Binder composition for electrochemical element, current collector for electrochemical element, electrode for electrochemical element, electrochemical element, and method for producing binder composition for electrochemical element

Abstract

A binder composition for electrochemical element including a particulate polymer, the particulate polymer having a volume-based particle diameter ((D50)) of greater than 1.0 µm and less than or equal to 10.0 µm and a glass transition temperature below 10°C.

Description

Binder composition for electrochemical element, current collector for electrochemical element, electrode for electrochemical element, electrochemical element, and method for producing binder composition for electrochemical element

[0001] The present invention relates to a binder composition for an electrochemical element, a current collector for an electrochemical element, an electrode for an electrochemical element, an electrochemical element, and a method for producing a binder composition for an electrochemical element.

[0002] Electrochemical devices such as non-aqueous secondary batteries, 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] Known electrodes for these electrochemical elements include an electrode in which a composite layer containing an active material and a binder is provided on a current collector. Examples of methods for producing the composite layer include a method in which a slurry containing at least the active material and the binder dispersed in a solvent is applied to the current collector and dried, a method in which composite particles containing at least the active material and the binder are formed into a layer on the current collector and the resulting molded layer is compressed, and a method in which an amorphous kneaded material containing at least the active material and the binder is compressed multiple times with a calendar roll, and then the kneaded material is attached to the current collector and compressed.

[0004] Furthermore, electrodes having an adhesive layer between a current collector and a composite layer are also known. For example, Patent Document 1 discloses an adhesive coating liquid for forming such an adhesive layer, which contains a binder and water, and in which the amount of aggregates generated in a Marlon mechanical stability test of the coating liquid is less than 0.3 wt. % relative to the solid content, the contact angle with copper foil is less than 60°, and the measurement result in a loop tack test is 0.5 N / 25 mm or greater. Furthermore, the same document discloses that the binder is preferably particulate, and the average particle size of the binder in the binder aqueous dispersion is preferably 50 to 500 nm, more preferably 70 to 400 nm (paragraph

[0026] of the specification of Patent Document 1). The document describes that the adhesive coating liquid for coating a current collector can provide an adhesive coating liquid for coating a current collector that can produce an electrochemical element electrode having good performance when forming an electrode active material layer on a long current collector (Patent Document 1, paragraph

[0006] ).

[0005] International Publication No. 2015 / 115177

[0006] However, the conventional binders described above have room for improvement in terms of further enhancing the adhesiveness and tackiness of the adhesive layer. Therefore, an object of the present invention is to provide a binder composition for electrochemical elements that has excellent adhesiveness and tackiness, and to provide a current collector for electrochemical elements, an electrode for electrochemical elements, and an electrochemical element that use the binder composition.

[0007] The present inventors have conducted extensive research to solve the above problems. ５０ The present inventors have newly found that a binder composition for an electrochemical element containing a particulate polymer having a particle size of more than 1.0 μm and not more than 10.0 μm and a glass transition temperature of less than 10° C. can improve adhesiveness and tackiness, and have completed the present invention.

[0008] That is, an object of the present invention is to advantageously solve the above-mentioned problems, and the present invention provides [1] a binder composition for an electrochemical element containing a particulate polymer, wherein the particulate polymer has a volume-based particle diameter (D ５０The binder composition for electrochemical elements has a volume-based particle diameter (D ) of more than 1.0 μm and not more than 10.0 μm, and a glass transition temperature of less than 10° C. The binder composition for electrochemical elements has excellent adhesiveness and tackiness. Furthermore, an electrochemical element obtained by using the binder composition for electrochemical elements has excellent rate characteristics and cycle characteristics. The volume-based particle diameter (D ５０ ) is a volume-based median diameter (a particle diameter at which the cumulative volume calculated from the small diameter side in the particle size distribution (volume basis) is 50%), and can be measured according to the method described in the examples of this specification.

[0009] [2] Here, the binder composition for an electrochemical element according to the above [1] has a particle size distribution (D ５０ / D １０ When the particle size distribution of the particulate polymer is equal to or less than the upper limit, the binder composition for electrochemical elements can have even more excellent adhesiveness. １０ is the particle size at which the cumulative volume calculated from the small diameter side in the particle size distribution (volume basis) becomes 10%, and can be calculated according to the method described in the examples of this specification.

[0010] [3] The binder composition for an electrochemical element according to the above [1] or [2] may further contain a dispersion medium.

[0011] [4] In the binder composition for electrochemical elements according to any one of [1] to [3] above, when the binder composition for electrochemical elements is sheared for 900 seconds using a rheometer, the viscosity 900 seconds after the start of shearing is preferably 2.00 times or less than the viscosity 20 seconds after the start of shearing. If the viscosity ratio when sheared using a rheometer is equal to or less than the upper limit described above, the binder composition for electrochemical elements will have even better mechanical stability. The viscosity when sheared using a rheometer can be measured according to the method described in the Examples section of this specification.

[0012] [5] In the binder composition for electrochemical elements according to any one of the above [1] to [4], the particulate polymer preferably contains an acidic group-containing monomer unit. If the particulate polymer contains an acidic group-containing monomer unit, the binder composition for electrochemical elements has even better adhesiveness.

[0013] [6] In the binder composition for electrochemical elements according to [5] above, it is preferable that the content of the acidic group-containing monomer unit in the particulate polymer is 1.0 mass % or more and 20.0 mass % or less. When the content of the acidic group-containing monomer unit in the particulate polymer is equal to or less than the upper limit, an electrochemical element obtained by using the binder composition for electrochemical elements can have even more excellent rate characteristics.

[0014] [7] In the binder composition for electrochemical elements according to any one of the above [1] to [6], the particulate polymer preferably contains a hydroxyl group-containing monomer unit. If the particulate polymer contains a hydroxyl group-containing monomer unit, the binder composition for electrochemical elements has even better mechanical stability.

[0015] [8] In the binder composition for electrochemical elements according to [7] above, it is preferable that the content of the hydroxyl group-containing monomer unit in the particulate polymer is 1.0 mass % or more and 20.0 mass % or less. When the content of the hydroxyl group-containing monomer unit in the particulate polymer is equal to or less than the upper limit, an electrochemical element obtained by using the binder composition for electrochemical elements can have even more excellent rate characteristics.

[0016] [9] The binder composition for an electrochemical element according to any one of the above [3] to [8] preferably further contains a water-soluble polymer. If the binder composition for an electrochemical element contains a water-soluble polymer, the binder composition for an electrochemical element has even better adhesiveness.

[0017]

[10] In the binder composition for electrochemical elements according to [9] above, the water-soluble polymer preferably has a weight-average molecular weight of 10,000 or more and less than 5,000,000.

[0018] The present invention also provides

[11] a current collector for an electrochemical element, comprising an intermediate layer formed using the binder composition for an electrochemical element according to any one of [1] to

[10] above.

[0019] Furthermore, the present invention provides

[12] an electrode for an electrochemical element comprising a current collector and a composite layer, wherein the current collector is the current collector for an electrochemical element described above in

[11] , and the composite layer is a layer containing an electrode active material and a composite layer binder, and is disposed on the surface of the intermediate layer provided on the current collector.

[0020] Furthermore, the present invention provides

[13] an electrochemical element comprising the electrode for an electrochemical element according to

[12] above.

[0021] The present invention also provides

[14] a method for producing the binder composition for electrochemical elements according to the above [7] or [8], which comprises a suspension polymerization step of suspension polymerizing a monomer composition containing a hydroxyl group-containing monomer to obtain a particulate polymer.

[0022] According to the present invention, it is possible to provide a binder composition for electrochemical elements that has excellent adhesiveness and tackiness, as well as a current collector for electrochemical elements, an electrode for electrochemical elements, and an electrochemical element that use the binder composition.

[0023] Hereinafter, embodiments of the present invention will be described in detail. Here, the binder composition for electrochemical elements of the present invention is suitably used, for example, as a material for producing an intermediate layer included in the current collector for electrochemical elements of the present invention. The current collector for electrochemical elements of the present invention is produced using the binder composition for electrochemical elements of the present invention and is suitably used, for example, as a part of the electrode for electrochemical elements of the present invention. In the electrode for electrochemical elements, the intermediate layer is a layer (also referred to as an "undercoat") disposed between the electrode mixture layer and the current collector substrate (such as a current collector foil). Furthermore, the electrochemical element of the present invention comprises at least the electrode for electrochemical elements of the present invention. The method for producing the binder composition for electrochemical elements of the present invention is suitably used, for example, for producing the binder composition for electrochemical elements of the present invention.

[0024] (Binder Composition for Electrochemical Device) The binder composition for electrochemical devices of the present invention (hereinafter also simply referred to as "binder composition") contains a particulate polymer, and the particulate polymer has a volume-based particle diameter (D ５０ ) is more than 1.0 μm and 10.0 μm or less, and the glass transition temperature is less than 10° C. Therefore, the binder composition of the present invention is excellent in adhesiveness and tackiness. Furthermore, an electrochemical device obtained by using the binder composition of the present invention is excellent in rate characteristics and cycle characteristics.

[0025] <Particulate Polymer> The particulate polymer contained in the binder composition of the present invention is a component that can function as an adhesive that exhibits adhesiveness when, for example, in producing the current collector for an electrochemical element of the present invention, the binder composition is applied to the surface of a current collecting foil or the like and dried to form an intermediate layer having adhesiveness.

[0026] <<Volume-based particle diameter>> The volume-based particle diameter (D ５０ ) must be greater than 1.0 μm, preferably 1.1 μm or more, more preferably 1.2 μm or more, even more preferably 1.5 μm or more, and even more preferably 1.7 μm or more, and must be 10.0 μm or less, preferably 9.8 μm or less, more preferably 5.0 μm or less, and even more preferably 3.0 μm or less. Specifically, the volume-based particle diameter (D ５０) is preferably more than 1.0 μm and not more than 10.0 μm, more preferably more than 1.0 μm and not more than 9.8 μm, more preferably more than 1.0 μm and not more than 5.0 μm, more preferably more than 1.0 μm and not more than 3.0 μm, more preferably more than 1.1 μm and not more than 10.0 μm, more preferably more than 1.1 μm and not more than 9.8 μm, more preferably more than 1.1 μm and not more than 5.0 μm, more preferably more than 1.1 μm and not more than 3.0 μm, more preferably 1.2 μm or more and not more than 10.0 μm, more preferably more than 1.2 μm and not more than 9.8 μm,

[0033] The volume-based particle size of the particulate polymer is preferably 2 μm or more and 5.0 μm or less, preferably 1.2 μm or more and 3.0 μm or less, preferably 1.5 μm or more and 10.0 μm or less, preferably more than 1.5 μm and 9.8 μm or less, preferably 1.5 μm or more and 5.0 μm or less, preferably 1.5 μm or more and 3.0 μm or less, preferably 1.7 μm or more and 10.0 μm or less, preferably more than 1.7 μm and 9.8 μm or less, preferably 1.7 μm or more and 5.0 μm or less, preferably 1.7 μm or more and 3.0 μm or less. If the volume-based particle size of the particulate polymer is equal to or greater than the above-mentioned lower limit, the particulate polymer has a certain height or more, and the particulate polymer having adhesive properties is likely to protrude from other components when the binder composition is applied. This is presumably because the adhesiveness and tackiness of the binder composition, as well as the rate characteristics and cycle characteristics of an electrochemical device obtained using the binder composition, can be improved. Furthermore, when the volume-based particle size of the particulate polymer is equal to or less than the above upper limit, it is presumed that this is because the number of particulate polymer particles that contribute to adhesion contained in unit mass of the particulate polymer is sufficiently large, and this can improve the adhesiveness and tackiness of the binder composition, as well as the rate characteristics and cycle characteristics of an electrochemical device obtained using the binder composition.

[0027] <<Glass Transition Temperature>> The particulate polymer must have a glass transition temperature of less than 10° C., preferably 5° C. or lower, more preferably 0° C. or lower, even more preferably −5° C. or lower, and even more preferably −10° C. or lower. There are no particular restrictions on the lower limit of the glass transition temperature of the particulate polymer, but it is generally preferably −70° C. or higher, more preferably −60° C. or higher, even more preferably −65° C. or higher, even more preferably −55° C. or higher, and particularly preferably −50° C. or higher. Specifically, the glass transition temperature of the particulate polymer is preferably -70°C or more and less than 10°C, preferably -70°C or more and less than 5°C, preferably -70°C or more and less than 0°C, preferably -70°C or more and less than -5°C, preferably -70°C or more and less than -10°C, preferably -65°C or more and less than 10°C, preferably -65°C or more and less than 5°C, preferably -65°C or more and less than 0°C, preferably -65°C or more and less than -5°C, preferably -65°C or more and less than -10°C, preferably -60°C or more and less than 10°C, preferably -60°C or more and less than 5°C, Preferably, the temperature is -60°C or higher and 0°C or lower, preferably -60°C or higher and -5°C or lower, preferably -60°C or higher and -10°C or lower, preferably -55°C or higher and lower than 10°C, preferably -55°C or higher and lower than 5°C, preferably -55°C or higher and lower than 0°C, preferably -55°C or higher and lower than -5°C, preferably -55°C or higher and lower than -10°C, preferably -50°C or higher and lower than 10°C, preferably -50°C or higher and lower than 5°C, preferably -50°C or higher and lower than 0°C, preferably -50°C or higher and lower than -5°C, preferably -50°C or higher and lower than -10°C. When the glass transition temperature of the particulate polymer is the upper limit or lower, the adhesiveness and tackiness of the binder composition can be improved. Furthermore, when the glass transition temperature of the particulate polymer is the lower limit or higher, the coating stability of the binder composition can be improved.

[0028] The particulate polymer preferably has a volumetric particle size of 1.1 μm or more and 9.8 μm or less and a glass transition temperature of −65° C. or more and 0° C. or less, and more preferably has a volumetric particle size of 1.7 μm or more and 5.0 μm or less and a glass transition temperature of −55° C. or more and −5° C. or less. When the volumetric particle size and glass transition temperature of the particulate polymer are within the above-mentioned ranges, the adhesiveness, tackiness, and coating stability of the binder composition, as well as the rate characteristics and cycle characteristics of an electrochemical device obtained using the binder composition, can be further improved.

[0029] <<Particle size distribution>> The particulate polymer has a particle size distribution (D ５０ / D １０ ) is preferably 2.0 or less, more preferably 1.7 or less, even more preferably 1.5 or less, and even more preferably 1.3 or less. The lower limit of the particle size distribution of the particulate polymer is not particularly limited, but may generally be 1.05 or more, or 1.2 or more. Specifically, the particle size distribution of the particulate polymer is preferably 1.05 or more and 2.0 or less, preferably 1.05 or more and 1.7 or less, preferably 1.05 or more and 1.5 or less, preferably 1.05 or more and 1.3 or less, preferably 1.2 or more and 2.0 or less, preferably 1.2 or more and 1.7 or less, preferably 1.2 or more and 1.5 or less, and preferably 1.2 or more and 1.3 or less. If the particle size distribution of the particulate polymer is not more than the above upper limit, the number of particulate polymer particles that contribute to adhesion contained in unit mass of the particulate polymer is sufficiently large, and therefore the adhesiveness of the binder can be further improved. Furthermore, when the particle size distribution of the particulate polymer is equal to or greater than the above lower limit, it becomes easier to accommodate expansion and contraction of the electrode active material in an electrochemical device obtained using the binder composition, and therefore the cycle characteristics of the electrochemical device can be further improved.

[0030] <<Composition of Particulate Polymer>> The composition of the particulate polymer contained in the binder composition of the present invention is not particularly limited as long as the desired effects of the present invention can be obtained. Therefore, as the particulate polymer, for example, a known particulate polymer that can be used as a material for an adhesive layer when producing a current collector for an electrochemical element can be used.

[0031] Examples of monomer units (structural units) constituting the particulate polymer include (meth)acrylic acid ester monomer units, aromatic vinyl monomer units, and crosslinkable monomer units. The particulate polymer may contain one type of these monomer units alone, or may contain two or more types in any ratio. Specifically, the particulate polymer preferably contains one or more types of monomer units selected from the group consisting of (meth)acrylic acid ester monomer units, aromatic vinyl monomer units, and crosslinkable monomer units, and more preferably contains (meth)acrylic acid ester monomer units, aromatic vinyl monomer units, and crosslinkable monomer units. In the present invention, the phrase "containing a monomer unit (structural unit)" means that "a polymer obtained using that monomer contains a structural unit derived from that monomer."

[0032] [(Meth)acrylic acid ester monomer unit] Examples of (meth)acrylic acid ester monomers that can form the (meth)acrylic acid ester monomer unit include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, butyl acrylates such as n-butyl acrylate and t-butyl acrylate, octyl acrylates such as pentyl acrylate, hexyl acrylate, heptyl acrylate and 2-ethylhexyl acrylate, acrylic acid esters such as nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate and stearyl acrylate. alkyl esters; and methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, butyl methacrylates such as n-butyl methacrylate and t-butyl methacrylate, octyl methacrylates such as pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, and 2-ethylhexyl methacrylate, and methacrylic acid alkyl esters such as nonyl methacrylate, decyl methacrylate, lauryl methacrylate, n-tetradecyl methacrylate, and stearyl methacrylate. Among these, 2-ethylhexyl acrylate is preferred. Note that these (meth)acrylic acid ester monomers may be used alone or in combination of two or more types in any ratio. Note that, in the present invention, "(meth)acrylic" means acrylic and / or methacrylic.

[0033] The content of the (meth)acrylic acid ester monomer units in the particulate polymer is preferably 50% by mass or more, more preferably 55% by mass or more, even more preferably 60% by mass or more, and preferably 90% by mass or less, more preferably 85% by mass or less, when the total repeating units of the particulate polymer are taken as 100% by mass. If the content of the (meth)acrylic acid ester monomer units is not more than the above upper limit, the glass transition temperature of the particulate polymer can be made not less than the above lower limit, thereby improving the coating stability of the binder composition. On the other hand, if the content of the (meth)acrylic acid ester monomer units is not less than the above lower limit, the glass transition temperature of the particulate polymer can be made not more than the above upper limit, thereby improving the adhesiveness and tackiness of the binder composition.

[0034] [Aromatic vinyl monomer unit] Examples of aromatic vinyl monomers that can form aromatic vinyl monomer units include, but are not limited to, styrene, α-methylstyrene, styrene sulfonic acid, 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.

[0035] The content of the aromatic vinyl monomer units in the particulate polymer is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, even more preferably 4.0% by mass or more, and preferably 35.0% by mass or less, more preferably 30.0% by mass or less, and even more preferably 25.0% by mass or less, when the total amount of all monomer units in the particulate polymer is taken as 100% by mass. If the content of the aromatic vinyl monomer units is equal to or greater than the lower limit, the glass transition temperature of the particulate polymer increases, and coalescence due to collision between particles is suppressed. As a result, aggregation during coating is suppressed, thereby further improving the coating stability of the binder composition. On the other hand, if the content of the aromatic vinyl monomer units is equal to or less than the upper limit, the flexibility of the particulate polymer is increased, thereby further improving the adhesiveness and tackiness of the binder composition.

[0036] [Crosslinkable Monomer Unit] A crosslinkable monomer unit is a monomer unit that can form a crosslinked structure during or after polymerization by heating or irradiation with energy rays. Examples of monomers that can form crosslinkable monomer units include polyfunctional monomers having two or more polymerization reactive groups in the monomer. 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 an epoxy group such as allyl glycidyl ether and glycidyl methacrylate. Among these, ethylene glycol dimethacrylate and glycidyl methacrylate are preferred. These crosslinkable monomers may be used alone or in combination of two or more kinds in any ratio.

[0037] The content of the crosslinkable monomer units in the particulate polymer is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and preferably 5.0% by mass or less, more preferably 1.0% by mass or less, when the total repeating units of the particulate polymer are taken as 100% by mass. If the content of the crosslinkable monomer units is equal to or less than the above upper limit, the tackiness of the particulate polymer is improved, thereby further improving the adhesiveness and tackiness of the binder composition. On the other hand, if the content of the crosslinkable monomer units is equal to or more than the above lower limit, the shape of the particulate polymer is maintained even after the binder composition is applied to the current collector foil, thereby increasing the surface area contributing to adhesion and further improving the adhesiveness and tackiness of the binder composition.

[0038] [Other Monomer Units] The particulate polymer may further contain other monomer units. The other monomer units that can be contained in the particulate polymer are not particularly limited, and include nitrile group-containing monomer units, amide group-containing monomer units, acidic group-containing monomer units, and hydroxyl group-containing monomer units. The particulate polymer particularly preferably contains an acidic group-containing monomer unit, preferably contains a hydroxyl group-containing monomer unit, and more preferably contains an acidic group-containing monomer unit and a hydroxyl group-containing monomer unit. Note that, from the viewpoint of the mechanical stability of the binder composition, it is preferable that the particulate polymer does not contain a fluorine-containing monomer unit such as polyvinylidene fluoride (PVDF).

[0039] Examples of nitrile group-containing monomers capable of forming nitrile group-containing monomer units include α,β-ethylenically unsaturated compounds having a nitrile group, such as acrylonitrile; α-halogenoacrylonitriles such as α-chloroacrylonitrile and α-bromoacrylonitrile; and α-alkylacrylonitriles such as methacrylonitrile and α-ethylacrylonitrile. The content of the nitrile group-containing monomer units in the particulate polymer is not particularly limited and can be 0% by mass or more and 10% by mass or less, where the total repeating units of the particulate polymer are taken as 100% by mass. Examples of amide group-containing monomers capable of forming amide group-containing monomer units include acrylamide and methacrylamide. The content of the amide group-containing monomer units in the particulate polymer is not particularly limited and can be 0% by mass or more and 10% by mass or less, where the total repeating units of the particulate polymer are taken as 100% by mass. These monomers may be used alone, or two or more types may be used in combination at any ratio.

[0040] -Acidic Group-Containing Monomer Unit- Examples of acidic group-containing monomers that can form acidic group-containing monomer units include monomers having a carboxylic acid group, monomers having a sulfonic acid group, and monomers having a phosphoric acid group. From the viewpoint of further improving the adhesiveness of the binder composition, monomers having a carboxylic acid group and monomers having a sulfonic acid group are preferred, and monomers having a carboxylic acid group are more preferred.

[0041] 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. Among these, methacrylic acid is preferred. 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, and 3-allyloxy-2-hydroxypropanesulfonic acid. Among these, vinyl sulfonic acid is preferred. In this specification, "(meth)allyl" means allyl and / or methallyl. 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, the term "(meth)acryloyl" means acryloyl and / or methacryloyl. These acidic group-containing monomers may be used alone or in combination of two or more in any ratio.

[0042] The content of the acidic group-containing monomer unit in the particulate polymer is preferably 1.0% by mass or more, more preferably 2.0% by mass or more, and even more preferably 3.0% by mass or more, and is preferably 20.0% by mass or less, more preferably 15.0% by mass or less, and even more preferably 10.0% by mass or less, when the total repeating units of the particulate polymer is 100% by mass. Specifically, the content of the acidic group-containing monomer units in the particulate polymer is preferably 1.0% by mass or more and 20.0% by mass or less, preferably 1.0% by mass or more and 15.0% by mass or less, preferably 1.0% by mass or more and 10.0% by mass or less, preferably 2.0% by mass or more and 20.0% by mass or less, preferably 2.0% by mass or more and 15.0% by mass or less, preferably 2.0% by mass or more and 10.0% by mass or less, preferably 3.0% by mass or more and 20.0% by mass or less, preferably 3.0% by mass or more and 15.0% by mass or less, preferably 3.0% by mass or more and 10.0% by mass or less, when the total repeating units of the particulate polymer are taken as 100% by mass. If the content of the acidic group-containing monomer units is equal to or more than the lower limit, for example, when the binder composition is applied to a current collector, the adhesion of the binder composition can be further improved by hydrogen bonding between the particulate polymer and the functional groups present on the current collector surface. On the other hand, when the content ratio of the acidic group-containing monomer unit is not more than the above upper limit, the swelling degree of the particulate polymer is suppressed to an appropriate range, and the rate characteristics of an electrochemical element obtained using the binder composition can be further improved.

[0043] -Hydroxyl Group-Containing Monomer Unit- Examples of hydroxyl group-containing monomers that can form hydroxyl group-containing monomer units include hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, etc. These hydroxyl group-containing monomers may be used alone or in combination of two or more in any ratio.

[0044] The content of the hydroxyl group-containing monomer units in the particulate polymer is preferably 1.0% by mass or more, more preferably 2.0% by mass or more, even more preferably 3.0% by mass or more, even more preferably 5.0% by mass or more, and particularly preferably 6.5% by mass or more, when the total repeating units of the particulate polymer is taken as 100% by mass, and is preferably 20.0% by mass or less, more preferably 15.0% by mass or less, even more preferably 12.0% by mass or less, even more preferably 11.0% by mass or less, and particularly preferably 10.0% by mass or less.Specifically, the content of the hydroxyl group-containing monomer unit in the particulate polymer is preferably 1.0% by mass or more and 20.0% by mass or less, preferably 1.0% by mass or more and 15.0% by mass or less, preferably 1.0% by mass or more and 12.0% by mass or less, preferably 1.0% by mass or more and 11.0% by mass or less, preferably 1.0% by mass or more and 10.0% by mass or less, preferably 2.0% by mass or more and 20.0% by mass or less, preferably 2.0% by mass or more and 15.0% by mass or less, preferably 2.0% by mass or more and 12.0% by mass or less, preferably 2.0% by mass or more and 11.0% by mass or less, preferably 2.0% by mass or more and 10.0% by mass or less, preferably 3.0% by mass or more and 20.0% by mass or less, preferably 3.0% by mass or more and 15.0% by mass or less. , preferably 3.0% by mass or more and 12.0% by mass or less, preferably 3.0% by mass or more and 11.0% by mass or less, preferably 3.0% by mass or more and 10.0% by mass or less, preferably 5.0% by mass or more and 20.0% by mass or less, preferably 5.0% by mass or more and 15.0% by mass or less, preferably 5.0% by mass or more and 12.0% by mass or less, preferably 5.0% by mass or more and 11.0% by mass or less, preferably 5.0% by mass or more and 10.0% by mass or less, preferably 6.5% by mass or more and 20.0% by mass or less, preferably 6.5% by mass or more and 15.0% by mass or less, preferably 6.5% by mass or more and 12.0% by mass or less, preferably 6.5% by mass or more and 11.0% by mass or less, preferably 6.5% by mass or more and 10.0% by mass or less, and preferably 10.0% by mass or more and 11.0% by mass or less. When the content ratio of the hydroxyl group-containing monomer unit is equal to or greater than the above lower limit, the mechanical stability of the binder composition can be further improved, and the tackiness can be further improved, thereby enabling the cycle characteristics of an electrochemical element obtained using the binder composition to be further improved.On the other hand, when the content ratio of the hydroxyl group-containing monomer unit is equal to or less than the above upper limit, the swelling degree of the particulate polymer is suppressed within an appropriate range, thereby further improving the rate characteristics of an electrochemical element obtained using the binder composition.

[0045] <<Method for Preparing 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.

[0046] The polymerization method is not particularly limited, and any method such as a suspension polymerization method, an emulsion polymerization aggregation method, a pulverization method, or a dissolution suspension method can be used. Among them, from the viewpoint of efficiently preparing a particulate polymer, the suspension polymerization method and the emulsion polymerization aggregation method are preferred, and the suspension polymerization method is more preferred. Furthermore, any reaction such as radical polymerization or living radical polymerization can be used as the polymerization reaction.

[0047] Here, as an example, a method for preparing a particulate polymer by suspension polymerization will be described.

[0048] [Preparation of particulate polymer by suspension polymerization method] (1) Preparation of monomer composition First, the monomers constituting the desired particulate polymer and other compounding agents added as needed are mixed to prepare the monomer composition. (2) Formation of droplets Next, the monomer composition is dispersed in water, a polymerization initiator is added, and then droplets of the monomer composition are formed. Here, the method for forming the droplets is not particularly limited, and for example, the droplets can be formed by shearing and stirring an aqueous medium containing the monomer composition using a disperser such as an emulsifying disperser.

[0049] In this case, examples of the polymerization initiator to be used include oil-soluble polymerization initiators such as t-butylperoxy-2-ethylhexanoate, azobisisobutyronitrile, etc. The polymerization initiator may be added after the monomer composition is dispersed in water and before droplets are formed, or may be added to the monomer composition before it is dispersed in water.

[0050] From the viewpoint of stabilizing the formed droplets of the monomer composition in water, it is preferable to form the droplets of the monomer composition by adding a dispersion stabilizer to the water. In this case, examples of the dispersion stabilizer that can be used include polyvinyl alcohol, metal hydroxides such as magnesium hydroxide, and sodium dodecylbenzenesulfonate.

[0051] (3) Polymerization After forming droplets of the monomer composition, the water containing the formed droplets is heated to initiate polymerization, 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.

[0052] In the suspension polymerization method, sodium alkyldiphenyl ether disulfonate, polyvinyl alcohol, or the like can be used as a suspension stabilizer. Here, as the sodium alkyldiphenyl ether disulfonate, for example, a compound having an alkyl group having 4 to 30 carbon atoms can be used. Specific examples include commercially available products such as Dowfax 2A1 (manufactured by The Dow Chemical Company), Perex SS-H (manufactured by Kao Corporation), and Perex SS-L (manufactured by Kao Corporation). The amount of the suspension stabilizer added is preferably 0.1 parts or more, more preferably 0.5 parts or more, and preferably 2.0 parts or less, and more preferably 1.5 parts or less, per 100 parts of the monomer composition. When the amount of the suspension stabilizer added is above the lower limit, the stability of the particulate polymer during polymerization can be improved and aggregation can be suppressed. When the amount of the suspension stabilizer added is below the upper limit, foaming can be suppressed when the binder composition obtained using the particulate polymer is applied.

[0053] <Other Components> The binder composition of the present invention may further contain other components in addition to the particulate polymer described above. Examples of other components include a dispersion medium, a water-soluble polymer, and other additives.

[0054] <<Dispersion Medium>> The dispersion medium that can be optionally contained in the binder composition of the present invention is one that can make the binder composition into a slurry (hereinafter, the slurry binder composition may be referred to as a "binder coating liquid"). Note that, in the formation of the intermediate layer, which includes a drying step of the binder coating liquid, as described below, the dispersion medium volatilizes. As a result, an intermediate layer made of the solid content (dried product) of the binder coating liquid is obtained.

[0055] As the dispersion medium, any medium can be used that can be volatilized during the formation of the intermediate layer, has low dissolving properties for components such as the particulate polymer, and can maintain the dispersion state of the components such as the particulate polymer. An aqueous medium is preferred as the dispersion medium. The aqueous medium is water or a mixture of water and a medium other than water. By using an aqueous medium as the dispersion medium, the environmental load can be reduced and the handling of the binder coating liquid can be made easier. Of these, water is preferably used as the dispersion medium.

[0056] Examples of aqueous media that can be used in combination with water include cyclic aliphatic hydrocarbon compounds such as cyclopentane and cyclohexane; aromatic hydrocarbon compounds such as toluene and xylene; ketone compounds such as ethyl methyl ketone and cyclohexanone; ester compounds such as ethyl acetate, butyl acetate, γ-butyrolactone, and ε-caprolactone; nitrile compounds such as acetonitrile and propionitrile; ether compounds such as tetrahydrofuran and ethylene glycol diethyl ether; alcohol compounds such as methanol, ethanol, isopropanol, ethylene glycol, and ethylene glycol monomethyl ether; and amide compounds such as N-methylpyrrolidone (NMP) and N,N-dimethylformamide. These may be used alone, or two or more may be used in any combination at any ratio. The amount of the medium other than water is preferably 5 parts by mass or less per 100 parts by mass of water.

[0057] The amount of the dispersion medium in the binder coating liquid is preferably set so that the solid content concentration of the binder coating liquid falls within a desired range. Specific solid content concentrations of the binder coating liquid are preferably 10% by mass or more, more preferably 15% by mass or more, and preferably 80% by mass or less, more preferably 75% by mass or less, even more preferably 70% by mass or less, and particularly preferably 65% ​​by mass or less. By setting the solid content concentration within the above range, the binder coating liquid can have properties suitable for the coating and drying processes.

[0058] <Water-Soluble Polymer> The water-soluble polymer that can be optionally contained in the binder composition of the present invention can be any known water-soluble polymer. Herein, "water-soluble" refers to a polymer that has an insoluble content of less than 0.5% by weight when 0.5 g of the polymer is dissolved in 100 g of water at 25°C. Specific examples of water-soluble polymers include cellulose-based polymers such as carboxymethyl cellulose, methyl cellulose, and hydroxypropyl cellulose, and their ammonium and alkali metal salts; (modified) poly(meth)acrylic acid and their ammonium and alkali metal salts; (modified) polyvinyl alcohols such as copolymers of acrylic acid or acrylic acid salts with vinyl alcohol, and copolymers of maleic anhydride or maleic acid or fumaric acid with vinyl alcohol; polyethylene glycol, polyethylene oxide, polyvinylpyrrolidone, modified polyacrylic acid, oxidized starch, starch phosphate, casein, various modified starches, and hydrogenated acrylonitrile-butadiene copolymers. In the present invention, "(modified) poly" refers to either "unmodified poly" or "modified poly." These may be used alone or in combination of two or more in any ratio.

[0059] The water-soluble polymer preferably has a weight-average molecular weight of 10,000 or more, more preferably 50,000 or more, and even more preferably 100,000 or more, and preferably less than 5,000,000, more preferably 1,000,000 or less, even more preferably 800,000 or less, still more preferably 600,000 or less, and particularly preferably 500,000 or less. Specifically, the weight average molecular weight of the water-soluble polymer is preferably 10,000 or more and less than 5,000,000, more preferably 10,000 or more and less than 1,000,000, more preferably 10,000 or more and less than 800,000, more preferably 10,000 or more and less than 600,000, more preferably 10,000 or more and less than 500,000, more preferably 50,000 or more and less than 5,000,000, more preferably 50,000 or more and less than 1,000,000, and more preferably 50,000 or more and less than 50,000,000. Preferably, the weight average molecular weight is 1,000 or more and 800,000 or less, more preferably 50,000 or more and 600,000 or less, more preferably 50,000 or more and 500,000 or less, more preferably 100,000 or more and less than 5,000,000, more preferably 100,000 or more and 1,000,000 or less, more preferably 100,000 or more and 800,000 or less, more preferably 100,000 or more and 600,000 or less, and more preferably 100,000 or more and 500,000 or less. If the weight average molecular weight of the water-soluble polymer is equal to or greater than the above lower limit, the coating stability when the binder coating liquid is applied can be further improved. Furthermore, if the weight average molecular weight of the water-soluble polymer is equal to or less than the above upper limit, the handleability of the binder coating liquid can be improved.

[0060] The content of the water-soluble polymer in the binder coating liquid is preferably set so that the solids concentration of the binder coating liquid falls within a desired range. Specific solids concentration of the binder coating liquid is preferably 10% by mass or more, more preferably 15% by mass or more, and preferably 80% by mass or less, more preferably 75% by mass or less, even more preferably 70% by mass or less, and particularly preferably 65% ​​by mass or less. By setting the solids concentration within the above range, the binder coating liquid can have properties suitable for the coating and drying processes.

[0061] Other additives that may be optionally contained in the binder composition include dispersants. Examples of dispersants that can be used include carboxylic acid copolymers such as ammonium polycarboxylate. The amounts of other additives used in the binder composition can be appropriately set within a range that achieves the desired effects of the present invention.

[0062] <Viscosity Ratio of Binder Composition> When the binder composition of the present invention is sheared for 900 seconds using a rheometer, the viscosity 900 seconds after the start of shearing is preferably 2.10 times or less, more preferably 2.00 times or less, even more preferably 1.50 times or less, even more preferably 1.30 times or less, and particularly preferably 1.10 times or less, of the viscosity 20 seconds after the start of shearing. That is, the ratio of the viscosity 900 seconds after the start of shearing to the viscosity 20 seconds after the start of shearing (hereinafter also referred to as the viscosity ratio) of the binder composition of the present invention is preferably 2.10 or less, more preferably 2.00 or less, even more preferably 1.50 or less, even more preferably 1.30 or less, and particularly preferably 1.10 or less. The lower limit of the viscosity ratio is not particularly limited, but may generally be 0.90 or more, or may be 0.95 or more. Specifically, the viscosity ratio of the binder composition is preferably 0.90 or more and 2.10 or less, preferably 0.90 or more and 2.00 or less, preferably 0.90 or more and 1.50 or less, preferably 0.90 or more and 1.30 or less, preferably 0.90 or more and 1.10 or less, preferably 0.95 or more and 2.10 or less, preferably 0.95 or more and 2.00 or less, preferably 0.95 or more and 1.50 or less, preferably 0.95 or more and 1.30 or less, preferably 0.95 or more and 1.10 or less. If the viscosity ratio of the binder composition is equal to or less than the upper limit, the mechanical stability of the binder composition can be further improved. Furthermore, if the viscosity ratio of the binder composition is equal to or more than the lower limit, the handleability of the binder composition can be further improved. The viscosity ratio of the binder composition can be increased by, for example, reducing the amount of hydroxyl group-containing monomer units in the particulate polymer or reducing the amount of water-soluble polymer added, and can be decreased by, for example, increasing the amount of hydroxyl group-containing monomer units in the particulate polymer or increasing the amount of water-soluble polymer added.

[0063] (Method for producing binder composition for electrochemical element) The method for producing the binder composition of the present invention is not particularly limited, and includes a step of preparing a particulate polymer by the method described above in the section "Method for preparing a particulate polymer". The step of preparing a particulate polymer preferably includes a suspension polymerization step of carrying out the suspension polymerization method described above in the section "Preparation of a particulate polymer by suspension polymerization method", and more preferably includes a suspension polymerization step of suspension polymerizing a monomer composition containing a hydroxyl group-containing monomer.

[0064] The method for producing the binder composition of the present invention may further include a step of preparing a binder coating liquid by mixing the above-mentioned particulate polymer with a dispersion medium, and optionally a water-soluble polymer and / or other additives. The dispersion medium, water-soluble polymer, and other additives may be those described above in the "Other Components" section. While the mixing method is not particularly limited, mixing is typically performed using a disperser as a mixing device to efficiently disperse each component. The disperser is preferably a device capable of uniformly dispersing and mixing the above components. Examples include a ball mill, a sand mill, a pigment disperser, a crusher, an ultrasonic disperser, a homogenizer, and a planetary mixer. Furthermore, from the viewpoint of being able to impart a high dispersion shear, high-dispersion devices such as a bead mill, a roll mill, and a Filmix may also be used.

[0065] (Current Collector for Electrochemical Device) The current collector for an electrochemical device of the present invention (hereinafter also simply referred to as "current collector") is characterized by having an intermediate layer formed using the binder composition of the present invention. The current collector of the present invention is obtained by applying the binder composition of the present invention to a suitable substrate, for example, a current collecting foil, and drying the coating to form an intermediate layer. The intermediate layer formed on the substrate can impart excellent adhesion and tackiness to the current collector. Furthermore, the current collector may further have one or more other layers on the substrate other than the above-mentioned intermediate layer that exhibit a desired function.

[0066] <Current Collector Foil> The material of the current collector foil, which serves as the substrate of the current collector, is preferably a material that is electrically conductive and electrochemically durable. Specific examples of the material of the current collector foil include metals, carbon, and conductive polymers, with metals being preferred. Examples of metals include copper, aluminum, platinum, nickel, tantalum, titanium, stainless steel, and alloys thereof. Among these, copper, aluminum, and aluminum alloys are preferred in terms of conductivity and voltage resistance. When high voltage resistance is required, high-purity aluminum as disclosed in JP 2001-176757 A can be preferably used. Among these, aluminum is preferred as the material of the current collector foil used for the positive electrode, and copper is preferred as the material of the current collector foil used for the negative electrode. These materials may be used alone or in combination of two or more.

[0067] The current collector foil generally has a film or sheet shape. The thickness of the current collector foil may be appropriately selected depending on the intended use, and is preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 8 μm or more, and is preferably 200 μm or less, more preferably 100 μm or less, and even more preferably 50 μm or less.

[0068] <Intermediate Layer> The intermediate layer of the current collector is formed by applying the binder composition of the present invention to the above-described substrate and drying it. The binder composition applied to the substrate contains a particulate polymer and optionally contains a dispersion medium, a water-soluble polymer, and / or other additives. As the particulate polymer, the particulate polymer described in the section "Binder composition for electrochemical elements" can be used. Furthermore, as the dispersion medium, water-soluble polymer, and other additives, those described in the section "Other components" can be used in the content ratios described above. From the viewpoint of ease of application of the binder composition, the binder composition is preferably in the form of a slurry containing a dispersion medium (binder coating liquid).

[0069] The intermediate layer has a weight per unit area of ​​0.005 mg / cm after drying. ２ It is preferable that the concentration is 0.010 mg / cm or more. ２ More preferably, it is 0.015 mg / cm or more. ２More preferably, it is 0.020 mg / cm or more. ２ It is particularly preferable that the concentration is 0.100 mg / cm or more. ２ Preferably, it is 0.080 mg / cm or less. ２ More preferably, it is 0.060 mg / cm or less. ２ More preferably, it is 0.040 mg / cm or less. ２ It is particularly preferable that the weight per unit area of ​​the intermediate layer is equal to or greater than the above lower limit. If the weight per unit area of ​​the intermediate layer is equal to or greater than the above lower limit, a sufficient amount of the binder composition is applied to the substrate, thereby further improving the adhesion of the current collector. Furthermore, if the weight per unit area of ​​the intermediate layer is equal to or less than the above upper limit, the surface of the current collector foil is prevented from being completely covered with the particulate polymer, enabling good electrical conductivity between the current collector foil and the composite layer, and further improving the rate characteristics of an electrochemical element obtained using the current collector.

[0070] <Method for producing current collector> The method for producing a current collector of the present invention includes a step of preparing a binder composition containing a particulate polymer (preparation step), and a step of applying the binder composition to a substrate and drying it (intermediate layer formation step).

[0071] <<Preparation Step>> In the preparation step, a binder composition containing a particulate polymer is prepared. The preparation step is not particularly limited and includes, for example, a step of preparing a particulate polymer by the method described above in the section "Method for Preparing a Particulate Polymer." The preparation step may further include a step of preparing a binder coating liquid by mixing the particulate polymer with a dispersion medium, and optionally a water-soluble polymer and / or other additives. Note that the dispersion medium, water-soluble polymer, and other additives described above in the section "Other Components" can be used. Here, the mixing method is not particularly limited, but in order to efficiently disperse each component, mixing is usually performed using a disperser as a mixing device. As the disperser, the one described above in the section "Method for Producing a Binder Composition for an Electrochemical Device" can be used.

[0072] <<Intermediate Layer Forming Step>> In the intermediate layer forming step, the binder composition prepared in the preparation step is applied to a substrate and then dried to form an intermediate layer on the substrate. Specifically, the binder composition is applied to a substrate such as the current collector foil described above or to the other layer formed on the substrate (hereinafter referred to as the "substrate, etc.") and then dried. Methods for forming an intermediate layer on a substrate, etc., include the following: 1) a method of applying the binder composition to the surface of the substrate, etc., and then drying; 2) a method of immersing the substrate, etc., in the binder composition and then drying it; and 3) a method of applying the binder composition to a release substrate, drying it to form an intermediate layer, and transferring the resulting intermediate layer to the surface of the substrate, etc. Among these, method 1) is particularly preferred because it makes it easy to control the basis weight of the intermediate layer. Method 1) specifically includes a step of applying the binder composition to the substrate, etc. (applying step) and a step of drying the binder composition applied to the substrate, etc. to form an intermediate layer (drying step).

[0073] [Coating Step] In the coating step, the method for coating the binder composition onto the substrate or the like is not particularly limited, and examples thereof include a doctor blade method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, and a brush coating method.

[0074] In the coating step, the binder composition may be applied to the entire surface or partially (for example, in an island pattern) of at least one surface of the substrate, etc. From the viewpoint of further improving the adhesiveness and tackiness of the current collector and the rate characteristics and cycle characteristics of an electrochemical device obtained using the current collector, it is preferable to apply the binder composition to the entire surface of at least one surface of the substrate, etc.

[0075] [Drying Step] In the drying step, the method for drying the binder composition on the substrate or the like is not particularly limited, and known methods can be used. Examples of drying methods include drying with warm air, hot air, or low-humidity air, vacuum drying, and drying by irradiation with infrared rays or electron beams. The drying temperature is preferably less than 200°C, more preferably less than 150°C, and is preferably 100°C or higher, more preferably 110°C or higher. The drying time is preferably 1 minute or longer and 10 minutes or shorter.

[0076] (Electrode for electrochemical element) The electrode for electrochemical element of the present invention (hereinafter also simply referred to as "electrode") is characterized by comprising a composite layer disposed on the surface of the current collector of the present invention and an intermediate layer provided on the current collector. By disposing the composite layer on the surface of the adhesive intermediate layer, peeling between the composite layer and the current collector substrate (current collector foil, etc.) is suppressed, and an electrochemical element obtained using the electrode of the present invention can be made to have excellent rate characteristics and cycle characteristics.

[0077] <Composition Layer> In this specification, the composition layer is a layer containing an electrode active material and a composition layer binder. The composition layer binder is a material that can bind together the electrode active material, which is usually in the form of particles. In the composition layer, the electrode active material and the composition layer binder may form composite particles.

[0078] <<Electrode Active Material>> The electrode active material contained in the composite layer is not particularly limited, and any known electrode active material can be used. The electrode active material is preferably graphite. When graphite is used as the electrode active material, it can function as a negative electrode active material in a normal lithium ion secondary battery. Therefore, the electrode of this embodiment can function as a negative electrode in a lithium ion secondary battery.

[0079] The graphite may be natural graphite, artificial graphite, etc. The shape of the graphite is not particularly limited, and any of flake graphite, flat graphite, and spherical graphite may be used, or two or more of these may be used in combination. The graphite may be surface-treated, for example, by coating with amorphous carbon.

[0080] <<Composition Layer Binder>> The composite layer binder contained in the composite layer may be the binder composition of the present invention described above in the section "Binder composition for electrochemical elements," or may be any other known binder. The composite layer binder is not particularly limited as long as it is a material that can bind electrode active materials together, and any known binder can be used.

[0081] <<Other Components>> The composite layer may contain any component in addition to the electrode active material and composite layer binder described above. Examples of the optional component include a thickener, a dispersant, and a conductive material.

[0082] The composite layer may contain a thickener or may not contain a thickener. The thickener may be the polymer described above in the "Water-soluble polymer" section. One type of thickener may be used alone, or two or more types may be used in combination.

[0083] The composite layer may contain a dispersant or may not contain a dispersant. Examples of dispersants include soluble modified acrylonitrile rubber. One type of dispersant may be used alone, or two or more types may be used in combination.

[0084] The composite layer may or may not contain a conductive material. Examples of the conductive material include carbon black. The conductive material may be used alone or in combination of two or more.

[0085] <Method for manufacturing electrode> The electrode of the present invention can be manufactured by forming a composite layer on the surface of the intermediate layer provided on the current collector of the present invention. A known method for forming the composite layer can be used. Specifically, for example, the method described in JP 2013-145763 A can be used.

[0086] (Electrochemical device) The electrochemical device of the present invention is characterized by comprising the electrode for electrochemical devices of the present invention described above. Since the electrochemical device of the present invention comprises the electrode for electrochemical devices of the present invention described above, it can exhibit excellent electrochemical properties (rate characteristics, cycle characteristics).

[0087] The electrochemical device of the present invention is not particularly limited, and may be, for example, a lithium ion secondary battery or an electric double layer capacitor, and is preferably a lithium ion secondary battery.

[0088] Hereinafter, a lithium ion secondary battery will be described as an example of an electrochemical element of the present invention. The lithium ion secondary battery according to the present invention includes the electrode for an electrochemical element of the present invention described above. More specifically, the lithium ion secondary battery includes a positive electrode, a negative electrode, a separator, and an electrolyte, and at least one of the positive electrode and the negative electrode is made of the electrode for an electrochemical element of the present invention described above.

[0089] As the positive electrode, negative electrode, and electrolyte solution described above, known positive electrodes, negative electrodes, and electrolyte solutions used in lithium ion secondary batteries can be used.

[0090] Specifically, the electrodes (positive and negative electrodes) can be electrodes in which an electrode mixture layer is formed on a known current collector. The known current collectors can be made of metal materials such as iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, and platinum. Among these, a current collector made of copper is preferably used as the negative electrode current collector. Furthermore, a current collector made of aluminum is preferably used as the positive electrode current collector. Furthermore, a layer containing a known electrode active material and a binder can be used as the electrode mixture layer.

[0091] <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, (CF３ CO) ２ NLi, (CF ３ SO ２ ) ２ NLi, (C ２ F ５ SO ２ Among them, LiPF is particularly preferred because it is easily soluble in solvents and shows a high degree of dissociation. ６ , LiClO ４ , C.F. ３ SO ３ Li is preferred. Note that one type of electrolyte may be used alone, or two or more types may be used in combination. Generally, the lithium ion conductivity tends to increase as the supporting electrolyte with a higher degree of dissociation is used, so the lithium ion conductivity can be adjusted by the type of supporting electrolyte.

[0092] 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), ethyl methyl carbonate (EMC), and vinylene carbonate (VC) are suitable. esters such as γ-butyrolactone and methyl formate are also suitable. Ethers such as 1,2-dimethoxyethane and tetrahydrofuran are also suitable. Sulfur-containing compounds such as sulfolane and dimethyl sulfoxide are also suitable. Mixtures of these solvents may also be used. Among these, carbonates are preferred due to their high dielectric constant and wide stable potential range. Generally, the lower the viscosity of the solvent used, the higher the lithium ion conductivity. Therefore, the lithium ion conductivity can be adjusted by the type of solvent. The concentration of the electrolyte in the electrolyte can be adjusted as appropriate. Known additives may also be added to the electrolyte.

[0093] <Method for Manufacturing Electrochemical Device> The electrochemical device of the present invention can be manufactured using the electrode for electrochemical devices of the present invention described above. Specifically, for example, when manufacturing a lithium ion secondary battery, a positive electrode and a negative electrode are stacked with a separator interposed therebetween, and the stack is wound, folded, or the like as necessary and placed in a battery container. An electrolyte solution is poured into the battery container and sealed, thereby manufacturing a lithium ion secondary battery. At least one of the positive electrode or the negative electrode is manufactured using the electrode of the present invention described above. Here, the battery container may optionally contain an expanded metal, an overcurrent prevention element such as a fuse or a PTC element, a lead plate, or the like to prevent pressure buildup within the battery and overcharging and discharging. The shape of the battery may be, for example, any of a coin type, a button type, a sheet type, a cylindrical type, a rectangular type, a flat type, or the like.

[0094] 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 monomer 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. In the examples, various measurements and evaluations were carried out using the following methods.

[0095] (Physical Property Measurement) <Glass Transition Temperature of Particulate Polymer> The particulate polymer prepared in the examples was used as a measurement sample. 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 measuring device ("EXSTAR DSC6220" manufactured by SII NanoTechnology Inc.) with an empty aluminum pan as a reference, within a measurement temperature range of -100°C to 500°C, at a heating rate of 10°C / min, 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) is 0.05 mW / min / mg or more and the tangent to the DSC curve at the first inflection point that appears after the endothermic peak.

[0096] <Volume-based particle diameter of the particulate polymer (D ５０ )>Volume-based particle diameter D of the particulate polymer prepared in the examples ５０ was measured by a laser diffraction method. Specifically, an aqueous dispersion solution (adjusted to a solid content concentration of 0.1% by mass) containing the prepared particulate polymer was used as a sample. 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 D at which the cumulative volume calculated from the smallest diameter side reached 50% was determined. ５０ was taken as the volume-based particle size.

[0097] <Particle size distribution of particulate polymer> The particle size distribution of the particulate polymer prepared in the examples was measured by a laser diffraction method. Specifically, an aqueous dispersion solution (adjusted to a solid content concentration of 0.1% by mass) containing the prepared particulate polymer was used as a sample. Then, in the particle size distribution (volume basis) measured using a laser diffraction particle size distribution measuring device (manufactured by Beckman Coulter, Inc., "LS-230"), the particle size at which the cumulative volume calculated from the smallest diameter side becomes 50% was defined as D ５０ The particle diameter at which the cumulative volume becomes 10% is D １０ And D ５０ / D １０ The value was taken as the particle size distribution.

[0098] <Viscosity Ratio (Mechanical Stability) of Binder Composition> The mechanical stability of the binder coating liquid was measured using a rheology measurement device. Specifically, the binder coating liquid containing a particulate polymer with a solids content of 20% by mass prepared in the examples was dropped onto the base of an Anton Paar apparatus (MCR-XX). A PP-50 was attached as a cone plate, and the gap between the base and the cone plate was set to 0.015 mm. In this state, the apparatus was rotated at 100,000 rpm to perform shearing, and the viscosity was measured 20 seconds and 900 seconds after the start of rotation, and the viscosity ratio (viscosity after 900 seconds / viscosity after 20 seconds) was calculated. Note that, since the viscosity increases as the mechanical stability of the binder coating liquid deteriorates, a smaller viscosity ratio indicates higher mechanical stability.

[0099] (Evaluation) <Peel Strength> The negative electrode (first negative electrode blank) prepared in the example after one-side coating was cut into a piece of 10 mm width and 50 mm length. This test piece was placed with the current collector side of the negative electrode facing downward, and cellophane tape was attached to the surface of the negative electrode. The cellophane tape used was specified in JIS Z1522. The cellophane tape was fixed to a horizontal test table. One end of the electrode was then pulled vertically upward at a pulling rate of 100 mm / min to measure the stress when peeled off. The average stress obtained from the measurement using the above negative electrode three times was calculated as the peel strength (N / m) and evaluated according to the following evaluation criteria. A: Peel strength 20 N / m or more B: Peel strength 15 N / m or more and less than 20 N / m C: Peel strength 10 N / m or more and less than 15 N / m D: Peel strength 5 N / m or more and less than 10 N / m E: Peel strength less than 5 N / m

[0100] <Tack Strength> A binder coating liquid was applied to one surface of the copper foil by gravure coating. At this time, the amount of the binder coating liquid applied was 0.025 mg / cm ２ The binder coating solution was then applied to the copper foil, which was then dried at 120°C for 2 minutes to remove the water serving as the dispersion medium, to form a current collector having an intermediate layer (a layer formed by drying the binder coating solution) as a test specimen. A natural rubber sheet having a durometer hardness of A70 (JIS K 6253-3) and a thickness of 3 mm was placed underneath the resulting test specimen, and the tack strength of the surface of the test specimen facing the intermediate layer was measured by the probe tack method using a tack tester (manufactured by Rhesca, "TAC-1000") equipped with a stainless steel probe (diameter: 5 mm). Specifically, the probe was pressed against the intermediate layer of the test specimen under the following conditions, and the tack strength (adhesive strength) was measured during the process of peeling it off, and the results were evaluated according to the following evaluation criteria. Ambient temperature: 25°C Pressing speed: 1 mm / sec Pressing load: 2.0 MPa Pressing holding time: 10 sec Evaluation criteria A: Tack strength 1.0 N or more B: Tack strength 0.5 N or more and less than 1.0 N C: Tack strength 0.2 N or more and less than 0.5 N D: Tack strength less than 0.2 N

[0101] <Coating Stability> The coated portion of the current collector foil (first intermediate) prepared in the Examples, after coating one side with the binder coating liquid, was cut into a length of 30 cm in the MD direction and 20 cm in the TD direction. The number of particulate polymer aggregates was visually measured and evaluated according to the following evaluation criteria: A: Number of aggregates: 0 B: Number of aggregates: 1 to 3 C: Number of aggregates: 4 to 9 D: Number of aggregates: 10 or more

[0102] <Rate Characteristics of Secondary Battery> The 800 mAh stacked lithium ion secondary battery manufactured in the examples was left standing for 24 hours in a 25°C environment, and then charged at 0.1 C by constant current / constant voltage (CCCV) to 4.35 V (end current: 0.04 C) in a 25°C environment, and then discharged to 3.0 V by a 0.1 C constant current method to measure the initial capacity C0. After aging treatment at a temperature of 60°C for 10 hours, the battery was charged at 0.1 C by constant current / constant voltage (CCCV) to 4.35 V (end current: 0.04 C) in a 25°C environment, and then discharged to 3.0 V by a 2 C constant current method to measure the capacity C1. The rate characteristics were calculated as ΔC = (C0 - C1) / C0 × 100 (%) and evaluated according to the following evaluation criteria. A larger ΔC value indicates better rate characteristics. A: ΔC is 90% or more B: ΔC is 85% or more but less than 90% C: ΔC is less than 85%

[0103] <Cycle Characteristics of Secondary Battery> After injecting the electrolyte, the lithium-ion secondary battery prepared in the example was left standing at 25°C for 5 hours. Next, it was charged to a cell voltage of 3.65 V at 25°C using a constant current method at 0.2 C, and then aged for 12 hours at 60°C. Then, it was discharged to a cell voltage of 3.00 V using a constant current method at 25°C and 0.2 C. Thereafter, it was subjected to CC-CV charging (upper limit cell voltage 4.20 V) using a constant current method at 0.2 C (cut-off current value 0.05 C), and CC discharge to 3.00 V using a constant current method at 0.2 C. This charge-discharge at 0.2 C was repeated three times. Thereafter, 100 cycles of charge-discharge were performed in an environment at 25°C, with a cell voltage of 4.20-3.00 V and a charge-discharge rate of 1.0 C. At this time, 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 evaluation criteria. A larger value of the capacity retention rate ΔC' indicates that the secondary battery has better cycle characteristics at 100 cycles. 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%

[0104] Example 1 <Preparation of binder composition> <<Preparation of monomer composition>> A monomer composition (A) was prepared by mixing 4.5 parts of styrene as an aromatic vinyl monomer, 80 parts of 2-ethylhexyl acrylate as a (meth)acrylic acid ester monomer, 5.0 parts of methacrylic acid as an acidic group-containing monomer, 10.0 parts of hydroxyethyl methacrylate as a hydroxyl group-containing monomer, and 0.5 parts of ethylene glycol dimethacrylate as a crosslinkable monomer.

[0105] <<Suspension Polymerization of Particulate Polymer>> A particulate polymer was prepared by suspension polymerization. Specifically, 1 part, in terms of solids, of Dowfax 2a1 (manufactured by Dow Chemical Co.) as a suspension stabilizer was added to 350 parts of ion-exchanged water and stirred. 100 parts of the monomer composition (A) obtained as described above was added and further stirred, followed by the addition of 2.0 parts of t-butylperoxy-2-ethylhexanoate (manufactured by NOF Corporation, "Perbutyl O") as a polymerization initiator to obtain a mixed solution. The obtained mixed solution was subjected to high-shear stirring at a rotation speed of 15,000 rpm for 1 minute using an in-line emulsifying disperser (manufactured by Pacific Machinery Works, Ltd., "Cavitron") to form droplets of the heavy monomer composition (A) in water containing the suspension stabilizer. The aqueous dispersion (A) in which droplets of the monomer composition (A) were formed 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).

[0106] <<Preparation of Binder Coating Liquid>> To 100 parts of the particulate polymer (A), 3 parts of sodium polyacrylate ("Aron A-20L" manufactured by Toa Gosei Co., Ltd., weight average molecular weight 500,000) as a water-soluble polymer and 1 part of ammonium polycarboxylate ("Aron A-6114" manufactured by Toa Gosei Co., Ltd.) as a dispersant were added. Further, ion-exchanged water was added so that the solid content concentration became 20%, to obtain a slurry composition (binder coating liquid).

[0107] <Production of Negative Electrode> <<Preparation of Negative Electrode Composite Layer Binder>> 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 were placed in a 5 MPa pressure vessel equipped with a stirrer, and after thorough stirring, the mixture was heated to 50 ° C to initiate polymerization. When the polymerization conversion rate reached 96%, the reaction was stopped by cooling, and a mixture containing a negative electrode composite layer binder (SBR) was obtained. A 5% aqueous sodium hydroxide solution was added to the mixture containing the negative electrode composite layer binder, 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 negative electrode composite layer binder.

[0108] <<Preparation of Negative Electrode Composite Slurry Composition>> 97.7 parts of artificial graphite (average particle size: 24.5 μm, graphite interlayer distance (interplanar spacing (d value) of the (002) plane by X-ray diffraction method): 0.354 nm) as a negative electrode active material, 1.6 parts (solid content equivalent) of the negative electrode composite layer binder obtained in the above-mentioned "Preparation of Negative Electrode Composite Layer Binder", and 0.7 parts (solid content equivalent) of carboxymethyl cellulose (BSH-12; manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) as a thickener were mixed. Ion-exchanged water was further added to the mixture so that the solid content concentration was 35% by mass, and these were mixed to disperse the solid content in water, thereby obtaining a negative electrode composite slurry composition.

[0109] <<Formation of Composite Particles>> The negative electrode composite slurry composition obtained above was supplied to a spray dryer (manufactured by Okawara Chemical Engineering Co., Ltd.) equipped with a rotating disk type pin atomizer (diameter 84 mm) at a rate of 255 mL / min, and spray drying and granulation were carried out under conditions of a rotation speed of 17,000 rpm, a hot air temperature of 150°C, and a particle recovery outlet temperature of 90°C, thereby obtaining a bulk powder of negative electrode composite particles.

[0110] The obtained composite particle bulk powder was classified. Specifically, the bulk powder was passed through a first sieve with a mesh size of 125 μm to remove coarse particles on the sieve. Subsequently, the composite particles that passed through the first sieve were passed through a second sieve with a mesh size of 106 μm to remove the particles that had passed through. When the particle size of the composite particles remaining on the second sieve was measured, it was found that particles of 40 μm or less accounted for 0% of the total in the particle size distribution based on number, and that the cumulative 95% diameter (D ９５ The cumulative 50% diameter (D ５０ The diameter was 110 μm.

[0111] <<Preparation of Negative Electrode Current Collector Having Intermediate Layer>> Ion-exchanged water was added to the binder coating liquid obtained in the above-mentioned step of “Preparation of Binder Coating Liquid” so that the solid content concentration was 10%, and the mixture was stirred. This was then coated onto one side of a copper foil (thickness: 10 μm) serving as a negative electrode current collector foil in a thickness of 1000 m by gravure coating at a forming speed of 20 m / min, and dried at 120° C. for 2 minutes, thereby obtaining a first intermediate having an intermediate layer (a layer formed by drying the binder coating liquid) on the current collector foil (step 1).

[0112] <<Formation of Composite Layer>> Next, the negative electrode composite particles obtained in the "composite particle formation" step were supplied from a hopper and deposited on the surface of the first intermediate body on which the intermediate layer was provided. A roller squeegee was then applied to the deposit while rotating to level the deposit, thereby forming a layer of negative electrode composite particles. This operation yielded a second intermediate body (step 2), which further included a layer of negative electrode composite particles on the surface of the intermediate layer provided on one surface of the negative electrode current collector.

[0113] Next, the second intermediate was passed through the gap between the peripheral surfaces of a pair of pressure rolls to press the second intermediate. This pressed the layer of the negative electrode composite particles, forming a first negative electrode composite layer (Step 3). This resulted in a first negative electrode blank sheet having a first negative electrode composite layer on the surface of the intermediate layer provided on one surface of the negative electrode current collector. The basis weight of the first negative electrode composite layer was 12.5 mg / cm. ２ It was.

[0114] Furthermore, the same operations as in steps 1 to 3 were performed on the other surface of the negative electrode current collector of the first negative electrode raw sheet, forming an intermediate layer and a second negative electrode composite layer disposed on the surface of the intermediate layer on the other surface of the negative electrode current collector, thereby obtaining a second negative electrode raw sheet. The second negative electrode raw sheet was further compressed by pressure using a pressure roll, resulting in a density of 1.65 g / cm. ３ A negative electrode was fabricated.

[0115] <Production of Positive Electrode> <<Preparation of Positive Electrode Composite Slurry Composition>> 96.5 parts of NMC532 (LiNi0.5Mn0.3Co0.2O2) as the positive electrode active material, 2.0 parts of carbon black (manufactured by Denka Co., Ltd., trade name "Li-100") as a conductive material, 0.4 parts of a dispersant (manufactured by Nippon Zeon Co., Ltd., trade name "BM-720H") as a solid content equivalent, and 1.1 parts of polyvinylidene fluoride (manufactured by Solvay, trade name "Solef5130") as another component, in solid content equivalent, were charged into a planetary mixer and mixed, and further N-methyl-2-pyrrolidone (NMP) was gradually added and stirred to obtain a positive electrode composite slurry composition. The viscosity of the positive electrode mixture slurry composition measured with a Brookfield viscometer at 60 rpm (rotor M4) and 25±3° C. was 3,600 mPa·s.

[0116] <<Preparation of Positive Electrode>> The positive electrode composite slurry composition obtained in the above “Preparation of Positive Electrode Composite Slurry Composition” was applied using a comma coater onto a 15 μm thick aluminum foil current collector so that the weight of the composite layer after drying was 20.5 mg / cm ２ The composite slurry composition on the aluminum foil was then dried to obtain a positive electrode raw sheet having a positive electrode composite layer formed on the current collector. Thereafter, the positive electrode composite layer side of the prepared positive electrode raw sheet was subjected to a roll press in an environment at a temperature of 25±3°C, so that the density of the positive electrode composite layer became 3.40 g / cm. ３ A positive electrode of 1000 .mu.m was obtained.

[0117] <Fabrication of Lithium-Ion Secondary Battery> The negative electrode fabricated as described above was cut out to obtain a negative electrode piece. The negative electrode piece had a negative electrode composite layer with rectangular dimensions of 4.0 cm x 3.0 cm. A negative electrode composite layer non-forming portion was provided as a current collecting tab on the outer side of the end of the negative electrode composite layer of the negative electrode piece. The negative electrode piece was vacuum dried at 150°C for 4 hours.

[0118] Next, the prepared positive electrode was cut out to obtain a positive electrode piece. The positive electrode piece had a positive electrode composite layer with rectangular dimensions of 3.8 cm × 2.8 cm. A positive electrode composite layer non-forming portion was provided as a current collecting tab on the outer side of the end of the positive electrode side.

[0119] A single-layer separator substrate made of polypropylene was prepared as the separator.

[0120] Positive electrode pieces were laminated on both sides of the vacuum-dried negative electrode pieces with separators interposed therebetween to prepare an element. The orientation of the negative electrode pieces and the positive electrode sides was such that the positive electrode composite layer-forming surface of the positive electrode side faced the negative electrode composite layer-forming surface of the negative electrode piece. In one element, the area of ​​the portion where the positive electrode composite layer of the positive electrode and the negative electrode composite layer of the negative electrode faced each other was 21.28 cm. ２A terminal with a sealant was ultrasonically welded to each of the current collecting tabs of the negative electrode piece and the positive electrode piece. The element was placed in a rectangular aluminum packaging material, and three of the four sides of the aluminum packaging material were heat-sealed to produce a laminated lithium-ion secondary battery cell with three sides heat-sealed and one side open before electrolyte injection. The battery cell was then vacuum-dried at 60°C for 10 hours, and then a 1.0 M LiPF 6000 electrolyte was added. ６ A solution (solvent: a mixed solvent of ethylene carbonate (EC) / diethyl carbonate (DEC) = 3 / 7 (volume ratio), additive: containing 2 volume % vinylene carbonate (solvent ratio)) was filled in. Furthermore, the opening of the aluminum packaging material was heat-sealed under reduced pressure to complete a stacked laminate-type lithium ion secondary battery.

[0121] The particulate polymer, binder composition, intermediate, and lithium ion secondary battery obtained through the above-mentioned operations were subjected to various measurements and evaluations. The results are shown in Tables 1-3.

[0122] (Examples 2-16 and Comparative Examples 1-3) In Examples 2 and 3, various operations, measurements, and evaluations were carried out in the same manner as in Example 1, except that the composition of the monomer units constituting the particulate polymer was changed as shown in Table 1. In Example 4, various operations, measurements, and evaluations were carried out in the same manner as in Example 1, except that 1 part, in terms of solid content, of PVA (polyvinyl alcohol) that had been dissolved in water in advance was used as a suspension stabilizer in the preparation of the particulate polymer. In Examples 5 and 6, various operations, measurements, and evaluations were carried out in the same manner as in Example 1, except that the composition of the monomer units constituting the particulate polymer was changed as shown in Table 1. In Example 7, various operations, measurements, and evaluations were carried out in the same manner as in Example 1, except that the water-soluble polymer used in preparing the binder coating liquid was changed from sodium polyacrylate ("Aron A-20L" manufactured by Toa Gosei Co., Ltd., weight-average molecular weight 500,000) to ammonium polyacrylate ("Aron A-30" manufactured by Toa Gosei Co., Ltd., weight-average molecular weight 100,000). In Examples 8 and 9 and Comparative Example 2, various operations, measurements, and evaluations were carried out in the same manner as in Example 1, except that the type and amount of suspension stabilizer added were changed as shown in Table 2. In Comparative Example 2, 3 parts, in terms of solids, of PVP (polyvinylpyrrolidone) dissolved in water in advance was used as the suspension stabilizer. In Comparative Example 3 and Example 10, various operations, measurements, and evaluations were carried out in the same manner as in Example 1, except that the composition of the monomer units constituting the particulate polymer was changed as shown in Table 2. In Example 11, various operations, measurements, and evaluations were carried out in the same manner as in Example 1, except that Neopelex G51 (manufactured by Kao Corporation) was used as a suspension stabilizer in the preparation of the particulate polymer. In Example 12, various operations, measurements, and evaluations were carried out in the same manner as in Example 1, except that the composition of the monomer units constituting the particulate polymer was changed as shown in Table 2, and no water-soluble polymer was used in the preparation of the binder coating liquid. In Examples 13 to 16, various operations, measurements, and evaluations were carried out in the same manner as in Example 1, except that the composition of the monomer units constituting the particulate polymer was changed as shown in Table 3.

[0123] (Comparative Example 1) In Comparative Example 1, various operations, measurements, and evaluations were carried out in the same manner as in Example 1, except that a particulate polymer was prepared as follows. <<Polymerization of Particulate Polymer>> A particulate polymer was prepared by emulsion polymerization. Specifically, the preparation was carried out according to the following procedure. 70 parts of ion-exchanged water, 0.15 parts of polyoxyethylene lauryl ether (manufactured by Kao Chemical Corporation, "Emulgen (registered trademark) 120") as an emulsifier, and 0.5 parts of ammonium persulfate were supplied to a reactor A equipped with a stirrer, and 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 polyoxyethylene lauryl ether (manufactured by Kao Chemical Corporation, "Emulgen (registered trademark) 120") as an emulsifier, 4.5 parts of styrene, 80 parts of 2-ethylhexyl acrylate as a (meth)acrylic acid ester monomer, 5 parts of methacrylic acid as an acid monomer, 10 parts of hydroxyethyl methacrylate as a hydroxyl group-containing monomer, and 0.5 parts of ethylene glycol dimethacrylate as a crosslinkable monomer were mixed to obtain a monomer composition. This monomer composition was continuously added to the above-mentioned reactor A over 4 hours to carry out polymerization. During the addition, the reaction was carried out at 70°C. After completion of the addition, the mixture was further stirred at 80°C for 3 hours to terminate the reaction, and an aqueous dispersion containing particulate polymer X, an acrylic polymer, was obtained.

[0124] The results of the measurements and evaluations of Examples 2 to 7 are shown in Table 1. In the table, the abbreviations for the monomers represent the following substances: 2EHA: 2-ethylhexyl acrylate ST: styrene EDMA: ethylene glycol dimethacrylate HEMA: hydroxyethyl methacrylate MAA: methacrylic acid

[0125]

[0126]

[0127]

[0128] From Table 1-3, the volume-based particle diameter (D ５０It can be seen that a binder composition containing a particulate polymer having a particle size of more than 1.0 μm and not more than 10.0 μm and a glass transition temperature of less than 10° C. has both excellent adhesiveness and tackiness. Furthermore, a comparison between Examples 1 and 2 shows that if the particulate polymer contains a hydroxyl group-containing monomer unit, the binder composition has even better mechanical stability and coating stability. Furthermore, a comparison between Examples 1 and 3 shows that if the particulate polymer contains an acidic group-containing monomer unit, the binder composition has even better adhesiveness.

[0129] According to the present invention, it is possible to provide a binder composition for electrochemical elements that has excellent adhesiveness and tackiness, as well as a current collector for electrochemical elements, an electrode for electrochemical elements, and an electrochemical element that use the binder composition.

Claims

1. A binder composition for electrochemical elements containing a particulate polymer, wherein the particulate polymer has a volume-based particle diameter (D ５０ ) is more than 1.0 μm and 10.0 μm or less, and the glass transition temperature is lower than 10°C.

2. The particle size distribution (D ５０ / D １０ 2. The binder composition for an electrochemical element according to claim 1, wherein the value of (a) is 2.0 or less.

3. The binder composition for an electrochemical element according to claim 1, further comprising a dispersion medium.

4. The binder composition for electrochemical elements according to claim 3, wherein when the binder composition for electrochemical elements is sheared for 900 seconds using a rheometer, the viscosity 900 seconds after the start of shearing is 2.00 times or less of the viscosity 20 seconds after the start of shearing.

5. The binder composition for electrochemical elements according to claim 1, wherein the particulate polymer contains an acidic group-containing monomer unit.

6. The binder composition for electrochemical elements according to claim 5, wherein the content of the acidic group-containing monomer unit in the particulate polymer is 1.0 mass % or more and 20.0 mass % or less.

7. The binder composition for electrochemical elements according to claim 1, wherein the particulate polymer contains a hydroxyl group-containing monomer unit.

8. The binder composition for electrochemical elements according to claim 7, wherein the content of the hydroxyl group-containing monomer unit in the particulate polymer is 1.0 mass % or more and 20.0 mass % or less.

9. The binder composition for an electrochemical element according to claim 3, further comprising a water-soluble polymer.

10. The binder composition for electrochemical elements according to claim 9, wherein the weight average molecular weight of the water-soluble polymer is 10,000 or more and less than 5,000,000.

11. A current collector for an electrochemical element, comprising an intermediate layer formed using the binder composition for an electrochemical element according to any one of claims 1 to 10.

12. An electrode for an electrochemical element comprising a current collector and a composite layer, wherein the current collector is the current collector for an electrochemical element described in claim 11, and the composite layer is a layer containing an electrode active material and a composite layer binder, and is disposed on the surface of the intermediate layer provided on the current collector.

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

14. A method for producing a binder composition for electrochemical elements according to claim 7, comprising a suspension polymerization step of obtaining a particulate polymer by suspension polymerization of a monomer composition containing a hydroxyl group-containing monomer.

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