Composition for electrochemical element functional layer, method for producing said composition, functional layer for electrochemical element, laminate for electrochemical element, and electrochemical element

Abstract

The composition for an electrochemical element functional layer comprises a binder material and a particulate polymer having a sea-island structure wherein, in observation of the cross section using prescribed conditions, the number of island phases per unit area is 1 to 200.

Description

Composition for electrochemical device functional layer and method for producing the same, functional layer for electrochemical device, laminate for electrochemical device, and electrochemical device

[0001] The present invention relates to a composition for a functional layer of an electrochemical device, a method for producing the same, a functional layer for an electrochemical device, a laminate for an electrochemical device, and an electrochemical device.

[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-ion secondary batteries. To achieve these improvements, attempts have been made to laminate a layer (functional layer) on a separator substrate to achieve desired functions such as heat resistance and adhesiveness. Specifically, Patent Document 1, for example, discloses a composition for an electrochemical element functional layer, which contains a particulate polymer having an average circularity of 0.90 to less than 0.99 and a volume-average particle diameter of 1.0 μm to 10.0 μm, a binder, and inorganic particles. Patent Document 2, for example, discloses an adhesive resin composition for secondary batteries containing an adhesive resin having a core-shell heterophase structure and / or a sea-island heterophase structure. In the examples, an adhesive resin having a core-shell heterophase structure is actually synthesized.

[0005] International Publication No. 2020 / 175292 Patent No. 6051731

[0006] In recent years, novel compositions for functional layers have been needed to further improve the performance of electrochemical devices. Therefore, an object of the present invention is to provide a composition for functional layers containing a particulate polymer having a novel structure, and a method for producing such a composition for functional layers. Another object of the present invention is to provide a laminate for electrochemical devices including a functional layer for electrochemical devices formed using the composition for functional layers of the present invention, and an electrochemical device including the laminate.

[0007] The present inventors have conducted extensive research to achieve the above object, and have created a composition for an electrochemical device functional layer, which comprises a particulate polymer having an island-in-sea structure, the number of island phases per unit area being 1 to 200 when a cross section of the polymer is observed under specified conditions, and a binder.

[0008] 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 and a binder, wherein the particulate polymer has a sea-island structure comprising an island phase made of polymer A and a sea phase made of polymer B, and a method for obtaining cross-sectional images of a plurality of the particulate polymers, and selecting, from each of the cross sections of the plurality of particulate polymers contained in the cross-sectional images, a plurality of cross sections having a circumscribed circle diameter of the cross section within a range of 0.6 to 1.2 times the volume average particle diameter of the particulate polymer as observation objects, and measuring a unit area of ​​1 μm for the cross sections of the plurality of particulate polymers selected as observation objects. 2 When the number of island phases having a diameter of 1 / 5 or less of the volume average particle diameter per calculated unit area of ​​1 μm 2The composition for a functional layer is characterized in that the number of island phases per unit area is 1 to 200. Thus, a composition for a functional layer containing a particulate polymer having a sea-island structure in which the number of island phases per unit area is 1 to 200 when the cross section is observed under specified conditions is a composition for a functional layer containing a particulate polymer having a novel structure. The structure of the particulate polymer can be confirmed by the method described in the Examples. The volume-average particle diameter of the particulate polymer refers to the particle diameter D50 at which the cumulative volume calculated from the smallest diameter side by laser diffraction is 50%, and can be measured by the method described in the Examples.

[0009] In the composition for electrochemical device functional layers of the present invention, the volume average particle diameter of the particulate polymer is preferably 1.0 μm or more and 10.0 μm or less. If the composition for electrochemical device functional layers contains a particulate polymer having the above structure and a volume average particle diameter within the above range, the uniformity and adhesiveness of the functional layer can be improved. The volume average particle diameter of the particulate polymer can be measured according to the method described in the Examples.

[0010] Furthermore, the composition for an electrochemical device functional layer of the present invention preferably further contains heat-resistant fine particles. If the composition for an electrochemical device functional layer further contains heat-resistant fine particles, heat resistance can be imparted to the resulting functional layer.

[0011] In addition, in the composition for electrochemical device functional layers of the present invention, the polymer A preferably contains (meth)acrylic acid ester monomer units. If the polymer A constituting the island phase of the particulate polymer contains (meth)acrylic acid ester monomer units, an excessive decrease in the glass transition temperature of the particulate polymer can be prevented, and the resulting functional layer can be prevented from blocking during storage. Hereinafter, the property of being less susceptible to blocking may be referred to as "blocking resistance." In addition, in this specification, "(meth)acrylic" means acrylic or methacrylic. In addition, in this specification, when a polymer "contains a monomer unit," it means that "a polymer obtained using that monomer contains a structural unit derived from the monomer."

[0012] In the composition for an electrochemical device functional layer of the present invention, the glass transition temperature of the polymer A is preferably higher than 20° C. and not higher than 90° C. If the glass transition temperature of the polymer A constituting the island phase of the particulate polymer is within the above range, blocking resistance and process adhesion can be improved. The glass transition temperature of the polymer A can be measured according to the method described herein.

[0013] In addition, in the composition for electrochemical device functional layers of the present invention, the content ratio of the polymer A based on the content mass of the polymer B is preferably 0.1% by mass or more and 20% by mass or less. When the content ratio of the polymer A based on the content mass of the polymer B is 0.1% by mass or more and 20% by mass or less, the desired attributes that the polymer A can exhibit and the desired attributes that the polymer B can exhibit can be exhibited in a well-balanced manner.

[0014] In the composition for an electrochemical device functional layer of the present invention, the electrolyte swelling degree S of the polymer B is B The electrolyte swelling degree S of the polymer B is preferably 1.0 times or more and 8.0 times or less. B When the ratio is 1.0 to 8.0, the resulting functional layer can have improved adhesion after immersion in an electrolyte solution and can also have improved injectability. The "electrolyte swelling degree" of the polymer can be measured according to the method described in the Examples.

[0015] In the composition for an electrochemical device functional layer of the present invention, the electrolyte swelling degree S of the polymer A is A The electrolyte swelling degree S of the polymer A is preferably 4.0 times or more. A When the ratio is 4.0 times or more, the adhesiveness of the resulting functional layer after immersion in an electrolyte solution can be improved.

[0016] In the composition for an electrochemical device functional layer of the present invention, the electrolyte swelling degree S of the polymer A is A The electrolyte swelling degree S of the polymer B is B The electrolyte swelling degree S of polymer A is preferably 1.2 times or more. A is the electrolyte swelling degree S of polymer B BIf the thickness is 1.2 times or more, the adhesiveness of the resulting functional layer after immersion in the electrolyte solution can be improved.

[0017] The present invention also aims to advantageously solve the above-mentioned problems, and provides a method for producing a composition for an electrochemical device functional layer, comprising the steps of preparing the particulate polymer by a suspension polymerization method, a dissolution suspension method, or a pulverization method. According to the method, a composition for a functional layer containing the particulate polymer having the novel structure can be efficiently produced.

[0018] Furthermore, the functional layer for electrochemical devices of the present invention is a functional layer for electrochemical devices formed using the composition for electrochemical functional layers of the present invention described above, and the functional layer for electrochemical devices has a structure in which a part of the particulate polymer is embedded in a heat-resistant fine particle layer containing the heat-resistant fine particles, and is characterized in that the volume average particle diameter of the particulate polymer is larger than the thickness of the heat-resistant fine particle layer. A functional layer having such a structure and in which the volume average particle diameter of the particulate polymer is larger than the thickness of the heat-resistant fine particle layer has excellent process adhesion and adhesion after immersion in an electrolyte solution.

[0019] Furthermore, the laminate for electrochemical devices of the present invention comprises a substrate and a functional layer for electrochemical devices formed on the substrate, and is characterized in that the functional layer for electrochemical devices is a functional layer for electrochemical devices formed using the composition for electrochemical device functional layers of the present invention described above.

[0020] Furthermore, the laminate for an electrochemical device of the present invention is characterized by comprising the above-mentioned laminate for an electrochemical device of the present invention.

[0021] According to the present invention, it is possible to provide a composition for a functional layer containing a particulate polymer having a novel structure, a method for producing such a composition for a functional layer, a laminate for an electrochemical device including a functional layer for an electrochemical device formed using the composition for a functional layer of the present invention, and an electrochemical device including the same.

[0022] 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 the "functional layer composition") is used to form the functional layer for an electrochemical device of the present invention (hereinafter also simply referred to as the "functional layer"). The composition for a functional layer of the present invention can be efficiently produced according to the production method of the present invention. The laminate for an electrochemical device of the present invention comprises the functional layer of the present invention. Furthermore, the electrochemical device of the present invention is an electrochemical device comprising at least the laminate for an electrochemical device of the present invention.

[0023] (Composition for electrochemical device functional layer) The composition for electrochemical device functional layer of the present invention contains a predetermined particulate polymer and a binder, and preferably further contains heat-resistant fine particles. The composition for electrochemical device functional layer of the present invention may further contain other components as desired.

[0024] <Particulate polymer> The particulate polymer contained in the composition for functional layer has a novel structure. Because the particulate polymer has such a novel structure, it can exhibit the inherent attributes of polymer A and polymer B constituting the particulate polymer in a well-balanced manner. Note that, after bonding members together via a functional layer formed using the composition for functional layer, the particulate polymer may be in a particulate form or any other shape.

[0025] <<Structure of Particulate Polymer>> The particulate polymer has an islands-in-a-sea structure including an island phase made of polymer A and a sea phase made of polymer B. The islands-in-a-sea structure refers to a structure in which an isolated phase (island phase) exists in a phase made of a continuous phase (sea phase). In this specification, the continuous phase as a matrix is ​​referred to as the sea phase, and the isolated island-like separated phase is referred to as the island phase. The shape of the island phase is not particularly limited, but may be approximately circular.

[0026] << Unit area 1 μm 2 The number of islands per unit area of ​​1 μm is calculated according to a specific method. 2 The number of island phases per unit area of ​​1 μm must be 1 or more and 200 or less. 2In calculating the number of island phases per unit area of ​​1 μm, first, cross-sectional images of a plurality of particulate polymers are obtained according to a predetermined method. Among the cross sections of a plurality of particulate polymers contained in the obtained cross-sectional images, a plurality of cross sections having a circumscribed circle diameter within a range of 0.6 to 1.2 times the volume average particle diameter of the particulate polymer are selected as observation objects. Then, for the cross sections of the plurality of particulate polymers selected as observation objects, the particulate polymers are selected as observation objects. 2 When the number of island phases whose diameter is 1 / 5 or less of the volume average particle diameter per calculated unit area of ​​1 μm 2 The number of island phases per particle is 1 or more and 200 or less. The details of the calculation method will be described in Examples, but the method described in Examples is an example of a method for observing the cross section of a particulate polymer, and the observation magnification and the material used for staining can be changed as necessary. If the particulate polymer has a novel structure that satisfies these conditions, it can be made to exhibit the desired properties that polymer A can exhibit and the desired properties that polymer B can exhibit in a well-balanced manner.

[0027] Furthermore, the unit area of ​​1 μm calculated by cross-sectional observation according to the above-mentioned predetermined method 2 The number of island phases per unit area of ​​1 μm is preferably 10 or more, more preferably 20 or more, and is preferably 150 or less, more preferably 100 or less. For example, as will be described later, in the case where polymer A is capable of exhibiting high adhesive ability when swollen in an electrolyte solution, the number of island phases per unit area of ​​1 μm is 2 When the number of island phases per unit area of ​​1 μm is equal to or greater than the lower limit, polymer A effectively acts as an anchor when exerting adhesive power, thereby improving the adhesiveness of the functional layer after immersion in an electrolyte solution. 2 If the number of island phases per unit area is equal to or less than the upper limit, the elasticity of the particulate polymer can be maintained after immersion in the electrolyte solution, thereby improving the adhesion of the functional layer after immersion in the electrolyte solution.

[0028] <<Polymer A>> Polymer A is a component that constitutes the island phase of the particulate polymer. The composition of polymer A is not particularly limited, but it preferably contains (meth)acrylic acid ester monomer units. If polymer A contains (meth)acrylic acid ester monomer units, it is possible to prevent the glass transition temperature of the particulate polymer from decreasing excessively, and to prevent the resulting functional layer from blocking during storage. Furthermore, polymer A may contain other monomer units such as crosslinkable monomer units and acidic group-containing monomer units in addition to the (meth)acrylic acid ester monomer units.

[0029] Examples of (meth)acrylic acid ester monomers that can be used to form the (meth)acrylic acid ester monomer units 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. acrylic acid alkyl esters; and monofunctional methacrylic acid alkyl esters such as 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 and stearyl methacrylate. Among these, n-butyl acrylate, 2-ethylhexyl acrylate and methyl methacrylate are preferred. These (meth)acrylic acid ester monomers may be used alone or in combination of two or more in any ratio.

[0030] The content of (meth)acrylic acid ester monomer units in polymer A is preferably 5% by mass or more, more preferably 50% by mass or more, and preferably 99.9% by mass or less, based on 100% by mass of all repeating units contained in polymer A. If the content of (meth)acrylic acid ester monomer units in polymer A is equal to or greater than the above-mentioned lower limit, the process adhesion of the resulting functional layer can be further improved. Furthermore, if the content of (meth)acrylic acid ester monomer units in polymer A is equal to or less than the above-mentioned upper limit, the slurry stability can be improved.

[0031] 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, allyl methacrylate is preferred.

[0032] The content of the crosslinkable monomer units in polymer A is preferably 0.05% by mass or more, more preferably 0.5% by mass or more, and preferably 7% by mass or less, more preferably 5% by mass or less, and even more preferably 3% 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 equal to or greater than the above-mentioned lower limit, the sea-island structure of the particulate polymer can be made favorable. Furthermore, when the content of the crosslinkable monomer units in polymer A is equal to or less than the above-mentioned upper limit, the adhesion of the resulting functional layer after immersion in an electrolyte solution can be improved.

[0033] Examples of acidic group-containing monomers that can be used to form the acidic group-containing monomer units include monomers having a carboxylic acid group, monomers having a sulfonic acid group, monomers having a phosphoric acid group, and monomers having a hydroxyl group. Among these, monomer units having a carboxylic acid group are preferred, and (meth)acrylic acid monomer units are more preferred. If the acidic group-containing monomer units of polymer A are monomer units having a carboxylic acid group, particularly (meth)acrylic acid monomer units, a functional layer with even more excellent process adhesion and blocking resistance can be formed.

[0034] Examples of monomers having a carboxylic acid group include monocarboxylic acids and dicarboxylic acids. Examples of monocarboxylic acids include acrylic acid, methacrylic acid, and crotonic acid. Examples of dicarboxylic acids include maleic acid, fumaric acid, and itaconic acid. Examples of monomers 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, 3-allyloxy-2-hydroxypropanesulfonic acid, and p-styrenesulfonic acid, as well as salts thereof. In this specification, "(meth)allyl" refers to allyl and / or methallyl, and (meth)acrylic refers to acrylic and / or methacrylic. Examples of monomers having a phosphate group include 2-(meth)acryloyloxyethyl phosphate, methyl-2-(meth)acryloyloxyethyl phosphate, and ethyl-(meth)acryloyloxyethyl phosphate. In this specification, "(meth)acryloyl" means acryloyl and / or methacryloyl. Examples of monomers having a hydroxyl group include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate. These acidic group-containing monomers may be used alone or in combination of two or more at any ratio.

[0035] The content of the acidic group-containing monomer units in polymer A is not particularly limited, but is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and preferably 5% by mass or less, more preferably 1% by mass or less, and even more preferably 0.5% by mass or less, based on 100% by mass of all repeating units contained in polymer A. If the content of the acidic group-containing monomer units in polymer A is equal to or greater than the above-mentioned lower limit, the slurry stability of the functional layer composition can be improved, and the blocking resistance of the resulting functional layer can be further improved. Furthermore, if the content of the acidic group-containing monomer units in polymer A is equal to or less than the above-mentioned upper limit, the stability during production of the particulate polymer can be improved.

[0036] Incidentally, examples of the monomer that can be used to form other monomer units that can constitute the polymer A include aromatic vinyl monomers. As the aromatic vinyl monomer, various monomer units that will be described later as monomers that can be used to form aromatic vinyl monomer units that can be contained in the polymer B can be used.

[0037] The content of the other monomer units in polymer A is not particularly limited, but is preferably 10% by mass or less, where the total amount of all 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.

[0038] [Glass Transition Temperature of Polymer A] The glass transition temperature of polymer A is preferably higher than 20°C, more preferably 25°C or higher, and even more preferably 30°C or higher, and is preferably 90°C or lower, more preferably 80°C or lower, and even more preferably 70°C or lower. If the glass transition temperature of polymer A is equal to or higher than the above lower limit, the blocking resistance of the resulting functional layer can be improved. If the glass transition temperature of polymer A is equal to or lower than the above upper limit, the adhesiveness and process adhesiveness of the resulting functional layer after immersion in an electrolyte solution can be further improved.

[0039] [Electrolyte swelling degree S of polymer A A Furthermore, the polymer A has an electrolyte swelling degree SA is preferably 4.0 times or more, more preferably 6.0 times or more, even more preferably 7.0 times or more, even more preferably 8.0 times or more, and is preferably 20.0 times or less, more preferably 18.0 times or less, and even more preferably 16.0 times or less. A If the degree of swelling of polymer A in electrolyte solution is equal to or greater than the above lower limit, when the resulting functional layer is immersed in an electrolyte solution, polymer A swells in the electrolyte solution, and the swollen portion penetrates between the electrode active materials, thereby exhibiting a good anchor effect, and as a result, adhesive strength can be increased. A If the swelling degree S of the polymer A in the electrolyte is equal to or less than the upper limit, the resistance of the resulting functional layer in the electrolyte solution is reduced, and the battery characteristics of a secondary battery including such a functional layer can be improved. A When the value is equal to or less than the upper limit, excessive narrowing of the voids in the functional layer due to excessive swelling of the polymer A in the electrolyte solution can be suppressed, and as a result, the injectability of the functional layer can be improved.

[0040] [Content of polymer A based on the mass of polymer B] The content of polymer A based on the mass of polymer B 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. When the content of polymer A based on the mass of polymer B is within the above range, the desired attributes that polymer A can exhibit and the desired attributes that polymer B can exhibit can be exhibited in a better balance. Note that, when polymer A can exhibit high adhesive performance when swollen in an electrolyte solution, the content of polymer A being equal to or greater than the above lower limit can improve the wet adhesion of the resulting functional layer. Furthermore, when polymer A can exhibit high adhesive performance when swollen in an electrolyte solution, when the content of polymer A is equal to or less than the above upper limit, the elasticity of the particulate polymer can be maintained after immersion in an electrolyte solution, thereby improving the adhesion of the functional layer after immersion in an electrolyte solution.

[0041] <<Polymer B>> Polymer B is a component that constitutes the sea phase of the particulate polymer. The composition of Polymer B is not particularly limited as long as it is different from that of Polymer A. For example, Polymer B may contain aromatic vinyl monomer units, (meth)acrylic acid ester monomer units, crosslinkable monomer units, and other monomer units other than these.

[0042] 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, butoxystyrene, vinylnaphthalene, etc. Among these, styrene is preferred. These aromatic vinyl monomers may be used alone or in combination of two or more at any ratio.

[0043] The content of the aromatic vinyl monomer units in Polymer B 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 B. When the content of the aromatic vinyl monomer units in Polymer B is within the above range, good adhesion between the functional layer and the substrate can be achieved.

[0044] As a monomer that can be used to form the (meth)acrylic acid ester monomer unit that can be contained in polymer B, the same monomers as those listed for polymer A can be used. Among them, n-butyl acrylate, 2-ethylhexyl acrylate, and methyl methacrylate are preferred, and 2-ethylhexyl acrylate is more preferred.

[0045] The content of the (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 50% by mass or less, and more preferably 40% by mass or less, based on 100% by mass of all repeating units contained in polymer B. If the content of the (meth)acrylic acid ester monomer units in polymer B is equal to or greater than the above-mentioned lower limit, the process adhesion of the resulting functional layer can be further improved. If the content of the (meth)acrylic acid ester monomer units in polymer B is equal to or less than the above-mentioned upper limit, the stability of the slurry composition can be improved when it is prepared.

[0046] As a monomer that can be used to form a crosslinkable monomer unit that can be contained in polymer B, the same monomers as those listed for polymer A can be used. Among them, ethylene glycol dimethacrylate is preferred.

[0047] The content of the crosslinkable monomer unit in polymer B is preferably 0.05% by mass or more and 10% by mass or less, relative to 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 process adhesion of the resulting functional layer can be improved.

[0048] Polymer B may contain monomer units other than those described above (in other words, monomer units other than aromatic vinyl monomer units, (meth)acrylic acid ester monomer units, and crosslinkable monomer units). Examples of monomers that can be used to form such monomer units include acidic group-containing monomers.

[0049] The acidic group-containing monomer that can be used to form the acidic group-containing monomer unit is not particularly limited, and those mentioned above for polymer A can be used.

[0050] The content of the monomer units other than those described above in polymer B is not particularly limited, but is preferably 10% by mass or less, where the total amount of all repeating units contained in polymer B is 100% by mass. Alternatively, it may be 0% by mass, i.e., polymer B may contain no monomer units other than those described above.

[0051] [Glass transition temperature of polymer B] The glass transition temperature of polymer B is preferably higher than 10°C, more preferably 20°C or higher, and even more preferably 30°C or higher, and is 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 B is equal to or higher than the above lower limit, the blocking resistance of the resulting functional layer can be improved. If the glass transition temperature of polymer A is equal to or lower than the above upper limit, the process adhesion of the resulting functional layer can be further improved.

[0052] [Electrolyte swelling degree S of polymer B Ｂ Furthermore, the polymer B has an electrolyte swelling degree S Ｂ is preferably 1.0 times or more, more preferably 1.2 times or more, and even more preferably 1.3 times or more, and is preferably 8.0 times or less, more preferably 6.0 times or less, and even more preferably 4.0 times or less. Ｂ When the degree of swelling in electrolyte of polymer B is equal to or greater than the lower limit, the particulate polymer swells appropriately in the electrolyte solution, and the adhesion of the functional layer after immersion in the electrolyte solution can be improved. Ｂ If the swelling degree S of the polymer B in the electrolyte is equal to or less than the upper limit, the resistance of the resulting functional layer in the electrolyte solution is reduced, and the battery characteristics of a secondary battery including such a functional layer can be improved. Ｂ When the value of (I) is equal to or less than the upper limit, excessive narrowing of the voids in the functional layer due to excessive swelling of the polymer B in the electrolyte solution can be suppressed, and as a result, the injectability of the functional layer can be improved and the rate characteristics of the obtained secondary battery can also be improved.

[0053] <<Swelling ratio between polymer A and polymer B>> The swelling ratio S of polymer A in the electrolyte solution is A is the electrolyte swelling degree S of polymer B B The degree of swelling of the polymer A in an electrolyte solution is preferably 1.2 times or more, more preferably 1.3 times or more, and even more preferably 1.5 times or more. A is the electrolyte swelling degree S of polymer BB The electrolyte swelling degree S of polymer A can be 20 times or less. A / Degree of swelling of polymer B in electrolyte solution S B ) is equal to or greater than the lower limit, the portion of polymer B occupying more than 50 mass % of the mass of the particulate polymer maintains elasticity even in the electrolyte, resulting in high adhesive strength. In addition, the portion of polymer A present has a sufficiently high swelling degree in the electrolyte compared to polymer B, so that polymer A penetrates well between the electrode active materials, exerts an anchoring effect, and can improve process adhesiveness.

[0054] <<Volume Average Particle Diameter of Particulate Polymer>> The volume average particle diameter of the particulate polymer may be 0.8 μm or more, preferably 1.0 μm or more, more preferably 2.5 μm or more, even more preferably 5.0 μm or more, preferably 10.0 μm or less, more preferably 9.0 μm or less, and even more preferably 8.0 μm or less. If the volume average particle diameter of the particulate polymer is equal to or greater than the above-mentioned lower limit, a portion of the particulate polymer can be protruded from the surface of the functional layer. If the particulate polymer is capable of exhibiting adhesive properties as described above, this is thought to improve the process adhesion of the functional layer and the adhesion after immersion in an electrolyte solution. By exhibiting even higher adhesive properties, the cycle characteristics of the resulting secondary battery can also be improved. Furthermore, if the volume average particle diameter of the particulate polymer is equal to or less than the above-mentioned upper limit, it is thought that the particulate polymer can be prevented from falling off the functional layer during formation of the functional layer, thereby improving the uniformity of the resulting functional layer. The volume average particle diameter of the particulate polymer can be adjusted, for example, by the type and amount of metal hydroxide used when preparing the particulate polymer.

[0055] <<Amount of Particulate Polymer>> The amount of the particulate polymer in the composition for the functional layer is preferably a ratio of heat-resistant fine particles:particulate polymer of 75:25 to 60:40, and more preferably 70:30 to 65:35, on a volume basis.

[0056] <<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.

[0057] The polymerization method may be any of suspension polymerization, emulsion polymerization aggregation, dissolution suspension, and pulverization, among which suspension polymerization, dissolution suspension, and pulverization are preferred. Among these, suspension polymerization is more preferred from the viewpoint of efficiently producing a particulate polymer having a desired structure. The polymerization reaction may be any of radical polymerization, living radical polymerization, and the like.

[0058] [Other Compounding Agents] In addition, other compounding agents 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 can be compounded in any compounding amount into the monomer composition used when preparing the particulate polymer.

[0059] Here, as an example, a method for preparing a particulate polymer by suspension polymerization will be described.

[0060] [Preparation of particulate polymer by suspension polymerization method] (1) Preparation of polymer A and preparation of monomer composition of polymer B First, polymer A is prepared by polymerizing polymer A according to a standard method. At this time, the volume average particle diameter of polymer A is preferably 0.01 μm or more, more preferably 0.02 μm or more, even more preferably 0.03 μm or more, preferably 0.5 μm or less, more preferably 0.3 μm or less, and even more preferably 0.2 μm or less. If the volume average particle diameter of polymer A is above the above lower limit, and if polymer A can exhibit high adhesive properties when swollen in an electrolyte solution, polymer A can effectively act as an anchor when exhibiting adhesive properties in the resulting functional layer, thereby improving the adhesiveness of the functional layer after immersion in an electrolyte solution. Furthermore, if the volume average particle diameter of polymer A is below the above upper limit, the elasticity of the particulate polymer can be maintained after immersion in an electrolyte solution, thereby improving the adhesiveness of the functional layer after immersion in an electrolyte solution. The volume average particle diameter of polymer A can be measured by the method described in the Examples. The volume average particle diameter of polymer A can be controlled by, for example, the amount of polymerization initiator added when polymerizing polymer A.

[0061] Also, a monomer composition (B) is prepared having a composition corresponding to that of polymer B. At this time, various monomers are blended in accordance with the composition of polymer B, and further, other blending agents are added as necessary.

[0062] (2) Formation of Droplets Next, a colloidal dispersion containing a dispersion stabilizer is prepared, and the polymer A and the monomer composition (B) obtained above are added thereto, followed by the addition of a polymerization initiator to form a mixed liquid, and mixed droplets containing the polymer A and the monomer composition (B) are formed in the colloidal dispersion containing the dispersion stabilizer. Here, the method for forming the mixed droplets is not particularly limited, and examples thereof include a method of shear stirring using a disperser such as an emulsifying disperser.

[0063] Examples of the polymerization initiator used in this case include oil-soluble polymerization initiators such as t-butylperoxy-2-ethylhexanoate and azobisisobutyronitrile, etc. Examples of the dispersion stabilizer include metal oxides such as magnesium hydroxide, and sodium dodecylbenzenesulfonate.

[0064] (3) Polymerization After the mixed droplets are formed, the water containing the formed mixed droplets is heated to initiate polymerization. The polymerization is continued until the polymerization conversion rate is sufficiently increased, thereby forming a particulate polymer in the water. At this time, 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.

[0065] (4) Washing, Filtration, Dehydration, and Drying Steps After the polymerization is completed, the water containing the particulate polymer is washed, filtered, and dried in accordance with a conventional method, thereby obtaining the particulate polymer.

[0066] <Binder> The binder binds the heat-resistant fine particles together in the functional layer. Examples of the binder include known polymers used as binders, such as conjugated diene polymers, acrylic polymers and modified products thereof (e.g., sulfonic acid modified acrylic polymers and carboxylic acid modified acrylic polymers), polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVOH), copolymers containing acrylamide monomer units that may have a substituent, and copolymers containing fluorine-containing monomer units. One type of binder may be used alone, or two or more types 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, and acrylic polymers containing (meth)acrylic acid ester monomer units are even more preferred. If the binder is an acrylic polymer containing a (meth)acrylic acid ester monomer unit, the process adhesion of the functional layer can be improved and the electrochemical properties of the resulting electrochemical element can be improved. Note that when the functional layer composition is used to coat a positive electrode, the use of a conjugated diene polymer is excluded. In the present invention, a 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% by mass or more. These binders may be used alone or in combination of two or more in any ratio.

[0067] 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.

[0068] 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.

[0069] 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 process adhesion of the functional layer can be improved. Furthermore, by making the proportion equal to or less than the upper limit, the electrochemical properties of an electrochemical element including the functional layer can be further improved.

[0070] Furthermore, 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. Furthermore, 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.

[0071] 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.

[0072] The acrylic polymer may contain other monomer units.

[0073] <<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 30° C. or lower, more preferably 20° C. or lower, and even more preferably 15° C. or lower. If the glass transition temperature of the binder is equal to or higher than 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 equal to or lower than the upper limit, the flexibility of the functional layer can be increased.

[0074] [Binder Content] The binder content 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 25 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 binder content 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 binder content 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 element can be suppressed.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] When the binder is particulate, the volume average particle diameter of the binder may be, for example, 0.1 μm or more and 0.5 μm or less. When the volume average particle diameter of the binder is within this range, the heat shrinkage resistance and process adhesion of the resulting functional layer and the output characteristics of the resulting secondary battery can be further improved.

[0079] <Heat-resistant fine particles> Here, the heat-resistant fine particles optionally contained in the composition for functional layer are not particularly limited, and 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 use environment of an electrochemical element.When the composition for functional layer contains heat-resistant fine particles, the functional layer obtained using the composition for functional layer can be imparted with heat resistance.In addition, 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.

[0080] <<Inorganic fine particles>> Examples of inorganic fine particles include aluminum oxide (alumina, Al ２ O ３ ), hydrated aluminum oxide (boehmite, AlOOH), gibbsite (Al(OH) ３ ), silicon oxide, magnesium oxide (magnesia), magnesium hydroxide, calcium oxide, titanium oxide (titania), barium titanate (BaTiO ３ Examples of inorganic oxide particles include inorganic oxide particles such as 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. Note that one type of inorganic fine particle may be used alone, or two or more types may be used in combination.

[0081] <<Organic Fine Particles>> Unlike the above-mentioned specific particulate polymers and binders, 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 crosslinks, polystyrene, polyimide, polyamide, polyamideimide, melamine resin, phenolic resin, and benzoguanamine-formaldehyde condensate; heat-resistant polymer particles such as polysulfone, polyacrylonitrile, polyaramid, polyacetal, and thermoplastic polyimide; and modified products and derivatives thereof. The organic fine particles may be used alone or in combination of two or more types. 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 constitutes the organic fine particles is preferably 150°C or higher.

[0082] Among the heat-resistant fine particles described above, inorganic fine particles are preferred from the viewpoint of further improving the heat resistance of the resulting functional layer, and particles made of alumina (alumina particles), particles made of boehmite (boehmite particles), particles made of barium sulfate (barium sulfate particles), and particles made of magnesium hydroxide (magnesium hydroxide particles) are more preferred.

[0083] <<Properties of Heat-Resistant Particles>> The heat-resistant 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. If the volume-average particle diameter of the heat-resistant particles is 0.1 μm or more, a decrease in the ionic conductivity of the functional layer due to excessively dense packing of the heat-resistant particles in the functional layer can be suppressed, allowing the electrochemical element to exhibit excellent rate characteristics. On the other hand, if the volume-average particle diameter of the heat-resistant particles is 1.5 μm or less, even if the functional layer is thinned, the element member made of a laminate including the functional layer can fully exhibit excellent heat resistance. Therefore, the capacity of the electrochemical element can be increased while sufficiently ensuring the heat resistance of the element member.

[0084] <Other Components> 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.

[0085] <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, any heat-resistant fine particles, water as a dispersion medium, and other components used as needed. Note that 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. Furthermore, 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.

[0086] 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.

[0087] 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 binder and any heat-resistant fine particles. 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.

[0088] (Functional Layer for Electrochemical Device) The functional layer for electrochemical devices can be formed, for example, on a suitable substrate using the above-described functional layer composition. In other words, the functional layer for electrochemical devices can be a molded product formed by coating the above-described functional layer composition. Here, the functional layer contains at least the above-described particulate polymer and binder, and other components used as needed, such as heat-resistant fine particles. Note that the components contained in the functional layer are those contained in the above-described functional layer composition, and the preferred abundance ratio of each component is the same as the preferred abundance ratio of each component in the functional layer composition. Note that the functional layer is not particularly limited and can be formed according to the method described in the section (Laminate for Electrochemical Device).

[0089] In the functional layer formed using the functional layer composition, a plurality of heat-resistant fine particles are usually arranged so as to be stacked in the thickness direction of the functional layer. The plurality of heat-resistant fine particles are stacked in the thickness direction of the functional layer to form a layer (hereinafter also referred to as a "heat-resistant fine particle layer"). The functional layer has a structure in which a portion of the particulate polymer described above is embedded in the heat-resistant fine particle layer.

[0090] The thickness of the layer formed by stacking the heat-resistant fine particles 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 1.0 μm or more, and preferably 6.0 μm or less, more preferably 5.0 μm or less, and even more preferably 3.5 μm or less. If the thickness of the heat-resistant fine particle layer is equal to or greater than the above lower limit, the heat resistance of the functional layer becomes extremely good. On the other hand, if the thickness of the heat-resistant fine particle layer is equal to or less than the above upper limit, the ion diffusibility of the functional layer can be ensured, and the rate characteristics of the electrochemical element can be further improved.

[0091] [Relationship between the thickness of the heat-resistant fine particle layer and the volume average particle diameter of the particulate polymer] In addition, the relationship between the thickness of the heat-resistant fine particle layer and the volume average particle diameter of the particulate polymer preferably satisfies that the volume average particle diameter of the particulate polymer is larger than the thickness of the heat-resistant fine particle layer. Note that 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) may be 0.4 or more, preferably more than 1.0, more preferably 1.5 or more, particularly preferably 2.5 or more, and preferably 10.0 or less, more preferably 9.0 or less, and even more preferably 8.0 or less. If the volume average particle diameter of the particulate polymer is larger than the thickness of the heat-resistant fine particle layer, the particulate polymer will easily protrude from the surface of the heat-resistant fine particles on the thickness direction surface of the functional layer, so that good adhesiveness can be exhibited. In addition, 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 number of adhesion points of the particulate polymer will increase, so that good adhesiveness can be exhibited.

[0092] (Laminate for electrochemical device) The laminate for electrochemical device comprises a substrate and a functional layer for electrochemical device formed on the substrate using the above-mentioned functional layer composition. The functional layer for electrochemical device contains at least the above-mentioned particulate polymer and binder, optional heat-resistant fine particles, and other components used as needed. Note that each component contained in the functional layer is the same as that contained in the above-mentioned functional layer composition, and the preferred abundance ratio of each component is the same as the preferred abundance ratio of each component in the functional layer composition.

[0093] <Substrate> 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. Furthermore, when the laminate of the present invention is used as an electrode, an electrode substrate is used as the substrate.

[0094] <<Separator Substrate>> The separator substrate is not particularly limited, and examples thereof include known separator substrates such as organic separator substrates. The organic separator substrate is a porous member made of an organic material. 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, microporous membranes made of polyolefin resins are preferred from the viewpoint of increasing the ratio of electrode active material in the electrochemical device and increasing the capacity per volume. The thickness of the separator substrate can be any thickness, and is preferably 5 μm to 30 μm, more preferably 5 μm to 20 μm, and even more preferably 5 μm to 18 μm.

[0095] <<Electrode Substrate>> The electrode substrate (positive electrode substrate and negative electrode substrate) is not particularly limited, but examples thereof include an electrode substrate 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 electrode mixture layer binders (positive electrode mixture layer binder, negative electrode mixture layer binder) in the electrode mixture layer, and the method for forming the electrode mixture layer on the current collector can be known methods, and for example, the method described in JP 2013-145763 A can be used.

[0096] <Method for manufacturing laminate> The method for manufacturing 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 manufacturing efficiency, it is preferable to manufacture 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).

[0097] <<Supplying Step>> 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, since the thickness of the functional layer produced can be easily controlled, it is preferable to apply the functional layer composition to the surface of the substrate. The method for applying the functional layer composition to the surface of the substrate is not particularly limited, and examples thereof include a doctor blade method, a reverse roll method, a direct roll method, a gravure coating method, a bar coating method, an extrusion method, and a brush coating method. In the supplying step, a coating of the functional layer composition may be formed on only one side of the substrate, or a coating of the functional layer composition may be formed on both sides of the substrate.

[0098] <<Drying Step>> 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 functional layer composition is not particularly limited and any known method can be used, including drying with warm air, hot air, or low-humidity air, vacuum drying, and drying by irradiation with infrared rays or electron beams. 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.

[0099] 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.

[0100] (Electrochemical element) The electrochemical element of the present invention is characterized by comprising an electrode and a separator, and comprising the laminate of the present invention as at least one of the electrode and the separator. The electrochemical element of the present invention has excellent electrochemical properties because it uses the laminate of the present invention as at least one of the element components of the electrode and the separator.

[0101] 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.

[0102] 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.

[0103] <Positive Electrode and Negative Electrode> 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.

[0104] <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 a lithium ion secondary battery, a lithium salt is used as the supporting electrolyte. For example, LiPF ６ , LiAsF ６ , LiBF ４ , LiSbF ６ , LiAlCl ４ , LiClO ４ , C.F. ３ SO ３ Li, C ４ F ９ SO ３ Li, CF ３ COOLi, (CF ３ CO) ２ NLi, (CF ３ SO ２ ) ２ NLi, (C ２ F ５ SO ２ Among them, LiPF is preferred because it is easily soluble in solvents and shows a high degree of dissociation. ６ , LiClO ４ , C.F. ３ SO ３Li is preferred. The electrolyte may be used alone or in combination of two or more. 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.

[0105] 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.

[0106] 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 electrolyte solution can be adjusted as appropriate. Known additives may also be added to the electrolyte solution.

[0107] <Method for Manufacturing Electrochemical Element> The method for manufacturing 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 manufactured 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, an overcurrent prevention element such as a fuse or 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.

[0108] The present invention will be described in detail 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 a structural unit 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.

[0109] In the examples and comparative examples, the measurement and evaluation of various attributes were carried out as follows.

[0110] <Glass Transition Temperature> The particulate polymers (polymer A and polymer B) and binder prepared in the examples and comparative examples were used as measurement samples. 10 mg of the measurement sample was weighed into an aluminum pan, and measurement was carried out under the conditions specified in JIS Z 8703 using a differential scanning calorimetry (DSC) measuring device ("EXSTAR DSC6220" manufactured by SII NanoTechnology Inc.) at a temperature range of -100°C to 500°C and a heating rate of 10°C / min, using an empty aluminum pan as a reference, to obtain a differential scanning calorimetry (DSC) curve. During this heating process, the glass transition temperature (°C) was determined as the intersection point between the baseline immediately before the appearance of an endothermic peak in the DSC curve at which the differential signal (DDSC) was 0.05 mW / min / mg or more and the tangent to the DSC curve at the first inflection point that appeared after the endothermic peak. Note that the measurement samples for the particulate polymers having a sea-island structure (Examples 1 to 12) or a multilayer structure (Comparative Example 2) were prepared as follows. When forming the sea-island structure (heterogeneous phase structure) or the multilayer structure, the monomers and various additives used in forming each phase or each layer were used to prepare aqueous dispersions containing each polymer as measurement samples under the same polymerization conditions as those used in forming each phase or each layer. The prepared aqueous dispersions were then dried to obtain measurement samples.

[0111] <Electrolyte swelling degree S A and S B > The measurement samples were prepared in the same manner as in preparing the glass transition temperature measurement samples. The aqueous dispersions of each measurement sample were dispersed in ion-exchanged water and placed in polytetrafluoroethylene petri dishes. The aqueous dispersions in the petri dishes were dried at 25°C for 48 hours to obtain powder samples. Approximately 0.2 g of each sample was pressed at 200°C and 5 MPa for 2 minutes to obtain test pieces. The weight of each test piece was measured and designated W0. Next, each test piece was immersed in an electrolyte solution (solvent: ethylene carbonate / diethyl carbonate / vinylene carbonate (volume ratio) = 68.5 / 30 / 1.5, electrolyte: 1 mol LiPF6) at 60°C for 72 hours. After immersion, the test pieces were removed from the electrolyte solution, and the electrolyte solution on the surface of the test piece was wiped off. The weight of the test piece after immersion was measured and designated W1. The measured W0 and W1 were used to calculate the electrolyte swelling degree S. A and SB (fold) was calculated according to the formula: S = (W1 / W0).

[0112] <Volume average particle diameter of binder and polymer A> The volume average particle diameters of the binder and polymer A prepared in the examples were measured by a laser diffraction method. Specifically, an aqueous dispersion containing polymer A (adjusted to a solids concentration of 0.1% by mass) was used as a measurement sample, prepared in the same manner as when measuring the prepared binder / glass transition temperature. Then, in the particle size distribution (volume basis) measured using a laser diffraction particle size distribution analyzer (manufactured by Beckman Coulter, Inc., "LS-230"), the particle diameter D50 at which the cumulative volume calculated from the smallest diameter side reached 50% was taken as the volume average particle diameter.

[0113] <Volume Average Particle Diameter of Particulate Polymer> The particulate polymers prepared in the examples and comparative examples were used as measurement samples. An amount equivalent to 0.1 g of the measurement 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 to 30 mL of a diluent (Beckman Coulter, Inc., "Isoton II") was further added to the beaker, and the mixture was dispersed for 3 minutes using a 20 W (Watt) ultrasonic disperser. Thereafter, the volume average particle diameter (Dv) of the measurement sample was measured using a particle size analyzer (Beckman Coulter, Inc., "Multisizer") under the following conditions: aperture diameter: 20 μm, medium: Isoton II, and number of particles measured: 100,000.

[0114] <Volume average particle diameter of heat-resistant fine particles> In the particle diameter distribution (volume basis) measured by laser diffraction, the particle diameter (D50) at which the cumulative volume calculated from the smallest diameter side becomes 50% was defined as the volume average particle diameter of the heat-resistant fine particles.

[0115] <Thickness of Heat-Resistant Particle Layer> The cross section of the separator with the functional layer was observed using a field emission scanning electron microscope (FE-SEM), and the thickness of the heat-resistant particle layer was calculated from the obtained SEM image. The thickness of the heat-resistant particle layer was defined as the distance from the surface of the separator substrate on which the functional layer was formed to the heat-resistant particle furthest in the vertical direction.

[0116] <Ratio of Volume Average Particle Diameter D50 of Particulate Polymer in Functional Layer to Thickness T of Heat-Resistant Microparticle Layer> Based on the volume average particle diameter of the particulate polymer in the functional layer and the thickness of the heat-resistant microparticle layer obtained as described above, 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 particulate polymer / thickness of heat-resistant microparticle layer) was determined.

[0117] <Volume ratio of heat-resistant fine particles to particulate polymer> The volume ratio of heat-resistant fine particles to particulate polymer (heat-resistant fine particles / particulate polymer) (heat-resistant fine particles / particulate polymer) was 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 12 was 1 g / cm ３ It was calculated as:

[0118] <Structural observation of particulate polymer and unit area 1 μm in the cross section of particulate polymer 2Measurement of the Number of Island Phases per 1000 Particulate Polymers> The particulate polymers prepared in the Examples and Comparative Examples were dispersed in an epoxy resin, cured, cooled to -80°C, and cut with a microtome to prepare thin sections. The thin sections were stained with a 0.5% aqueous solution of ruthenium tetroxide for approximately 5 minutes and observed with a transmission electron microscope (TEM) to observe the structure of the particulate polymers. As a result of the observation, if 20 particulate polymers observed according to the following criteria had a structure in which isolated island-like separated phases were scattered in a matrix consisting of a continuous phase, the result was judged to be "sea-island structure present." While a sea-island structure was observed for the particulate polymers of all Examples, no phase separation was observed for the particulate polymers of Comparative Examples 1 and 3, and a core layer and a shell layer surrounding at least a portion of the core layer were observed for the particulate polymer of Comparative Example 2. Here, the concentration of the particulate polymer in the sample dispersed in the epoxy resin was adjusted so that 5 to 10 colored particle cross sections could be included in an image within an area of ​​28 μm × 35 μm. Among the images within the 28 μm × 35 μm area, those in which the entire cross section of the particulate polymer was not captured, and those in which the size of the cross section of the particulate polymer (the diameter of the circumscribed circle of the cross section) was not within the range of 0.6 to 1.2 times the volume average particle size of the particulate polymer were excluded from the evaluation, and 20 of the other particulate polymers were selected as observation targets, the cross sections of these observation targets were observed on the screen, and the number of island-like separated phases was visually counted. From the total area of ​​observation regions set randomly for the particles to be observed and the total number of island-like separated phases present in such observation regions, the unit area of ​​1 μm 2 The number of islands per unit area was calculated.

[0119] <Process 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. The positive electrode and separator, and the negative electrode and separator, were laminated together and pressed for 10 seconds using a flat press at a temperature of 80°C and a load of 0.5 kN to obtain a test specimen. This test specimen was placed with the negative electrode current collector side facing down, and cellophane tape was attached to the surface of the electrode. The cellophane tape used was specified in JIS Z1522. The cellophane tape was fixed to a horizontal test table. One end of the separator substrate was then pulled vertically upward at a pulling rate of 50 mm / min, and the stress was measured when peeled off. Separately prepared negative electrode and separator test specimens were also subjected to stress measurements three times in the same manner as the positive electrode. The average value of the stress obtained three times in the measurement using the positive electrode and negative electrode was calculated as the peel strength (N / m), and the process adhesion between the electrode and the separator via the functional layer was evaluated according to the following criteria. A: Peel strength of 3 N / m or more B: Peel strength of less than 3 N / m

[0120] <Adhesion after immersion in electrolyte> The separator with the functional layer was cut into a 10 mm x 50 mm strip. Then, the separator with the functional layer was placed along the surface of the porous membrane of the negative electrode with the porous membrane to prepare a laminate including a negative electrode and a separator with the functional layer, and this laminate was used as a test specimen. The test specimen was placed in a laminate packaging material together with approximately 300 μL of electrolyte. After 12 hours, the test specimen was hot-pressed together with the laminate packaging material at a temperature of 80 ° C. and a load of 0.5 kN using a flat press for 20 minutes to prepare a laminate including a negative electrode and a separator with the functional layer. Here, the electrolyte was a mixed solvent of EC, DEC, and vinylene carbonate (VC) (EC / DEC / VC (volume mixture ratio at 25 ° C.) = 68.5 / 30 / 1.5), with LiPF as a supporting electrolyte. ６A solution of 1 mol / L of ethylenediaminetetraacetic acid (ETA-2) dissolved in a 1 mol / L solution was used. 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 surface facing the negative electrode current collector facing downwards, and cellophane tape was applied to the surface facing the negative electrode current collector. The cellophane tape used was specified in JIS Z1522. The cellophane tape was fixed to a horizontal test table. One end of the separator was then pulled vertically upward at a pulling rate of 50 mm / min to measure the stress when peeled off. This measurement was performed three times, and the average stress value was calculated as the peel strength P and evaluated according to the following criteria. The evaluation results are shown in Table 1. A higher peel strength P indicates better adhesion of the functional layer in the electrolyte and stronger adhesion between the negative electrode and the separator. A: Peel strength P2 is 5.0 N / m or more. B: Peel strength P2 is 3.0 N / m or more and less than 5.0 N / m. C: Peel strength P2 is less than 3.0 N / m.

[0121] <Heat Resistance of Functional Layer> The bonded assembly of the separator with functional layer and electrode prepared in the Examples and Comparative Examples was cut into a circular shape with a diameter of 1.6 cm to prepare a test specimen. This test specimen was placed in a pressure-resistant container together with a mixed solvent of EC, DEC, and vinylene carbonate (VC) (EC / DEC / VC (volume ratio at 25°C) = 68.5 / 30 / 1.5) and placed in a thermostatic chamber at 150°C for 1 hour, then allowed to cool and removed. After wiping off the solvent from the removed sample, either the positive electrode or the negative electrode was carefully peeled off, and the diameter of the separator attached to the positive electrode or negative electrode was measured. The thermal shrinkage was calculated as {1 - ((longest diameter of the separator circle after heating (cm) ÷ 1.6 (cm))) + (shortest diameter of the separator circle after heating (cm) ÷ 1.6 (cm)))) ÷ 2} × 100 and evaluated according to the following criteria. The smaller the heat shrinkage rate, the better the heat resistance of the separator with functional layer. A: Heat shrinkage rate less than 3% B: Heat shrinkage rate 3% or more but less than 5% C: Heat shrinkage rate 5% or more

[0122] <Blocking Resistance of Functional Layer> Two test pieces measuring 4 cm wide x 4 cm long were cut out from the separators with functional layers prepared in the Examples and Comparative Examples. The two test pieces obtained were stacked with the functional layer sides facing each other, and then pressed for 2 minutes using a flat press at a temperature of 40°C and a load of 8 kN to obtain a pressed body. One end of the pressed body obtained was fixed, and the other end of the pressed body was pulled vertically upward at a tensile speed of 50 mm / min to peel it off, measuring the stress. The obtained stress was then taken as the blocking strength. The blocking strength was then evaluated according to the following criteria. A smaller blocking strength indicates that the functional layer better suppresses the occurrence of blocking, i.e., the functional layer has higher blocking resistance. A: Less than 2 N / m B: 2 N / m or more

[0123] <Electrolyte Injectability> An electrolyte was injected into the lithium ion secondary batteries produced in the Examples and Comparative Examples. The pressure inside the lithium ion secondary batteries was reduced to -100 kPa and maintained in that state for 1 minute. Heat sealing was then carried out. After 10 minutes, the electrode (positive electrode) was disassembled and the state of electrolyte impregnation in the electrode was visually confirmed. Evaluation was then carried out according to the following criteria. The more the portion of the electrode impregnated with the electrolyte, the higher the electrolyte injectability. A: The electrolyte is impregnated on all surfaces of the electrode. B: The portion of the electrode not impregnated with the electrolyte is 1 cm ２ C: The part of the electrode that is not impregnated with electrolyte is less than 1 cm ２ 1.5cm or more ２ Less than remains.

[0124] <Rate characteristics of secondary battery> 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. Thereafter, 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 x 100 (%), with a larger value indicating better rate characteristics. A: ΔC is 90% or more B: ΔC is less than 90%

[0125] <Cycle Characteristics of Secondary Battery> After injecting the electrolyte, the lithium-ion secondary batteries prepared in the Examples and Comparative Examples were left standing at 25°C for 5 hours. Next, they were charged to a cell voltage of 3.65 V at 25°C using a constant current of 0.2 C, and then aged for 12 hours at 60°C. Then, they were discharged to a cell voltage of 3.00 V using a constant current of 0.2 C at 25°C. Subsequently, they were subjected to CC-CV charging (upper limit cell voltage: 4.20 V) using a constant current of 0.2 C, and CC discharging to 3.00 V using a constant current of 0.2 C. This 0.2 C charge-discharge cycle was repeated three times. Subsequently, 100 cycles of charge-discharge were performed at a 25°C environment, with a cell voltage of 4.20-3.00 V and a charge-discharge rate of 1.0 C. The discharge capacity at the first cycle was defined as X1, and the discharge capacity at the 100th cycle as X2. Then, using the discharge capacities X1 and X2, the capacity retention rate ΔC' = (X2 / X1) × 100 (%) was calculated 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. It is presumed that the reason why the secondary battery has excellent cycle characteristics at 100 cycles is because the functional layer provided in the secondary battery can well retain the electrolyte. A: Capacity retention rate ΔC' is 93% or more B: Capacity retention rate ΔC' is 90% or more but less than 93% C: Capacity retention rate ΔC' is less than 90%

[0126] Example 1 Preparation of Polymer (A) 0.20 parts of sodium dodecyl sulfate, 0.40 parts of ammonium persulfate, and 180 parts of ion-exchanged water were mixed in a reactor A equipped with a stirrer, and the mixture was heated to 65°C. Meanwhile, in a separate vessel, 81 parts of methyl methacrylate and 17.6 parts of butyl acrylate as monofunctional (meth)acrylic acid ester monomers, 0.4 parts of methacrylic acid as an acidic group-containing monomer, 1 part of allyl methacrylate as a crosslinkable monomer, 0.8 parts of sodium dodecyl sulfate, and 40 parts of ion-exchanged water were mixed to prepare a monomer composition for Polymer (A). This monomer composition for Polymer (A) was continuously added to the reactor A over 4 hours to carry out a polymerization reaction. The temperature inside the reactor during the continuous addition of the monomer composition for Polymer (A) was maintained at 65°C. After the completion of the continuous addition, the polymerization reaction was continued for another 3 hours at 80°C. This resulted in an aqueous dispersion of Polymer (A). The volume average particle size of the polymer (A) was measured according to the above method.

[0127] <Preparation of Monomer Composition (B)> 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 were mixed to prepare a monomer composition (B).

[0128] <Preparation of Metal Hydroxide> 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.

[0129] [Suspension Polymerization Method] A particulate polymer was prepared by suspension polymerization. Specifically, the polymer (A) and the monomer composition (B) obtained as described above were added to the colloidal dispersion (A) containing magnesium hydroxide, followed by further stirring. Then, 2.0 parts of t-butylperoxy-2-ethylhexanoate (NOF Corporation, "Perbutyl O") as a polymerization initiator was added to obtain a mixed solution. When adding the polymer (A), an amount of aqueous dispersion of the polymer (A) was weighed so that the solid content was 1% (by mass) based on the total solid content of the monomer components contained in the monomer composition (B). The obtained mixed solution was subjected to high-shear stirring at 15,000 rpm for 1 minute using an in-line emulsifying disperser (Pacific Machinery Works, Ltd., "Cavitron") to form droplets of the monomer composition (B) containing the polymer (A) in the colloidal dispersion (A) containing magnesium hydroxide.

[0130] The colloidal dispersion (A) containing magnesium hydroxide and having droplets of the monomer composition (B) formed therein was placed in a reactor, heated to 90°C, and subjected to a polymerization reaction for 5 hours to obtain an aqueous dispersion containing a particulate polymer (A).

[0131] 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 repeated 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 volume average particle diameter of the obtained particulate polymer was measured as described above. Furthermore, the cross section was observed by a transmission electron microscope as described above. The results are shown in Table 1.

[0132] <Preparation of Aqueous Dispersion Containing Binder (α)> 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 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, 0.5 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 resulting monomer composition (α) was continuously added to the above-mentioned reactor equipped with a stirrer over a period of 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 to obtain 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.

[0133] Preparation of Slurry Composition (Functional Layer Composition) 0.5 parts of polyacrylic acid as a water-soluble polymer was added to 100 parts of alumina (manufactured by Sumitomo Chemical Co., Ltd., "AKP3000", volume average particle diameter: 0.7 μm) as heat-resistant fine particles, and ion-exchanged water was added to a solids concentration of 55%. The mixture was mixed using a ball mill to obtain a pre-mixing slurry. 0.2 parts of sodium dodecylbenzenesulfonate (manufactured by Kao Chemical Co., Ltd., "Neopelex G-15") as a dispersant was added to 100 parts of the particulate polymer. Furthermore, 6 parts of an aqueous dispersion containing a binder (α) in terms of solids content and 1.5 parts of carboxymethyl cellulose as a thickener were mixed to a solids concentration of 40% per 100 parts of the heat-resistant fine particles, and the resulting mixture was added to the pre-mixing slurry obtained as described above. The mixing ratio was adjusted so that 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. Further, ion-exchanged water was added to the slurry composition so that the solid content concentration was 40%, thereby obtaining a slurry composition (composition for functional layer).

[0134] <Preparation of Separator with Functional Layer> A polyethylene microporous membrane (thickness: 12 μm; Gurley value: 100 s / 100 cc) 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. The coating was dried at 50°C. The same procedure as above was then performed on the other side of the separator substrate, producing a separator with a functional layer having a heat-resistant fine particle layer with a thickness of 2.0 μm on each side of the separator substrate. The blocking resistance of the resulting separator with a functional layer was evaluated as described above. The results are shown in Table 1.

[0135] <Preparation of Positive Electrode> LiCoO as a Positive Electrode Active Material ２100 parts of acetylene black (volume average particle diameter: 12 μm), 2 parts of acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd., "HS-100") as a conductive material, 2 parts of polyvinylidene fluoride (manufactured by Kureha Corporation, "#7208") as a binder for the positive electrode composite layer in terms of solid content, and N-methylpyrrolidone as a solvent were mixed to a total solids concentration of 70%. These were mixed using a planetary mixer to prepare a positive electrode slurry composition. The positive electrode slurry composition was applied using a comma coater onto a 20 μm thick aluminum foil current collector so that the film thickness after drying was approximately 150 μm, and then dried. This drying was performed by conveying the aluminum foil at a speed of 0.5 m / min in an oven at 60 ° C. for 2 minutes. Thereafter, the aluminum foil was heat-treated at 120 ° C. for 2 minutes to obtain a pre-press positive electrode blank. This pre-pressed positive electrode blank was rolled with a roll press to obtain a pressed positive electrode having a positive electrode mixture layer (thickness: 60 μm).

[0136] <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 rate reached 96%, the mixture was cooled to stop the reaction, and a mixture containing a binder (SBR) for the negative electrode composite layer was obtained. A 5% aqueous sodium hydroxide solution was added to the mixture containing the binder for the negative electrode composite layer, and the pH was adjusted to 8. Unreacted monomers were then removed by heated vacuum distillation. The mixture was then cooled to 30 ° C or below 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), 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 was added in solids equivalent, and ion-exchanged water was mixed to adjust the solid concentration to 68%, and then further mixed at 25 ° C. for 60 minutes. The solid 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. To this mixed solution, 1.5 parts of the aqueous dispersion containing the binder for the negative electrode composite layer in solids equivalent and ion-exchanged water were added, and the final solid concentration was adjusted to 52%, and 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 to a dried film thickness of 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 heated 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).

[0137] <Fabrication of Lithium-Ion Secondary Battery> The pressed positive electrode prepared as described above was cut into a 49 cm x 5 cm rectangle and placed with the surface on the positive electrode composite layer facing up. The functional layer-equipped separator cut to 120 cm x 5.5 cm was placed on the positive electrode composite layer so that the positive electrode was located 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 on the negative electrode composite layer faced the functional layer-equipped separator and the negative electrode was located on the other side of the functional layer-equipped separator in the longitudinal direction. At this time, the 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, which was then wrapped in an aluminum packaging material as the exterior of the battery, and an electrolyte solution [solvent: ethylene carbonate / diethyl carbonate / vinylene carbonate (volume ratio) = 68.5 / 30 / 1.5, electrolyte: LiPF with a concentration of 1 mol] was added. ６ )] was injected into the aluminum packaging so that no air remained. The opening of the aluminum packaging was then heat-sealed at 150°C to close the opening, producing a wound-type lithium-ion secondary battery with a capacity of 800 mAh. The resulting lithium-ion secondary battery was used to evaluate its injection properties, as well as its rate and cycle characteristics. The results are shown in Table 1.

[0138] (Example 2) A slurry composition was prepared in the same manner as in Example 1, except that the amount of polymer A added was 0.3% when the amount of monomer composition B was taken as 100% by mass, and various measurements and evaluations were carried out. The results are shown in Table 1.

[0139] (Example 3) A slurry composition was prepared in the same manner as in Example 1, except that the amount of polymer A added was 0.1% when the amount of monomer composition B was taken as 100% by mass, and various measurements and evaluations were carried out. The results are shown in Table 1.

[0140] (Example 4) A slurry composition was prepared in the same manner as in Example 1, except that the amount of polymer A added was 6.0% relative to the amount of monomer composition B taken as 100, and various measurements and evaluations were carried out. The results are shown in Table 1.

[0141] (Example 5) In preparing polymer (A), the conditions were changed as follows to obtain polymer (A2), and the same operations, measurements, and evaluations were carried out as in Example 1. The results are shown in Table 1. <Preparation of polymer (A2)> In preparing the monomer composition, the amount of sodium dodecyl sulfate was changed to 0.15 parts, the amount of ammonium persulfate was changed to 0.20 parts, and further, the polymerization reaction time at 80°C after the polymerization reaction at 65°C for 4 hours was changed to 5 hours. An aqueous dispersion of polymer (A2) was obtained in the same manner as in Example 1. The volume average particle diameter of polymer (A2) was measured according to the method described above.

[0142] Example 6 When preparing a slurry composition, no heat-resistant fine particles were added, and 0.2 parts of sodium dodecylbenzenesulfonate ("Neopelex G-15" manufactured by Kao Chemical Corporation) was added as a dispersant to 100 parts of the particulate polymer. Furthermore, 10 parts of an aqueous dispersion containing a binder (α) was mixed with 100 parts of the particulate polymer in terms of solid content, and the resulting mixture was diluted with ion-exchanged water to obtain a slurry composition for a functional layer (solid content concentration: 10%). Then, when preparing a separator with a functional layer, the slurry composition was applied by a bar coater method to one side of a separator substrate of the same type as that used in Example 1, resulting in a coating weight of 0.3 g / m after drying. ２ The separator coated with the slurry composition was then dried at 50°C for 1 minute to obtain a separator having a functional layer on one side. The same operation as above was performed on the other side of the separator substrate to produce a separator with a functional layer having functional layers on both sides of the separator substrate. Other than these points, the same operations, measurements (except for the thickness of the heat-resistant fine particle layer and the ratio between the volume average particle diameter D50 of the particulate polymer and the thickness T of the heat-resistant fine particle layer) and evaluations were performed as in Example 1. The results are shown in Table 1.

[0143] Example 7 In preparing a particulate polymer, the same operations, measurements, and evaluations as in Example 6 were carried out, except that the metal hydroxide preparation step was not carried out and the suspension polymerization conditions were changed as follows. The results are shown in Table 1. That is, in this Example 7, a slurry composition containing a particulate polymer A2 having a volume average particle diameter different from that of Example 1 and not containing heat-resistant fine particles was prepared, and a secondary battery, etc. was fabricated and subjected to various evaluations (excluding the thickness of the heat-resistant fine particle layer and the ratio of the volume average particle diameter D50 of the particulate polymer to the thickness T of the heat-resistant fine particle layer). <Suspension Polymerization in the Particulate Polymer Preparation Step> After 400 parts of ion-exchanged water and 1 part of sodium dodecylbenzenesulfonate as a dispersion stabilizer were supplied to a reactor equipped with a stirrer, the polymer (A) and the monomer composition (B) were added and further stirred, and then 2.0 parts of t-butylperoxy-2-ethylhexanoate (manufactured by NOF Corporation, "Perbutyl O") as a polymerization initiator was added to obtain a mixed solution. When adding the polymer (A), an amount of the aqueous dispersion of the polymer (A) was weighed so that the solid content was 1% (by mass) based on the total solid content of the monomer components contained in the monomer composition (B). The resulting mixture was stirred at high shear for 1 minute using an in-line emulsifying disperser (manufactured by Pacific Machinery Works, Ltd., "Cavitron") at 15,000 rpm to form droplets of the monomer composition (B2). The dispersion (A2) containing the formed droplets of the monomer composition (B2) was placed in a reactor, heated to 90°C, and subjected to a polymerization reaction for 5 hours to obtain an aqueous dispersion containing a particulate polymer (A2).

[0144] (Example 8) In preparing a slurry composition, various operations, measurements and evaluations were carried out in the same manner as in Example 1, except that the particulate polymer (A2) prepared in the same manner as in Example 7 was used. The results are shown in Table 1.

[0145] Example 9 In preparing the particulate polymer, various operations, measurements, and evaluations were performed in the same manner as in Example 1, except that the preparation conditions for polymer (A) were changed as follows to obtain polymer (A3). The results are shown in Table 1. <Preparation of Polymer (A3)> 0.20 parts of sodium dodecyl sulfate, 0.40 parts of ammonium persulfate, and 180 parts of ion-exchanged water were mixed into a reactor A equipped with a stirrer, and the mixture was heated to 65°C. Meanwhile, in a separate vessel, 32 parts of methyl methacrylate and 63.6 parts of butyl acrylate as monofunctional (meth)acrylic acid ester monomers, 0.4 parts of methacrylic acid as an acidic group-containing monomer, 3 parts of allyl methacrylate as a crosslinkable monomer, 0.8 parts of sodium dodecyl sulfate, and 40 parts of ion-exchanged water were mixed to prepare a monomer composition for polymer A3. This monomer composition for polymer A was polymerized under the same conditions as in Example 1 to obtain an aqueous dispersion of polymer (A3).

[0146] (Example 10) In preparing a particulate polymer, various operations, measurements and evaluations were carried out in the same manner as in Example 1, except that a monomer composition (B2) prepared as follows was used. The results are shown in Table 1. <Preparation of Monomer Composition (B2)> A monomer composition (B2) was prepared by mixing 71.9 parts of styrene as an aromatic vinyl monomer, 10 parts of methyl methacrylate and 18 parts of butyl acrylate as (meth)acrylic acid ester monomers, and 0.1 part of ethylene glycol dimethacrylate as a crosslinkable monomer.

[0147] (Example 11) In preparing the particulate polymer, various operations, measurements, and evaluations were performed in the same manner as in Example 1, except that the preparation conditions for polymer (A) were changed as follows to obtain polymer (A4). The results are shown in Table 1. <Preparation of Polymer (A4)> 0.20 parts of sodium dodecyl sulfate, 0.40 parts of ammonium persulfate, and 180 parts of ion-exchanged water were added to reactor A equipped with a stirrer and mixed to form a mixture, which was then heated to 65°C. Meanwhile, in a separate vessel, 76 parts of methyl methacrylate and 17.6 parts of butyl acrylate as monofunctional (meth)acrylic acid ester monomers, 0.4 parts of methacrylic acid as an acidic group-containing monomer, 5 parts of allyl methacrylate as a crosslinkable monomer, 0.8 parts of sodium dodecyl sulfate, and 40 parts of ion-exchanged water were mixed to prepare a monomer composition for polymer A4. The prepared monomer composition for polymer A4 was polymerized under the same conditions as in Example 1 to obtain an aqueous dispersion of polymer (A4).

[0148] Example 12 When preparing a composition for a functional layer, various operations, measurements, and evaluations were performed in the same manner as in Example 1, except that organic fine particles prepared as follows were used instead of alumina particles as the heat-resistant fine particles. The results are shown in Table 1. <Preparation of Organic Fine Particles (Heat-Resistant Fine Particles)> 0.20 parts of sodium dodecyl sulfate, 0.30 parts of ammonium persulfate, and 180 parts of ion-exchanged water were mixed into a reactor A equipped with a stirrer to form a mixture, which was then heated to 65°C. Meanwhile, in a separate vessel, 80.0 parts of n-butyl acrylate (a (meth)acrylic acid ester monomer), 10.0 parts of methacrylic acid (an acid group-containing monomer), 10.0 parts of acrylonitrile (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 monomer composition for seed particles 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 during the continuous addition of the monomer composition for seed particles was maintained at 65°C. After the completion of the continuous addition, the polymerization reaction was continued for an additional 3 hours at 80°C. This resulted in an aqueous dispersion of seed particles. Next, a reactor equipped with a stirrer was charged with 20 parts of the aqueous dispersion of seed particles (based on solids content) (including 16 parts of n-butyl acrylate units, 2 parts of methacrylic acid units, and 2 parts of acrylonitrile units), 80 parts of ethylene glycol dimethacrylate (Kyoeisha Chemical Co., Ltd., product name "Light Ester EG") as a crosslinkable monomer, 0.8 parts of sodium dodecylbenzenesulfonate, 3.2 parts of t-butylperoxy-2-ethylhexanoate (NOF Corporation, product name "Perbutyl O") as a polymerization initiator, and 160 parts of ion-exchanged water, and the mixture was stirred at 35°C for 12 hours, thereby allowing the crosslinkable monomer and polymerization initiator to be completely absorbed into the seed particles. Thereafter, the temperature inside the reactor was 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, yielding 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.

[0149] Comparative Example 1 Various operations, measurements and evaluations were carried out in the same manner as in Example 1, except that polymer A was not added during the preparation of the particulate polymer. The results are shown in Table 1.

[0150] Comparative Example 2 Various operations, measurements, and evaluations were performed in the same manner as in Example 1, except that a particulate polymer having a multilayer structure (core-shell structure) prepared as follows was used. The results are shown in Table 1. <Preparation of Particulate Polymer> <<Preparation of Core Monomer Composition>> A core monomer composition 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. <<Preparation of Shell Monomer Composition>> A shell monomer composition was prepared by mixing 81 parts of methyl methacrylate and 17.6 parts of butyl acrylate as monofunctional (meth)acrylic acid ester monomers, 0.4 parts of methacrylic acid as an acidic group-containing monomer, and 1 part of allyl methacrylate as a crosslinkable monomer.

[0151] <<Preparation of Metal Hydroxide>> An aqueous solution prepared by dissolving 5.6 parts of sodium hydroxide in 50 parts of ion-exchanged water was gradually added under stirring to an aqueous solution prepared by dissolving 8.0 parts of magnesium chloride in 200 parts of ion-exchanged water to prepare a colloidal dispersion containing magnesium hydroxide as the metal hydroxide.

[0152] [Suspension Polymerization Method] A particulate polymer was prepared by suspension polymerization method. Specifically, the core monomer composition obtained as described above was added to the colloidal dispersion containing the magnesium hydroxide, and after further stirring, 2.0 parts of t-butylperoxy-2-ethylhexanoate (manufactured by NOF Corporation, "Perbutyl O") as a polymerization initiator was added to obtain a mixed solution. The obtained mixed solution was subjected to high-shear stirring at 15,000 rpm for 1 minute using an in-line emulsifying disperser (manufactured by Pacific Machinery Works, "Cavitron") to form droplets of the core monomer composition in the colloidal dispersion containing magnesium hydroxide.

[0153] The magnesium hydroxide-containing colloidal dispersion in which droplets of the monomer composition had been formed was placed in a reactor, and the temperature was raised to 90°C to carry out a polymerization reaction. When the polymerization conversion rate reached nearly 100%, 0.1 parts of a shell polymerization initiator, 2,2'-azobis(2-methyl-N-(2-hydroxyethyl)-propionamide) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., trade name: VA-086, water-soluble), dissolved in 1 part of the shell monomer composition and 10 parts of ion-exchanged water, were added, and the reaction was continued at 90°C for 4 hours, after which the reaction was stopped by water cooling, and an aqueous dispersion containing a particulate polymer was obtained. Note that the shell monomer composition was added in an amount of 1 part per 100 parts of the core monomer composition.

[0154] (Comparative Example 3) Various operations, measurements, and evaluations were carried out in the same manner as in Example 6, except that the particulate polymer prepared in Comparative Example 1 was used as the particulate polymer. That is, in this Comparative Example 3, a slurry composition containing a particulate polymer not having a sea-island structure but not containing heat-resistant fine particles was prepared, and a secondary battery, etc. was fabricated and subjected to various evaluations (excluding the thickness of the heat-resistant fine particle layer and the ratio of the volume average particle diameter D50 of the particulate polymer to the thickness T of the heat-resistant fine particle layer). The results are shown in Table 1.

[0155] In Table 1, "AA" represents acrylic acid, "MMA" represents methyl methacrylate, "BA" represents n-butyl acrylate, "ST" represents styrene, "2EHA" represents 2-ethylhexyl acrylate, "EDMA" represents ethylene glycol dimethacrylate, "AN" represents acrylonitrile, "AMA" represents allyl methacrylate, "MAA" represents methacrylic acid, and "AGE" represents allyl glycidyl ether.

[0156]

[0157] From Table 1, it can be seen that the functional layer compositions according to Examples 1 to 12 contained particulate polymers having novel structures.

[0158] According to the present invention, it is possible to provide a composition for a functional layer containing a particulate polymer having a novel structure, a method for producing such a composition for a functional layer, a laminate for an electrochemical device including a functional layer for an electrochemical device formed using the composition for a functional layer of the present invention, and an electrochemical device including the same.

Claims

1. A composition for an electrochemical element functional layer, comprising a particulate polymer and a binder, the particulate polymer has a sea-island structure including an island phase made of a polymer A and a sea phase made of a polymer B, A plurality of cross-sectional images of the particulate polymer are obtained, and among the cross sections of the plurality of particulate polymers contained in the cross-sectional images, a plurality of cross sections having a circumscribing circle diameter within a range of 0.6 times to 1.2 times the volume average particle diameter of the particulate polymer are selected as observation objects, and a unit area of ​​1 μm is measured for each of the cross sections of the plurality of particulate polymers selected as the observation objects. 2 When the number of island phases having a diameter of 1 / 5 or less of the volume average particle size per one particle is calculated, Calculated unit area 1 μm 2 the number of the island phases per one particle is 1 or more and 200 or less; A composition for an electrochemical device functional layer.

2. 2. The composition for an electrochemical device functional layer according to claim 1, wherein the volume average particle size of the particulate polymer is 1.0 μm or more and 10.0 μm or less.

3. The composition for an electrochemical device functional layer according to claim 1 , further comprising heat-resistant fine particles.

4. The composition for an electrochemical device functional layer according to claim 1 , wherein the polymer A contains a (meth)acrylic acid ester monomer unit.

5. The composition for an electrochemical device functional layer according to claim 1 , wherein the glass transition temperature of the polymer A is higher than 20° C. and not higher than 90° C.

6. 2 . The composition for an electrochemical device functional layer according to claim 1 , wherein a content ratio of the polymer A based on a content mass of the polymer B is 0.1 mass % or more and 20 mass % or less.

7. The electrolyte swelling degree S of the polymer B B The composition for electrochemical device functional layers according to claim 1 , wherein the ratio of the thickness of the coating to the thickness of the coating is 1.0 to 8.

0.

8. The electrolyte swelling degree S of the polymer A A The composition for an electrochemical device functional layer according to claim 1 , wherein the ratio of the total weight of the functional layer to the total weight of the electrochemical device functional layer is 4.0 times or more.

9. The electrolyte swelling degree S of the polymer A A The electrolyte swelling degree S of the polymer B B The composition for electrochemical device functional layers according to claim 1 , wherein the molecular weight of the polymer is 1.2 times or more.

10. The particulate polymer is produced according to a suspension polymerization method, a dissolution suspension method, or a pulverization method; A method for producing the composition for electrochemical device functional layers according to any one of claims 1 to 9.

11. A functional layer for an electrochemical element formed using the composition for an electrochemical functional layer according to claim 3, the functional layer for an electrochemical element comprising: a heat-resistant fine particle layer containing the heat-resistant fine particles and a part of the particulate polymer embedded therein; The particulate polymer has a volume average particle diameter larger than a thickness of the heat-resistant fine particle layer.

12. A substrate and a functional layer for an electrochemical device formed on the substrate, The functional layer for an electrochemical device is a functional layer for an electrochemical device formed using the composition for an electrochemical device functional layer according to any one of claims 1 to 9. Laminate for electrochemical devices.

13. An electrochemical device comprising the laminate for an electrochemical device according to claim 12.