electrochemical elements generally have multiple electrodes and separators that isolate these electrodes and prevent internal short circuits.

In recent years, techniques have been developed to suppress abnormal heat generation in an electrochemical element even when an internal short circuit occurs in the electrochemical element.
For example, in Patent Document 1, a secondary battery having a positive electrode, a negative electrode, and an electrolyte is proposed, in which the positive electrode comprises a positive electrode current collector, an intermediate layer formed on the positive electrode current collector, and a positive electrode composite layer formed on the intermediate layer, the intermediate layer contains a predetermined thermally expandable material and an insulating inorganic material, and the contents of these materials are within a predetermined range. In a secondary battery having such a positive electrode, when an internal short circuit occurs, the insulating inorganic material in the intermediate layer becomes a resistance component between the positive electrode current collector and the positive electrode composite layer, and a sudden drop in resistance is suppressed, and the heat generation speed (temperature rise speed) of the secondary battery is mitigated. Then, before the battery temperature of the secondary battery becomes high, the thermally expandable material contained in a predetermined amount in the intermediate layer thermally expands, and the positive electrode composite layer and the intermediate layer or the positive electrode current collector and the intermediate layer are separated, and the electrical connection between the positive electrode composite layer and the positive electrode current collector via the intermediate layer is interrupted, and as a result, the increase in the heat generation temperature of the secondary battery is suppressed, that is, the maximum temperature reached by the secondary battery is reduced.

Patent No. 6857862

However, although conventional electrochemical elements such as secondary batteries are excellent in terms of suppressing abnormal heat generation and ensuring a high level of safety, there is still room for improvement in terms of the cycle characteristics of the electrochemical elements.

The present inventors have conducted extensive research with the aim of solving the above problems. The present inventors have newly discovered that the above problems can be solved by using an electrochemical element electrode member that includes a current collector and a conductive thermal expansion material-containing portion located on the current collector, in which the coverage of the conductive thermal expansion material on the current collector side surface of the conductive thermal expansion material-containing portion is within a predetermined range, and the product of the coverage and the average particle size of the conductive thermal expansion material is within a predetermined range, and thus have completed the present invention.

That is, the present invention aims to advantageously solve the above-mentioned problems, and provides: [1] an electrochemical element electrode member comprising a current collector and a conductive thermally expandable material-containing portion located on the current collector, wherein a coverage rate of the conductive thermally expandable material on a current collector side arrangement surface of the conductive thermally expandable material-containing portion is 20% or more and 98% or less, and the product of the coverage rate and an average particle diameter of the conductive thermally expandable material is 500 or more and 15,000 or less.
The above-mentioned electrochemical device electrode member can provide the electrochemical device with excellent cycle characteristics while ensuring a high level of safety of the electrochemical device.
In this specification, the term "conductive thermal expansion material" refers to a material that is conductive and has a thermal expansion coefficient of at least 2 times that measured according to the method described in the Examples. Note that in this specification, "conductive" means that the electrical conductivity is at least 1 S/m.
In this specification, the average particle diameter of the conductive thermal expansion material in the conductive thermal expansion material-containing portion (hereinafter, sometimes referred to as "average particle diameter A") can be measured using a field emission scanning electron microscope (FE-SEM) according to the method described in the examples.
In this specification, the coverage can be measured using an FE-SEM according to the method described in the Examples. In this specification, the unit of coverage is "%" and the unit of average particle size A is "μm". Therefore, although omitted, the unit of the product of the coverage and the average particle size A is "μm·%".

[2] In the electrochemical element electrode member according to the above [1], it is preferable that the coverage is 30% or more and the product is 1,500 or more.
If the coverage is equal to or greater than the above lower limit and the product is equal to or greater than the above lower limit, the safety of the electrochemical device can be improved.

[3] In the electrochemical element electrode member according to [1] above, it is preferable that the coverage is 95% or less, the average particle size is 20 μm or more and 160 μm or less, and the product is 9,500 or less.
When the coverage is equal to or less than the above upper limit, the average particle size is within the above range, and the product is equal to or less than the above upper limit, the cycle characteristics of the electrochemical device can be improved.

[4] In the electrochemical element electrode member according to [1] above, it is preferable that the coverage is 30% or more and 95% or less, the average particle size is 20 μm or more and 160 μm or less, and the product is 1,500 or more and 9,500 or less.
When the coverage rate is within the above range, the average particle size is within the above range, and the product is within the above range, the safety and cycle characteristics of the electrochemical device can be improved.

[5] In the electrochemical element electrode member according to any one of the above [1] to [4], the conductive thermal expansion material preferably has an average thickness of 0.2 μm or more and 5 μm or less.
When the average thickness of the conductive thermal expansion material is within the above range, the conductive thermal expansion material is effectively disposed in the conductive thermal expansion material-containing portion, and the safety of the electrochemical element can be improved.
In this specification, the average thickness of the conductive thermal expansion material in the conductive thermal expansion material-containing portion (hereinafter, sometimes referred to as "average thickness A") can be measured using an FE-SEM according to the method described in the examples.

[6] In the electrochemical element electrode member according to any one of the above [1] to [5], the conductive thermal expansion material is preferably expandable graphite.
If the conductive thermal expansion material is expanded graphite, the safety of the electrochemical device can be improved.

[7] In the electrochemical element electrode member according to any one of the above [1] to [6], the conductive thermal expansion material-containing portion is preferably a coating layer.
If the conductive thermal expansion material-containing portion is a coating layer, the productivity of the electrochemical element electrode member can be improved.

[8] In the electrochemical element electrode member according to the above [7], it is preferable that the coating layer is formed directly on the surface of the current collector.
If the coating layer is formed directly on the surface of the current collector, the cycle characteristics of the electrochemical element can be improved.

[9] In any one of the electrochemical element electrode members [1] to [8] above, it is preferable that the conductive thermal expansion material-containing portion further contains a conductive assistant, and the mass ratio of the conductive assistant to the conductive thermal expansion material is 0.01 or more and 0.5 or less.
If the conductive thermal expansion material-containing portion further contains a conductive assistant, it is possible to impart more excellent cycle characteristics to the electrochemical element.
Furthermore, when the mass ratio of the conductive assistant to the conductive thermal expansion material is equal to or more than the above lower limit, the cycle characteristics of the electrochemical device can be improved.
On the other hand, when the mass ratio of the conductive assistant to the conductive thermal expansion material is equal to or less than the above upper limit, the safety of the electrochemical device can be improved.
In this specification, the term "conductive assistant" refers to a material that has electrical conductivity and has a thermal expansion coefficient that is less than twice that of the conductive thermal expansion material, as measured by the same method.

[10] In the electrochemical element electrode member according to any one of the above [1] to [9], it is preferable that the conductive thermal expansion material-containing portion further contains a binder.
If the electrically conductive thermally expandable material-containing portion further contains a binder, the cycle characteristics of the electrochemical device can be improved.

[11] It is preferable that the electrochemical element electrode member according to any one of [1] to [10] above comprises an electrode mixture layer, the electrode mixture layer having a first surface located on the current collector side and a second surface located on the opposite side to the first surface, and the conductive thermal expansion material-containing portion is located between the current collector and the second surface.
By using the above-mentioned electrochemical device electrode member as an electrode, it is possible to impart excellent cycle characteristics to the electrochemical device while ensuring a high level of safety of the electrochemical device.

The present invention also aims to advantageously solve the above problems, and [12] the present invention is an electrochemical element comprising an electrode formed using the electrochemical element electrode member according to any one of [1] to [11] above.
The electrochemical element described above ensures a high degree of safety and has excellent cycle characteristics.

According to the present invention, it is possible to provide an electrode member for an electrochemical device that can impart excellent cycle characteristics to an electrochemical device while ensuring a high level of safety of the electrochemical device.
Furthermore, according to the present invention, it is possible to provide an electrochemical element which is highly safe and has excellent cycle characteristics.

1 is a schematic cross-sectional view showing an example of an electrochemical element electrode member of the present invention. 1 is a schematic cross-sectional view showing an example of an electrochemical element electrode member of the present invention. 1 is a schematic cross-sectional view showing an example of an electrochemical element electrode member of the present invention. 1 is a graph summarizing the safety evaluation results in Examples 1-1 to 11-8 and Comparative Examples 1-1 to 13-11. 1 is a graph summarizing evaluation results of cycle characteristics in Examples 1-1 to 11-8 and Comparative Examples 1-1 to 13-11.

Hereinafter, an embodiment of the present invention will be described in detail.
Here, the electrochemical element electrode member of the present invention (hereinafter may be simply referred to as "electrode member") is used for an electrochemical element electrode (hereinafter may be simply referred to as "electrode"). Specifically, the electrochemical element electrode member of the present invention may (1) not have an electrode mixture layer and be used as a substrate when forming an electrode mixture layer to manufacture an electrode, or (2) have an electrode mixture layer and be used as an electrode as it is. Here, the electrochemical element electrode can be used as an electrode for electrochemical elements such as a lithium ion secondary battery, an electric double layer capacitor, and a lithium ion capacitor.
The electrochemical device of the present invention includes an electrode formed using the electrochemical device electrode member of the present invention.

(Electrode member for electrochemical element)
The electrochemical element electrode member of the present invention comprises a current collector and a conductive thermal expansion material-containing portion located on the current collector, and may optionally comprise an electrode mixture layer. The electrode member of the present invention may also comprise a layer other than the current collector, the conductive thermal expansion material-containing portion, and the electrode mixture layer (hereinafter, sometimes referred to as "other layers"). The electrode member of the present invention may or may not have an electrode mixture layer. An electrochemical element electrode member that does not have an electrode mixture layer can be used as a substrate when forming an electrode mixture layer to manufacture an electrode, and an electrochemical element electrode member that has an electrode mixture layer can be used as an electrode as it is.
The electrode member of the present invention can be used for either the positive electrode or the negative electrode of an electrochemical element, but is preferably used for the positive electrode, i.e., the electrode member of the present invention is preferably a positive electrode member.

Figures 1 to 3 are schematic cross-sectional views showing an example of an electrochemical element electrode member of the present invention. Of these, the electrochemical element electrode member shown in Figure 1 does not have an electrode mixture layer and is used as a substrate when manufacturing an electrode by forming an electrode mixture layer on top, while the electrochemical element electrode members shown in Figures 2 and 3 have an electrode mixture layer and are used as an electrode as is. Each figure will be explained below.

1 includes a current collector 11 and a conductive thermal expansion material-containing portion 12 located on the current collector 11. The conductive thermal expansion material-containing portion 12 contains a conductive thermal expansion material 121. The conductive thermal expansion material-containing portion 12 has a current collector side mounting surface 122.
In FIG. 1, the collector side mounting surface 122 is the surface of the collector 11, but if another layer (not shown) is present between the collector 11 and the conductive thermal expansion material-containing portion 12, the collector side mounting surface 122 becomes the surface of that other layer.

The electrochemical element electrode member 20 shown in Fig. 2 includes a current collector 11, a conductive thermal expansion material-containing portion 12 located on the current collector 11, and an electrode mixture layer 21. The electrode mixture layer 21 has a first surface 211 located on the current collector 11 side (lower side in Fig. 2) and a second surface 212 located on the opposite side to the first surface 211 (upper side in Fig. 2). Here, the conductive thermal expansion material-containing portion 12 is located between the current collector 11 and the second surface 212.
2 , the conductive thermal expansion material-containing portion 12 contains a conductive thermal expansion material 121, and is located inside the electrode mixture layer 21 (in other words, it constitutes a part of the electrode mixture layer 21). That is, the electrode mixture layer 21 includes the conductive thermal expansion material-containing portion 12. The current collector side arrangement surface 122 of the conductive thermal expansion material-containing portion 12 is the surface of the current collector 11.

The electrochemical element electrode member 20 shown in Fig. 3 includes a current collector 11, a conductive thermal expansion material-containing portion 12 located on the current collector 11, and an electrode mixture layer 21. The electrode mixture layer 21 has a first surface 211 located on the current collector 11 side (lower side in Fig. 3) and a second surface 212 located on the opposite side to the first surface 211 (upper side in Fig. 3). Here, the conductive thermal expansion material-containing portion 12 is located between the current collector 11 and the second surface 212, but unlike Fig. 2, the conductive thermal expansion material-containing portion 12 located on the current collector 11 constitutes a layer separate from the electrode mixture layer 21.
3 , the conductive thermal expansion material-containing portion 12 contains a conductive thermal expansion material 121, and is located between the current collector 11 and the first surface 211. The current collector-side arrangement surface 122 of the conductive thermal expansion material-containing portion 12 is the surface of the current collector 11.
3 , when the conductive thermal expansion material-containing portion 12 is located between the current collector 11 and the first surface 211, the current collector-side mounting surface 122 refers to the surface of the current collector 11 only in a portion where the electrode mixture layer 21 is present on the conductive thermal expansion material-containing portion 12. In other words, the surface of the current collector 11 in a portion where the electrode mixture layer 21 is not present on the conductive thermal expansion material-containing portion 12 (for example, the surface of the current collector 11 in a portion where the conductive thermal expansion material-containing portion 12 is exposed) does not correspond to the current collector-side mounting surface 122.

Here, the electrode member of the present invention comprises a current collector and a conductive thermal expansion material-containing portion located on the current collector, and the coverage of the conductive thermal expansion material on the current collector side surface of the conductive thermal expansion material-containing portion is 20% or more and 98% or less, and the product of the coverage and the average particle size A is 500 or more and 15,000 or less. With such an electrode member, it is possible to impart excellent cycle characteristics to an electrochemical element while ensuring a high level of safety of the electrochemical element. The reason for this is presumed to be as follows.
First, when a short circuit occurs inside the electrochemical element due to contamination of the inside of the electrochemical element, poor electrode manufacturing, or design error of the electrochemical element, a current flows through the short circuit portion, generating Joule heat. When the separator melts due to this Joule heat and the area of the short circuit portion expands, the electrochemical element is considered to generate abnormal heat. Here, in the electrode member of the present invention, when the inside of the electrochemical element becomes hot due to Joule heat, the conductive thermal expansion material of the conductive thermal expansion material-containing portion may suddenly expand. This sudden expansion of the conductive thermal expansion material destroys the electrode structure, cuts off the conductive path, and suppresses abnormal heat generation of the electrochemical element, so that it is presumed that a high level of safety of the electrochemical element can be ensured. Furthermore, by setting the coverage rate of the conductive thermal expansion material on the collector side surface of the conductive thermal expansion material-containing portion to 20% or more and 98% or less, and setting the product of the coverage rate and the average particle diameter A to 500 or more and 15,000 or less, the conductive thermal expansion material-containing portion effectively expands when the electrochemical element becomes hot, and on the other hand, during normal use of the electrochemical element, the conductivity inside the electrochemical element is high. Therefore, it is presumed that the electrode member of the present invention can impart excellent cycle characteristics to the electrochemical element while ensuring a high level of safety for the electrochemical element.

<Current collector>
As the current collector, a material having electrical conductivity and electrochemical durability can be selected and used according to the type of electrochemical element. For example, as the current collector of the electrode for a lithium ion secondary battery, a current collector made of iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, platinum, etc. can be used. In addition, it is preferable to use a metal foil as the current collector. Among them, copper foil is particularly preferable as the current collector used for the negative electrode. In addition, aluminum foil is particularly preferable as the current collector used for the positive electrode. Note that the above materials may be used alone or in combination of two or more kinds at any ratio.

<Conductive Thermal Expansion Material-Containing Part>
The conductive thermal expansion material-containing portion contains a conductive thermal expansion material, and may optionally contain a conductive assistant and/or a binder. The conductive thermal expansion material-containing portion may contain components other than the conductive thermal expansion material, the conductive assistant, and the binder (hereinafter, may be referred to as "other components"). For example, as shown in FIG. 2, when the conductive thermal expansion material-containing portion constitutes a part of the electrode mixture layer, the conductive thermal expansion material-containing portion may contain an electrode active material.

The coverage rate of the conductive thermal expansion material on the collector side surface of the conductive thermal expansion material-containing portion must be 20% or more, preferably 30% or more, and more preferably 40% or more, and must be 98% or less, preferably 95% or less, and preferably 70% or less.
The coverage rate can be adjusted by the solids concentration and the amount of each component of the slurry composition for electrochemical element electrode members used when forming the conductive thermal expansion material-containing portion, as well as the application conditions and drying conditions of the slurry composition for electrochemical element electrode members.

The product of the coverage rate and the average particle size A must be 500 or more, preferably 1500 or more, and more preferably 2500 or more, and must be 15000 or less, preferably 9500 or less, and more preferably 6000 or less.

The conductive thermal expansion material-containing portion is preferably a coating layer, since it is easy to form the conductive thermal expansion material-containing portion and can improve the productivity of the electrochemical element electrode member. Furthermore, when the conductive thermal expansion material-containing portion is a coating layer, the coating layer as the conductive thermal expansion material-containing portion is preferably formed directly on the surface of the current collector, for example, as shown in Figures 1 and 3, since it can improve the cycle characteristics of the electrochemical element. In other words, the surface of the coating layer as the conductive thermal expansion material-containing portion that is disposed on the current collector side is preferably the surface of the current collector.

<<Conductive thermal expansion material>>
The conductive thermal expansion material is not particularly limited as long as it is conductive and has a thermal expansion coefficient of at least two times as measured according to the method described in the examples.
The conductive thermal expansion material is preferably a carbon-containing material that is conductive and has the above-mentioned thermal expansion coefficient. Examples of such carbon-containing materials include expandable graphite. As the expandable graphite, a conventionally known material (Japanese Patent No. 2529058) can be used.
The conductive thermal expansion material is preferably expanded graphite, since it can increase the resistance increase rate of the electrode and improve the safety of the electrochemical device.

The conductive thermal expansion material is preferably one that foams when the electrochemical element becomes hot, since this effectively destroys the electrode structure and effectively ensures a high level of safety for the electrochemical element. The conductive thermal expansion material is preferably one that foams at a temperature of 200°C to 500°C.

The average particle size A is preferably 10 μm or more, more preferably 20 μm or more, even more preferably 30 μm or more, even more preferably 40 μm or more, even more preferably 60 μm or more, preferably 200 μm or less, more preferably 160 μm or less, even more preferably 120 μm or less, and even more preferably 100 μm or less.

The average thickness (average thickness A) of the conductive thermal expansion material in the conductive thermal expansion material-containing portion is preferably 0.2 μm or more, more preferably 0.5 μm or more, and is preferably 5 μm or less, more preferably 4 μm or less.
If the average thickness A is within the above range, the conductive thermal expansion material is effectively disposed in the conductive thermal expansion material-containing portion, and the safety of the electrochemical element can be improved. Note that the conductive thermal expansion material having the average thickness A in the above range can be called a scaly particle.

The content of the conductive thermal expansion material in the conductive thermal expansion material-containing portion is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more, and is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less, assuming that the total solid content in the conductive thermal expansion material-containing portion is 100% by mass.

<<Conductive assistant>>
The conductive thermal expansion material-containing portion preferably further contains a conductive assistant in addition to the conductive thermal expansion material. The conductive assistant is a component that forms a conductive path in the conductive thermal expansion material-containing portion and can effectively ensure conduction between the current collector and the electrode mixture layer. Therefore, if the conductive thermal expansion material-containing portion further contains a conductive assistant, the electrochemical element can be provided with better cycle characteristics.

The conductive assistant is not particularly limited as long as it has electrical conductivity and has a thermal expansion coefficient less than twice that of the conductive thermal expansion material, measured by the same method.
Here, as the conductive assistant, for example, a conductive carbon material and fibers or foils of various metals can be used, but a conductive carbon material is preferred. Examples of the conductive carbon material include carbon black (e.g., acetylene black, Ketjen Black (registered trademark), furnace black, etc.), single-layer or multi-layer carbon nanotubes (multi-layer carbon nanotubes include cup-stack type), carbon nanohorns, vapor-grown carbon fibers, milled carbon fibers obtained by crushing polymer fibers after baking, single-layer or multi-layer graphene, and carbon nonwoven fabric sheets obtained by baking nonwoven fabric made of polymer fibers. Among these, it is preferable to use carbon black as the conductive assistant, and it is more preferable to use acetylene black. Note that one type of conductive assistant may be used alone, or two or more types may be used in combination at any ratio.

The content of the conductive assistant in the conductive thermal expansion material-containing portion is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 5% by mass or more, and is preferably 60% by mass or less, more preferably 40% by mass or less, even more preferably 20% by mass or less, and even more preferably 15% by mass or less, when the total solid content in the conductive thermal expansion material-containing portion is 100% by mass.
When the content of the conductive assistant in the conductive thermal expansion material-containing portion is equal to or higher than the above lower limit, electrical continuity between the current collector and the electrode mixture layer can be sufficiently ensured, and the cycle characteristics of the electrochemical element can be improved.
On the other hand, if the content of the conductive assistant in the conductive thermal expansion material-containing portion is equal to or less than the above upper limit, the safety of the electrochemical element can be improved.

The mass ratio of the conductive assistant to the conductive thermal expansion material in the conductive thermal expansion material-containing portion (conductive assistant content/conductive thermal expansion material content) is preferably 0.01 or more, more preferably 0.05 or more, and is preferably 0.5 or less, more preferably 0.3 or less, and even more preferably 0.15 or less.
When the mass ratio of the conductive assistant to the conductive thermal expansion material in the conductive thermal expansion material-containing portion is equal to or greater than the above lower limit, electrical continuity between the current collector and the electrode mixture layer can be sufficiently ensured, thereby improving the cycle characteristics of the electrochemical element.
On the other hand, if the mass ratio of the conductive assistant to the conductive thermal expansion material in the conductive thermal expansion material-containing portion is equal to or less than the above upper limit, the safety of the electrochemical element can be improved.

<<Binding material>>
The conductive thermal expansion material-containing portion preferably further contains a binder in addition to the conductive thermal expansion material. The binder is a component that can suppress the conductive thermal expansion material from being detached from the conductive thermal expansion material-containing portion. Therefore, if the conductive thermal expansion material-containing portion further contains a binder, the cycle characteristics of the electrochemical element can be improved.

[Type of binder]
The binder is not particularly limited as long as it can be used in an electrochemical element. For example, a polymer (synthetic polymer, for example, an addition polymer obtained by addition polymerization) obtained by polymerizing a monomer composition containing a monomer capable of exhibiting binding properties can be used as the binder. Examples of such polymers include aliphatic conjugated diene/aromatic vinyl copolymers (polymers mainly containing aliphatic conjugated diene monomer units and aromatic vinyl monomer units), acrylic polymers (polymers containing (meth)acrylic acid ester monomer units), fluorine-based polymers (polymers mainly containing fluorine-containing monomer units), acrylic acid/acrylamide copolymers (polymers mainly containing (meth)acrylic acid units and (meth)acrylamide units), acrylonitrile polymers (polymers mainly containing (meth)acrylonitrile units), and the like. These may be used alone or in combination of two or more types at any ratio. Among these, aliphatic conjugated diene/aromatic vinyl copolymers, acrylic polymers, acrylic acid/acrylamide copolymers, and fluorine-based polymers are preferred.
Here, the aliphatic conjugated diene monomer capable of forming the aliphatic conjugated diene monomer unit of the aliphatic conjugated diene/aromatic vinyl copolymer, the aromatic vinyl monomer capable of forming the aromatic vinyl monomer unit of the aliphatic conjugated diene/aromatic vinyl copolymer, the (meth)acrylic acid ester monomer capable of forming the (meth)acrylic acid ester monomer unit of the acrylic polymer, and the fluorine-containing monomer capable of forming the fluorine-containing monomer unit of the fluorine-containing polymer may be any known one.
In this specification, "containing a monomer unit" means that "a polymer obtained by using the monomer contains a repeating unit derived from the monomer".
In addition, in this specification, "mainly containing" one or more types of monomer units means that "when the amount of all monomer units contained in the polymer is taken as 100 mass%, the content of that one type of monomer unit or the total content of the multiple types of monomer units exceeds 50 mass%."
In this specification, (meth)acrylic means acrylic and/or methacrylic, and (meth)acrylo means acrylo and/or methacrylo.

[Functional Group of Binder]
The functional groups that can be contained in the polymer as a binder are not particularly limited, and examples thereof include carboxyl groups, hydroxyl groups, cyano groups, amino groups, epoxy groups, oxazoline groups, isocyanate groups, and sulfonic acid groups (hereinafter, these functional groups may be collectively referred to as "specific functional groups"). One type of these may be used alone, or two or more types may be used in combination at any ratio. Among these, carboxyl groups, hydroxyl groups, cyano groups, amino groups, and sulfonic acid groups are preferred.

The method of introducing the specific functional group into the polymer as the binder is not particularly limited. A polymer may be prepared using a monomer containing the specific functional group (specific functional group-containing monomer) to obtain a polymer containing a specific functional group-containing monomer unit, or an arbitrary polymer may be modified at its terminal to obtain a polymer having the specific functional group at its terminal, but the former is preferred. That is, the polymer as the binder contains at least one of a carboxyl group-containing monomer unit, a hydroxyl group-containing monomer unit, a cyano group-containing monomer unit, an amino group-containing monomer unit, an epoxy group-containing monomer unit, an oxazoline group-containing monomer unit, an isocyanate group-containing monomer unit, and a sulfonic acid group-containing monomer unit as the specific functional group-containing monomer unit, and preferably contains at least one of a carboxyl group-containing monomer unit, a hydroxyl group-containing monomer unit, a cyano group-containing monomer unit, an amino group-containing monomer unit, and a sulfonic acid group-containing monomer unit.

Examples of the carboxyl group-containing monomer capable of forming the carboxyl group-containing monomer unit include monocarboxylic acids and derivatives thereof, dicarboxylic acids and acid anhydrides thereof, and derivatives thereof.
Examples of the monocarboxylic acid include acrylic acid, methacrylic acid, and crotonic acid.
Examples of the monocarboxylic acid derivatives include 2-ethylacrylic acid, isocrotonic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, α-chloro-β-E-methoxyacrylic acid, and the like.
The dicarboxylic acid includes maleic acid, fumaric acid, itaconic acid, and the like.
Examples of dicarboxylic acid derivatives include methylmaleic acid, dimethylmaleic acid, phenylmaleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid, and maleic acid monoesters such as nonyl maleate, decyl maleate, dodecyl maleate, octadecyl maleate, and fluoroalkyl maleate.
Examples of the acid anhydrides of dicarboxylic acids include maleic anhydride, acrylic anhydride, methylmaleic anhydride, and dimethylmaleic anhydride.
In addition, as the carboxyl group-containing monomer, an acid anhydride that generates a carboxyl group by hydrolysis can also be used. Among them, as the carboxyl group-containing monomer, acrylic acid and methacrylic acid are preferable. In addition, as the carboxyl group-containing monomer, one type may be used alone, or two or more types may be used in combination at any ratio.

Examples of hydroxyl group-containing monomers capable of forming the hydroxyl group-containing monomer unit include ethylenically unsaturated alcohols such as (meth)allyl alcohol, 3-buten-1-ol, and 5-hexen-1-ol; alkanol esters of ethylenically unsaturated carboxylic acids such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, di-2-hydroxyethyl maleate, di-4-hydroxybutyl maleate, and di-2-hydroxypropyl itaconate; and esters of ethylenically unsaturated carboxylic acids represented by the general formula: CH ₂ ═CR _a -COO-(C _q H _2q O) _p -H (wherein p is an integer of 2 to 9, q is an integer of 2 to 4, and R _a represents a hydrogen atom or a methyl group) and (meth)acrylic acid esters; mono(meth)acrylic acid esters of dihydroxy esters of dicarboxylic acids such as 2-hydroxyethyl-2'-(meth)acryloyloxyphthalate and 2-hydroxyethyl-2'-(meth)acryloyloxysuccinate; vinyl ethers such as 2-hydroxyethyl vinyl ether and 2-hydroxypropyl vinyl ether; mono(meth)allyl ethers of alkylene glycols such as (meth)allyl-2-hydroxyethyl ether, (meth)allyl-2-hydroxypropyl ether, (meth)allyl-3-hydroxypropyl ether, (meth)allyl-2-hydroxybutyl ether, (meth)allyl-3-hydroxybutyl ether, (meth)allyl-4-hydroxybutyl ether, and (meth)allyl-6-hydroxyhexyl ether; diethylene glycol mono(meth)allyl ether, dipropylene glycol Examples of the hydroxyl group-containing monomer include polyoxyalkylene glycol mono(meth)allyl ethers such as pyrene glycol mono(meth)allyl ether; mono(meth)allyl ethers of halogen- and hydroxy-substituted (poly)alkylene glycols such as glycerin mono(meth)allyl ether, (meth)allyl-2-chloro-3-hydroxypropyl ether, and (meth)allyl-2-hydroxy-3-chloropropyl ether; mono(meth)allyl ethers of polyhydric phenols such as eugenol and isoeugenol and halogen-substituted derivatives thereof; (meth)allyl thioethers of alkylene glycols such as (meth)allyl-2-hydroxyethyl thioether and (meth)allyl-2-hydroxypropyl thioether; and amides having a hydroxyl group such as N-hydroxymethylacrylamide (N-methylolacrylamide), N-hydroxymethylmethacrylamide, N-hydroxyethylacrylamide, and N-hydroxyethylmethacrylamide. The hydroxyl group-containing monomer may be used alone or in combination of two or more kinds in any ratio.
In the present invention, "(meth)allyl" means allyl and/or methallyl, and "(meth)acryloyl" means acryloyl and/or methacryloyl.

Cyano group-containing monomers capable of forming cyano group-containing monomer units include α,β-ethylenically unsaturated nitrile monomers. Specifically, the α,β-ethylenically unsaturated nitrile monomer is not particularly limited as long as it is an α,β-ethylenically unsaturated compound having a cyano group, but examples include acrylonitrile; α-halogenoacrylonitriles such as α-chloroacrylonitrile and α-bromoacrylonitrile; α-alkylacrylonitriles such as methacrylonitrile and α-ethylacrylonitrile; and the like. The cyano group-containing monomers may be used alone or in combination of two or more types in any ratio.

Examples of amino group-containing monomers capable of forming amino group-containing monomer units include dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, aminoethyl vinyl ether, dimethylaminoethyl vinyl ether, etc. The amino group-containing monomers may be used alone or in combination of two or more kinds in any ratio.
In the present invention, the term "(meth)acrylate" means acrylate and/or methacrylate.

The epoxy group-containing monomer capable of forming the epoxy group-containing monomer unit includes a monomer containing a carbon-carbon double bond and an epoxy group.
Examples of monomers containing a carbon-carbon double bond and an epoxy group include unsaturated glycidyl ethers such as vinyl glycidyl ether, allyl glycidyl ether, butenyl glycidyl ether, and o-allylphenyl glycidyl ether; monoepoxides of dienes or polyenes such as butadiene monoepoxide, chloroprene monoepoxide, 4,5-epoxy-2-pentene, 3,4-epoxy-1-vinylcyclohexene, and 1,2-epoxy-5,9-cyclododecadiene; 3,4-epoxy-1-butene alkenyl epoxides such as 1,2-epoxy-5-hexene, 1,2-epoxy-9-decene, etc.; glycidyl acrylate, glycidyl methacrylate, glycidyl crotonate, glycidyl-4-heptenoate, glycidyl sorbate, glycidyl linoleate, glycidyl-4-methyl-3-pentenoate, glycidyl ester of 3-cyclohexene carboxylic acid, glycidyl ester of 4-methyl-3-cyclohexene carboxylic acid, etc. The epoxy group-containing monomer may be used alone or in combination of two or more kinds in any ratio.

Examples of oxazoline group-containing monomers capable of forming oxazoline group-containing monomer units include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-methyl-2-oxazoline, and 2-isopropenyl-5-ethyl-2-oxazoline. The oxazoline group-containing monomers may be used alone or in combination of two or more in any ratio.

Examples of isocyanate group-containing monomers that can form isocyanate group-containing monomer units include 2-isocyanatoethyl methacrylate, 2-isocyanatoethyl acrylate, 2-(0-[1'-methylpropylideneamino]carboxyamino)ethyl methacrylate, 2-[(3,5-dimethylpyrazolyl)carbonylamino]ethyl methacrylate, and 1,1-(bisacryloyloxymethyl)ethyl isocyanate. Note that one type of isocyanate group-containing monomer may be used alone, or two or more types may be used in combination in any ratio.

Sulfonic acid group-containing monomers that can form sulfonic acid group-containing monomer units include vinyl sulfonic acid, methyl vinyl sulfonic acid, (meth)allyl sulfonic acid, styrene sulfonic acid, (meth)acrylic acid-2-ethyl sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, 3-allyloxy-2-hydroxypropanesulfonic acid, etc. The sulfonic acid group-containing monomers may be used alone or in combination of two or more types in any ratio.

When the amount of all monomer units contained in the polymer as a binder is taken as 100 mass%, the content of the specific functional group-containing monomer unit in the polymer is preferably 0.3 mass% or more, more preferably 0.5 mass% or more, preferably 20 mass% or less, and more preferably 10 mass% or less. If the content of the specific functional group-containing monomer unit in the polymer as a binder is within the above range, the adhesion between the electrode mixture layer and the current collector, and the cycle characteristics of the electrochemical element can be improved.

[Method of preparing binder]
The method for preparing the polymer as the binder is not particularly limited. The polymer as the binder is produced, for example, by polymerizing a monomer composition containing the above-mentioned monomers in an aqueous solvent. The content ratio of each monomer in the monomer composition can be determined according to the content ratio of a desired monomer unit (repeating unit) in the polymer.

The polymerization method is not particularly limited, and any of the following methods can be used: solution polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, etc. The polymerization reaction can be any of the following reactions: ionic polymerization, radical polymerization, living radical polymerization, various condensation polymerizations, addition polymerization, etc. In addition, known emulsifiers and polymerization initiators can be used during polymerization, if necessary.

[Binder content]
The content of the binder in the conductive thermal expansion material-containing portion is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 2% by mass or more, and is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less, when the total solid content in the conductive thermal expansion material-containing portion is 100% by mass.
When the content of the binder in the conductive thermally expandable material-containing portion is within the above range, the cycle characteristics of the electrochemical element can be further improved.

<<Other ingredients>>
Other components optionally contained in the conductive thermal expansion material-containing portion are not particularly limited. The conductive thermal expansion material-containing portion may contain, for example, a dispersant. The dispersant is a component that is blended to improve the dispersibility of the conductive thermal expansion material, etc. Examples of dispersants include nonionic dispersants such as polyvinylpyrrolidone and polyvinyl butyral, metal salts of β-naphthalenesulfonic acid-formalin condensates, and carboxymethyl cellulose.
From the viewpoint of improving the safety of the electrochemical element, the conductive thermal expansion material-containing portion may contain a flame retardant such as a phosphorus-based compound or a silicone-based compound. The content of the flame retardant is, for example, 30 parts by mass or less, or may be 15 parts by mass or less per 100 parts by mass of the binder.
These other components may be used alone or in combination of two or more. In addition, when the conductive thermal expansion material-containing portion constitutes a part of the electrode mixture layer, the conductive thermal expansion material-containing portion may contain an electrode active material.

<<Thickness of conductive thermal expansion material-containing portion>>
The thickness of the conductive thermal expansion material-containing portion is not particularly limited as long as it does not impair the object of the present invention, but is preferably 1 μm or more, more preferably 3 μm or more, and is preferably 10 μm or less, and more preferably 7 μm or less.

<Electrode mixture layer>
The electrode mixture layer is not particularly limited, and for example, an electrode mixture layer containing an electrode active material and an electrode mixture layer binder can be selected and used according to the type of electrochemical element. For example, the electrode active material (positive electrode active material, negative electrode active material) and the electrode mixture layer binder (positive electrode mixture layer binder, negative electrode mixture layer binder) in the electrode mixture layer of the lithium secondary battery electrode can be known ones described in, for example, JP 2013-145763 A.

In the electrode member of the present invention, the thermal expansion coefficient of the conductive thermal expansion material in the conductive thermal expansion material-containing portion is preferably 5 times or more the thermal expansion coefficient of the electrode active material in the electrode mixture layer. With such an electrode member, the electrode structure of the electrochemical element can be effectively destroyed, and the safety of the electrochemical element can be improved.
In this specification, the thermal expansion coefficient of the electrode active material can be measured in the same manner as that of the conductive thermal expansion material.

<Other demographics>
The other layer may be located, for example, between the current collector and the conductive thermal expansion material-containing portion. The other layer located between the current collector and the conductive thermal expansion material-containing portion is not particularly limited, but is usually a layer that does not contain a conductive thermal expansion material, for example, an adhesive layer that contains a conductive assistant and a binder.

When the electrode member of the present invention has an electrode mixture layer, other layers may be provided on the electrode mixture layer, such as a known porous membrane layer provided for the purpose of improving heat resistance, or a known adhesive layer provided for the purpose of improving adhesion to a separator, etc.

<Preferred embodiment of electrochemical element electrode member>
In one embodiment, it is preferable that the coverage of the conductive thermal expansion material on the collector side surface of the conductive thermal expansion material-containing portion of the electrode member is 30% or more, and the product of the coverage and the average particle size A is 1,500 or more.
If the coverage is equal to or greater than the above lower limit and the product is equal to or greater than the above lower limit, the safety of the electrochemical device can be improved.

In another embodiment, it is preferable that the electrode member has a coverage rate of the conductive thermal expansion material on the collector side arrangement surface of the conductive thermal expansion material-containing portion of 95% or less, an average particle diameter A of 20 μm or more and 160 μm or less, and a product of the coverage rate and the average particle diameter A of 9,500 or less.
When the coverage is equal to or less than the upper limit, the average particle size A is within the above range, and the product is equal to or less than the upper limit, the cycle characteristics of the electrochemical device can be improved.

In a more preferred embodiment of the electrode member of the present invention, the coverage of the conductive thermal expansion material on the collector side surface of the conductive thermal expansion material-containing portion is 95% or less, the average particle diameter A is 20 μm or more and 160 μm or less, and the product of the coverage and the average particle diameter A is 9,500 or less.
When the coverage rate is within the above range, the average particle size A is within the above range, and the product is within the above range, the safety and cycle characteristics of the electrochemical device can be improved.

<Method of manufacturing an electrochemical element electrode member>
The method for producing the electrode member of the present invention is not particularly limited as long as it is possible to form a conductive thermally expandable material-containing portion on a current collector.
For example, in the case of the examples shown in Figures 1 and 3, the electrode member of the present invention is manufactured through a process in which a composition (slurry composition for electrochemical element electrode members) containing a predetermined amount of conductive thermal expansion material and a solvent, and which may optionally contain a conductive assistant, a binder, and other components, is applied to a surface of a conductive thermal expansion material-containing portion such as a collector, and the applied slurry composition for electrochemical element electrode members is dried to form a conductive thermal expansion material-containing portion (conductive thermal expansion material-containing portion formation process).
In addition, when an electrode mixture layer is formed on the electrode member of the present invention such as the example shown in Figure 1 and used as an electrode, the formation of the electrode mixture layer is not particularly limited and can be performed using a known method for forming an electrode mixture layer.
On the other hand, in the case where the conductive thermally expandable material-containing portion constitutes a part of the electrode mixture layer as in the example shown in FIG. 2, the electrode member of the present invention is manufactured through a process of applying a composition (slurry composition for the electrode mixture layer containing conductive thermally expandable material) containing a predetermined amount of conductive thermally expandable material, electrode active material, binder for the electrode mixture layer, and solvent, and optionally containing conductive assistant, binder, and other components, to the surface of the conductive thermally expandable material-containing portion of a collector or the like, and simultaneously drying the conductive thermally expandable material in the applied slurry composition for the electrode mixture layer containing conductive thermally expandable material to be unevenly distributed (so-called migration) toward the collector side, thereby forming an electrode mixture layer containing the conductive thermally expandable material-containing portion therein (electrode mixture layer formation process).

<<Slurry composition for electrochemical element electrode members>>
The slurry composition for an electrochemical element electrode member (hereinafter, sometimes simply referred to as "slurry composition") used in the manufacture of the electrode member of the present invention contains a conductive thermal expansion material and a solvent, and optionally contains an electrode active material, a conductive assistant, a binder, and other components. When the slurry composition for an electrochemical element electrode member contains an electrode active material, it can be called a slurry composition for an electrode mixture layer containing a conductive thermal expansion material.

Here, the average particle diameter of the conductive thermal expansion material in the slurry composition (hereinafter, sometimes referred to as "average particle diameter B") is preferably 10 μm or more, more preferably 20 μm or more, even more preferably 30 μm or more, even more preferably 40 μm or more, even more preferably 60 μm or more, preferably 200 μm or less, more preferably 160 μm or less, even more preferably 120 μm or less, and even more preferably 100 μm or less.
The average particle size B can be measured using an FE-SEM according to the method described in the Examples.

In addition, the average thickness of the conductive thermal expansion material in the slurry composition (hereinafter sometimes referred to as "average thickness B") is preferably 0.2 μm or more, more preferably 0.5 μm or more, and is preferably 5 μm or less, more preferably 4 μm or less.
In this specification, the average thickness B can be measured using an FE-SEM according to the method described in the Examples.

The solvent used in the slurry composition is not particularly limited, and may be either water or an organic solvent. Examples of the organic solvent that may be used include acetonitrile, N-methyl-2-pyrrolidone, tetrahydrofuran, acetone, acetylpyridine, cyclopentanone, dimethylformamide, dimethylsulfoxide, methylformamide, methylethylketone, furfural, ethylenediamine, dimethylbenzene (xylene), methylbenzene (toluene), cyclopentyl methyl ether, and isopropyl alcohol.
These solvents may be used alone or in combination in any desired ratio.

The slurry composition can be prepared by mixing the above components in predetermined amounts. Specifically, the slurry composition can be prepared by mixing the above components in predetermined amounts using a mixer such as a ball mill, sand mill, bead mill, pigment disperser, crusher, ultrasonic disperser, homogenizer, planetary mixer, or Filmix.

<<Conductive Thermal Expansion Material-Containing Part Forming Process>>
The method for applying the slurry composition for electrochemical element electrode members onto a current collector is not particularly limited, and examples thereof include a doctor blade method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, and a brush coating method.
The method for drying the slurry composition for electrochemical element electrode members applied on the current collector is not particularly limited, and any known method can be used. Examples of the drying method include drying with warm air, hot air, or low-humidity air, vacuum drying, and drying by irradiation with infrared rays or electron beams. The drying temperature is not particularly limited as long as it is within a range that does not impair the object of the present invention, but is preferably 80° C. or higher and 120° C. or lower from the viewpoint of the thermal expansion of the conductive thermal expansion material.

<<Electrode mixture layer forming process>>
The method for applying the slurry composition for the electrode mixture layer containing the conductive thermal expansion material onto the current collector is not particularly limited, and the same method as that described above in the section "Conductive thermal expansion material-containing portion forming process" can be used.

As a method for migrating the conductive thermal expansion material in the applied slurry composition for the electrode mixture layer containing the conductive thermal expansion material to the current collector side, for example, a method using thermal convection can be mentioned. That is, when drying the slurry composition for the electrode mixture layer containing the conductive thermal expansion material, the direction, strength, temperature, etc. of the thermal convection can be appropriately adjusted to form an electrode mixture layer in which the conductive thermal expansion material has migrated to the current collector side.

(Electrochemical element)
The electrochemical element of the present invention is not particularly limited, and may be, for example, a lithium ion secondary battery, an electric double layer capacitor, or a lithium ion capacitor, and is preferably a lithium ion secondary battery. The electrochemical element of the present invention is characterized by comprising an electrode made of the electrode member of the present invention. Since the electrochemical element of the present invention comprises an electrode made of the electrode member of the present invention, safety is highly ensured and the cycle characteristics are excellent. In the electrochemical element of the present invention, when the electrode member does not comprise an electrode mixture layer, the electrode mixture layer is formed on the conductive thermal expansion material-containing portion of the electrode member before use as an electrode.
In the following, a case where the electrochemical element is a lithium ion secondary battery will be described as an example, but the present invention is not limited to the following example. A lithium ion secondary battery as the electrochemical element of the present invention usually includes electrodes (positive and negative electrodes), an electrolyte, and a separator, and uses an electrode made of the electrode member of the present invention for at least one of the positive and negative electrodes.

<Electrodes>
Here, the electrode other than the electrode made of the above-mentioned electrochemical element electrode member of the present invention that can be used in the lithium ion secondary battery as the electrochemical element of the present invention is not particularly limited, and any known electrode can be used. Specifically, the electrode other than the electrode made of the above-mentioned electrochemical element electrode member of the present invention can be an electrode formed by forming an electrode mixture layer on a current collector using a known manufacturing method.

<Separator>
The separator is not particularly limited, and for example, those described in JP 2012-204303 A can be used. Among these, a microporous film made of a polyolefin resin (polyethylene, polypropylene, polybutene, polyvinyl chloride) is preferred, since it can reduce the thickness of the entire separator, thereby increasing the ratio of the electrode active material in the lithium ion secondary battery and increasing the capacity per volume.

<Electrolyte>
As the electrolyte, an organic electrolyte in which a supporting electrolyte is dissolved in an organic solvent is usually used. As the supporting electrolyte, for example, a lithium salt is used in a lithium ion secondary battery. As the lithium salt, for example, LiPF ₆ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAlCl ₄ , LiClO ₄ , CF ₃ SO ₃ Li, C ₄ F ₉ SO ₃ Li, CF ₃ COOLi, (CF ₃ CO) ₂ NLi, (CF ₃ SO ₂ ) ₂ NLi, (C ₂ F ₅ SO ₂ ) NLi, etc. are listed. Among them, LiPF ₆ , LiClO ₄ , and CF ₃ SO ₃ Li are preferred because they are easily dissolved in a solvent and show a high degree of dissociation. Note that one type of electrolyte may be used alone, or two or more types may be used in combination. Generally, the lithium ion conductivity tends to increase as the supporting electrolyte with a higher degree of dissociation is used, and therefore the lithium ion conductivity can be adjusted by the type of supporting electrolyte.

The organic solvent used in the electrolyte is not particularly limited as long as it can dissolve the supporting electrolyte. For example, in a lithium ion secondary battery, carbonates such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate (BC), ethyl methyl carbonate (EMC), vinylene carbonate (VC), etc.; esters such as γ-butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; sulfur-containing compounds such as sulfolane and dimethyl sulfoxide; and the like are preferably used. A mixture of these solvents may also be used. Among them, carbonates are preferred because they have a high dielectric constant and a wide stable potential region. Usually, the lower the viscosity of the solvent used, the higher the lithium ion conductivity tends to be, so the lithium ion conductivity can be adjusted by the type of solvent.
The concentration of the electrolyte in the electrolytic solution can be appropriately adjusted. Known additives may also be added to the electrolytic solution.

<Method of manufacturing lithium-ion secondary battery>
The lithium ion secondary battery according to the present invention can be manufactured, for example, by stacking a positive electrode and a negative electrode with a separator therebetween, rolling or folding the stack as necessary, placing the stack in a battery container, injecting an electrolyte into the battery container, and sealing the battery container. At least one of the positive electrode and the negative electrode is an electrode made of the electrochemical element electrode member of the present invention. In addition, the battery container may be filled with an expand metal, a fuse, an overcurrent prevention element such as a PTC element, a lead plate, or the like as necessary to prevent pressure rise inside the battery and overcharging and discharging. The shape of the battery may be any of a coin type, a button type, a sheet type, a cylindrical type, a square type, a flat type, and the like.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. In the following description, "%" and "parts" expressing amounts are based on mass unless otherwise specified.
In addition, in a polymer produced by polymerizing a plurality of types of monomers, the ratio of a monomer unit formed by polymerizing a certain monomer in the polymer usually coincides with the ratio (feed ratio) of that monomer to all monomers used in the polymerization of the polymer, unless otherwise specified.
Furthermore, in the examples and comparative examples, the thermal expansion coefficient of the conductive thermal expansion material, the average particle diameter (average particle diameter B) of the conductive thermal expansion material in the slurry composition for electrochemical element electrode members, the average thickness (average thickness B) of the conductive thermal expansion material in the slurry composition for electrochemical element electrode members, the average particle diameter (average particle diameter A) of the conductive thermal expansion material in the conductive thermal expansion material-containing portion, the average thickness (average thickness A) of the conductive thermal expansion material in the conductive thermal expansion material-containing portion, the coverage, the safety of the electrochemical element, and the cycle characteristics of the electrochemical element were measured and evaluated by the following procedures.

<Thermal expansion coefficient of conductive thermal expansion material>
A 20% solids aqueous solution of the conductive thermal expansion material:CMC 90:10 (mass ratio) was prepared using a conductive thermal expansion material, carboxymethylcellulose (CMC), and purified water. The prepared aqueous solution was placed in a petri dish and dried to prepare a measurement film with a thickness of 1 mm. The measurement film was set in a thermomechanical analysis (TMA) and the thickness of the measurement film was measured while heating it from 25°C to 500°C at a heating rate of 5°C/min under a helium atmosphere. The ratio of the maximum measured thickness between 200°C and 500°C to the thickness of the measurement film before heating (thickness of the measurement film at 25°C) of 1 mm ("maximum measured thickness (unit: mm)"/"1 mm") was taken as the thermal expansion coefficient of the conductive thermal expansion material. For the thermomechanical analysis (TMA), a TMA402 F1 Hyperion (manufactured by NETZSCH) was used.

<Average particle size (average particle size B) of conductive thermal expansion material in slurry composition for electrochemical element electrode member>
First, the slurry composition for electrochemical element electrode members prepared in the examples and comparative examples was applied onto an aluminum foil, which was then dried to prepare an aluminum foil with a coating layer. The obtained aluminum foil with a coating layer was subjected to cross-section processing for observation using a cross-section polisher (IB-09020CP manufactured by JEOL Ltd.). Next, cross-section observation was performed using an FE-SEM (JSM-7800F manufactured by JEOL Ltd.). The observation was performed under the conditions of a magnification of 1000 times, an irradiation voltage of 10 kV, and an irradiation current of 5.0 × 10 ^-8 A. In the obtained cross-sectional image, the diameter obtained by fitting a circumscribing circle to the conductive thermal expansion material in the coating layer was defined as the maximum diameter of the conductive thermal expansion material. The average value of the maximum diameters of any 50 points was taken as the average particle diameter B.

<Average thickness (average thickness B) of conductive thermal expansion material in slurry composition for electrochemical element electrode member>
First, the slurry composition for electrochemical element electrode members prepared in the examples and comparative examples was applied onto an aluminum foil, which was then dried to prepare an aluminum foil with a coating layer. The obtained aluminum foil with a coating layer was subjected to cross-section processing for observation using a cross-section polisher (IB-09020CP manufactured by JEOL Ltd.). Next, cross-section observation was performed using an FE-SEM (JSM-7800F manufactured by JEOL Ltd.). The observation was performed under the conditions of a magnification of 1000 times, an irradiation voltage of 10 kV, and an irradiation current of 5.0 × 10 ^-8 A. In the obtained cross-sectional image, the diameter obtained by fitting an inscribed circle to the conductive thermal expansion material in the coating layer was defined as the minimum diameter of the conductive thermal expansion material. The average value of the minimum diameter of any 50 points was taken as the average thickness B.

<Average particle size (average particle size A) of the conductive thermal expansion material in the conductive thermal expansion material-containing portion>
The positive electrodes prepared in the examples and comparative examples were processed for cross-section observation using a cross-section polisher (IB-09020CP manufactured by JEOL Ltd.). Next, cross-section observation was performed using an FE-SEM (JSM-7800F manufactured by JEOL Ltd.). The observation was performed under the conditions of a magnification of 1000 times, an irradiation voltage of 10 kV, and an irradiation current of 5.0 × 10 ^-8 A. In the obtained cross-sectional image, the diameter obtained by fitting a circumscribing circle to the conductive thermal expansion material in the coating layer was defined as the maximum diameter of the conductive thermal expansion material. The average value of the maximum diameters at any 50 points was defined as the average particle diameter A.

<Average thickness (average thickness A) of the conductive thermal expansion material in the conductive thermal expansion material-containing portion>
The positive electrodes prepared in the examples and comparative examples were processed for cross-section observation using a cross-section polisher (IB-09020CP manufactured by JEOL Ltd.). Next, cross-section observation was performed using an FE-SEM (JSM-7800F manufactured by JEOL Ltd.). The observation was performed under the conditions of a magnification of 1000 times, an irradiation voltage of 10 kV, and an irradiation current of 5.0 × 10 ^-8 A. In the obtained cross-sectional image, the diameter obtained by fitting an inscribed circle to the conductive thermal expansion material in the coating layer was defined as the minimum diameter of the conductive thermal expansion material. The average value of the minimum diameter of any 50 points was taken as the average thickness A.

<Coverage rate>
The positive electrodes prepared in the examples and comparative examples were processed to expose cross sections for observation using a cross-section polisher (IB-09020CP manufactured by JEOL Ltd.). Next, cross-section observation was performed using an FE-SEM (JSM-7800F manufactured by JEOL Ltd.). The observation was performed under the conditions of a magnification of 1000 times, an irradiation voltage of 10 kV, and an irradiation current of 5.0 × 10 ^-8 A. In the obtained cross-sectional image, the area where the conductive thermal expansion material is present on the foil was defined as a covered area, and the area where the conductive thermal expansion material is not present on the foil was defined as a non-covered area. The coverage rate of the conductive thermal expansion material with respect to the collector-side arrangement surface of the conductive thermal expansion material-containing portion was calculated using the following calculation formula (1). Note that the "covered area + non-covered area" in the following calculation formula (1) corresponds to the above-mentioned "collector-side arrangement surface of the conductive thermal expansion material-containing portion".
Coverage rate = Covered part / (Coated part + Non-coated part) × 100 (1)

<Safety of electrochemical elements>
The prepared positive electrode was heated using a heating element (manufactured by Kurosaki Harima Co., Ltd.), and the behavior of the resistance during heating was measured. Specifically, the positive electrode was heated from room temperature (25° C.) to 500° C. at a temperature increase rate of 50° C./sec, and the resistance increase rate was calculated using the minimum resistance value during heating and the maximum resistance value during heating after the resistance reached the minimum value by the following calculation formula (2), and the safety of the electrochemical element was evaluated according to the following criteria. The higher the resistance increase rate, the safer the electrochemical element.
Resistance increase ratio = maximum resistance value / minimum resistance value (2)
A: Resistance increase ratio is 5 or more B: Resistance increase ratio is 2 or more but less than 5 C: Resistance increase ratio is less than 2

<Cycle characteristics of electrochemical element>
First, the lithium ion secondary battery was left to stand at a temperature of 25°C for 5 hours after injecting the electrolyte. Next, the battery was charged to a cell voltage of 3.65V at a constant current of 0.2C at a temperature of 25°C, and then aged for 12 hours at a temperature of 60°C. Then, the battery was discharged to a cell voltage of 3.00V at a constant current of 0.2C at a temperature of 25°C. Then, the battery was CC-CV charged (upper cell voltage 4.25V) at 0.2C, and CC discharged to 3.00V at a constant current of 0.2C. This charge and discharge at 0.2C was repeated three times to perform initialization.
The initialized lithium ion secondary battery was heated to a temperature of 45° C., and then charged at a constant current of 1.0 C to a cell voltage of 4.10 V. It was then discharged at 1.0 C to a cell voltage of 3.00 V. 100 charge/discharge cycles were performed, and the cycle capacity retention rate was calculated using the discharge capacity at the first cycle and the discharge capacity at the 100th cycle according to the following calculation formula (3), and the cycle characteristics of the electrochemical element were evaluated according to the following criteria. A higher cycle capacity retention rate indicates that the electrochemical element has better cycle characteristics.
Cycle capacity retention rate = 100th cycle discharge capacity / 1st cycle discharge capacity × 100 (3)
A: Cycle capacity retention rate is 90% or more. B: Cycle capacity retention rate is 80% or more but less than 90%. C: Cycle capacity retention rate is less than 79%.

(Example 1-1)
<Preparation of Polymer (Binder)>
A monomer composition was obtained by charging 100 parts of ion-exchanged water, as well as 35 parts by mass of acrylonitrile, 62 parts by mass of 1,3-butadiene, and 3 parts by mass of methacrylic acid (a carboxyl group-containing monomer) as monomers into a reactor having an internal volume of 10 L. To the monomer composition, 2 parts of potassium oleate as an emulsifier, 0.1 parts of potassium phosphate as a stabilizer, and 0.5 parts of 2,2',4,6,6'-pentamethylheptane-4-thiol (TIBM) as a molecular weight regulator were added, and emulsion polymerization was carried out at 30°C in the presence of 0.35 parts of potassium persulfate as a polymerization initiator.
When the polymerization conversion rate reached 90%, 0.2 parts of hydroxylamine sulfate was added per 100 parts of monomer to terminate the polymerization. Then, the mixture was heated and steam distilled at about 70° C. under reduced pressure to recover the residual monomer, and 2 parts of alkylated phenol were added as an antioxidant to obtain an aqueous dispersion of the polymer.
Next, 400 mL of the aqueous dispersion of the obtained polymer (total solid content: 48 g) was put into a 1-liter autoclave equipped with a stirrer, and nitrogen gas was passed through for 10 minutes to remove dissolved oxygen in the aqueous dispersion. Then, 50 mg of palladium acetate as a hydrogenation catalyst was dissolved in 180 mL of water to which nitric acid was added in an amount four times the moles of palladium, and the hydrogenation catalyst solution was added to the aqueous dispersion. After replacing the inside of the system twice with hydrogen gas, the contents of the autoclave were heated to 50° C. while pressurizing with hydrogen gas up to 3 MPa, and hydrogenation reaction was carried out for 6 hours.
Thereafter, the contents were returned to room temperature, the inside of the system was conditioned with nitrogen, and the contents were concentrated using an evaporator until the solid content reached 40%, to obtain an aqueous dispersion of the polymer (binder).

<Preparation of Slurry Composition for Electrochemical Element Electrode Member>
80 parts of expanded graphite as a conductive thermal expansion material, 10 parts of acetylene black (C65 manufactured by Denka) as a conductive assistant, 7.5 parts (solid content equivalent) of carboxymethyl cellulose (CMC) as a dispersant, and 2.5 parts (solid content equivalent) of the aqueous dispersion of the binder prepared above were mixed. 400 parts of ion-exchanged water as a solvent was added to this mixture to make the slurry solid content concentration 20%, and 2.5 parts of Na salt of β-naphthalenesulfonic acid formalin condensate (Demol T45 manufactured by Kao) (referred to as "formalin condensate" in the table) was added as a further dispersant, and the mixture was stirred for 30 minutes with a three-one motor to prepare a slurry composition.
The obtained slurry composition was used to measure the average particle size B and the average thickness B. The results are shown in Table 1.
The thermal expansion coefficient of the expanded graphite as the conductive thermal expansion material was measured by the above-mentioned method, and the thermal expansion coefficient of the expanded graphite was found to be 15 times that of the expanded graphite. The electrical conductivity of the expanded graphite was also found to be 100 S/m.

<Preparation of electrode member>
The above slurry composition was applied to a current collector of 20 μm thick aluminum foil with a doctor blade to a coating thickness of 5 μm. The slurry composition on the aluminum foil was then dried by leaving it in an oven at 90° C. for 10 minutes to obtain an electrode member having a coating layer formed on the aluminum foil.

<Preparation of Positive Electrode>
96.0 parts of NMC811 ( _{LiNi0.8Mn0.1Co0.1O2} ) as a positive _electrode active material _, 2.0 parts of carbon black (manufactured by Denka, product name "Li- ₁₀₀ ") as a conductive assistant in terms of solid content, and 2.0 parts of polyvinylidene fluoride (manufactured by Solvay, product name "Solef (registered trademark) 5130") were charged into a planetary mixer and mixed. Furthermore, N-methylpyrrolidone (NMP) was gradually added and stirred and mixed at a temperature of 25±3°C and a rotation speed of 60 rpm to obtain a slurry composition for a positive electrode mixture layer with a viscosity of 3,600 mPa·s (measured with a Brookfield viscometer at 25±3°C and 60 rpm (rotor M4)).
The slurry composition for the positive electrode composite layer was applied to the coating layer of the electrode member with an applicator so that the coating amount was 18±0.5 mg/cm ^2. Furthermore, the slurry composition for the positive electrode composite layer on the coating layer of the electrode member was dried by conveying it through an oven at a temperature of 120° C. for 2 minutes, and a positive electrode raw sheet in which a positive electrode composite layer was formed on the coating layer of the electrode member was obtained. Thereafter, the prepared positive electrode raw sheet was roll-pressed under a temperature of 25±3° C. and a load of 14 t (tons) to obtain a positive electrode having a density of a positive electrode composite layer of 3.30 g/cm ³ .
The average particle diameter A, the average thickness A, and the coverage of the obtained positive electrode were measured. The resistance increase rate of the electrode was also measured to evaluate the safety of the electrochemical device. The results are shown in Table 1.

<Preparation of negative electrode>
In a 5 MPa pressure vessel equipped with a stirrer, 63 parts of styrene, 34 parts of 1,3-butadiene, 2 parts of itaconic acid, 1 part of 2-hydroxyethyl acrylate, 0.3 parts of t-dodecyl mercaptan as a molecular weight regulator, 5 parts of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of ion-exchanged water, and 1 part of potassium persulfate as a polymerization initiator were added, and after sufficient stirring, the temperature was raised to 55 ° C. to start polymerization. When the polymerization conversion rate reached 95.0%, the reaction was stopped by cooling. A 5% aqueous sodium hydroxide solution was added to the aqueous dispersion containing the polymer thus obtained, and the pH was adjusted to 8. Thereafter, unreacted monomers were removed by heating and reduced pressure distillation. Further, by cooling to a temperature of 30 ° C. or less, an aqueous dispersion containing a binder for a negative electrode (a binder composition for a negative electrode) was obtained.
Into a planetary mixer, 48.75 parts of artificial graphite (theoretical capacity 360 mAh / g) as a negative electrode active material, 48.75 parts of natural graphite (theoretical capacity 360 mAh / g), and 1 part of carboxymethyl cellulose in solid content equivalent were added. Further, the mixture was diluted with ion-exchanged water so that the solid content concentration was 60%, and then kneaded for 60 minutes at a rotation speed of 45 rpm. Then, 1.5 parts of the negative electrode binder composition obtained above in solid content equivalent were added, and kneaded for 40 minutes at a rotation speed of 40 rpm. Then, ion-exchanged water was added so that the viscosity was 3000 ± 500 mPa · s (measured at 25 ° C. and 60 rpm) to prepare a slurry composition for a negative electrode composite layer.
The above-mentioned slurry composition for the negative electrode composite layer was applied to the surface of a 15 μm thick copper foil as a current collector with a comma coater so that the coating amount was 11±0.5 mg/cm ^2. Then, the copper foil coated with the slurry composition for the negative electrode composite layer was conveyed at a speed of 400 mm/min through an oven at a temperature of 80° C. for 2 minutes and then through an oven at a temperature of 110° C. for 2 minutes, thereby drying the slurry composition for the negative electrode composite layer on the copper foil, and obtaining a negative electrode raw sheet having a negative electrode composite layer formed on the current collector. Then, the negative electrode composite layer side of the prepared negative electrode raw sheet was roll-pressed under a temperature of 25±3° C. and a linear pressure of 11 t (tons), to obtain a negative electrode having a density of 1.60 g/cm ³ for the negative electrode composite layer.

<Preparing the separator>
As a separator, a single-layer polypropylene separator substrate (manufactured by Celgard, product name "#2500") was prepared.

<Preparation of secondary battery>
A single-layer laminate cell (equivalent to an initial design discharge capacity of 30 mAh) was produced using the negative electrode, positive electrode and separator obtained above. At this time, the functional layer of the separator was arranged so as to face the positive electrode. The obtained laminate was placed in an aluminum packaging material and vacuum dried at 60 ° C. for 10 hours. Then, a 1.0 M LiPF ₆ solution (solvent: mixed solvent of ethylene carbonate (EC) / diethyl carbonate (DEC) = 3 / 7 (volume ratio), additive: containing 2 vol% vinylene carbonate (solvent ratio)) was filled as an electrolyte. Furthermore, in order to seal the opening of the aluminum packaging material, the aluminum packaging material was closed by heat sealing at a temperature of 150 ° C., and a lithium ion secondary battery was produced.
The capacity retention rate of this lithium ion secondary battery was measured, and the cycle characteristics of the electrochemical device were evaluated. The results are shown in Table 1.

(Examples 1-2 to 1-10, Comparative Example 1-1)
In preparing the slurry composition for an electrochemical element electrode member, various operations, measurements, and evaluations were carried out in the same manner as in Example 1-1, except that the expandable graphite used as the conductive thermal expansion material was changed to one having an average particle size B shown in Table 1. The measurement and evaluation results are shown in Table 1.

(Example 2-1)
In the preparation of the slurry composition for an electrochemical element electrode member, the amount of each component was changed as shown in Table 2, and in the production of the electrode member, the gap of the doctor blade was changed to adjust the application amount of the slurry composition for an electrochemical element electrode member, thereby changing the coating rate as shown in Table 2. Except for this, various operations, measurements, and evaluations were carried out in the same manner as in Example 1-1. The measurement and evaluation results are also shown in Table 2.

(Examples 2-2 to 2-10, Comparative Example 2-1)
In preparing the slurry composition for an electrochemical element electrode member, various operations, measurements, and evaluations were carried out in the same manner as in Example 2-1, except that the expandable graphite used as the conductive thermal expansion material was changed to one having an average particle size B shown in Table 2. The results of the measurements and evaluations are shown in Table 2.

(Example 3-1)
In the preparation of the slurry composition for an electrochemical element electrode member, the amount of each component was changed as shown in Table 3, and in the production of the electrode member, the gap of the doctor blade was changed to adjust the application amount of the slurry composition for an electrochemical element electrode member, thereby changing the coating rate as shown in Table 3. Except for this, various operations, measurements, and evaluations were carried out in the same manner as in Example 1-1. The measurement and evaluation results are also shown in Table 3.

(Examples 3-2 to 3-10, Comparative Example 3-1)
In preparing the slurry composition for an electrochemical element electrode member, various operations, measurements, and evaluations were carried out in the same manner as in Example 3-1, except that the expandable graphite used as the conductive thermal expansion material was changed to one having an average particle size B shown in Table 3. The results of the measurements and evaluations are shown in Table 3.

(Example 4-1)
In the preparation of the slurry composition for an electrochemical element electrode member, the amount of each component was changed as shown in Table 4, and in the production of the electrode member, the gap of the doctor blade was changed to adjust the application amount of the slurry composition for an electrochemical element electrode member, thereby changing the coating rate as shown in Table 4. Except for this, various operations, measurements, and evaluations were carried out in the same manner as in Example 1-1. The measurement and evaluation results are also shown in Table 4.

(Examples 4-2 to 4-9, Comparative Examples 4-1 and 4-2)
In preparing the slurry composition for an electrochemical element electrode member, various operations, measurements, and evaluations were carried out in the same manner as in Example 4-1, except that the expandable graphite used as the conductive thermal expansion material was changed to one having an average particle size B shown in Table 4. The results of the measurements and evaluations are shown in Table 4.

(Example 5-1)
In the preparation of the slurry composition for an electrochemical element electrode member, the amount of each component was changed as shown in Table 5, and in the production of the electrode member, the gap of the doctor blade was changed to adjust the application amount of the slurry composition for an electrochemical element electrode member, thereby changing the coating rate as shown in Table 5. Except for this, various operations, measurements, and evaluations were carried out in the same manner as in Example 1-1. The measurement and evaluation results are also shown in Table 5.

(Examples 5-2 to 5-9, Comparative Examples 5-1 and 5-2)
In preparing the slurry composition for an electrochemical element electrode member, various operations, measurements, and evaluations were carried out in the same manner as in Example 5-1, except that the expandable graphite used as the conductive thermal expansion material was changed to one having an average particle size B shown in Table 5. The results of the measurements and evaluations are shown in Table 5.

(Example 6-1)
In the preparation of the slurry composition for an electrochemical element electrode member, the amount of each component was changed as shown in Table 6, and in the production of the electrode member, the gap of the doctor blade was changed to adjust the application amount of the slurry composition for an electrochemical element electrode member, thereby changing the coating rate as shown in Table 6. Except for this, various operations, measurements, and evaluations were carried out in the same manner as in Example 1-1. The measurement and evaluation results are also shown in Table 6.

(Examples 6-2 to 6-8, Comparative Examples 6-1 to 6-3)
In preparing the slurry composition for an electrochemical element electrode member, various operations, measurements, and evaluations were carried out in the same manner as in Example 6-1, except that the expandable graphite used as the conductive thermal expansion material was changed to one having an average particle size B shown in Table 6. The results of the measurements and evaluations are shown in Table 6.

(Example 7-1)
In the preparation of the slurry composition for an electrochemical element electrode member, the amount of each component was changed as shown in Table 7, and in the production of the electrode member, the gap of the doctor blade was changed to adjust the application amount of the slurry composition for an electrochemical element electrode member, thereby changing the coating rate as shown in Table 7. Except for this, various operations, measurements, and evaluations were carried out in the same manner as in Example 1-1. The measurement and evaluation results are shown in Table 7.

(Examples 7-2 to 7-8, Comparative Examples 7-1 to 7-3)
In preparing the slurry composition for an electrochemical element electrode member, various operations, measurements, and evaluations were carried out in the same manner as in Example 7-1, except that the expandable graphite used as the conductive thermal expansion material was changed to one having an average particle size B shown in Table 7. The results of the measurements and evaluations are shown in Table 7.

(Example 8-1)
In the preparation of the slurry composition for an electrochemical element electrode member, the amount of each component was changed as shown in Table 8, and in the production of the electrode member, the gap of the doctor blade was changed to adjust the application amount of the slurry composition for an electrochemical element electrode member, thereby changing the coating rate as shown in Table 8. Except for this, various operations, measurements, and evaluations were carried out in the same manner as in Example 1-1. The measurement and evaluation results are shown in Table 8.

(Examples 8-2 to 8-9, Comparative Examples 8-1 and 8-2)
In preparing the slurry composition for an electrochemical element electrode member, various operations, measurements, and evaluations were carried out in the same manner as in Example 8-1, except that the expandable graphite used as the conductive thermal expansion material was changed to one having an average particle size B shown in Table 8. The results of the measurements and evaluations are shown in Table 8.

(Example 9-1)
In the preparation of the slurry composition for an electrochemical element electrode member, the amount of each component was changed as shown in Table 9, and in the production of the electrode member, the gap of the doctor blade was changed to adjust the application amount of the slurry composition for an electrochemical element electrode member, thereby changing the coating rate as shown in Table 9. Except for this, various operations, measurements, and evaluations were carried out in the same manner as in Example 1-1. The measurement and evaluation results are also shown in Table 9.

(Examples 9-2 to 9-9, Comparative Examples 9-1 and 9-2)
In preparing the slurry composition for the electrochemical element electrode member, various operations, measurements, and evaluations were carried out in the same manner as in Example 9-1, except that the expandable graphite used as the conductive thermal expansion material was changed to one having an average particle size B shown in Table 9. The results of the measurements and evaluations are shown in Table 9.

(Example 10-1)
In the preparation of the slurry composition for an electrochemical element electrode member, the amount of each component was changed as shown in Table 10, and in the production of the electrode member, the gap of the doctor blade was changed to adjust the coating amount of the slurry composition for an electrochemical element electrode member, thereby changing the coating rate as shown in Table 10. Except for this, various operations, measurements, and evaluations were carried out in the same manner as in Example 1-1. The measurement and evaluation results are also shown in Table 10.

(Examples 10-2 to 10-9, Comparative Examples 10-1 and 10-2)
In preparing the slurry composition for an electrochemical element electrode member, various operations, measurements, and evaluations were carried out in the same manner as in Example 10-1, except that the expandable graphite used as the conductive thermal expansion material was changed to one having an average particle size B shown in Table 10. The results of the measurements and evaluations are shown in Table 10.

(Example 11-1)
In the preparation of the slurry composition for an electrochemical element electrode member, the amount of each component was changed as shown in Table 11, and in the production of the electrode member, the gap of the doctor blade was changed to adjust the coating amount of the slurry composition for an electrochemical element electrode member, thereby changing the coating rate as shown in Table 11. Except for this, various operations, measurements, and evaluations were carried out in the same manner as in Example 1-1. The measurement and evaluation results are shown in Table 11.

(Examples 11-2 to 11-8, Comparative Examples 11-1 to 11-3)
In preparing the slurry composition for an electrochemical element electrode member, various operations, measurements, and evaluations were carried out in the same manner as in Example 11-1, except that the expandable graphite used as the conductive thermal expansion material was changed to one having an average particle size B shown in Table 11. The results of the measurements and evaluations are shown in Table 11.

(Comparative Example 12-1)
In the preparation of the slurry composition for an electrochemical element electrode member, the amount of each component was changed as shown in Table 12, and in the production of the electrode member, the gap of the doctor blade was changed to adjust the coating amount of the slurry composition for an electrochemical element electrode member, thereby changing the coating rate as shown in Table 12. Except for this, various operations, measurements, and evaluations were carried out in the same manner as in Example 1-1. The measurement and evaluation results are shown in Table 12.

(Comparative Examples 12-2 to 12-11)
In preparing the slurry composition for an electrochemical element electrode member, various operations, measurements, and evaluations were carried out in the same manner as in Comparative Example 12-1, except that the expandable graphite used as the conductive thermal expansion material was changed to one having an average particle size B shown in Table 12. The results of the measurements and evaluations are shown in Table 12.

(Comparative Example 13-1)
In the preparation of the slurry composition for an electrochemical element electrode member, the amount of each component was changed as shown in Table 13, and in the production of the electrode member, the gap of the doctor blade was changed to adjust the coating amount of the slurry composition for an electrochemical element electrode member, thereby changing the coating rate as shown in Table 13. Except for this, various operations, measurements, and evaluations were carried out in the same manner as in Example 1-1. The measurement and evaluation results are also shown in Table 13.

(Comparative Examples 13-2 to 13-11)
In preparing the slurry composition for an electrochemical element electrode member, various operations, measurements, and evaluations were carried out in the same manner as in Comparative Example 13-1, except that the expandable graphite used as the conductive thermal expansion material was changed to one having an average particle size B shown in Table 13. The results of the measurements and evaluations are shown in Table 13.

(Comparative Example 14)
In preparing the slurry composition for an electrochemical element electrode member, the amount of each component was changed as shown in Table 14, i.e., the slurry composition for an electrochemical element electrode member was prepared without using the conductive thermal expansion material, and the same operations, measurements, and evaluations were carried out as in Example 1-1. The results of the measurements and evaluations are shown in Table 14.

(Example 15)
In preparing the slurry composition for the electrochemical element electrode member, the amount of expandable graphite used as the conductive thermal expansion material was changed from 80 parts to 30 parts, and the amount of acetylene black used as the conductive assistant was changed from 10 parts to 60 parts, but other than that, various operations, measurements, and evaluations were carried out in the same manner as in Example 1-1. The measurement and evaluation results are shown in Table 14.

(Example 16)
In preparing the slurry composition for the electrochemical element electrode member, the amount of expandable graphite used as the conductive thermal expansion material was changed from 80 parts to 89.5 parts, and the amount of acetylene black used as the conductive assistant was changed from 10 parts to 0.5 parts. Except for this, various operations, measurements, and evaluations were carried out in the same manner as in Example 1-1. The measurement and evaluation results are shown in Table 14.

(Example 17)
In the preparation of the slurry composition for the electrochemical element electrode member, various operations, measurements, and evaluations were carried out in the same manner as in Example 1-1, except that the aqueous dispersion of the polymer as the binder was not used, and the amount of carboxymethyl cellulose used as the dispersant was changed from 7.5 parts to 10 parts. The measurement and evaluation results are shown in Table 14.

As is clear from Tables 1 to 14, by using the electrochemical element electrode members of the examples, it is possible to impart excellent cycle characteristics to the electrochemical element while ensuring a high level of safety for the electrochemical element. Also, as is clear from Figures 4 and 5, the evaluation results for safety and cycle characteristics for those using the electrochemical element electrode members of the examples are both "B" or higher.

According to the present invention, it is possible to provide an electrode member for an electrochemical device that can provide an electrochemical device with excellent cycle characteristics while ensuring a high level of safety for the electrochemical device.
Furthermore, according to the present invention, it is possible to provide an electrochemical element which ensures a high level of safety and has excellent cycle characteristics.

10: Electrochemical element electrode member 11: Current collector 12: Conductive thermal expansion material-containing portion 121: Conductive thermal expansion material 122: Current collector side arrangement surface 20: Electrochemical element electrode member 21: Electrode mixture layer 211: First surface 212: Second surface

Claims

An electrochemical element electrode member comprising a current collector and a conductive thermal expansion material-containing portion located on the current collector,
a coverage rate of the conductive thermal expansion material with respect to a collector side surface of the conductive thermal expansion material-containing portion is 20% or more and 98% or less;
The product of the coverage and the average particle size of the conductive thermal expansion material is 500 or more and 15,000 or less.
The coverage is 30% or more,
2. The electrode member for an electrochemical element according to claim 1, wherein the product is 1,500 or more.
The coverage is 95% or less,
The average particle size is 20 μm or more and 160 μm or less,
2. The electrode member for an electrochemical element according to claim 1, wherein the product is 9,500 or less.
The coverage is 30% or more and 95% or less,
The average particle size is 20 μm or more and 160 μm or less,
2. The electrode member for an electrochemical element according to claim 1, wherein the product is 1,500 or more and 9,500 or less.
The electrochemical element electrode member according to claim 1, wherein the conductive thermal expansion material has an average thickness of 0.2 μm or more and 5 μm or less.
The electrochemical element electrode member according to claim 1, wherein the conductive thermal expansion material is expanded graphite.
The electrochemical element electrode member according to claim 1, wherein the conductive thermal expansion material-containing portion is a coating layer.
The electrochemical element electrode member according to claim 7, wherein the coating layer is formed directly on the surface of the current collector.
The conductive thermal expansion material-containing portion further contains a conductive assistant,
2. The electrode member for an electrochemical element according to claim 1, wherein a mass ratio of said conductive assistant to said conductive thermal expansion material is 0.01 or more and 0.5 or less.
The electrochemical element electrode member according to claim 1, wherein the conductive thermal expansion material-containing portion further contains a binder.
An electrode mixture layer is provided,
the electrode mixture layer has a first surface located on the current collector side and a second surface located on the opposite side to the first surface,
11. The electrode member for an electrochemical element according to claim 1, wherein the electrically conductive thermally expandable material-containing portion is located between the current collector and the second surface.
An electrochemical element comprising an electrode formed using the electrochemical element electrode member according to claim 11.