Composition for electrochemical device functional layer, laminate for electrochemical device, and electrochemical device

Abstract

A composition for an electrochemical element functional layer, the composition including a particulate polymer, a binding material, and heat-resistant fine particles. The particulate polymer is characterized by having a core-shell structure that comprises core parts that comprise a polymer A and shell parts that comprise a polymer B, the degree SA to which polymer A swells in an electrolyte being 1–8 times, the degree SB to which polymer B swells in an electrolyte being at least 4 times, and SB / SA being equal to or greater than 1.2. The particulate polymer is also characterized by having a volume average particle diameter of 1.0–10.0 μm.

Description

[Technical Field]

[0001] The present invention relates to a composition for a functional layer of an electrochemical device, a laminate for an electrochemical device, and an electrochemical device. [Background technology]

[0002] Electrochemical devices such as lithium-ion secondary batteries and electric double-layer capacitors are small, lightweight, have high energy density, and can be repeatedly charged and discharged, and are therefore used in a wide range of applications.

[0003] Here, for example, a lithium ion secondary battery generally includes battery components such as a positive electrode, a negative electrode, and a separator that separates the positive electrode from the negative electrode to prevent short-circuiting between the positive electrode and the negative electrode.

[0004] In recent years, further improvements in electrochemical element components such as positive electrodes, negative electrodes, and separators have been investigated with the aim of further improving the performance of lithium secondary batteries. In such improvements, attempts have been made to laminate layers (functional layers) on separator substrates to exhibit desired functions such as heat resistance and adhesiveness. Specifically, for example, Patent Document 1 discloses an aqueous resin composition for a lithium-ion secondary battery binder, which contains core-shell particles and an aqueous medium, characterized in that the core portion of the core-shell particles contains a predetermined proportion of styrene units, and the shell portion contains a predetermined proportion of methyl methacrylate units and (meth)acrylate units having an alkyl group having 4 or more carbon atoms. Patent Document 1 also discloses the formation of an adhesive layer on the surface of a separator using the above composition. Furthermore, for example, Patent Document 2 proposes a separator comprising a microporous polyolefin film carrying polymer particles having a core-shell structure. Furthermore, for example, Patent Document 3 proposes a structure in which an active layer formed using a composition containing an acrylic resin having a core-shell structure is disposed on a separator substrate containing polyethylene and polypropylene. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2018 / 043200 [Patent Document 2] Patent Publication No. 2018-200786 [Patent Document 3] Patent Publication No. 2018-101614 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, with the expansion of applications of electrochemical elements, there has been a demand for further improvement in the adhesiveness of functional layers when immersed in an electrolyte (hereinafter, also referred to as "wet adhesiveness"). More specifically, there is a need for functional layers that can exhibit good wet adhesiveness even under conditions where high pressing pressure cannot be applied. In addition, electrochemical elements equipped with functional layers are required to have excellent electrolyte injectability and rate characteristics.

[0007] However, the separators formed according to the above-mentioned conventional techniques have room for improvement in terms of wet adhesion, as well as in terms of further improving the electrolyte injection properties and rate characteristics of the resulting electrochemical device.

[0008] Therefore, an object of the present invention is to provide a composition for a functional layer that can form a functional layer having excellent wet adhesion and that can improve the electrolyte injectability and rate characteristics of the resulting electrochemical device. Another object of the present invention is to provide a laminate for electrochemical devices, which includes a functional layer with excellent wet adhesion, capable of improving the electrolyte injectability and rate characteristics of the resulting electrochemical device, and an electrochemical device that includes such a laminate for electrochemical devices and has excellent electrolyte injectability and rate characteristics. [Means for solving the problem]

[0009] The present inventors have conducted extensive research to achieve the above object, and have newly discovered that a functional layer formed using a composition for an electrochemical device functional layer containing a particulate polymer having a predetermined core-shell structure and a volume average particle diameter of 1.0 μm to 10.0 μm exhibits excellent wet adhesion and can improve the electrolyte injectability and rate characteristics of the resulting electrochemical device, thereby completing the present invention.

[0010] That is, the present invention has an object to advantageously solve the above-mentioned problems, and the composition for an electrochemical device functional layer of the present invention is a composition for an electrochemical device functional layer comprising a particulate polymer, a binder, and heat-resistant fine particles, wherein the particulate polymer has a core-shell structure comprising a core portion made of polymer A and a shell portion made of polymer B covering at least a part of the outer surface of the core portion, and the degree of swelling of the polymer A in an electrolyte solution S A is 1 to 8 times, and the electrolyte swelling degree S of the polymer B is B is 4 times or more, and the electrolyte swelling degree S A and the electrolyte swelling degree S B But, S B / S A ≧1.2, and the volume average particle diameter of the particulate polymer is 1.0 μm or more and 10.0 μm or less. In this way, the composition for an electrochemical device functional layer containing a particulate polymer having a core-shell structure formed by polymers A and B whose electrolyte swelling degrees satisfy the predetermined relationship and whose volume average particle diameter is within a predetermined range can form a functional layer having excellent wet adhesion that can improve the electrolyte injectability and rate characteristics of the resulting electrochemical device. The degree of swelling of each polymer in an electrolyte solution can be measured by the method described in the examples of this specification. The "volume average particle size" of the particulate polymer can be measured by the method described in the examples of this specification. Furthermore, the "core-shell structure" of the particulate polymer can be confirmed by observing the particulate polymer using a scanning electron microscope.

[0011] In the composition for an electrochemical device functional layer of the present invention, the particulate polymer preferably has a core to shell ratio, on a mass basis, within a range of 99.9:0.1 to 50:50. When the core to shell ratio of the particulate polymer is within the above-mentioned range, a functional layer having even more excellent wet adhesion can be formed, which can further improve the electrolyte injectability and rate characteristics of the resulting electrochemical device.

[0012] In addition, in the composition for an electrochemical device functional layer of the present invention, it is preferable that the polymer B contains at least one of an aromatic vinyl monomer unit and a nitrile group-containing monomer unit. If the particulate polymer B constituting the shell portion of the particulate polymer contains at least one of an aromatic vinyl monomer unit and a nitrile group-containing monomer unit, a functional layer having even more excellent wet adhesion can be formed. In the present invention, the phrase "containing a monomer unit" means that "a polymer obtained using the monomer contains a structural unit derived from the monomer."

[0013] In addition, in the composition for electrochemical device functional layers of the present invention, the particle size distribution of the particulate polymer is preferably 1.5 or less. If the particle size distribution of the particulate polymer is 1.5 or less, the cycle characteristics of the resulting electrochemical device can be further improved. The particle size distribution of the particulate polymer can be measured according to the method described in the examples of this specification.

[0014] The present invention also aims to advantageously solve the above-mentioned problems, and provides a laminate for electrochemical devices comprising a substrate and a functional layer formed on the substrate using any one of the compositions for electrochemical device functional layers described above. As described above, a laminate for electrochemical devices comprising a functional layer formed using the composition for electrochemical device functional layers of the present invention has excellent wet adhesion, and can improve the electrolyte injectability and rate characteristics of the resulting electrochemical device.

[0015] The present invention has an object to advantageously solve the above-mentioned problems, and provides an electrochemical device comprising the above-mentioned laminate for an electrochemical device. The electrochemical device comprising the laminate for an electrochemical device of the present invention has excellent electrolyte injection properties and rate characteristics. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a composition for a functional layer that can form a functional layer having excellent wet adhesion and that can improve the electrolyte injectability and rate characteristics of the resulting electrochemical device. Furthermore, according to the present invention, it is possible to provide a laminate for electrochemical devices that includes a functional layer with excellent wet adhesion, which can improve the electrolyte injectability and rate characteristics of the resulting electrochemical device, and an electrochemical device that includes such a laminate for electrochemical devices and has excellent electrolyte injectability and rate characteristics. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments of the present invention will be described in detail. Herein, the composition for an electrochemical device functional layer of the present invention (hereinafter also simply referred to as "functional layer composition") is used to form an electrochemical device functional layer (hereinafter also simply referred to as "functional layer") provided in the electrochemical device laminate of the present invention. The electrochemical device laminate of the present invention comprises a functional layer formed using the composition for an electrochemical device functional layer of the present invention. Furthermore, the electrochemical device of the present invention is an electrochemical device comprising at least the electrochemical device laminate of the present invention.

[0018] (Composition for electrochemical device functional layer) The composition for an electrochemical device functional layer of the present invention contains a predetermined particulate polymer, a binder, and heat-resistant fine particles, and may further contain other components. By using the composition for a functional layer of the present invention, a functional layer having excellent wet adhesion can be formed, which can improve the electrolyte injectability and rate characteristics of the resulting electrochemical device.

[0019] <Particulate polymer> The particulate polymer contained in the composition for a functional layer is a particulate polymer that satisfies predetermined structure and properties and has a volume average particle diameter within a predetermined range, as described in detail below. Note that, after bonding members together via a functional layer formed using the composition for a functional layer, the particulate polymer may be in a particulate form or any other shape.

[0020] <<Structure of particulate polymer>> The particulate polymer has a core-shell structure including a core made of polymer A and a shell made of polymer B that covers at least a portion of the outer surface of the core. Here, the shell may cover the entire outer surface of the core, or may cover only a portion of the outer surface. When the particulate polymer has such a core-shell structure, it is possible to improve the wet adhesion of the functional layer and to improve the electrolyte injectability and rate characteristics of the resulting electrochemical device in a balanced manner.

[0021] <<Electrolyte swelling degree S of polymer A constituting the core part A >> Electrolyte swelling degree S of polymer A that constitutes the core part A The electrolyte swelling ratio S must be between 1 and 8 times. A is preferably 1.2 times or more, more preferably 1.3 times or more, and is preferably 6 times or less, more preferably 4 times or less. A If the degree of swelling in electrolyte solution S is equal to or greater than the lower limit, the adhesion of the functional layer in the electrolyte solution can be improved. A If the electrolyte swelling degree S is equal to or less than the upper limit, the electrolyte flow path is less likely to be constricted due to excessive swelling, and the electrolyte injectability of the electrochemical device is improved, thereby reducing the internal resistance of the electrochemical device and improving the rate characteristics of the electrochemical device. A When the modulus of elasticity of the particulate polymer is equal to or less than the upper limit, the modulus of elasticity of the particulate polymer can be prevented from becoming excessively low, and the cycle characteristics of the electrochemical device can be improved.

[0022] <<Glass transition temperature of polymer A that constitutes the core>> The polymer A constituting the core portion of the particulate polymer preferably has a glass transition temperature of 10°C or higher, more preferably 20°C or higher, even more preferably 30°C or higher, particularly preferably 40°C or higher, and preferably 110°C or lower, more preferably 90°C or lower, and even more preferably 80°C or lower. If the glass transition temperature of polymer A is equal to or higher than the above-mentioned lower limit, the blocking resistance of the resulting functional layer can be improved. Note that the "blocking resistance" of the functional layer refers to the property of suppressing unintended adhesion (blocking) when the functional layer is laminated with other components, not for the purpose of adhesion, during the manufacturing process of the electrochemical device. Furthermore, if the glass transition temperature of polymer A is equal to or lower than the above-mentioned upper limit, the dry adhesion of the resulting functional layer can be further improved. The "glass transition temperature" of polymer A can be measured according to the method described in the Examples. The glass transition temperature of polymer A can be adjusted by changing the composition of polymer A.

[0023] <<Core composition of particulate polymer>> The core portion is composed of polymer A. The composition of polymer A is not particularly limited, but for example, polymer A may contain (meth)acrylic acid ester monomer units, aromatic vinyl monomer units, crosslinkable monomer units, and other monomer units.

[0024] [(Meth)acrylic acid ester monomer unit] Examples of (meth)acrylic acid ester monomers that can form the (meth)acrylic acid ester monomer unit include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, butyl acrylates such as n-butyl acrylate and t-butyl acrylate, octyl acrylates such as pentyl acrylate, hexyl acrylate, heptyl acrylate and 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate, and stearyl acrylate. alkyl esters; and methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, butyl methacrylates such as n-butyl methacrylate and t-butyl methacrylate, octyl methacrylates such as pentyl methacrylate, hexyl methacrylate, heptyl methacrylate and 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, lauryl methacrylate, n-tetradecyl methacrylate, stearyl methacrylate, and other methacrylic acid alkyl esters. Among these, n-butyl acrylate, 2-ethylhexyl acrylate, and methyl methacrylate are preferred. In this specification, "(meth)acrylic" refers to acrylic or methacrylic. These (meth)acrylic acid ester monomers may be used singly or in combination of two or more kinds in any ratio.

[0025] The content of (meth)acrylic acid ester monomer units in polymer A is preferably 10% by mass or more, more preferably 15% by mass or more, and preferably 80% by mass or less, more preferably 75% by mass or less, based on 100% by mass of all repeating units contained in polymer A. When the content of (meth)acrylic acid ester monomer units in polymer A is equal to or greater than the above-mentioned lower limit, the glass transition temperature of polymer A can be prevented from decreasing excessively, and the blocking resistance of the resulting functional layer can be improved. When the content of (meth)acrylic acid ester monomer units is equal to or less than the above-mentioned upper limit, the adhesion between the functional layer and the substrate can be improved.

[0026] [Aromatic vinyl monomer unit] The aromatic vinyl monomer that can be used to form the aromatic vinyl monomer unit is not particularly limited, and examples thereof include styrene, α-methylstyrene, styrene sulfonic acid, butoxystyrene, vinylnaphthalene, etc. Among these, styrene is preferred. Note that these aromatic vinyl monomers may be used alone or in combination of two or more at any ratio.

[0027] The content of aromatic vinyl monomer units in polymer A is preferably 20% by mass or more, preferably 90% by mass or less, and more preferably 85% by mass or less, based on 100% by mass of all repeating units contained in polymer A. When the content of aromatic vinyl monomer units in polymer A is within the above range, the dry adhesion of the resulting functional layer can be further improved.

[0028] [Crosslinkable monomer unit] Examples of monomers capable of forming crosslinkable monomer units include polyfunctional monomers having two or more polymerization reactive groups. Examples of such polyfunctional monomers include divinyl compounds such as allyl methacrylate and divinylbenzene; di(meth)acrylic acid ester compounds such as diethylene glycol dimethacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, and 1,3-butylene glycol diacrylate; tri(meth)acrylic acid ester compounds such as trimethylolpropane trimethacrylate and trimethylolpropane triacrylate; and ethylenically unsaturated monomers containing epoxy groups such as allyl glycidyl ether and glycidyl methacrylate. These may be used alone or in combination of two or more. Among these, ethylene glycol dimethacrylate is preferred.

[0029] The content of the crosslinkable monomer units in polymer A is preferably 0.05% by mass or more and 2% by mass or less, based on 100% by mass of all repeating units contained in polymer A. When the content of the crosslinkable monomer units in polymer A is within the above range, the balance between the dry adhesion and the degree of swelling in an electrolyte of the resulting functional layer can be further improved.

[0030] [Other monomer units] Examples of monomers that can be used to form the other monomer units include acidic group-containing monomers and nitrile group-containing monomer units, which will be described later.

[0031] The acidic group-containing monomer that can be used to form the acidic group-containing monomer unit is not particularly limited, and examples thereof include a monomer having a carboxylic acid group, a monomer having a sulfonic acid group, a monomer having a phosphoric acid group, and a monomer having a hydroxyl group.

[0032] Examples of the monomer having a carboxylic acid group include monocarboxylic acids and dicarboxylic acids. Examples of the monocarboxylic acids include acrylic acid, methacrylic acid, and crotonic acid. Examples of the dicarboxylic acids include maleic acid, fumaric acid, and itaconic acid. Examples of the monomer having a sulfonic acid group include vinyl sulfonic acid, methyl vinyl sulfonic acid, (meth)allyl sulfonic acid, (meth)acrylic acid-2-ethyl sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, and 3-allyloxy-2-hydroxypropanesulfonic acid. In this specification, "(meth)allyl" means allyl and / or methallyl, and "(meth)acrylic" means acrylic and / or methacrylic. Furthermore, examples of the monomer having a phosphate group include 2-(meth)acryloyloxyethyl phosphate, methyl-2-(meth)acryloyloxyethyl phosphate, and ethyl-(meth)acryloyloxyethyl phosphate. In this specification, the term "(meth)acryloyl" means acryloyl and / or methacryloyl. Examples of the monomer having a hydroxyl group include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate. These acid group-containing monomers may be used alone or in combination of two or more kinds in any ratio.

[0033] The content of the other monomer units in polymer A is not particularly limited, but is preferably 10% by mass or less, assuming that the total repeating units contained in polymer A is 100% by mass. Alternatively, it may be 0% by mass, i.e., polymer A may not contain any other monomer units.

[0034] <<Electrolyte swelling degree S of polymer B constituting the shell part B >> Electrolyte swelling degree S of polymer A that constitutes the shell B The swelling degree S of the electrolyte solution must be 4 times or more, preferably 6 times or more, more preferably 7 times or more, and even more preferably 8 times or more, and is preferably 20 times or less, more preferably 18 times or less, and even more preferably 16 times or less. B If the degree of swelling in electrolyte solution S is equal to or greater than the lower limit, the adhesion of the functional layer in the electrolyte solution can be improved. B If the electrolyte swelling degree S is equal to or less than the upper limit, the electrolyte flow path is less likely to be constricted due to excessive swelling, and the electrolyte injectability of the electrochemical device is improved, thereby reducing the internal resistance of the electrochemical device and improving the rate characteristics of the electrochemical device. B When the modulus of elasticity of the particulate polymer is equal to or less than the upper limit, the modulus of elasticity of the particulate polymer can be prevented from becoming excessively low, and the cycle characteristics of the electrochemical device can be improved.

[0035] <<Glass transition temperature of polymer B that constitutes the shell portion>> Polymer B constituting the shell portion of the particulate polymer preferably has a glass transition temperature of 70°C or higher, more preferably 80°C or higher, and even more preferably 90°C or higher, and preferably 150°C or lower, more preferably 120°C or lower, and even more preferably 110°C or lower. If the glass transition temperature of polymer B is equal to or higher than the above lower limit, the blocking resistance of the resulting functional layer can be improved. Furthermore, if the glass transition temperature of polymer B is equal to or lower than the above upper limit, the dry adhesion of the resulting functional layer can be further improved. The "glass transition temperature" of polymer B can be measured according to the method described in the Examples. The glass transition temperature of polymer B can be adjusted by changing the composition of polymer B. More specifically, for example, the glass transition temperature of polymer B can be increased by increasing the amount of crosslinkable monomer used in preparing polymer B.

[0036] <<Shell composition of particulate polymer>> The shell portion is made of polymer B. Polymer B preferably contains at least one of an aromatic vinyl monomer unit and a nitrile group-containing monomer unit. If polymer B contains at least one of an aromatic vinyl monomer unit and a nitrile group-containing monomer unit, the wet adhesion of the functional layer can be further improved. Furthermore, from the viewpoint of further enhancing this effect, polymer B preferably contains both an aromatic vinyl monomer unit and a nitrile group-containing monomer unit. In addition to these monomer units, polymer B may also contain (meth)acrylic acid ester monomer units, crosslinkable monomer units, and other monomer units.

[0037] [Aromatic vinyl monomer unit] As the aromatic vinyl monomer unit, the above-mentioned units can be used, among which styrene is preferred.

[0038] When polymer B contains aromatic vinyl monomer units, the content of aromatic vinyl monomer units in polymer B, when the total amount of repeating units contained in polymer B is taken as 100% by mass, is preferably 30% by mass or more, more preferably 45% by mass or more, and preferably 80% by mass or less, and more preferably 70% by mass or less. When the content of aromatic vinyl monomer units is within the above range, the wet adhesion of the functional layer can be further improved. Furthermore, when the content of aromatic vinyl monomer units is equal to or less than the above upper limit, the cycle characteristics of the electrochemical device can be further improved.

[0039] [Nitrile group-containing monomer unit] Examples of nitrile group-containing monomers capable of forming nitrile 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 nitrile group, and examples thereof include acrylonitrile; α-halogenoacrylonitriles such as α-chloroacrylonitrile and α-bromoacrylonitrile; and α-alkylacrylonitriles such as methacrylonitrile and α-ethylacrylonitrile. Among these, acrylonitrile is preferred. These nitrile group-containing monomers may be used alone or in combination of two or more kinds in any ratio.

[0040] When polymer B contains nitrile group-containing monomer units, the content of the nitrile group-containing monomer units in polymer B is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 20% by mass or more, and preferably 60% by mass or less, and more preferably 50% by mass or less, based on 100% by mass of all repeating units contained in polymer B. When the content of the nitrile group-containing monomer units is within the above range, the wet adhesion of the functional layer can be further improved.

[0041] The total proportion of the aromatic vinyl monomer units and the nitrile group-containing monomer units in polymer B is preferably 5% by mass or more, more preferably 10% by mass or more, and is preferably 95% by mass or less, and more preferably 90% by mass or less, when the total repeating units contained in polymer B is taken as 100% by mass. When the total proportion of the aromatic vinyl monomer units and the nitrile group-containing monomer units in polymer B is within the above range, the wet adhesion of the functional layer can be further improved.

[0042] [(Meth)acrylic acid ester monomer unit] As the (meth)acrylic acid ester monomer unit, those mentioned above can be used, among which n-butyl acrylate and methyl methacrylate are preferred.

[0043] The content of (meth)acrylic acid ester monomer units in polymer B is preferably 5% by mass or more, more preferably 10% by mass or more, and preferably 95% by mass or less, more preferably 90% by mass or less, based on 100% by mass of all repeating units contained in polymer B. When the content of (meth)acrylic acid ester monomer units is equal to or greater than the above-mentioned lower limit, an excessive decrease in the glass transition temperature of polymer B can be prevented, and the blocking resistance of the resulting functional layer can be improved. When the content of (meth)acrylic acid ester monomer units is equal to or less than the above-mentioned upper limit, the adhesion between the functional layer and the substrate can be improved.

[0044] [Crosslinkable monomer unit] As the crosslinkable monomer unit, those mentioned above can be used, among which ethylene glycol dimethacrylate is preferred.

[0045] The content of the crosslinkable monomer unit in polymer B is preferably 0.1% by mass or more, preferably 5 parts by mass or less, and more preferably 2 parts by mass or less, based on 100% by mass of all repeating units contained in polymer B. When the content of the crosslinkable monomer unit in polymer B is within the above range, the balance between the dry adhesion and the degree of swelling in an electrolyte of the resulting functional layer can be further improved.

[0046] [Other monomer units] The other monomers capable of forming the other monomer units are not particularly limited, and examples thereof include the above-mentioned acidic group-containing monomer units.

[0047] The content of other monomer units in polymer B is not particularly limited, but is preferably 10% by mass or less, assuming that the total repeating units contained in polymer B is 100% by mass. Alternatively, it may be 0% by mass, i.e., polymer B may not contain any other monomer units.

[0048] <<Electrolyte swelling degree S A and electrolyte swelling degree S B Ratio S B / S A >> The electrolyte swelling degree S mentioned above A and electrolyte swelling degree S B is the ratio S B / S A The ratio S must be 1.2 or more, preferably 1.3 or more, and more preferably 1.5 or more. B / S A The upper limit of the value of the ratio S is not particularly limited, but may be 10.0 or less. B / S AIf the value of is equal to or greater than the above lower limit, the elastic force of the core portion tends to be higher than the elastic force of the shell portion in the particulate polymer immersed in the electrolyte solution, and the core portion maintains its particle shape while the shell portion follows the expansion and contraction to maintain the adhesive state between the members when the electrochemical device undergoes repeated charge and discharge. In other words, the core portion does not deform in response to the expansion and contraction of the members, but the shell portion deforms to accommodate it.

[0049] <<Core to shell ratio>> The particulate polymer preferably has a core to shell ratio (core:shell) based on mass within the range of 99.9:0.1 to 50:50, more preferably 99:1 to 55:45, even more preferably 95:5 to 60:40, and particularly preferably 90:10 to 65:35. When the core ratio is equal to or greater than the lower limit, the particulate polymer can be prevented from spreading while exerting its adhesive ability in the electrolyte, thereby preventing an increase in the internal resistance of the electrochemical device. As a result, the rate characteristics and electrolyte injectability of the electrochemical device can be improved. When the core ratio is equal to or less than the upper limit, the particulate polymer swells appropriately in the electrolyte, further improving the wet adhesion of the functional layer.

[0050] <<Volume average particle size of particulate polymer>> The particulate polymer must have a volume average particle diameter of 1.0 μm or more and 10.0 μm or less, preferably 2.5 μm or more, more preferably 5.0 μm or more, preferably 9.0 μm or less, and more preferably 8.0 μm or less. When the volume average particle diameter of the particulate polymer is within the above range, the dry adhesion of the resulting functional layer can be further improved. Although the reason for this is unclear, it is believed that when the volume average particle diameter of the particulate polymer is equal to or greater than the above lower limit, a portion of the particulate polymer can protrude from the surface of the functional layer, thereby improving the dry adhesion of the functional layer surface. Furthermore, when the volume average particle diameter of the particulate polymer is equal to or less than the above upper limit, it is believed that the particulate polymer can be prevented from falling off the functional layer during formation of the functional layer, thereby improving the dry adhesion of the resulting functional layer. The volume average particle size of the particulate polymer can be adjusted, for example, by changing the type and amount of metal hydroxide used when preparing the particulate polymer.

[0051] <<Particle size distribution of particulate polymer>> The particulate polymer preferably has a particle size distribution of 1.5 or less, more preferably 1.3 or less. If the particle size distribution of the particulate polymer is equal to or less than the upper limit, the thickness variation of the functional layer after adhesion is reduced, and the cycle characteristics of the electrochemical device can be further improved. The lower limit of the particle size distribution is not particularly limited, but can be, for example, 1.0 or more.

[0052] [Preparation of particulate polymer] The particulate polymer can be prepared by polymerizing a monomer composition containing the above-mentioned monomers in an aqueous solvent such as water. Here, the proportion of each monomer in the monomer composition is usually the same as the proportion of each monomer unit in the particulate polymer.

[0053] The polymerization method is not particularly limited, and any of methods such as suspension polymerization, emulsion polymerization aggregation, and pulverization can be used. Among them, from the viewpoint of simplicity and cost-effectiveness, suspension polymerization and emulsion polymerization aggregation are preferred, and suspension polymerization is more preferred. Furthermore, any of reactions such as radical polymerization and living radical polymerization can be used as the polymerization reaction.

[0054] [Other compounding agents] Further, the monomer composition used in preparing the particulate polymer may contain other additives such as a chain transfer agent, a polymerization regulator, a polymerization reaction retarder, a reactive fluidizing agent, a filler, a flame retardant, an antioxidant, and a colorant in any blending amount.

[0055] Here, as an example, a method for preparing a particulate polymer by suspension polymerization will be described.

[0056] [Preparation of particulate polymers by suspension polymerization] (1) Preparation of Monomer Composition First, a monomer composition (A) having a composition corresponding to the composition of polymer A of the core portion and a monomer composition (B) having a composition corresponding to the composition of polymer B of the shell portion are prepared. At this time, various monomers are blended according to the compositions of polymer A and polymer B, and other compounding ingredients are further mixed in as needed. (2) Droplet formation Next, the monomer composition (A) is dispersed in water, a polymerization initiator is added, and then droplets of the monomer composition (A) are formed. Here, the method for forming the droplets is not particularly limited, and for example, the droplets can be formed by shearing and stirring water containing the monomer composition (A) using a disperser such as an emulsifying disperser.

[0057] In this case, examples of the polymerization initiator to be used include oil-soluble polymerization initiators such as t-butylperoxy-2-ethylhexanoate, azobisisobutyronitrile, etc. The polymerization initiator may be added after the monomer composition (A) is dispersed in water and before droplets are formed, or may be added to the monomer composition (A) before it is dispersed in water.

[0058] From the viewpoint of stabilizing the formed droplets of the monomer composition (A) in water, it is preferable to add a dispersion stabilizer to water to form droplets of the monomer composition (A). In this case, the dispersion stabilizer may be, for example, a metal hydroxide such as magnesium hydroxide, or sodium dodecylbenzenesulfonate.

[0059] (3) Polymerization After forming droplets of the monomer composition (A), the water containing the formed droplets is heated to initiate polymerization. When the polymerization conversion rate has reached a sufficient level, the monomer composition (B) is added to continue the polymerization, thereby forming a particulate polymer having a core-shell structure in the water. The polymerization reaction temperature is preferably 50°C or higher and 95°C or lower. The polymerization reaction time is preferably 1 hour or higher and 10 hours or lower, preferably 8 hours or lower, and more preferably 6 hours or lower.

[0060] (4) Washing, filtering, dehydration and drying process After the polymerization is completed, the water containing the particulate polymer is washed, filtered and dried in a conventional manner to obtain a particulate polymer having a core-shell structure.

[0061] In this example, in the step (3), the monomer composition (B) was continuously added to the same polymerization system as the monomer composition (A) to form a core-shell structure (formation of a core-shell structure by post-monomer addition). However, the method for producing a particulate polymer having a core-shell structure is not limited to the above example. For example, first, the monomer composition (B) is polymerized to obtain a polymer B, which is then dissolved in a solution containing the monomer composition (A). Then, the same step as in the step (2) above is carried out to form droplets containing the polymer B and the monomer composition (A). The water containing the formed droplets is then heated to initiate polymerization. The polymerization conditions can be the same as those described in the step (3). Then, a step similar to the step (4) above is carried out, whereby the polymer B undergoes phase separation to form a shell portion, thereby obtaining a particulate polymer having a core-shell structure (formation of a core-shell structure by phase separation). When the monomer composition (B) is polymerized to obtain the polymer B, a dispersion stabilizer such as polyvinyl alcohol can be added.

[0062] Of these production methods, the method described above, in which "in step (3), the core-shell structure is formed by continuously adding the monomer composition (B) to the same polymerization system as the monomer composition (A)," is preferred from the viewpoint of simplicity.

[0063] The quantitative ratio between the monomer composition (A) and the monomer composition (B) can be appropriately determined so as to satisfy the "ratio of the core part to the shell part" in the particulate polymer described above.

[0064] <Binding material> The binder binds the heat-resistant particles together in the functional layer. Examples of binders include known polymers used as binders, such as conjugated diene polymers, acrylic polymers, polyvinylidene fluoride (PVDF), and polyvinyl alcohol (PVOH). One binder may be used alone, or two or more binders may be used in combination. Preferred binders are water-insoluble polymers that can be dispersed in a dispersion medium such as water, such as conjugated diene polymers, acrylic polymers, and polyvinylidene fluoride (PVDF). Conjugated diene polymers and acrylic polymers are more preferred, with acrylic polymers being even more preferred. When the functional layer is applied to the positive electrode surface of an electrochemical device, it is preferable that the binder be other than a conjugated diene polymer. In the present invention, the polymer being "water-insoluble" means that when 0.5 g of the polymer is dissolved in 100 g of water at 25°C, the insoluble content is 90 mass % or more.

[0065] Here, the conjugated diene polymer refers to a polymer containing conjugated diene monomer units. Specific examples of the conjugated diene polymer include, but are not limited to, copolymers containing aromatic vinyl monomer units and aliphatic conjugated diene monomer units, such as styrene-butadiene copolymer (SBR), butadiene rubber (BR), acrylic rubber (NBR) (copolymers containing acrylonitrile units and butadiene units), and hydrogenated products thereof. Moreover, the acrylic polymer refers to a polymer containing a (meth)acrylic acid ester monomer unit. These binders may be used singly or in combination of two or more kinds in any ratio.

[0066] The acrylic polymer that can be preferably used as the binder is not particularly limited, and examples thereof include a polymer containing the above-mentioned crosslinkable monomer unit, a (meth)acrylic acid ester monomer unit, and an acidic group-containing monomer unit.

[0067] The proportion of (meth)acrylic acid ester monomer units in the acrylic polymer is preferably 50% by mass or more, more preferably 55% by mass or more, even more preferably 58% by mass or more, and preferably 98% by mass or less, more preferably 97% by mass or less, even more preferably 96% by mass or less. By making the proportion of (meth)acrylic acid ester monomer units equal to or greater than the lower limit of the above range, the adhesiveness of the functional layer can be improved. On the other hand, by making it equal to or less than the upper limit, the electrochemical properties of an electrochemical device including the functional layer can be further improved.

[0068] The proportion of crosslinkable monomer units in the acrylic polymer is preferably 0.1% by mass or more, more preferably 1.0% by mass or more, and preferably 3.0% by mass or less, more preferably 2.5% by mass or less. By making the proportion of crosslinkable monomer units equal to or greater than the above limit, the electrochemical properties of an electrochemical device including a functional layer can be further improved. By making the proportion of crosslinkable monomer units equal to or less than the above upper limit, the adhesiveness of the functional layer can be increased.

[0069] The proportion of the acid group-containing monomer units in the acrylic polymer is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, even more preferably 0.5% by mass or more, and preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less. By making the proportion of the acid group-containing monomer units equal to or greater than the above-mentioned lower limit, the dispersibility of the binder in the functional layer composition and in the functional layer can be improved, and the electrochemical properties of an electrochemical device including the functional layer can be sufficiently improved. Furthermore, by making the proportion of the acid group-containing monomer units equal to or less than the above-mentioned upper limit, the amount of residual moisture in the functional layer can be reduced, and the electrochemical properties of an electrochemical device can be sufficiently improved.

[0070] The acrylic polymer may contain other monomer units.

[0071] <<Glass transition temperature of binder>> The glass transition temperature (Tg) of the binder is preferably -100°C or higher, more preferably -90°C or higher, even more preferably -80°C or higher, and preferably less than 30°C, more preferably 20°C or lower, and even more preferably 15°C or lower. If the glass transition temperature of the binder is above the lower limit, the adhesiveness and strength of the functional layer can be increased. On the other hand, if the glass transition temperature of the binder is below the upper limit, the flexibility of the functional layer can be increased.

[0072] [Binder content] The content of the binder is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, even more preferably 0.5 parts by mass or more, and preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass of the heat-resistant fine particles. If the content of the binder is equal to or greater than the lower limit, the particulate polymer can be sufficiently prevented from falling off the functional layer, and the adhesiveness of the functional layer can be sufficiently increased. On the other hand, if the content of the binder is equal to or less than the upper limit, a decrease in the ionic conductivity of the functional layer can be suppressed, and a decrease in the rate characteristics of the electrochemical device can be suppressed.

[0073] The binder is not particularly limited and can be prepared, for example, by polymerizing a monomer composition containing the above-mentioned monomers in an aqueous solvent such as water. Here, the ratio of each monomer in the monomer composition is usually the same as the ratio of each monomer unit in the binder.

[0074] The polymerization method and polymerization reaction are not particularly limited, and for example, the polymerization methods and polymerization reactions exemplified above as the polymerization methods for the particulate polymer can be used.

[0075] Furthermore, the binder may be in a particulate or non-particulate form, but from the viewpoint of effectively preventing the components contained in the functional layer from falling off, it is preferable that the binder be in a particulate form.

[0076] <<Heat-resistant fine particles>> Here, the heat-resistant fine particles contained in the functional layer are not particularly limited, and examples thereof include fine particles made of inorganic materials (i.e., inorganic fine particles) and fine particles made of organic materials (i.e., organic fine particles) that are stable and electrochemically stable in the environment in which the electrochemical element is used. As the heat-resistant fine particles, inorganic fine particles and organic fine particles may be used alone, or inorganic fine particles and organic fine particles may be used in combination.

[0077] [Inorganic fine particles] Examples of inorganic fine particles include inorganic oxide particles such as aluminum oxide (alumina, Al2O3), aluminum oxide hydrate (boehmite, AlOOH), gibbsite (Al(OH)3), silicon oxide, magnesium oxide (magnesia), magnesium hydroxide, calcium oxide, titanium oxide (titania), barium titanate (BaTiO3), ZrO, and alumina-silica composite oxide; nitride particles such as aluminum nitride and boron nitride; covalently bonded crystalline particles such as silicon and diamond; sparingly soluble ionic crystalline particles such as barium sulfate, calcium fluoride, and barium fluoride; and clay fine particles such as talc and montmorillonite. These particles may be subjected to element substitution, surface treatment, solid solution formation, etc., as necessary. The inorganic fine particles may be used singly or in combination of two or more.

[0078] [Organic fine particles] Unlike the above-mentioned specific particulate polymer and binder, the organic fine particles are fine particles made of a polymer that does not have adhesive properties. Examples of organic fine particles include various crosslinked polymer particles such as crosslinked polymethyl methacrylate, crosslinked polystyrene, crosslinked polydivinylbenzene, styrene-divinylbenzene copolymer crosslinked products, polystyrene, polyimide, polyamide, polyamideimide, melamine resin, phenolic resin, and benzoguanamine-formaldehyde condensate, as well as heat-resistant polymer particles such as polysulfone, polyacrylonitrile, polyaramid, polyacetal, and thermoplastic polyimide, as well as modified products and derivatives thereof, and heat-resistant organic particles disclosed in International Publication No. 2019 / 065416. The organic fine particles may be used alone or in combination of two or more. As described above, the organic fine particles are made of a polymer that does not have adhesive properties. Specifically, the glass transition temperature of the polymer that makes up the organic fine particles is preferably 150° C. or higher.

[0079] Among the above-mentioned heat-resistant fine particles, from the viewpoint of further improving the heat resistance of the element member consisting of the laminate, inorganic fine particles and organic fine particles composed of a polymer having a glass transition temperature of 150°C or higher are preferred, inorganic fine particles are more preferred, and particles composed of alumina (alumina particles), particles composed of boehmite (boehmite particles), particles composed of barium sulfate (barium sulfate particles), and particles composed of magnesium hydroxide (magnesium hydroxide particles) are even more preferred.

[0080] [Properties of heat-resistant particles] The heat-resistant fine particles preferably have a volume-average particle diameter of 0.1 μm or more, more preferably 0.2 μm or more, even more preferably 0.3 μm or more, and preferably 1.0 μm or less, more preferably 0.9 μm or less, and even more preferably 0.8 μm or less. When the heat-resistant fine particles have a volume-average particle diameter of 0.1 μm or more, a decrease in the ionic conductivity of the functional layer due to excessively dense packing of the heat-resistant fine particles in the functional layer can be suppressed, allowing the electrochemical device to exhibit excellent rate characteristics. On the other hand, when the heat-resistant fine particles have a volume-average particle diameter of 1.0 μm or less, even when the functional layer is thinned, the device component comprising the laminate including the functional layer can fully exhibit excellent heat resistance. Therefore, the capacity of the electrochemical device can be increased while ensuring sufficient heat resistance of the device component.

[0081] <Volume ratio of heat-resistant fine particles to particulate polymer> The volume ratio of the heat-resistant fine particles to the particulate polymer is preferably within a range of 75:25 to 60:40, more preferably 70:30 to 65:35. When the volume ratio of the heat-resistant fine particles to the particulate polymer is within the above range, the balance between the heat shrinkage resistance and the adhesiveness of the functional layer is good.

[0082] <Other ingredients> The functional layer composition may contain any other components in addition to the components described above. The other components are not particularly limited as long as they do not affect the electrochemical reaction in the electrochemical element, and examples thereof include known additives such as dispersants, viscosity modifiers, and wetting agents. These other components may be used alone or in combination of two or more.

[0083] <Method for preparing composition for electrochemical device functional layer> The method for preparing the composition for the functional layer is not particularly limited, and can be prepared, for example, by mixing the above-mentioned particulate polymer, binder, heat-resistant fine particles, water as a dispersion medium, and other components used as needed. When the particulate polymer or binder is prepared by polymerizing a monomer composition in an aqueous solvent, the particulate polymer or binder may be mixed with other components as is in the form of an aqueous dispersion. When the particulate polymer or binder is mixed in the form of an aqueous dispersion, the water in the aqueous dispersion may be used as the dispersion medium.

[0084] Here, the method for mixing the above-mentioned components is not particularly limited, but in order to efficiently disperse each component, it is preferable to use a disperser as a mixing device. The disperser is preferably a device that can uniformly disperse and mix the above-mentioned components. Examples of dispersers include a ball mill, a sand mill, a pigment disperser, a crusher, an ultrasonic disperser, a homogenizer, and a planetary mixer.

[0085] Furthermore, it is preferable to premix the above-mentioned specific particulate polymer with a dispersant such as a nonionic surfactant, an anionic surfactant, a cationic surfactant, or an amphoteric surfactant before mixing it with the heat-resistant fine particles and the binder. Among these, anionic surfactants are preferably used as the dispersant. Specific examples of anionic surfactants include sulfate ester salts of higher alcohols such as sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecyl sulfate, ammonium dodecyl sulfate, sodium octyl sulfate, sodium decyl sulfate, sodium tetradecyl sulfate, sodium hexadecyl sulfate, and sodium octadecyl sulfate; alkylbenzenesulfonates such as sodium dodecylbenzenesulfonate, sodium laurylbenzenesulfonate, and sodium hexadecylbenzenesulfonate; and aliphatic sulfonates such as sodium laurylsulfonate, sodium dodecylsulfonate, and sodium tetradecylsulfonate. The amount of dispersant blended is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, even more preferably 0.1 parts by mass or more, and preferably 0.5 parts by mass or less, more preferably 0.4 parts by mass or less, and even more preferably 0.3 parts by mass or less, relative to 100 parts by mass of the particulate polymer. When the amount of dispersant blended is equal to or greater than the lower limit, uneven distribution of the particulate polymer in the functional layer can be suppressed, and the cycle characteristics of the resulting electrochemical device can be improved. When the amount of dispersant blended is equal to or less than the upper limit, an increase in the internal resistance of the resulting electrochemical device can be suppressed, and deterioration of the rate characteristics can be suppressed.

[0086] (Laminate for electrochemical devices) The electrochemical device laminate includes a substrate and a functional layer for an electrochemical device formed on the substrate using the above-described functional layer composition. The functional layer for an electrochemical device contains at least the above-described particulate polymer, binder, and heat-resistant fine particles, as well as other components used as needed. The components contained in the functional layer are the same as those contained in the above-described functional layer composition, and the preferred abundance ratios of the components are the same as the preferred abundance ratios of the components in the functional layer composition. The electrochemical device laminate includes a functional layer formed using the above-described functional layer composition, and therefore has excellent wet adhesion and can improve the electrolyte injectability and rate characteristics of an electrochemical device obtained using such a laminate.

[0087] <Base material> The substrate may be appropriately selected depending on the type of electrochemical element member in which the laminate of the present invention is used. For example, when the laminate of the present invention is used as a separator, a separator substrate is used as the substrate. For example, when the laminate of the present invention is used as an electrode, an electrode substrate is used as the substrate.

[0088] <<Separator substrate>> The separator substrate is not particularly limited, and examples thereof include known separator substrates such as organic separator substrates, which are porous members made of organic materials, and examples of organic separator substrates include microporous membranes or nonwoven fabrics containing polyolefin resins such as polyethylene, polypropylene, polybutene, and polyvinyl chloride, and aromatic polyamide resins. Among these, a microporous film made of a polyolefin resin is preferred from the viewpoint that the ratio of the electrode active material in the electrochemical device can be increased to increase the capacity per volume. The thickness of the separator substrate can be any thickness, preferably 5 μm or more and 30 μm or less, more preferably 5 μm or more and 20 μm or less, and even more preferably 5 μm or more and 18 μm or less.

[0089] <<Electrode base material>> The electrode substrates (positive electrode substrate and negative electrode substrate) are not particularly limited, but examples thereof include electrode substrates in which an electrode mixture layer is formed on a current collector. Here, the current collector, the electrode active materials (positive electrode active material, negative electrode active material) and binders for the electrode composite layer (binders for the positive electrode composite layer, binders for the negative electrode composite layer) in the electrode composite layer, and the method for forming the electrode composite layer on the current collector may be known, and for example, the method described in JP 2013-145763 A may be used.

[0090] <Method of manufacturing laminate> The method for producing the laminate of the present invention is not particularly limited, and for example, a method of forming a functional layer on a release sheet and transferring the functional layer onto a substrate can be used. However, from the viewpoint of eliminating the need for a transfer operation and improving production efficiency, it is preferable to produce the laminate through a step of supplying a functional layer composition onto a substrate (supplying step) and a step of drying the functional layer composition supplied onto the substrate (drying step).

[0091] <<Supply process>> In the supplying step, the functional layer composition of the present invention is supplied onto a substrate to form a coating of the functional layer composition on the substrate. The method for supplying the functional layer composition onto the substrate is not particularly limited, and the functional layer composition may be applied to the surface of the substrate, or the substrate may be immersed in the functional layer composition. Furthermore, it is preferable to apply the functional layer composition to the surface of the substrate, as this makes it easier to control the thickness of the functional layer to be produced. The method for applying the composition for the functional layer to the surface of the substrate is not particularly limited, and examples thereof include the doctor blade method, reverse roll method, direct roll method, gravure coating method, bar coating method, extrusion method, and brush coating method. In the supplying step, a coating of the composition for a functional layer may be formed on only one surface of the substrate, or a coating of the composition for a functional layer may be formed on both surfaces of the substrate.

[0092] <<Drying process>> In the drying step, the coating of the functional layer composition formed on the substrate in the supplying step is dried to remove the dispersion medium, thereby forming a functional layer. The method for drying the coating of the composition for functional layer is not particularly limited and any known method can be used, such as drying with warm air, hot air, or low-humidity air, vacuum drying, or drying by irradiation with infrared rays or electron beams, etc. The drying conditions are not particularly limited, but the drying temperature is preferably 50 to 150°C, and the drying time is preferably 1 to 30 minutes.

[0093] In addition, when manufacturing the laminate of the present invention, a supplying process and a drying process may be performed on one side of the substrate to form a functional layer, and then a supplying process and a drying process may be performed on the other side of the substrate to form a functional layer.

[0094] In a functional layer formed using a functional layer composition, a plurality of heat-resistant fine particles are typically arranged so as to be stacked in the thickness direction of the functional layer. The thickness of the layer (hereinafter also referred to as the "heat-resistant fine particle layer") in which the heat-resistant fine particles are stacked in the thickness direction of the functional layer is preferably 0.5 μm or more, more preferably 0.8 μm or more, even more preferably 1 μm or more, and preferably 6 μm or less, more preferably 5 μm or less, and even more preferably 3.5 μm or less. If the thickness of the heat-resistant fine particle layer is above the lower limit, the heat resistance of the functional layer is extremely good. On the other hand, if the thickness of the heat-resistant fine particle layer is below the upper limit, the ion diffusibility of the functional layer can be ensured, and the rate characteristics of the electrochemical device can be further improved.

[0095] [Ratio of volume average particle diameter of particulate polymer to thickness of heat-resistant particle layer] Furthermore, the ratio of the volume average particle diameter of the particulate polymer to the thickness of the heat-resistant fine particle layer (volume average particle diameter of the particulate polymer / thickness of the heat-resistant fine particle layer) is preferably 0.5 or more, more preferably 1.5 or more, even more preferably 2.5 or more, and preferably 10.0 or less, more preferably 9.0 or less, even more preferably 8.0 or less. If the ratio of the volume average particle diameter of the particulate polymer to the thickness of the heat-resistant fine particle layer is above the above lower limit, the particulate polymer is more likely to protrude from the surface of the heat-resistant fine particles on the thickness direction surface of the functional layer, thereby exhibiting good adhesiveness. If the ratio of the volume average particle diameter of the particulate polymer to the thickness of the heat-resistant fine particle layer is below the above upper limit, the particulate polymer has more adhesion points, thereby exhibiting good adhesiveness.

[0096] (electrochemical element) The electrochemical element of the present invention comprises an electrode and a separator, and is characterized in that at least one of the electrode and the separator comprises the laminate of the present invention. The electrochemical element of the present invention uses the laminate of the present invention as at least one of the element components, the electrode and the separator, and therefore has excellent electrolyte injectability and rate characteristics. An electrochemical element with excellent electrolyte injectability and rate characteristics can be used for rapid charging.

[0097] The electrochemical device 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.

[0098] Hereinafter, a lithium ion secondary battery will be taken as an example of the electrochemical element of the present invention, and a case where the above-described laminate of the present invention is used as a separator of the lithium ion secondary battery will be described, but the electrochemical element of the present invention is not limited thereto.

[0099] <Positive and negative electrodes> As the positive electrode and negative electrode, electrodes made of the known electrode substrates (positive electrode substrate and negative electrode substrate) described above in the section "Substrate" can be used.

[0100] <Electrolyte> As the electrolyte, an organic electrolyte solution in which a supporting electrolyte is dissolved in an organic solvent is usually used. For example, in lithium ion secondary batteries, a lithium salt is used as the supporting electrolyte. Examples of lithium salts include LiPF6, LiAsF6, LiBF4, LiSbF6, LiAlCl4, LiClO4, CF3SO3Li, CF4F9SO3Li, CF3COOLi, (CF3CO)2NLi, (CF3SO2)2NLi, and (C2F5SO2)NLi. Among these, LiPF6, LiClO4, and CF3SO3Li are preferred because they are easily soluble in solvents and exhibit a high degree of dissociation. 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, so the lithium ion conductivity can be adjusted by the type of supporting electrolyte.

[0101] The organic solvent used in the electrolyte is not particularly limited as long as it can dissolve the supporting electrolyte. For example, in lithium ion secondary batteries, carbonates such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate (BC), methyl ethyl carbonate (ethyl methyl carbonate (EMC)), and vinylene carbonate; 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 suitably used.

[0102] A mixture of these solvents may also be used. Among them, carbonates are preferred because of their high dielectric constant and wide stable potential range. Generally, 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 adjusted as appropriate. Known additives may also be added to the electrolytic solution.

[0103] <Method of manufacturing an electrochemical element> The method for producing the electrochemical element of the present invention is not particularly limited. For example, the lithium ion secondary battery, which is an example of the electrochemical element of the present invention described above, can be produced by stacking a positive electrode and a negative electrode with a separator interposed 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 container. At least one of the element components among the positive electrode, negative electrode, and separator is the laminate of the present invention. Furthermore, the battery container may contain an expanded metal, a fuse, an overcurrent prevention element such as a PTC element, a lead plate, or the like, as necessary, to prevent pressure buildup within the battery and overcharging and discharging. The shape of the battery may be any shape, such as a coin type, button type, sheet type, cylindrical type, rectangular type, or flat type. [Example]

[0104] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples. In the following description, "%" and "parts" representing amounts are based on mass unless otherwise specified. Furthermore, in a polymer produced by copolymerizing multiple types of monomers, the proportion of structural units formed by polymerizing a certain monomer in the polymer usually coincides with the ratio (feed ratio) of that certain monomer to all monomers used in the polymerization of the polymer, unless otherwise specified.

[0105] In the examples and comparative examples, the measurement and evaluation of various attributes were carried out as follows.

[0106] <Glass transition temperature of particulate polymer and binder> The particulate polymers and binders prepared in the Examples and Comparative Examples were used as measurement samples. 10 mg of the sample was weighed into an aluminum pan and measured using a differential scanning calorimetry (DSC) analyzer (SII NanoTechnology, Inc., "EXSTAR DSC6220") under the conditions specified in JIS Z 8703. The measurement temperature range was -100°C to 500°C, with a heating rate of 10°C / min. The DSC curve was obtained under the conditions specified in JIS Z 8703. The glass transition temperature (°C) was determined by the intersection of the baseline just before the endothermic peak of the DSC curve, where the differential signal (DDSC) was 0.05 mW / min / mg or greater, and the tangent to the DSC curve at the first inflection point after the endothermic peak. The measurement samples of the particulate polymer having a core-shell structure were prepared as follows. Using the monomers and various additives used to form the core and shell portions, aqueous dispersions containing the polymers (core polymer and shell polymer) to be used as the measurement samples were prepared under the same polymerization conditions as those for the core and shell portions. The prepared aqueous dispersions were then dried to obtain measurement samples.

[0107] <Electrolyte swelling rate> An aqueous dispersion containing the measurement sample was placed in a polytetrafluoroethylene dish and dried at 25°C for 48 hours to prepare a powder. Approximately 0.2 g of the obtained powder was pressed at 200°C and 5 MPa for 2 minutes to obtain a film. The obtained film was then cut into 1 cm squares to obtain test pieces. The mass W0 of this test piece was measured. The above test piece was immersed in an electrolyte solution for 72 hours at 60° C. Thereafter, the test piece was taken out of the electrolyte solution, the electrolyte solution on the surface of the test piece was wiped off, and the mass W1 of the test piece after the immersion test was measured. Using the measured masses W0 and W1, the degree of swelling in the electrolyte solution S (times) was calculated as S=W1 / W0. The electrolyte used was a mixed solvent of ethylene carbonate (EC), diethyl carbonate (DEC), and vinylene carbonate (VC) (volume ratio: EC / DEC / VC = 68.5 / 30 / 1.5) with LiPF6 dissolved as a supporting electrolyte at a concentration of 1 mol / L. Such measurements were carried out for each of the measurement samples of polymer A and polymer B, and the electrolyte swelling degree S A and S B Furthermore, based on the obtained values, S B / S A The value was calculated.

[0108] <Volume average particle size of binder> The volume-average particle diameter of the binder prepared in the examples was measured by laser diffraction. Specifically, an aqueous dispersion containing the prepared binder (adjusted to a solids concentration of 0.1% by mass) was used as a sample. The particle size distribution (volume basis) measured using a laser diffraction particle size distribution analyzer (manufactured by Beckman Coulter, Inc., "LS-230") was used. The particle diameter D50 at which the cumulative volume calculated from the smallest diameter side reached 50% was defined as the volume-average particle diameter.

[0109] <Volume average particle size and particle size distribution of particulate polymer> The particulate polymers prepared in the Examples and Comparative Examples were used as measurement samples. A 0.1 g sample was weighed and placed in a beaker, and 0.1 mL of an alkylbenzene sulfonic acid aqueous solution (Fujifilm Corporation, "Drywell") was added as a dispersant. 10-30 mL of diluent (Beckman Coulter, Inc., "Isoton II") was then added to the beaker, and the mixture was dispersed for 3 minutes using a 20 W (Watt) ultrasonic disperser. The volume-average particle diameter (Dv) of the measurement sample was then measured using a particle size analyzer (Beckman Coulter, Inc., "Multisizer") under the following conditions: aperture diameter: 20 μm, medium: Isoton II, and particle count: 100,000. The number-average particle diameter (Dn) of the particulate polymer was also measured, and the particle size distribution (Dv / Dn) was calculated.

[0110] <Volume average particle size of heat-resistant fine particles> In the particle size distribution (volume basis) measured by laser diffraction, the particle size (D50) at which the cumulative volume calculated from the smallest diameter side becomes 50% was defined as the volume average particle size of the heat-resistant fine particles.

[0111] <Thickness of heat-resistant fine particle layer> The cross section of the separator with the functional layer was observed using the field emission scanning electron microscope (FE-SEM) and the thickness of the heat-resistant particle layer was calculated from the SEM image, which was defined as the distance from the surface of the separator substrate on which the functional layer was formed to the furthest heat-resistant particle in the vertical direction.

[0112] <Ratio of Volume Average Particle Diameter of Particulate Polymer in Functional Layer to Thickness of Heat-Resistant Particle Layer> Based on the volume average particle diameter of the particulate polymer in the functional layer obtained as described above and the thickness of the heat-resistant microparticle layer, the ratio of the volume average particle diameter of the particulate polymer in the functional layer to the thickness of the heat-resistant microparticle layer (volume average particle diameter of the particulate polymer / thickness of the heat-resistant microparticle layer) was calculated.

[0113] <Volume and mass ratios of heat-resistant fine particles and particulate polymer> The volume ratio (heat-resistant fine particles / particulate polymer) and mass ratio (heat-resistant fine particles / particulate polymer) of the heat-resistant fine particles to the particulate polymer were calculated from the amounts of heat-resistant fine particles (alumina / organic fine particles) and particulate polymer charged when preparing the slurry composition. The density of alumina was 4 g / cm. 3 The density of the organic fine particles used in Example 13 was set to 1.

[0114] <Dry adhesion> The positive electrode, negative electrode, and separator with functional layer prepared in the examples and comparative examples were each cut into a 10 mm wide x 50 mm long piece, and the positive electrode and separator with functional layer were stacked and pressed using a roll press under conditions of a temperature of 50°C, a load of 8 kN / m, and a press speed of 30 m / min to obtain an integrated product in which the positive electrode and separator with functional layer were integrated. The surfaces of the positive electrode and separator with functional layer were stacked facing each other. The resulting integrated product was placed with the current collector side of the positive electrode facing downwards, and cellophane tape was attached to the surface of the electrode. The cellophane tape used conformed to JIS Z1522. The cellophane tape was fixed to a horizontal test table. One end of the separator with the functional layer was then pulled vertically upward at a pulling rate of 50 mm / min, and the stress when peeled off was measured. The negative electrodes prepared in the examples and comparative examples were also subjected to the same procedures as in the case of using the positive electrodes, and the stress was measured. The negative electrodes and the rear surfaces of the separators with functional layers were stacked so as to face each other. The above-mentioned stress measurement was performed three times for each of the integrated positive electrode and separator with functional layer, and the integrated negative electrode and separator with functional layer, for a total of six times, and the average stress value was calculated. The obtained average value was used as the peel strength (N / m). The calculated peel strength was then used to evaluate the dry adhesion between the electrode and the separator with the functional layer according to the following criteria: A higher peel strength indicates better dry adhesion of the functional layer (adhesion between battery components via the functional layer when not immersed in an electrolyte solution during the secondary battery manufacturing process). A: Peel strength 3N / m or more B: Peel strength 2N / m or more and less than 3N / m C: Peel strength 1N / m or more but less than 2N / m D: Peel strength less than 1N / m <Wet adhesion> The functional layer compositions obtained in the Examples and Comparative Examples were applied to the surface of a separator substrate, and the functional layer compositions on the separator substrate were dried at 50°C for 10 minutes to form a functional layer (thickness: 2 μm). This separator with this functional layer was used as a separator for evaluation. The separator with the functional layer was cut into a 10 mm x 100 mm strip. The separator was then aligned with the surface of the negative electrode (negative electrode composite layer side) prepared in the Examples and Comparative Examples, and then hot-pressed at a temperature of 85°C and a pressure of 0.5 MPa for 6 minutes to produce a laminate comprising a negative electrode and a separator with a functional layer. This laminate was used as a test specimen. The test piece was placed in a laminated packaging material together with approximately 400 μL of electrolyte. After 1 hour, the test piece and the laminated packaging material were pressed at 25°C under a pressure of 0.1 MPa for 60 minutes. The electrolyte used was a mixed solvent of EC, DEC, and vinylene carbonate (VC) (EC / DEC / VC (volume ratio at 25°C) = 68.5 / 30 / 1.5) with LiPF6 dissolved as a supporting electrolyte at a concentration of 1 mol / L. The test specimen was then removed, and the electrolyte solution adhering to the surface was wiped off. Next, the test specimen was placed with the negative electrode current collector side facing downwards, and cellophane tape was applied to the negative electrode current collector side. The cellophane tape used was specified in JIS Z1522. The cellophane tape was fixed to a horizontal test bench. One end of the separator substrate was then pulled vertically upward at a pulling rate of 50 mm / min to measure the stress when peeled. This measurement was performed three times, and the average stress value was calculated as the peel strength P2 (N / m) and evaluated according to the following criteria. The evaluation results are shown in Table 1. A higher peel strength P2 indicates better adhesion (wet adhesion) of the functional layer after immersion in the electrolyte, indicating strong adhesion between the electrode and the separator with the functional layer even in the electrolyte. A: Peel strength P2 is 2.0 N / m or more B: Peel strength P2 is 1.0 N / m or more and less than 2.0 N / m C: Peel strength P2 is 0.5 N / m or more and less than 1.0 N / m D: Peel strength P2 is less than 0.5 N / m

[0115] <Electrolyte injection performance> An electrolyte solution was injected into the lithium ion secondary batteries produced in the Examples and Comparative Examples. The pressure inside the lithium ion secondary batteries was then reduced to -100 kPa and maintained in that state for 1 minute. Heat sealing was then performed. After 10 minutes, the electrode (positive electrode) was disassembled, and the state of electrolyte impregnation in the electrode was visually confirmed. Evaluation was then performed according to the following criteria. The larger the area of ​​the electrode impregnated with the electrolyte solution, the higher the electrolyte injectability. A: The electrolyte is impregnated on all surfaces of the electrode. B: The part of the electrode that is not impregnated with electrolyte is 1 cm 2 Less than 100% of the surface is impregnated (except for all surfaces). C: The part of the electrode that is not impregnated with electrolyte is 1 cm 2 More than 1.5cm 2 Less than remaining D: The part of the electrode that is not impregnated with electrolyte is 1.5 cm 2 That's all that remains.

[0116] <Rate characteristics of secondary batteries> The 800 mAh stacked lithium ion secondary batteries manufactured in the examples and comparative examples were left standing for 24 hours in an environment at 25°C, and then charged and discharged at 4.35 V and 0.1 C, and discharged at 3.0 V and 0.1 C, in an environment at 25°C, to measure the initial capacity C0. Subsequently, the batteries were charged and discharged at 4.35 V and 0.1 C, and discharged at 3.0 V and 2 C, in an environment at 25°C, to measure the capacity C1. The rate characteristics were evaluated by ΔC = (C0 - C1) / C0 × 100 (%), with a larger value indicating better rate characteristics. A: ΔC is 90% or more B: ΔC is 85% or more and less than 90% C: ΔC is 80% or more and less than 85% D: ΔC is less than 80% <Cycle characteristics of secondary batteries> After injecting the electrolyte, the lithium-ion secondary batteries fabricated in the examples and comparative examples were left standing at 25°C for 5 hours. Next, they were charged at 25°C and a constant current of 0.2C to a cell voltage of 3.65V, and then aged at 60°C for 12 hours. Then, they were discharged at 25°C and a constant current of 0.2C to a cell voltage of 3.00V. Then, they were subjected to CC-CV charging at a constant current of 0.2C (upper limit cell voltage 4.20V), and CC discharging at a constant current of 0.2C to 3.00V. This charge / discharge cycle at 0.2C was repeated three times. Thereafter, 100 cycles of charge and discharge were performed at a temperature of 25°C, a cell voltage of 4.20-3.00V, and a charge and discharge rate of 1.0 C. The discharge capacity of the first cycle was defined as X1, and the discharge capacity of the 100th cycle as X2. Then, the capacity retention rate ΔC' = (X2 / X1) × 100 (%) was calculated using the discharge capacity X1 and the discharge capacity X2, and evaluated according to the following criteria. A larger value of the capacity retention rate ΔC' indicates that the secondary battery has better cycle characteristics at 100 cycles. The reason why the secondary battery has excellent cycle characteristics at 100 cycles is presumed to be because the functional layer of the secondary battery can retain the electrolyte well. A: Capacity retention rate ΔC' is 93% or more B: Capacity retention rate ΔC' is 90% or more and less than 93% C: Capacity retention rate ΔC' is 87% or more and less than 90% D: Capacity retention rate ΔC' is less than 87%

[0117] Example 1 <Preparation of Particulate Polymer (A)> [Preparation of Core Monomer Composition (A)] A core monomer composition (A) was prepared by mixing 65.5 parts of styrene as an aromatic vinyl monomer, 14.4 parts of 2-ethylhexyl acrylate as a (meth)acrylic acid ester monomer, and 0.1 parts of ethylene glycol dimethacrylate as a crosslinkable monomer. [Preparation of Monomer Composition (A) for Shell] A monomer composition (A) for the shell was prepared by mixing 9.9 parts of styrene as an aromatic vinyl monomer, 2.0 parts of butyl acrylate as a (meth)acrylic acid ester monomer, 8.0 parts of acrylonitrile as a nitrile group-containing monomer, and 0.1 parts of ethylene glycol dimethacrylate as a crosslinkable monomer.

[0118] [Preparation of metal hydroxides] A colloidal dispersion (A) containing magnesium hydroxide as the metal hydroxide was prepared by gradually adding, with stirring, an aqueous solution (A2) prepared by dissolving 5.6 parts of sodium hydroxide in 50 parts of ion-exchanged water to an aqueous solution (A1) prepared by dissolving 8.0 parts of magnesium chloride in 200 parts of ion-exchanged water.

[0119] [Suspension polymerization method] A particulate polymer was prepared by suspension polymerization. Specifically, the core monomer composition (A) obtained as described above was added to the colloidal dispersion (A) containing magnesium hydroxide, and after further stirring, 2.0 parts of t-butylperoxy-2-ethylhexanoate (NOF Corp., "Perbutyl O") was added as a polymerization initiator to obtain a mixed solution. The resulting mixed solution was subjected to high-shear stirring at 15,000 rpm for 1 minute using an in-line emulsifying disperser (Pacific Machinery Works, "Cavitron") to form droplets of the core monomer composition (A) in the colloidal dispersion (A) containing magnesium hydroxide.

[0120] The colloidal dispersion (A) containing magnesium hydroxide and containing droplets of the monomer composition (A) was placed in a reactor and heated to 90°C to carry out a polymerization reaction. When the polymerization conversion rate reached nearly 100%, the shell polymerizable monomer (B) and 0.1 parts of the shell polymerization initiator 2,2'-azobis(2-methyl-N-(2-hydroxyethyl)-propionamide) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., trade name: V-050, water-soluble) dissolved in 10 parts of ion-exchanged water were added, and the reaction was continued at 70°C for 4 hours, after which the reaction was stopped by water cooling, and an aqueous dispersion containing a particulate polymer was obtained. It was confirmed by scanning electron microscopy that the obtained particulate polymer had a core-shell structure.

[0121] Further, while stirring the aqueous dispersion containing the particulate polymer, sulfuric acid was added dropwise at room temperature (25°C) and acid washing was carried out until the pH became 6.5 or less. Next, filtration and separation were carried out, and 500 parts of ion-exchanged water was added to the obtained solid matter to re-slurry it, and water washing treatment (washing, filtration and dehydration) was carried out several times. Then, filtration and separation were carried out, and the obtained solid matter was placed in a container of a dryer and dried at 40°C for 48 hours to obtain a dried particulate polymer. The glass transition temperature, swelling degree in an electrolyte, volume average particle size, and particle size distribution of the obtained particulate polymer were measured. The results are shown in Table 1.

[0122] <Preparation of aqueous dispersion containing binder (α)> To a reactor equipped with a stirrer, 70 parts of ion-exchanged water, 0.15 parts of sodium lauryl sulfate (manufactured by Kao Chemical Corporation, "EMAL (registered trademark) 2F") as an emulsifier, and 0.5 parts of ammonium persulfate as a polymerization initiator were supplied, the gas phase was replaced with nitrogen gas, and the temperature was raised to 60°C. Meanwhile, in another container, 50 parts of ion-exchanged water, 0.5 parts of sodium dodecylbenzenesulfonate as a dispersion stabilizer, 94 parts of n-butyl acrylate as a (meth)acrylic acid ester monomer, 2 parts of methacrylic acid as an acid group-containing monomer, and 2 parts of acrylonitrile as a nitrile group-containing monomer, as well as 1 part of allyl methacrylate and 1 part of allyl glycidyl ether as crosslinkable monomers were mixed to prepare a monomer composition (α). The obtained monomer composition (α) was continuously added to the above-mentioned reactor equipped with a stirrer over 4 hours to carry out polymerization. During the addition, the reaction was carried out at 60°C. After the addition was completed, the mixture was stirred at 70°C for an additional 3 hours, and then the reaction was terminated, yielding an aqueous dispersion containing a particulate binder (α) as an acrylic polymer. The obtained binder (α) had a volume average particle diameter of 0.25 μm and a glass transition temperature of -40°C.

[0123] <Preparation of Slurry Composition (Functional Layer Composition)> To 100 parts of alumina (manufactured by Sumitomo Chemical Co., Ltd., "AKP3000", volume average particle diameter: 0.7 μm) as heat-resistant fine particles, 0.5 parts of polyacrylic acid as a water-soluble polymer was added, and ion-exchanged water was added so that the solid content concentration became 55%, followed by mixing using a ball mill to obtain a pre-mixing slurry. To 100 parts of the particulate polymer, 0.2 parts of sodium dodecylbenzenesulfonate ("Neopelex G-15" manufactured by Kao Chemical Co., Ltd.) was added as a dispersant. Furthermore, 6 parts of an aqueous dispersion containing a binder (α) in terms of solid content and 1.5 parts of carboxymethyl cellulose as a thickener were mixed to 100 parts of the heat-resistant fine particles to a solid content of 40%, and the resulting mixture was added to the pre-mixing slurry obtained as described above. Further, ion-exchanged water was added to a solid content of 40%, to obtain a slurry composition (composition for functional layer). The volume ratio of the heat-resistant fine particles (alumina) to the particulate polymer in the slurry composition (heat-resistant fine particles / particulate polymer) was 70 / 30.

[0124] <Fabrication of separator with functional layer> A polyethylene microporous film (thickness: 12 μm) was prepared as a separator substrate. The functional layer composition obtained above was applied to one side of the prepared separator substrate using a bar coater method. The coating was dried at 50°C. The same operation as above was then performed on the other side of the separator substrate, producing a separator with a functional layer, each of which had a heat-resistant fine particle layer with a thickness of 2.0 μm.

[0125] <Preparation of positive electrode> A mixture of 100 parts of LiCoO2 (volume average particle diameter: 12 μm) as a positive electrode active material, 2 parts of acetylene black (HS-100, manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive material, 2 parts of polyvinylidene fluoride (#7208, manufactured by Kureha Corporation) as a binder for the positive electrode composite layer in terms of solid content, and N-methylpyrrolidone as a solvent was mixed to a total solid content of 70%. These components were mixed using a planetary mixer to prepare a positive electrode slurry composition. The positive electrode slurry composition was applied to a 20 μm-thick aluminum foil current collector using a comma coater so that the dried film thickness was approximately 150 μm, and then dried. This drying was performed by transporting the aluminum foil at a speed of 0.5 m / min through an oven at 60°C for 2 minutes. The aluminum foil was then heat-treated at 120°C for 2 minutes to obtain a pre-pressed positive electrode blank. This pre-pressed positive electrode blank was rolled using a roll press to obtain a pre-pressed positive electrode having a positive electrode composite layer (thickness: 60 μm).

[0126] <Preparation of negative electrode> A 5 MPa pressure vessel equipped with a stirrer was charged with 33 parts of 1,3-butadiene, 3.5 parts of itaconic acid, 63.5 parts of styrene, 0.4 parts of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of ion-exchanged water, and 0.5 parts of potassium persulfate as a polymerization initiator. After thorough stirring, the mixture was heated to 50 °C to initiate polymerization. When the polymerization conversion reached 96%, the reaction was stopped by cooling, yielding a mixture containing a binder (SBR) for the negative electrode composite layer. A 5% aqueous sodium hydroxide solution was added to the mixture containing the binder for the negative electrode composite layer, adjusting the pH to 8, and then the unreacted monomer was removed by heated vacuum distillation. The mixture was then cooled to below 30 °C to obtain an aqueous dispersion containing the desired binder for the negative electrode composite layer. 80 parts of artificial graphite (volume average particle diameter: 15.6 μm) as the negative electrode active material (1) and 16 parts of silicon-based active material SiOx (volume average particle diameter: 4.9 μm) as the negative electrode active material (2) were blended, and 2.5 parts of a 2% aqueous solution of carboxymethylcellulose sodium salt (manufactured by Nippon Paper Industries Co., Ltd., "MAC350HC") as a viscosity modifier, equivalent to solids, and ion-exchanged water were mixed to adjust the solids concentration to 68%, and then further mixed at 25 ° C. for 60 minutes. The solids concentration was further adjusted to 62% with ion-exchanged water, and then further mixed at 25 ° C. for 15 minutes to obtain a mixed solution. 1.5 parts of the aqueous dispersion containing the above-mentioned binder for the negative electrode composite layer, equivalent to solids, and ion-exchanged water were added to this mixed solution, and the final solids concentration was adjusted to 52%, and then further mixed for 10 minutes to obtain a mixed solution. This mixed solution was degassed under reduced pressure to obtain a negative electrode slurry composition with good fluidity. The negative electrode slurry composition was applied to a 20 μm-thick copper foil current collector using a comma coater so that the dried film thickness was approximately 150 μm, and then dried. This drying was performed by transporting the copper foil at a speed of 0.5 m / min through an oven at 60°C for 2 minutes. The copper foil was then heat-treated at 120°C for 2 minutes to obtain a pre-pressed negative electrode blank. This pre-pressed negative electrode blank was rolled using a roll press to obtain a pre-pressed negative electrode having a negative electrode composite layer (thickness: 80 μm).

[0127] Using the separator with functional layer obtained as described above, the volume average particle size and particle size distribution of the particulate polymer in the functional layer, the ratio of the total area of ​​the particulate polymer and particle shed portions per unit area of ​​the functional layer when viewed in plan, the ratio of the area of ​​particle shed portions to the total area of ​​the particulate polymer and particle shed portions when viewed in plan, the thickness of the heat-resistant particulate layer, and the ratio of the volume average particle size of the particulate polymer to the thickness of the heat-resistant particulate layer were determined. Furthermore, using the separator with functional layer, positive electrode, and negative electrode obtained as described above, the dry adhesion and wet adhesion of the functional layer were evaluated. The results are shown in Table 1.

[0128] <Fabrication of lithium-ion secondary batteries> The pressed positive electrode prepared as described above was cut into a 49 cm x 5 cm rectangle and placed with the surface of the positive electrode composite layer facing up. The functional layer-equipped separator, cut to 120 cm x 5.5 cm, was placed on top of the positive electrode composite layer so that the positive electrode was positioned on one side of the functional layer-equipped separator in the longitudinal direction. Furthermore, the pressed negative electrode prepared as described above was cut into a 50 cm x 5.2 cm rectangle and placed on the functional layer-equipped separator so that the surface of the negative electrode composite layer faced the functional layer-equipped separator and the negative electrode was positioned on the other side of the functional layer-equipped separator in the longitudinal direction. The functional layer-equipped separator was then positioned so that the front surface of the functional layer-equipped separator faced the positive electrode and the back surface of the functional layer-equipped separator faced the negative electrode. The resulting laminate was then wound around a wound body to obtain a wound body. This wound body was pressed at 50°C and 1 MPa to form a flat body, then wrapped in an aluminum packaging exterior as the battery exterior, and an electrolyte solution [solvent: ethylene carbonate / diethyl carbonate / vinylene carbonate (volume ratio) = 68.5 / 30 / 1.5, electrolyte: LiPF6 concentration 1 mol)] was injected so that no air remained. The opening of the aluminum packaging exterior was then heat-sealed at a temperature of 150°C to produce a wound-type lithium-ion secondary battery with a capacity of 800 mAh. The obtained lithium ion secondary battery was used to evaluate the cycle characteristics and rate characteristics of the secondary battery. The results are shown in Table 1.

[0129] Example 2 A binder (α), a slurry composition, a separator with a functional layer, a positive electrode, and a negative electrode were prepared in the same manner as in Example 1, except that a core monomer composition (B) prepared as follows was used instead of the core monomer composition (A) in the preparation of the slurry composition of Example 1, and a lithium ion secondary battery was obtained. Various measurements and evaluations were then performed in the same manner as in Example 1. The results are shown in Table 1. The core monomer composition (B) was prepared by mixing 31.6 parts of styrene as an aromatic vinyl monomer, 17.6 parts of butyl acrylate and 30.4 parts of methyl methacrylate as (meth)acrylic acid ester monomers, and 0.4 parts of ethylene glycol dimethacrylate as a crosslinkable monomer. Various measurements and evaluations were then performed in the same manner as in Example 1. The results are shown in Table 1.

[0130] Example 3 A binder (α), a slurry composition, a separator with a functional layer, a positive electrode, and a negative electrode were prepared in the same manner as in Example 1, except that a core monomer composition (C) prepared as follows was used instead of the core monomer composition (A) in the preparation of the slurry composition of Example 1, and a lithium ion secondary battery was obtained. Various measurements and evaluations were then performed in the same manner as in Example 1. The results are shown in Table 1. The core monomer composition (C) was prepared by mixing 27.6 parts of styrene as an aromatic vinyl monomer, 17.6 parts of butyl acrylate and 34.4 parts of methyl methacrylate as (meth)acrylic acid ester monomers, and 0.4 parts of ethylene glycol dimethacrylate as a crosslinkable monomer. Various measurements and evaluations were then performed in the same manner as in Example 1. The results are shown in Table 1.

[0131] Example 4 In preparing the slurry composition of Example 1, except that the core monomer composition (A) was replaced with the core monomer composition (D) prepared as follows, and the shell monomer composition (A) was replaced with the shell monomer composition (B) prepared as follows, a binder (α), a slurry composition, a separator with a functional layer, a positive electrode, and a negative electrode were prepared, and a lithium-ion secondary battery was obtained. Various measurements and evaluations were then performed as in Example 1. The results are shown in Table 1. The core monomer composition (D) was prepared by mixing 57.5 parts of styrene as an aromatic vinyl monomer, 14.4 parts of butyl acrylate and 8.0 parts of methyl methacrylate as (meth)acrylic acid ester monomers, and 0.1 part of ethylene glycol dimethacrylate as a crosslinkable monomer. The shell monomer composition (B) was prepared by mixing 7.9 parts of styrene as an aromatic vinyl monomer, 4.4 parts of butyl acrylate and 7.6 parts of methyl methacrylate as (meth)acrylic acid ester monomers, and 0.1 part of ethylene glycol dimethacrylate as a crosslinkable monomer. Various measurements and evaluations were then carried out in the same manner as in Example 1. The results are shown in Table 1.

[0132] Example 5 A binder (α), a slurry composition, a separator with a functional layer, a positive electrode, and a negative electrode were prepared in the same manner as in Example 1, except that a shell monomer composition (C) prepared as follows was used instead of the shell monomer composition (A) in the preparation of the slurry composition of Example 1, and a lithium ion secondary battery was obtained. Various measurements and evaluations were then performed in the same manner as in Example 1. The results are shown in Table 1. The shell monomer composition (C) was prepared by mixing 14.9 parts of styrene as an aromatic vinyl monomer, 2.0 parts of butyl acrylate as a (meth)acrylic acid ester monomer, 3.0 parts of acrylonitrile as a nitrile group-containing monomer, and 0.1 part of ethylene glycol dimethacrylate as a cross-linkable monomer.

[0133] Example 6 A binder (α), a slurry composition, a separator with a functional layer, a positive electrode, and a negative electrode were prepared in the same manner as in Example 1, except that a shell monomer composition (D) prepared as follows was used instead of the shell monomer composition (A) in the preparation of the slurry composition of Example 1, and a lithium ion secondary battery was obtained. Various measurements and evaluations were then performed in the same manner as in Example 1. The results are shown in Table 1. The shell monomer composition (D) was prepared by mixing 17.8 parts of methyl methacrylate as a (meth)acrylic acid ester monomer, 2.0 parts of acrylonitrile as a nitrile group-containing monomer, and 0.2 parts of ethylene glycol dimethacrylate as a cross-linkable monomer.

[0134] Example 7 In preparing the slurry composition of Example 1, except that the core monomer composition (A) was replaced with the core monomer composition (E) prepared as follows, and the shell monomer composition (A) was replaced with the shell monomer composition (E) prepared as follows, the binder (α), slurry composition, separator with functional layer, positive electrode, and negative electrode were prepared in the same manner as in Example 1, and a lithium ion secondary battery was obtained. Then, various measurements and evaluations were performed in the same manner as in Example 1. The results are shown in Table 1. The core monomer composition (E) was prepared by mixing 81.8 parts of styrene as an aromatic vinyl monomer, 18.0 parts of 2-ethylhexyl acrylate as a (meth)acrylic acid ester monomer, and 0.1 part of ethylene glycol dimethacrylate as a cross-linkable monomer. The shell monomer composition (E) was prepared by mixing 0.0495 parts of styrene as an aromatic vinyl monomer, 0.01 parts of butyl acrylate as a (meth)acrylic acid ester monomer, 0.04 parts of acrylonitrile as a nitrile group-containing monomer, and 0.0005 parts of ethylene glycol dimethacrylate as a crosslinkable monomer. Various measurements and evaluations were then carried out in the same manner as in Example 1. The results are shown in Table 1.

[0135] Example 8 In preparing the slurry composition of Example 1, except that the core monomer composition (A) was replaced with the core monomer composition (F) prepared as follows, and the shell monomer composition (A) was replaced with the shell monomer composition (F) prepared as follows, the binder (α), slurry composition, separator with functional layer, positive electrode, and negative electrode were prepared in the same manner as in Example 1, and a lithium ion secondary battery was obtained. Then, various measurements and evaluations were performed in the same manner as in Example 1. The results are shown in Table 1. The core monomer composition (F) was prepared by mixing 73.7 parts of styrene as an aromatic vinyl monomer, 16.2 parts of 2-ethylhexyl acrylate as a (meth)acrylic acid ester monomer, and 0.1 part of ethylene glycol dimethacrylate as a cross-linkable monomer. The shell monomer composition (F) was prepared by mixing 4.95 parts of styrene as an aromatic vinyl monomer, 1.0 part of butyl acrylate as a (meth)acrylic acid ester monomer, 4.0 parts of acrylonitrile as a nitrile group-containing monomer, and 0.005 parts of ethylene glycol dimethacrylate as a crosslinkable monomer. Various measurements and evaluations were then carried out in the same manner as in Example 1. The results are shown in Table 1.

[0136] Example 9 In preparing the slurry composition of Example 1, except that the core monomer composition (A) was replaced with the core monomer composition (G) prepared as follows, and the shell monomer composition (A) was replaced with the shell monomer composition (G) prepared as follows, the binder (α), slurry composition, separator with functional layer, positive electrode, and negative electrode were prepared in the same manner as in Example 1, and a lithium ion secondary battery was obtained. Then, various measurements and evaluations were performed in the same manner as in Example 1. The results are shown in Table 1. The core monomer composition (G) was prepared by mixing 40.95 parts of styrene as an aromatic vinyl monomer, 9.0 parts of 2-ethylhexyl acrylate as a (meth)acrylic acid ester monomer, and 0.05 parts of ethylene glycol dimethacrylate as a cross-linkable monomer. The shell monomer composition (G) was prepared by mixing 24.75 parts of styrene as an aromatic vinyl monomer, 5.0 parts of butyl acrylate as a (meth)acrylic acid ester monomer, 20.0 parts of acrylonitrile as a nitrile group-containing monomer, and 0.25 parts of ethylene glycol dimethacrylate as a crosslinkable monomer. Various measurements and evaluations were then carried out in the same manner as in Example 1. The results are shown in Table 1.

[0137] Example 10 In preparing the slurry composition of Example 1, except that the core monomer composition (A) was replaced with the core monomer composition (H) prepared as follows, and the shell monomer composition (A) was replaced with the shell monomer composition (H) prepared as follows, a binder (α), a slurry composition, a separator with a functional layer, a positive electrode, and a negative electrode were prepared, and a lithium-ion secondary battery was obtained in the same manner as in Example 1. Various measurements and evaluations were then performed in the same manner as in Example 1. The results are shown in Table 1. The core monomer composition (H) was prepared by mixing 49.14 parts of styrene as an aromatic vinyl monomer, 10.8 parts of 2-ethylhexyl acrylate as a (meth)acrylic acid ester monomer, and 0.06 parts of ethylene glycol dimethacrylate as a cross-linkable monomer. The shell monomer composition (H) was prepared by mixing 19.8 parts of styrene as an aromatic vinyl monomer, 4.0 parts of butyl acrylate as a (meth)acrylic acid ester monomer, 16.0 parts of acrylonitrile as a nitrile group-containing monomer, and 0.2 parts of ethylene glycol dimethacrylate as a crosslinkable monomer. Various measurements and evaluations were then carried out in the same manner as in Example 1. The results are shown in Table 1.

[0138] Example 11 A binder (α), a slurry composition, a separator with a functional layer, a positive electrode, and a negative electrode were prepared in the same manner as in Example 1, except that a shell monomer composition (I) prepared as follows was used instead of the shell monomer composition (A) in the preparation of the slurry composition of Example 1, and a lithium ion secondary battery was obtained. Various measurements and evaluations were then performed in the same manner as in Example 1. The results are shown in Table 1. The shell monomer composition (I) was prepared by mixing 19.0 parts of methyl methacrylate as a (meth)acrylic acid ester monomer and 1.0 part of allyl methacrylate as a crosslinkable monomer.

[0139] Example 12 Except for changing the time of high shear stirring during suspension polymerization in preparing the particulate polymer to 10 seconds, the binder (α), slurry composition, separator with functional layer, positive electrode, and negative electrode were prepared in the same manner as in Example 1, and a lithium ion secondary battery was obtained. Then, various measurements and evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

[0140] Example 13 Except for using organic fine particles prepared as follows instead of alumina particles in preparing the functional layer composition, adhesive particles, a binder, a functional layer composition, a separator, a negative electrode, a positive electrode, and a lithium ion secondary battery were obtained in the same manner as in Example 1. Various evaluations were then performed in the same manner as in Example 1. The results are shown in Table 1. <Preparation of organic fine particles (heat-resistant fine particles)> In a reactor A equipped with a stirrer, 0.20 parts of sodium dodecyl sulfate, 0.30 parts of ammonium persulfate, and 180 parts of ion-exchanged water were mixed to form a mixture, and the mixture was heated to 65° C. Meanwhile, in a separate vessel, 80.0 parts of n-butyl acrylate as a (meth)acrylic acid ester monomer, 10.0 parts of methacrylic acid as an acid group-containing monomer, 10.0 parts of acrylonitrile as a nitrile group-containing monomer, 0.8 parts of sodium dodecyl sulfate, and 40 parts of ion-exchanged water were mixed to prepare a monomer composition for seed particles. This seed particle monomer composition was continuously added to the above-mentioned reactor A over a period of 4 hours to carry out a polymerization reaction. The temperature inside the reactor was maintained at 65°C during the continuous addition of the seed particle monomer composition. After the continuous addition was completed, the polymerization reaction was continued for an additional 3 hours at 80°C. This resulted in an aqueous dispersion of seed particles. The volume average particle diameter of the seed particles was measured in the same manner as for the binder and was found to be 120 nm. Next, 20 parts of the aqueous dispersion of the seed particles (based on solids content) (16 parts n-butyl acrylate units, 2 parts methacrylic acid units, and 2 parts acrylonitrile units), 80 parts ethylene glycol dimethacrylate (Kyoeisha Chemical Co., Ltd., product name "Light Ester EG") as a crosslinking monomer, 0.8 parts sodium dodecylbenzenesulfonate, 3.2 parts t-butylperoxy-2-ethylhexanoate (NOF Corporation, product name "Perbutyl O") as a polymerization initiator, and 160 parts ion-exchanged water were added to a reactor equipped with a stirrer, and the mixture was stirred at 35°C for 12 hours, allowing the crosslinking monomer and polymerization initiator to be completely absorbed into the seed particles. The temperature inside the reactor was then maintained at 90°C, and a polymerization reaction (seed polymerization) was carried out for 5 hours. Next, steam was introduced to remove unreacted monomers and initiator decomposition products, obtaining an aqueous dispersion of organic fine particles. The glass transition temperature of the obtained organic fine particles was measured in the same manner as for the adhesive particles and binder, but no peak was observed within the measurement temperature range (-100°C to 200°C). This confirmed that the glass transition temperature of the organic fine particles was above 200°C.

[0141] (Comparative Example 1) <Preparation of Particulate Polymer (A)> [Preparation of Monomer Composition (A)] A monomer composition (A) was prepared by mixing 81.9 parts of styrene as an aromatic vinyl monomer, 18 parts of 2-ethylhexyl acrylate as a (meth)acrylic acid ester monomer, and 0.1 parts of ethylene glycol dimethacrylate as a crosslinkable monomer.

[0142] [Preparation of metal hydroxides] A colloidal dispersion (A) containing magnesium hydroxide as the metal hydroxide was prepared by gradually adding, with stirring, an aqueous solution (A2) prepared by dissolving 5.6 parts of sodium hydroxide in 50 parts of ion-exchanged water to an aqueous solution (A1) prepared by dissolving 8 parts of magnesium chloride in 200 parts of ion-exchanged water.

[0143] [Suspension polymerization method] A particulate polymer (A) was prepared by suspension polymerization. Specifically, the monomer composition (A) obtained as described above was added to the colloidal dispersion (A) containing magnesium hydroxide, and after further stirring, 2.0 parts of t-butylperoxy-2-ethylhexanoate (NOF Corp., "Perbutyl O") was added as a polymerization initiator to obtain a mixed solution. The resulting mixed solution was subjected to high-shear stirring at 15,000 rpm for 1 minute using an in-line emulsifying disperser (Pacific Machinery Works, "Cavitron") to form droplets of the monomer composition (A) in the colloidal dispersion (A) containing magnesium hydroxide.

[0144] The colloidal dispersion (A) containing magnesium hydroxide and droplets of the monomer composition (A) was placed in a reactor, heated to 90°C, and polymerized for 5 hours to obtain an aqueous dispersion containing particulate polymer (A). Other than that, adhesive particles, a binder, a functional layer composition, a separator, a negative electrode, a positive electrode, and a lithium-ion secondary battery were obtained in the same manner as in Example 1. Various evaluations were then performed in the same manner as in Example 1. The results are shown in Table 2.

[0145] (Comparative Example 2) In the preparation of the slurry composition of Comparative Example 1, the binder (α), the slurry composition, and the mechanical properties were the same as in Example 1, except that the monomer composition (A) was replaced with the monomer composition (B) prepared as follows, the polymerization initiator was changed to 2.0 parts of t-butylperoxy-2-ethylhexanoate (NOF Corporation, "Perbutyl O") and 3.6 parts of di(3,5,5-trimethylhexanoyl peroxide" (NOF Corporation, "Peroyl 355"), and the temperature was raised to 70°C to carry out the polymerization reaction. A separator with an active layer, a positive electrode, and a negative electrode were prepared to obtain a lithium ion secondary battery. Various measurements and evaluations were then carried out in the same manner as in Example 1. The results are shown in Table 2. The monomer composition (B) was prepared by mixing 20.9 parts of n-butyl acrylate as a (meth)acrylic acid ester monomer, 20 parts of acrylonitrile as a nitrile group-containing monomer, 59 parts of methyl methacrylate as a (meth)acrylic acid ester monomer, and 0.1 part of ethylene glycol dimethacrylate as a crosslinkable monomer.

[0146] (Comparative Example 3) In preparing the slurry composition of Example 1, except that the core monomer composition (A) was replaced with the core monomer composition (I) prepared as follows, and the shell monomer composition (A) was replaced with the shell monomer composition (J) prepared as follows, the binder (α), slurry composition, separator with functional layer, positive electrode, and negative electrode were prepared in the same manner as in Example 1, and a lithium ion secondary battery was obtained. Then, various measurements and evaluations were performed in the same manner as in Example 1. The results are shown in Table 2. The core monomer composition (I) was prepared by mixing 56 parts of methyl methacrylate as a (meth)acrylic acid ester monomer, 20 parts of butyl acrylate, and 4 parts of allyl methacrylate as a crosslinkable monomer. The shell monomer composition (J) was prepared by mixing 9.9 parts of styrene as an aromatic vinyl monomer, 2.0 parts of butyl acrylate as a (meth)acrylic acid ester monomer, 8.0 parts of acrylonitrile as a nitrile group-containing monomer, and 0.1 part of ethylene glycol dimethacrylate as a cross-linkable monomer. Various measurements and evaluations were then carried out in the same manner as in Example 1. The results are shown in Table 2.

[0147] Comparative Example 4 In preparing the slurry composition of Example 1, except that the core monomer composition (A) was replaced with the core monomer composition (J) prepared as follows, and the shell monomer composition (A) was replaced with the shell monomer composition (K) prepared as follows, a binder (α), a slurry composition, a separator with a functional layer, a positive electrode, and a negative electrode were prepared, and a lithium-ion secondary battery was obtained. Various measurements and evaluations were then performed as in Example 1. The results are shown in Table 2. The core monomer composition (J) was prepared by mixing 55.1 parts of styrene as an aromatic vinyl monomer, 10.4 parts of methyl methacrylate and 14.4 parts of butyl acrylate as (meth)acrylic acid ester monomers, and 0.1 part of ethylene glycol dimethacrylate as a crosslinkable monomer. The shell monomer composition (K) was prepared by mixing 14.3 parts of styrene as an aromatic vinyl monomer, 2.0 parts of butyl acrylate as a (meth)acrylic acid ester monomer, 3.6 parts of acrylonitrile as a nitrile group-containing monomer, and 0.1 part of ethylene glycol dimethacrylate as a cross-linkable monomer. Various measurements and evaluations were then carried out in the same manner as in Example 1. The results are shown in Table 2.

[0148] (Comparative Example 5) A binder (α), a slurry composition, a separator with a functional layer, a positive electrode, and a negative electrode were prepared in the same manner as in Example 1, except that the shell monomer composition (L) was used instead of the shell monomer composition (A) in the preparation of the slurry composition of Example 1, and a lithium ion secondary battery was obtained. Various measurements and evaluations were then carried out in the same manner as in Example 1. The results are shown in Table 2. The shell monomer composition (L) contained 20 parts of acrylonitrile as the nitrile group-containing monomer. Various measurements and evaluations were then carried out in the same manner as in Example 1. The results are shown in Table 2.

[0149] (Comparative Example 6) In preparing the slurry composition of Example 1, except that core monomer composition (I) was used instead of core monomer composition (A) and shell monomer composition (M) prepared as follows was used instead of shell monomer composition (A), binder (α), slurry composition, separator with functional layer, positive electrode, and negative electrode were prepared in the same manner as in Example 1, and a lithium ion secondary battery was obtained. Various measurements and evaluations were then performed in the same manner as in Example 1. The results are shown in Table 2. Shell monomer composition (K) contained 20 parts of styrene as the aromatic vinyl monomer.

[0150] (Comparative Example 7) A separator with a functional layer, a positive electrode, and a negative electrode were produced in the same manner as in Example 1, except that a particulate polymer (C) prepared as follows was used instead of the particulate polymer (A) in preparing the slurry composition, and a lithium ion secondary battery was obtained. Then, various measurements and evaluations were performed in the same manner as in Example 1. The results are shown in Table 2. 100 parts of ion-exchanged water and 0.5 parts of ammonium persulfate were supplied to a reactor equipped with a stirrer, the gas phase was replaced with nitrogen gas, and the temperature was raised to 60°C. Meanwhile, in a separate vessel, 50 parts of ion-exchanged water, 0.3 parts of sodium dodecylbenzenesulfonate as an emulsifier, 63.1 parts of styrene as an aromatic vinyl monomer, 14.4 parts of 2-ethylhexyl acrylate as a (meth)acrylic acid alkyl ester monomer, 2.4 parts of methacrylic acid (MAA) as an acidic group-containing monomer, and 0.1 parts of ethylene dimethacrylate (EDMA) as a crosslinkable group-containing monomer were mixed to obtain a monomer mixture for the core portion. This monomer mixture was continuously added to the reactor over 4 hours and polymerization was carried out at 60°C. Polymerization was continued until the polymerization conversion reached 96%, yielding an aqueous dispersion containing particulate polymers that would form the core portion. This aqueous dispersion was then heated to 80°C. A mixture of 3 parts of styrene, 15.9 parts of methyl methacrylate, 1 part of methacrylic acid, and 0.1 parts of ethylene glycol dimethacrylate as a shell portion monomer was continuously added to the aqueous dispersion over 30 minutes, and polymerization was continued. When the polymerization conversion rate reached 96%, the reaction was stopped by cooling to prepare an aqueous dispersion containing particulate polymer B. The volume average particle diameter D50 of the obtained particulate polymer B was 500 nm. <Preparation of Slurry Composition (Functional Layer Composition)> To 100 parts of alumina (manufactured by Sumitomo Chemical Co., Ltd., "AKP3000", volume average particle diameter: 0.7 μm) as heat-resistant fine particles, 0.5 parts of polyacrylic acid as a water-soluble polymer was added, and ion-exchanged water was added so that the solid content concentration became 55%, followed by mixing using a ball mill to obtain a pre-mixing slurry. 100 parts of heat-resistant fine particles were mixed with 6 parts of an aqueous dispersion containing a binder (α) in terms of solid content and 1.5 parts of carboxymethyl cellulose as a thickener to a solid content of 40%, and the resulting mixture was added to the pre-mixing slurry obtained as described above. Further, ion-exchanged water was added to a solid content of 40%, to obtain a slurry composition (composition for functional layer). The volume ratio of the heat-resistant fine particles (alumina) to the particulate polymer (A) in the slurry composition (heat-resistant fine particles / particulate polymer (A)) was 70 / 30.

[0151] In addition, in Tables 1 and 2, "ST" indicates styrene, "2EHA" indicates 2-ethylhexyl acrylate, "EDMA" refers to ethylene glycol dimethacrylate; "BA" indicates n-butyl acrylate; "AN" indicates acrylonitrile, "MAA" indicates methacrylic acid, "MMA" indicates methyl methacrylate, "AMA" refers to allyl methacrylate.

[0152] [Table 1]

[0153] [Table 2]

[0154] From Tables 1 and 2, the particulate polymer having a core-shell structure, S B / S AIn Examples 1 to 13, which used compositions for electrochemical device functional layers containing a particulate polymer, a binder, and heat-resistant fine particles, which satisfy the relationship of 1.0 μm to 10.0 μm and have a volume average particle diameter of 1.0 μm to 10.0 μm, and which satisfy the relationship of 1.2, it was found that functional layers with excellent wet adhesion and electrochemical devices with excellent electrolyte injectability and rate characteristics were produced. B / S A It can be seen that in Comparative Examples 3 to 6, which used particulate polymers that did not satisfy the relationship of ≧1.2, and in Comparative Example 7, which used a particulate polymer with a volume average particle diameter of less than 1.0 μm, the wet adhesion of the functional layer, the electrolyte injectability of the electrochemical element, and the rate characteristics could not be sufficiently improved. [Industrial Applicability]

[0155] According to the present invention, it is possible to provide a composition for a functional layer that can form a functional layer having excellent wet adhesion and that can improve the electrolyte injectability and rate characteristics of the resulting electrochemical device. Furthermore, according to the present invention, it is possible to provide a laminate for electrochemical devices that includes a functional layer with excellent wet adhesion, which can improve the electrolyte injectability and rate characteristics of the resulting electrochemical device, and an electrochemical device that includes such a laminate for electrochemical devices and has excellent electrolyte injectability and rate characteristics.

Claims

1. A composition for an electrochemical device functional layer, comprising a particulate polymer, a binder, and heat-resistant fine particles, the particulate polymer is an adhesive polymer having a core-shell structure including a core portion made of polymer A and a shell portion made of polymer B covering at least a part of the outer surface of the core portion, The electrolyte swelling degree S of the polymer A Ａ is 1 to 8 times, and the electrolyte swelling degree S of the polymer B is Ｂ is more than four times The electrolyte swelling degree S Ａ and the electrolyte swelling degree S Ｂ But, S Ｂ / S Ａ ≧1.2, The volume average particle diameter of the particulate polymer is 1.0 μm or more and 10.0 μm or less, The polymer B contains at least one of an aromatic vinyl monomer unit and a nitrile group-containing monomer unit, or contains both a (meth)acrylic acid ester monomer unit and a crosslinkable monomer unit, and when the polymer B contains an aromatic vinyl monomer unit, the content of the aromatic vinyl monomer unit is 30% by mass or more and 80% by mass or less, with the total amount of all repeating units contained in the polymer B being 100% by mass, when the polymer B contains a nitrile group-containing monomer unit, the content of the nitrile group-containing monomer unit is 5% by mass or more and 60% by mass or less, with the total amount of all repeating units contained in the polymer B being 100% by mass, when the polymer B contains a (meth)acrylic acid ester monomer unit, the content of the (meth)acrylic acid ester monomer unit is 5% by mass or more and 95% by mass or less, with the total amount of all repeating units contained in the polymer B being 100% by mass, When the polymer B contains a crosslinkable monomer unit, the content of the crosslinkable monomer unit is 0.1% by mass or more and 5 parts by mass or less, with the total amount of all repeating units contained in the polymer B being 100% by mass. A composition for an electrochemical device functional layer.

2. 2. The composition for an electrochemical device functional layer according to claim 1, wherein the particulate polymer has a core portion to shell portion ratio in the range of 99.9:0.1 to 50:50 by mass.

3. 3. The composition for an electrochemical device functional layer according to claim 1, wherein the particle size distribution of the particulate polymer is 1.5 or less.

4. A laminate for electrochemical devices, comprising a substrate and a functional layer for electrochemical devices formed on the substrate, the functional layer for electrochemical devices being formed using the composition for electrochemical device functional layers according to any one of claims 1 to 3.

5. An electrochemical device comprising the laminate for an electrochemical device according to claim 4 .

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