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WO2024071057A1 - Élément pour électrode d'élément électrochimique, et élément électrochimique - Google Patents

Élément pour électrode d'élément électrochimique, et élément électrochimique Download PDF

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Publication number
WO2024071057A1
WO2024071057A1 PCT/JP2023/034795 JP2023034795W WO2024071057A1 WO 2024071057 A1 WO2024071057 A1 WO 2024071057A1 JP 2023034795 W JP2023034795 W JP 2023034795W WO 2024071057 A1 WO2024071057 A1 WO 2024071057A1
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Prior art keywords
thermal expansion
expansion material
electrochemical element
conductive thermal
electrode member
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Japanese (ja)
Inventor
明彦 宮崎
健彦 片山
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Zeon Corp
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Zeon Corp
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/26—Electrodes characterised by their structure, e.g. multi-layered, porosity or surface features
    • H01G11/28—Electrodes characterised by their structure, e.g. multi-layered, porosity or surface features arranged or disposed on a current collector; Layers or phases between electrodes and current collectors, e.g. adhesives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • the coverage can be measured using an FE-SEM according to the method described in the Examples.
  • the unit of coverage is "%” and the unit of average particle size A is " ⁇ m”. Therefore, although omitted, the unit of the product of the coverage and the average particle size A is " ⁇ m ⁇ %".
  • 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.
  • the coverage is 95% or less
  • the average particle size is 20 ⁇ m or more and 160 ⁇ m or less
  • the product is 9,500 or less.
  • the coverage is 30% or more and 95% or less
  • the average particle size is 20 ⁇ m or more and 160 ⁇ m or less
  • the product is 1,500 or more and 9,500 or less.
  • the conductive thermal expansion material preferably has an average thickness of 0.2 ⁇ m or more and 5 ⁇ m or less.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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”).
  • 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.
  • 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.
  • 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.
  • FIGS 1 to 3 are schematic cross-sectional views showing an example of an electrochemical element electrode member of the present invention.
  • 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.
  • the electrochemical element electrode members shown in Figures 2 and 3 have an electrode mixture layer and are used as an electrode as is.
  • 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).
  • 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).
  • 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.
  • 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.
  • 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 does not correspond to the current collector-side mounting surface 122.
  • 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.
  • 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.
  • the electrochemical element 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.
  • 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.
  • 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.
  • a material having electrical conductivity and electrochemical durability can be selected and used according to the type of electrochemical element.
  • a 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.
  • a metal foil as the current collector.
  • copper foil is particularly preferable as the current collector used for the negative electrode.
  • 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.
  • 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").
  • 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.
  • 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 ⁇ m or more, more preferably 20 ⁇ m or more, even more preferably 30 ⁇ m or more, even more preferably 40 ⁇ m or more, even more preferably 60 ⁇ m or more, preferably 200 ⁇ m or less, more preferably 160 ⁇ m or less, even more preferably 120 ⁇ m or less, and even more preferably 100 ⁇ m 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 ⁇ m or more, more preferably 0.5 ⁇ m or more, and is preferably 5 ⁇ m or less, more preferably 4 ⁇ m 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.
  • 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.
  • a conductive carbon material and fibers or foils of various metals can be used, but a conductive carbon material is preferred.
  • the conductive carbon material examples 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.
  • carbon black e.g., acetylene black, Ketjen Black (registered trademark), furnace black, etc.
  • single-layer or 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
  • carbon nonwoven fabric sheets obtained by baking nonwoven fabric made of polymer fibers.
  • it is preferable to use carbon black as the conductive assistant it
  • 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.
  • 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.
  • 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 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.
  • 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.
  • 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.
  • 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.
  • the binder is not particularly limited as long as it can be used in an electrochemical element.
  • a polymer synthetic polymer, for example, an addition polymer obtained by addition polymerization
  • a monomer composition containing a monomer capable of exhibiting binding properties can be used as the binder.
  • polymers examples 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.
  • aliphatic conjugated diene/aromatic vinyl copolymers acrylic polymers, acrylic acid/acrylamide copolymers, and fluorine-based polymers are preferred.
  • 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.
  • containing a monomer unit means that "a polymer obtained by using the monomer contains a repeating unit derived from the monomer”.
  • 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%.”
  • (meth)acrylic means acrylic and/or methacrylic
  • (meth)acrylo means acrylo and/or methacrylo.
  • 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").
  • specific functional groups One type of these may be used alone, or two or more types may be used in combination at any ratio.
  • 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.
  • 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, ⁇ -acetoxyacrylic acid, ⁇ -trans-aryloxyacrylic acid, ⁇ -chloro- ⁇ -E-methoxyacrylic acid, and the like.
  • the dicarboxylic acid includes maleic acid, fumaric acid, itaconic acid, and the like.
  • 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.
  • acid anhydrides of dicarboxylic acids include maleic anhydride, acrylic anhydride, methylmaleic anhydride, and dimethylmaleic anhydride.
  • 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.
  • the carboxyl group-containing monomer one type may be used alone, or two or more types may be used in combination at any ratio.
  • 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)
  • the hydroxyl group-containing monomer may be used alone or in combination of two or more kinds in any ratio.
  • “(meth)allyl” means allyl and/or methallyl
  • “(meth)acryloyl” means acryloyl and/or methacryloyl.
  • Cyano group-containing monomers capable of forming cyano group-containing monomer units include ⁇ , ⁇ -ethylenically unsaturated nitrile monomers.
  • the ⁇ , ⁇ -ethylenically unsaturated nitrile monomer is not particularly limited as long as it is an ⁇ , ⁇ -ethylenically unsaturated compound having a cyano group, but examples include acrylonitrile; ⁇ -halogenoacrylonitriles such as ⁇ -chloroacrylonitrile and ⁇ -bromoacrylonitrile; ⁇ -alkylacrylonitriles such as methacrylonitrile and ⁇ -ethylacrylonitrile; and the like.
  • the cyano group-containing monomers may be used alone or in combination of two or more types in any ratio.
  • 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.
  • (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.
  • 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-decen
  • 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.
  • 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.
  • 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.
  • 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.
  • known emulsifiers and polymerization initiators can be used during polymerization, if necessary.
  • 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.
  • the cycle characteristics of the electrochemical element can be further improved.
  • 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 ⁇ -naphthalenesulfonic acid-formalin condensates, and carboxymethyl cellulose.
  • 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.
  • the conductive thermal expansion material-containing portion may contain an electrode active material.
  • 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 ⁇ m or more, more preferably 3 ⁇ m or more, and is preferably 10 ⁇ m or less, and more preferably 7 ⁇ m or less.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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> 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.
  • 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 ⁇ m or more and 160 ⁇ m or less, and a product of the coverage rate and the average particle diameter A of 9,500 or less.
  • coverage is equal to or less than the upper limit
  • the average particle size A is within the above range
  • the product is equal to or less than the upper limit
  • 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 ⁇ m or more and 160 ⁇ m or less
  • the product of the coverage and the average particle diameter A is 9,500 or less.
  • 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.
  • 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).
  • 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).
  • a composition slurry composition for the electrode mixture layer containing conductive thermally expandable material
  • 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.
  • 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.
  • 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 ⁇ m or more, more preferably 20 ⁇ m or more, even more preferably 30 ⁇ m or more, even more preferably 40 ⁇ m or more, even more preferably 60 ⁇ m or more, preferably 200 ⁇ m or less, more preferably 160 ⁇ m or less, even more preferably 120 ⁇ m or less, and even more preferably 100 ⁇ m or less.
  • the average particle size B can be measured using an FE-SEM according to the method described in the Examples.
  • 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 ⁇ m or more, more preferably 0.5 ⁇ m or more, and is preferably 5 ⁇ m or less, more preferably 4 ⁇ m or less.
  • 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.
  • the organic solvent 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.
  • a mixer such as a ball mill, sand mill, bead mill, pigment disperser, crusher, ultrasonic disperser, homogenizer, planetary mixer, or Filmix.
  • 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.
  • 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.
  • 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.
  • 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.
  • the electrode mixture layer is formed on the conductive thermal expansion material-containing portion of the electrode member before use as an electrode.
  • 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.
  • 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.
  • 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.
  • 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.
  • a polyolefin resin polyethylene, polypropylene, polybutene, polyvinyl chloride
  • an organic electrolyte in which a supporting electrolyte is dissolved in an organic solvent is usually used.
  • a lithium salt is used in a lithium ion secondary battery.
  • 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.
  • 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.
  • one type of electrolyte may be used alone, or two or more types may be used in combination.
  • 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.
  • 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 ⁇ -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.
  • carbonates are preferred because they have a high dielectric constant and a wide stable potential region.
  • 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.
  • 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.
  • 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.
  • “%” and “parts” expressing amounts are based on mass unless otherwise specified.
  • 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.
  • ⁇ 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.
  • TMA thermomechanical analysis
  • 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 was taken as the thermal expansion coefficient of the conductive thermal expansion material.
  • TMA thermomechanical analysis
  • NETZSCH NETZSCH
  • 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.).
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.).
  • 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.
  • 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.
  • 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.).
  • 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.
  • 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 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)
  • the lithium ion secondary battery was left to stand at a temperature of 25°C for 5 hours after injecting the electrolyte.
  • 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.
  • the battery was discharged to a cell voltage of 3.00V at a constant current of 0.2C at a temperature of 25°C.
  • 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.
  • Cycle capacity retention rate 100th cycle discharge capacity / 1st cycle discharge capacity ⁇ 100 (3)
  • 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.
  • aqueous dispersion of the polymer 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.
  • 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).
  • 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 ⁇ m thick aluminum foil with a doctor blade to a coating thickness of 5 ⁇ m. 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.
  • NMP N-methylpyrrolidone
  • 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.
  • a slurry composition for a negative electrode composite layer was prepared.
  • the above-mentioned slurry composition for the negative electrode composite layer was applied to the surface of a 15 ⁇ m thick copper foil as a current collector with a comma coater so that the coating amount was 11 ⁇ 0.5 mg/cm 2.
  • 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.
  • 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.
  • a separator As a separator, a single-layer polypropylene separator substrate (manufactured by Celgard, product name "#2500”) was prepared.
  • 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.
  • 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.
  • Example 2-2 to 2-10 Comparative Example 2-1
  • 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.
  • 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
  • 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
  • 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.
  • Example 7-2 to 7-8 Comparative Examples 7-1 to 7-3
  • 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.
  • Example 8-2 to 8-9 Comparative Examples 8-1 and 8-2
  • 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.
  • Example 9-2 to 9-9 Comparative Examples 9-1 and 9-2
  • 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.
  • Example 10-2 to 10-9 Comparative Examples 10-1 and 10-2
  • 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
  • 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.
  • 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.
  • 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.
  • 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

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Abstract

Un but de la présente invention est de fournir un élément pour une électrode d'élément électrochimique, ledit élément étant apte à conférer des caractéristiques de cycle supérieures à l'élément électrochimique tout en garantissant que l'élément électrochimique est extrêmement sûr. La présente invention concerne un élément pour une électrode d'élément électrochimique, ledit élément comprenant un collecteur de courant et une section comprenant un matériau d'expansion thermique conducteur qui est située sur le collecteur de courant, le pourcentage de couverture par le matériau d'expansion thermique conducteur d'une surface de positionnement côté collecteur de courant de la section comprenant un matériau d'expansion thermique conducteur étant de 20 % à 98 %, et le produit de ce pourcentage de couverture et la taille de particule moyenne du matériau d'expansion thermique conducteur étant de 500 à 15 000.
PCT/JP2023/034795 2022-09-30 2023-09-25 Élément pour électrode d'élément électrochimique, et élément électrochimique Ceased WO2024071057A1 (fr)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008262785A (ja) * 2007-04-11 2008-10-30 Matsushita Electric Ind Co Ltd 非水電解質二次電池
JP2013080627A (ja) * 2011-10-04 2013-05-02 Toyota Motor Corp 非水電解液二次電池
WO2014050653A1 (fr) * 2012-09-28 2014-04-03 古河電気工業株式会社 Collecteur, structure d'électrode, batterie à électrolyte non aqueux, charge conductrice, et composant de stockage d'électricité
CN113113603A (zh) * 2020-01-13 2021-07-13 荣盛盟固利新能源科技有限公司 一种锂离子电池电极片、其制备方法和锂离子电池
WO2021166422A1 (fr) * 2020-02-20 2021-08-26 パナソニックＩｐマネジメント株式会社 Batterie

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008262785A (ja) * 2007-04-11 2008-10-30 Matsushita Electric Ind Co Ltd 非水電解質二次電池
JP2013080627A (ja) * 2011-10-04 2013-05-02 Toyota Motor Corp 非水電解液二次電池
WO2014050653A1 (fr) * 2012-09-28 2014-04-03 古河電気工業株式会社 Collecteur, structure d'électrode, batterie à électrolyte non aqueux, charge conductrice, et composant de stockage d'électricité
CN113113603A (zh) * 2020-01-13 2021-07-13 荣盛盟固利新能源科技有限公司 一种锂离子电池电极片、其制备方法和锂离子电池
WO2021166422A1 (fr) * 2020-02-20 2021-08-26 パナソニックＩｐマネジメント株式会社 Batterie

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