Binder products for secondary batteries

Abstract

The present invention aims to provide a binder product for a secondary battery that is resistant to aggregation in the binder composition even after long-term storage, and can also form a functional layer with excellent adhesive properties using said binder composition. The binder product of the present invention comprises a container having a receiving portion and a binder composition contained in the internal space of said receiving portion. The contact angle of the inner wall surface of said receiving portion with respect to water is 80° or greater. The binder composition comprises a binder, an antifoaming agent, and water, wherein the content of said antifoaming agent is 0.02 parts by mass or more and 0.3 parts by mass or less per 100 parts by mass of said binder. Furthermore, the surface tension of said binder composition is 20 mN / m or more and 60 mN / m or less.

Description

Technology Field

[0001] The present invention relates to a binder product in which a binder composition for a secondary battery is contained in a container. Background Technology

[0002] Secondary batteries, such as lithium-ion batteries, are widely used for various applications due to their characteristics of being small, lightweight, having high energy density, and capable of repeated charging and discharging. Additionally, secondary batteries generally comprise battery components such as electrodes (positive and negative electrodes) and a separator that isolates the positive and negative electrodes.

[0003] Here, as a battery member of a secondary battery, a member having a functional layer comprising a binder (binding material) and optionally a particle (hereinafter referred to as "functional particle") that is blended to exert a desired function on the battery member is used.

[0004] Specifically, as a separator for a secondary battery, a separator is used that comprises an adhesive layer containing a binder or a porous membrane layer containing a binder and non-conductive particles as functional particles on a separator substrate. Additionally, as an electrode for a secondary battery, an electrode is used that comprises an electrode composite layer containing a binder and electrode active material particles as functional particles on a current collector, or an electrode that further comprises the aforementioned adhesive layer or porous membrane layer on an electrode substrate having an electrode composite layer on a current collector.

[0005] In addition, conventionally, a binder used for forming a battery component is a binder composition formed by dissolving or dispersing the binder in a solvent such as water, and is stored in a container (see, for example, Patent Documents 1 and 2). Prior art literature

[0006] International Publication No. 2015 / 029835, Japanese Patent Publication No. 2017-220326 The problem to be solved

[0007] Here, the functional layer is required to exhibit excellent adhesion in order to adhere well to the substrate supporting the functional layer. In addition, for example, in order to adhere well to the electrode composite layer as a functional layer to the current collector as a substrate, a method can be considered to lower the surface tension of the binder composition to increase the affinity with the electrode active material particles or the current collector.

[0008] However, according to the inventors' review, when a binder composition with low surface tension (e.g., a surface tension of 60 mN / m or less) is filled into a container and stored for a long period in the state of a binder product, a problem arises in which binder aggregates are formed within the binder composition. If a large amount of such aggregates are formed, the binder becomes unevenly distributed within the resulting functional layer, thereby impairing the adhesiveness of the functional layer.

[0009] Accordingly, the present invention aims to provide a binder product for a secondary battery that is resistant to aggregation in the binder composition even after long-term storage, and can also form a functional layer with excellent adhesive properties using the said binder composition. means of solving the problem

[0010] The inventors conducted careful investigations with the aim of solving the above problem. The inventors discovered that if a predetermined binder composition is filled into a container having a receiving portion in which the contact angle of the inner wall surface with water is greater than or equal to a predetermined value, the formation of aggregates within the binder composition after long-term storage can be suppressed, and a functional layer with excellent adhesive properties can be formed even when the binder composition is used after long-term storage, thereby completing the present invention.

[0011] That is, the present invention aims to advantageously solve the above problem. The binder product for a secondary battery according to the present invention comprises a container having a receiving portion and a binder composition contained in the internal space of the receiving portion, wherein the contact angle with water on the inner wall surface of the receiving portion is 80° or more, the binder composition comprises a binder, an antifoaming agent, and water, the content of the antifoaming agent is 0.02 parts by mass or more and 0.3 parts by mass or less per 100 parts by mass of the binder, and the surface tension of the binder composition is 20 mN / m or more and 60 mN / m or less. The binder product described above is unlikely to form aggregates in the binder composition inside the container even when stored for a long period. Furthermore, using the binder composition contained in the binder product described above allows for the formation of a functional layer with excellent adhesive properties.

[0012] Meanwhile, in the present invention, the "contact angle with respect to water" and "surface tension" can both be measured using the method described in the examples.

[0013] Here, in the binder product for a secondary battery according to the present invention, it is preferable that the binder has at least one of an amide group and a hydroxyalkyl group. If the binder is a polymer having an amide group and / or a hydroxyalkyl group, the adhesion of the resulting functional layer can be further improved while further suppressing the formation of aggregates in the binder composition after long-term storage.

[0014] In addition, the binder product for a secondary battery according to the present invention preferably comprises at least one of an amide group-containing monomer unit and a hydroxyalkyl group-containing monomer unit, wherein the sum of the content ratio of the amide group-containing monomer unit and the content ratio of the hydroxyalkyl group-containing monomer unit in the binder is 0.05 mass% or more and 5 mass% or less. If the binder is a polymer having an amide group and / or a hydroxyalkyl group, the adhesion of the resulting functional layer can be further improved while further suppressing the formation of aggregates in the binder composition after long-term storage.

[0015] Meanwhile, in the present invention, the statement that a polymer such as a binder "contains monomer units" means that "a repeating unit derived from the monomer is included in the polymer obtained using the monomer."

[0016] In addition, in the present invention, the content ratio of each monomer unit in a polymer such as a binder is, 1 H-NMR and 13 It can be measured using nuclear magnetic resonance (NMR) methods such as C-NMR.

[0017] In addition, the binder product for a secondary battery according to the present invention preferably comprises a binder composition that further includes a preservative, wherein the content of the preservative is 0.01 parts by mass or more and 0.5 parts by mass or less per 100 parts by mass of the binder. If the binder composition contains the preservative in an amount within the above range, the formation of aggregates in the binder composition after long-term storage can be further suppressed, and the adhesion of the resulting functional layer can be further improved.

[0018] In addition, the binder product for a secondary battery according to the present invention preferably has a volume ratio of the void portion, excluding the volume occupied by the binder composition within the container from the content volume of the container, of 10 volume% or less relative to the content volume of the container. If the volume ratio of the void portion relative to the content volume of the container (hereinafter referred to as "void ratio") is less than or equal to the above value, the formation of aggregates in the binder composition after long-term storage can be further suppressed, and the adhesion of the resulting functional layer can be further improved.

[0019] In addition, the binder product for a secondary battery according to the present invention preferably has a solid content concentration of 30 mass% or more and 60 mass% or less of the binder composition. If the solid content concentration of the binder composition is within the above range, the formation of aggregates in the binder composition after long-term storage can be further suppressed, and the adhesion of the resulting functional layer can be further improved.

[0020] Here, in the binder product for a secondary battery according to the present invention, it is preferable that the defoaming agent comprises a mineral oil-based defoaming agent. By using a mineral oil-based defoaming agent, the formation of aggregates in the binder composition after long-term storage can be further suppressed, and the adhesion of the resulting functional layer can be further improved. Effects of the invention

[0021] The binder product for secondary batteries according to the present invention is unlikely to cause aggregation in the binder composition even after long-term storage, and can also form a functional layer with excellent adhesion using said binder composition. Brief explanation of the drawing

[0022] FIG. 1 is a schematic diagram showing the structure of an example of a binder product for a secondary battery according to the present invention. Specific details for implementing the invention

[0023] Hereinafter, the binder product for secondary batteries according to the present invention will be described.

[0024] The binder product of the present invention is formed by containing a binder composition in a container for storage, transportation, etc. of the binder composition. Then, the binder composition contained in the binder product of the present invention can be extracted, and functional particles, etc., can be added as needed to prepare a slurry composition for a functional layer (e.g., a slurry composition for an electrode, a slurry composition for an adhesive layer, a slurry composition for a porous membrane layer). Such a slurry composition for a functional layer can be used to form a functional layer of a secondary battery (e.g., an electrode composite layer, an adhesive layer, a porous membrane layer).

[0025] Here, the binder product of the present invention has a container having a receiving portion in which the contact angle with water on the inner wall surface is 80° or more, and the surface tension of the binder composition filled in the internal space of the receiving portion is 20 mN / m or more and 60 mN / m or less, and the binder composition contains an antifoaming agent in an amount of 0.02 parts by mass or more and 0.3 parts by mass or less per 100 parts by mass, so even when stored for a long time, it is difficult for aggregates to form in the binder composition, and a functional layer with excellent adhesive properties can be formed using the binder composition.

[0026] (courage)

[0027] The container has at least a receiving portion capable of receiving a binder composition. The container may consist only of a receiving portion, but from the perspective of facilitating the filling and extraction of the binder composition, it is preferable to have a receiving portion and a cap capable of sealing the opening of the receiving portion to seal the internal space of the receiving portion.

[0028] In addition, the shape of the container is not particularly limited and can be any shape, such as cylindrical, angular, or pouch-shaped.

[0029] An example of the shape of a container is described using FIG. 1. In FIG. 1, a binder product (100) for a secondary battery comprises a container (1) and a binder composition (2) contained within the container. Here, in FIG. 1, the container (1) comprises a cap (11) and a receiving portion (12). The internal space (14) of the container (1) is partitioned by the inner wall surface (13) of the receiving portion (12) and the cap (11), and the cap (11) seals the opening of the receiving portion (12). By separating the cap (11) from the receiving portion (12), the binder composition (2) can be extracted from the opening of the receiving portion (12).

[0030] <Contact angle with respect to water>

[0031] The contact angle of the inner wall surface of the receiving portion of the container with respect to water needs to be 80° or more as described above, preferably 100° or more, and more preferably 110° or more. It is inferred that if the contact angle of the inner wall surface of the receiving portion with respect to water is less than 80°, the affinity between the inner wall surface and the binder composition containing water becomes excessively high, thereby promoting the formation of aggregates due to contact between the inner wall surface and the binder composition, and thus the formation of aggregates in the binder composition after long-term storage cannot be sufficiently suppressed. Meanwhile, the upper limit of the contact angle of the inner wall surface of the receiving portion with respect to water is not particularly limited, but is, for example, 160° or less.

[0032] Here, the contact angle with water on the inner wall surface of the receiving section can be reduced by changing the material of the receiving section or by performing a hydrophobic treatment on the inner wall surface of the receiving section.

[0033] <Material>

[0034] The material of the container (in other words, the material of the receiving portion and / or optionally used cap) is not particularly limited and may be, for example, glass, resin, or metal. Among these, resin is preferred, polyethylene, polypropylene, and polycarbonate are more preferred, and polyethylene is even more preferred. That is, the container is preferably made of resin, more preferably made of polyethylene, polypropylene, or polycarbonate, and even more preferably made of polyethylene.

[0035] Meanwhile, regarding the material of the container, one type may be used alone, or two or more types may be used in combination. For example, as a receiving part constituting the container, a glass receiving part having a layer of resin formed on its surface (especially on the inner wall) may be used.

[0036] <Decimalization Processing>

[0037] Here, hydrophobization treatments that can be used to increase the contact angle of the inner wall surface of the receiving portion to water to a value greater than or equal to the aforementioned predetermined value include treatment with a silane coupling agent, treatment with a titanium coupling agent, treatment with an aluminum coupling agent, treatment with a fatty acid ester wax, and treatment with a fluoropolymer. These may be used individually or in combination of two or more types. Among these, treatment with a silane coupling agent and treatment with a fluoropolymer are preferred from the perspective of sufficiently increasing the contact angle of the inner wall surface of the receiving portion to water. That is, it is preferable that the inner wall surface of the receiving portion be coated by at least one of a layer (film) made of a silane coupling agent and a layer (film) made of a fluoropolymer.

[0038] <<Treatment by Silane Coupling Agent>>

[0039] Silane coupling agents are not particularly limited and include, for example, sulfur-containing silane coupling agents such as γ-mercaptopropyltrimethoxysilane, γ-mercaptomethyltrimethoxysilane, γ-mercaptomethyltriethoxysilane, γ-mercaptohexamethyldisilazane, bis(3-triethoxysilylpropyl)tetrasulfan, bis(3-triethoxysilylpropyl)disulfan; epoxy group-containing silane coupling agents such as γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane (3-glycidoxypropylmethyldimethoxysilane), β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane (3-glycidoxypropylmethyldiethoxysilane); Amino group-containing silane coupling agents such as N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane (γ-aminopropyltrimethoxysilane), γ-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane; Silane coupling agents containing (meth)acryloxy groups such as γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltris(β-methoxyethoxy)silane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-acryloxypropyltrimethoxysilane, etc.; silane coupling agents containing vinyl groups such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(β-methoxyethoxy)silane, vinyltrichlorosilane, vinyltriacetoxysilane, etc.; silane coupling agents containing chloropropyl groups such as 3-chloropropyltrimethoxysilane; silane coupling agents containing isocyanate groups such as 3-isocyanatepropyltriethoxysilane; Styryl group-containing silane coupling agents such as p-styryltrimethoxysilane; ureido group-containing silane coupling agents such as 3-ureidopropyltriethoxysilane; allyl group-containing silane coupling agents such as diallyldimethylsilane; alkoxy group-containing silane coupling agents such as tetraethoxysilane; phenyl group-containing silane coupling agents such as diphenyldimethoxysilane;Examples include fluorogroup-containing silane coupling agents such as trifluoropropyltrimethoxysilane; alkylgroup-containing silane coupling agents such as isobutyltrimethoxysilane and cyclohexylmethyldimethoxysilane; etc. These may be used individually or in combination of two or more types. Among these, epoxygroup-containing silane coupling agents are preferred, and 3-glycidoxypropylmethyldimethoxysilane is more preferred, from the perspective of further suppressing the formation of aggregates in the binder composition after long-term storage and further improving the adhesion of the resulting functional layer.

[0040] Meanwhile, treatment with a silane coupling agent is not particularly limited as long as a layer made of the silane coupling agent can be formed on the inner wall surface of the receiving portion, and known methods may be used. For example, a layer made of the silane coupling agent can be formed on the inner wall surface of the receiving portion by dissolving the silane coupling agent in a solvent such as water or cyclohexane, applying the obtained solution to the inner wall surface of the receiving portion, and then drying to remove the solvent.

[0041] <<Treatment with Fluoropolymer>>

[0042] Fluoropolymer resins are not particularly limited and examples include polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-ethylene copolymer, polyvinylidene fluoride, polychlorotrifluoroethylene, ethylene-chlorofluoroethylene copolymer, tetrafluoroethylene-perfluorodioxol copolymer, polyvinylidene fluoride, tetrafluoroethylene-propylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer, acrylic modified polytetrafluoroethylene, ester modified polytetrafluoroethylene, epoxy modified polytetrafluoroethylene, and silane modified polytetrafluoroethylene, as well as compounds containing perfluoropolyether groups. These may be used individually or in combination of two or more types. Among these, compounds containing perfluoropolyether groups are preferred.

[0043] Meanwhile, treatment with fluoropolymer resin is not particularly limited as long as a layer made of fluoropolymer resin can be formed on the inner wall surface of the receiving portion, and known methods may be used. For example, a fluoropolymer resin can be dissolved in a solvent such as water or cyclohexane, the resulting solution can be applied to the inner wall surface of the receiving portion, and then dried to remove the solvent, thereby forming a layer made of fluoropolymer resin on the inner wall surface of the receiving portion.

[0044] (Binder composition)

[0045] The binder composition contained in the receiving portion of the above-described container has a surface tension of 20 mN / m or more and 60 mN / m or less. The binder composition comprises at least a binder, an antifoaming agent, and water, and optionally comprises at least one selected from the group consisting of a preservative, an emulsifier, a wetting agent, and other components.

[0046] Surface Tension

[0047] As described above, the binder composition needs to have a surface tension of 20 mN / m or more and 60 mN / m or less, preferably 30 mN / m or more, preferably 50 mN / m or less, and more preferably 40 mN / m or less. If the surface tension of the binder composition is less than 20 mN / m, the adhesion of the functional layer is reduced. Although the reason for this is not clear, it is presumed that if the surface tension of the binder composition is less than 20 mN / m, the binder becomes more likely to adhere to the inner wall of the container in the void section, and if the film formed by the drying of the attached binder falls into the binder composition, the stability of the slurry composition is reduced as said film becomes a starting point. On the other hand, if the surface tension of the binder composition exceeds 60 mN / m, it is presumed that the affinity with the electrode active material particles or the current collector is reduced, and thus the adhesion of the functional layer is reduced. Furthermore, the viscosity stability of the slurry composition prepared using the binder composition is impaired due to a decrease in affinity with functional particles such as electrode active material particles.

[0048] Meanwhile, the surface tension of the binder composition can be controlled by changing the type and amount of the binder, defoamer, and optionally used emulsifier and wetting agent.

[0049] Binder

[0050] As for the binder, any polymer capable of being used as a binder can be used, provided that it possesses binding ability and is not particularly limited. For example, polyethylene, polypropylene, acid-modified polyolefin, fluorovinyl polymer, hydroxyl-containing olefin polymer, acrylic acid polymer, acrylic polymer, acrylonitrile polymer, diene polymer, silicon-containing polymer, etc., may be used. These may be used individually or in combination of two or more types. Among these, for example, when the binder composition is used to form a negative electrode composite layer, a diene polymer is preferred.

[0051] In addition, it is preferable that the binder has at least one of an amide group and a hydroxyalkyl group. According to the inventors' investigation, it has been found that while binders having amide and / or hydroxyalkyl groups have excellent binding ability, foaming is prone to occur during storage or transportation, and the formation of aggregates is promoted as the contact area between the binder composition and the inner wall surface of the receiving portion increases.

[0052] However, according to the binder product of the present invention, since the contact angle with water on the inner wall surface of the receiving portion is greater than a predetermined value and the binder composition contains a predetermined amount of defoaming agent, it is possible to sufficiently suppress the formation of aggregates in the binder composition after long-term storage, even when a polymer having amide groups and / or hydroxyalkyl groups is used as the binder.

[0053] Therefore, if the binder used has an amide group and / or a hydroxyalkyl group, the adhesion of the resulting functional layer can be further improved while sufficiently suppressing the formation of aggregates in the binder composition after long-term storage.

[0054] The method of introducing amide groups and / or hydroxyalkyl groups into a binder is not particularly limited, but a method of preparing a binder as a polymer using an amide group-containing monomer and / or a hydroxyalkyl group-containing monomer is preferred.

[0055] That is, the binder preferably comprises at least one of an amide group-containing monomer unit and a hydroxyalkyl group-containing monomer unit.

[0056] Meanwhile, examples of hydroxyalkyl groups include hydroxymethyl groups, hydroxyethyl groups, and hydroxypropyl groups, and among these, hydroxyethyl groups are preferred.

[0057] <<Amide group-containing monomer unit>>

[0058] Examples of amide-containing monomers capable of forming amide-containing monomer units include acrylamide, methacrylamide, dimethylacrylamide, diethylacrylamide, and diacetoneacrylamide. These may be used individually or in combination of two or more. Among these, acrylamide is preferred.

[0059] <<Hydroxyalkyl group-containing monomer unit>>

[0060] Examples of hydroxyalkyl group-containing monomers capable of forming hydroxyalkyl group-containing monomer units include hydroxymethylacrylamide, hydroxyethylacrylamide, hydroxypropylacrylamide, hydroxymethylmethacrylamide, hydroxyethylmethacrylamide, hydroxypropylmethacrylamide, hydroxymethylacrylate, hydroxyethylacrylate, hydroxypropylacrylate, hydroxybutylacrylate, hydroxymethylmethacrylate, hydroxyethylmethacrylate, hydroxypropylmethacrylate, and hydroxybutylmethacrylate. These may be used individually or in combination of two or more. Among these, hydroxyethylacrylate is preferred.

[0061] Meanwhile, in the present invention, a monomer having both a hydroxyalkyl group and an amide group is included in the hydroxyalkyl group-containing monomer and is not included in the amide group-containing monomer.

[0062] <<Content Ratio>>

[0063] In addition, the sum of the content ratio of amide group-containing monomer units and the content ratio of hydroxyalkyl group-containing monomer units in the binder is preferably 0.05 mass% or more, preferably 5 mass% or less, more preferably 3 mass% or less, and even more preferably 2 mass% or less, based on 100 mass% of the total monomer units contained in the binder. If the sum of the content ratios of amide group-containing monomer units and hydroxyalkyl group-containing monomer units is 0.05 mass% or more, the adhesion of the functional layer can be further improved, and if it is 5 mass% or less, foaming of the binder composition is suppressed, and the formation of aggregates in the binder composition after long-term storage can be sufficiently suppressed.

[0064] Diene-based polymers

[0065] Here, the composition of a diene-based polymer suitable as a binder is described. The diene-based polymer comprises an aliphatic conjugated diene monomer unit, and preferably comprises at least one of the above-described amide group-containing monomer unit and hydroxyalkyl group-containing monomer unit. Additionally, the diene-based polymer may optionally comprise monomer units other than the aliphatic conjugated diene monomer unit, the amide group-containing monomer unit, and the hydroxyalkyl group-containing monomer unit (other monomer units).

[0066] [Aliphatic conjugated diene monomer unit]

[0067] Examples of aliphatic conjugated diene monomers capable of forming aliphatic conjugated diene monomer units include 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), and 2,3-dimethyl-1,3-butadiene. These may be used individually or in combination of two or more types. Among these, 1,3-butadiene is preferred.

[0068] Here, the content ratio of aliphatic conjugated diene monomer units in the binder is preferably 25 mass% or more, more preferably 30 mass% or more, more preferably 60 mass% or less, and more preferably 50 mass% or less, with the total monomer units contained in the binder being 100 mass%.

[0069] [Other monomer units]

[0070] Other monomer units may include monomer units derived from known monomers copolymerizable with the aforementioned aliphatic conjugated diene monomer, amide group-containing monomer, and hydroxyalkyl group-containing monomer. Examples of such monomers include aromatic vinyl monomers, nitrile group-containing monomers, (meth)acrylic acid ester monomers, and carboxylic acid group-containing monomers. These may be used individually or in combination of two or more types. Among these, aromatic vinyl monomers, (meth)acrylic acid ester monomers, and carboxylic acid group-containing monomers are preferred, aromatic vinyl monomers and carboxylic acid group-containing monomers are more preferred, and aromatic vinyl monomers are even more preferred. That is, the diene-based polymer is particularly preferably an aliphatic conjugated diene-aromatic vinyl copolymer comprising an aliphatic conjugated diene monomer unit and an aromatic vinyl monomer unit.

[0071] Meanwhile, in the present invention, "(meth)acrylic" means acrylic and / or methacrylic.

[0072] Examples of aromatic vinyl monomers capable of forming aromatic vinyl monomer units include styrene, α-methylstyrene, vinyltoluene, and divinylbenzene. These may be used individually or in combination of two or more. Among these, styrene is preferred.

[0073] Here, the content ratio of aromatic vinyl monomer units in the binder is preferably 5 mass% or more, more preferably 10 mass% or more, preferably 80 mass% or less, and more preferably 70 mass% or less, with the total monomer units contained in the binder being 100 mass%.

[0074] (Meth)acrylic acid ester monomers capable of forming (meth)acrylic acid ester monomer units include alkyl acrylates such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, and 2-ethylhexyl acrylate; alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, and 2-ethylhexyl methacrylate; Examples include hydroxyl group-containing (meth)acrylic acid esters such as 2-hydroxyethyl acrylate, 2-hydroxymethacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, and 3-chloro-2-hydroxypropyl methacrylate. These may be used individually or in combination of two or more types. Among these, hydroxyl group-containing (meth)acrylic acid esters are preferred, and 2-hydroxyethyl acrylate is more preferred.

[0075] Here, the content ratio of (meth)acrylic acid ester monomer units in the binder is preferably 0.3 mass% or more, more preferably 0.5 mass% or more, even more preferably 0.6 mass% or more, preferably 2 mass% or less, and more preferably 1.5 mass% or less, with the total monomer units contained in the binder being 100 mass%.

[0076] Examples of monomers containing carboxylic acid groups include monocarboxylic acids and their derivatives, dicarboxylic acids and their acid anhydrides and their derivatives.

[0077] Examples of monocarboxylic acids include acrylic acid, methacrylic acid, and crotonic acid.

[0078] Derivatives of monocarboxylic acid include 2-ethylacrylic acid, isocrotonic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, α-chloro-β-E-methoxyacrylic acid, β-diaminoacrylic acid, etc.

[0079] Examples of dicarboxylic acids include maleic acid, fumaric acid, and itaconic acid.

[0080] Derivatives of dicarboxylic acids include methyl maleic acid, dimethyl maleic acid, phenyl maleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid, or maleic acid monoesters such as butyl maleic acid, nonyl maleic acid, decyl maleic acid, dodecyl maleic acid, octadecyl maleic acid, and fluoroalkyl maleic acid.

[0081] Examples of acid anhydrides of dicarboxylic acids include maleic anhydride, acrylic anhydride, methyl maleic anhydride, dimethyl maleic anhydride, and citraconic anhydride.

[0082] These may be used as a single type or in combination of two or more types. Among these, dicarboxylic acids, their derivatives, and their acid anhydrides are preferred, and itaconic acid is more preferred.

[0083] Here, the content ratio of the carboxylic acid group-containing monomer unit in the binder is preferably 2 mass% or more, more preferably 3 mass% or more, preferably 8 mass% or less, more preferably 6 mass% or less, and even more preferably 4 mass% or less, with the total monomer unit contained in the binder being 100 mass%.

[0084] <<Method of Preparing Binder>>

[0085] The method for preparing the binder is not particularly limited, and a method of polymerizing a monomer composition containing the monomer described above can be used by a known method.

[0086] Here, the ratio of each monomer in the monomer composition is typically equal to the ratio of each monomer unit in the desired binder. Furthermore, the polymerization method of the binder is not particularly limited and any method such as solution polymerization, suspension polymerization, bulk polymerization, or emulsion polymerization may be used. Additionally, for the polymerization reaction, addition polymerization such as ionic polymerization, radical polymerization, or living radical polymerization may be used. Moreover, the emulsifiers, dispersants, polymerization initiators, and polymerization aids used in the polymerization may be those commonly used, and the amounts used may also be those commonly used. Furthermore, seed particles may be used to perform seed polymerization during polymerization. Meanwhile, a binder prepared using suspension polymerization or emulsion polymerization dispersed in an aqueous solvent is preferred in that it offers excellent handling properties during transport and storage.

[0087] Antifoamer

[0088] The binder composition needs to include an antifoaming agent. By including an antifoaming agent, the binder composition in the container receiving portion can suppress foam generation when stored for a long period, thereby suppressing the formation of aggregates caused by contact with the inner wall surface of the receiving portion.

[0089] Here, examples of defoaming agents include silicone-based defoaming agents, mineral oil-based defoaming agents (modified hydrocarbon oils based on mineral oil), and polymer-based defoaming agents. One type of defoaming agent may be used alone, or two or more types may be used in combination. Furthermore, as for the defoaming agent, a mineral oil-based defoaming agent is preferred from the perspective of further suppressing the formation of aggregates in the binder composition after long-term storage while further improving the adhesion of the functional layer.

[0090] Here, known defoaming agents may be used, or various commercially available defoaming agents may be selected and used. For example, "DF6351" (manufactured by Seiko PMC) may be preferably used as a mineral oil-based defoaming agent.

[0091] <<Content>>

[0092] The amount of defoaming agent included in the binder composition needs to be at least 0.02 parts by mass and no more than 0.3 parts by mass per 100 parts by mass of binder, preferably 0.1 parts by mass or less, and more preferably 0.06 parts by mass or less. If the content of the defoaming agent is less than 0.02 parts by mass per 100 parts by mass of binder, the formation of aggregates in the binder composition after long-term storage cannot be sufficiently suppressed, and the adhesion of the functional layer is reduced. On the other hand, if the content of the defoaming agent exceeds 0.3 parts by mass per 100 parts by mass of binder, it is presumed that the adhesion of the functional layer is reduced because it inhibits adhesion by the binder by being present between electrode active material particles or at the binding interface between electrode active material particles and the current collector.

[0093] Preservatives

[0094] It is preferable that the binder composition includes a preservative. By including a preservative in the binder composition, bacterial growth is inhibited, and the formation of aggregates can be further inhibited. The preservative exhibits a particularly good effect in inhibiting bacterial growth with respect to a binder prepared using a suspension polymerization method or an emulsion polymerization method dispersed in an aqueous solvent.

[0095] Examples of preservatives include known preservatives such as isothiazoline compounds or 2-bromo-2-nitro-1,3-propanediol. Herein, isothiazoline compounds are not particularly limited and may be those described in Japanese Patent Publication No. 2013-211246, Japanese Patent Publication No. 2005-097474, and Japanese Patent Publication No. 2013-206624. Meanwhile, one type of preservative may be used alone, or two or more types may be used in combination. And as preservatives, 1,2-benzisothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one, and 2-bromo-2-nitro-1,3-propanediol are preferred, and 1,2-benzisothiazolin-3-one is more preferred.

[0096] The amount of preservative included in the binder composition is preferably 0.01 parts by mass or more per 100 parts by mass of binder, preferably 0.5 parts by mass or less, more preferably 0.4 parts by mass or less, and even more preferably 0.3 parts by mass or less. If the content of the preservative is 0.01 parts by mass or more per 100 parts by mass of binder, the formation of aggregates in the binder composition after long-term storage can be further suppressed, and if it is 0.5 parts by mass or less, the adhesion of the functional layer can be sufficiently improved.

[0097] Emulsifier

[0098] It is preferable that the binder composition includes an emulsifier. By including an emulsifier in the binder composition, the surface tension of the binder composition can be controlled to an appropriate value, and as a result, the formation of aggregates in the binder composition after long-term storage can be effectively suppressed while sufficiently improving the adhesion of the functional layer.

[0099] Herein, the emulsifiers include nonionic emulsifiers such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenol ethers, polyoxyethylene alkyl esters, and polyoxyethylene sorbitan alkyl esters; anionic emulsifiers such as alkylbenzene sulfonates (e.g., potassium dodecylbenzenesulfonate, sodium dodecylbenzenesulfonate), higher alcohol sulfate esters, alkyl sulfosuccinates, sodium salt of β-naphthalenesulfonic acid formalin condensate, dodecyl diphenyl oxide disulfonate (e.g., sodium dodecyl diphenyl oxide disulfonate), and lauryl sulfate (e.g., sodium lauryl sulfate); and cationic emulsifiers such as alkyltrimethylammonium chloride, dialkylammonium chloride, and benzylammonium chloride. Examples include copolymer emulsifiers such as sulfoesters of α,β-unsaturated carboxylic acids, sulfate esters of α,β-unsaturated carboxylic acids, and sulfoalkylaryl ethers.

[0100] One type of emulsifier may be used alone, or two or more types may be used in combination. As for the emulsifier, an anionic emulsifier is preferred from the perspective of further suppressing the formation of aggregates in the binder composition after long-term storage and further improving the adhesion of the functional layer, alkylbenzene sulfonate, sodium salt of formalin condensate of β-naphthalenesulfonic acid, dodecyl diphenyl oxide disulfonate, and lauryl sulfate are more preferred, and potassium dodecylbenzenesulfonate, sodium dodecylbenzenesulfonate, sodium salt of formalin condensate of β-naphthalenesulfonic acid, sodium dodecyl diphenyl oxide disulfonate, and sodium lauryl sulfate are more preferred.

[0101] The amount of emulsifier included in the binder composition is preferably 0.4 parts by mass or more per 100 parts by mass of binder, preferably 5 parts by mass or less, and more preferably 2 parts by mass or less. If the content of the emulsifier is 0.4 parts by mass or more per 100 parts by mass of binder, the viscosity stability of the slurry composition prepared using the binder composition can be increased while further improving the adhesion of the functional layer. In addition, the viscosity stability of the binder composition can be improved. On the other hand, if the content of the emulsifier is 5 parts by mass or less per 100 parts by mass of binder, the adhesion of the functional layer can be sufficiently improved.

[0102] Solid content concentration

[0103] Here, the binder composition preferably has a solid content concentration of 30 mass% or more, more preferably 40 mass% or more, preferably 60 mass% or less, and more preferably 50 mass% or less. If the solid content concentration of the binder composition is 30 mass% or more, when a slurry composition prepared using the binder composition is dried to form a functional layer, the uneven distribution of the binder within the resulting functional layer can be suppressed, thereby enabling even better adhesion to the functional layer. On the other hand, if the solid content concentration of the binder composition is 60 mass% or less, the formation of aggregates after long-term storage can be further suppressed.

[0104] Method for preparing a binder composition

[0105] A binder composition can be obtained by mixing each of the above-described components in the presence of water.

[0106] For example, a binder composition can be prepared by adding and mixing an antifoaming agent, and, if necessary, an emulsifier, a preservative, and / or other components to an aqueous solution or aqueous dispersion of a binder obtained after a polymerization reaction. Meanwhile, the antifoaming agent, the emulsifier, and the other components may be those that were already present in the aqueous solution or aqueous dispersion of the binder.

[0107] In addition, as other components, a wetting agent may be used, for example, to control the surface tension of the binder composition.

[0108] Method for manufacturing binder products

[0109] The binder product of the present invention is obtained by filling the receiving portion of the container with the binder composition. The method of filling the receiving portion of the container with the binder composition is not particularly limited and known methods may be used.

[0110] Here, it is preferable that the porosity of the binder product be 10 volume% or less. If the porosity is 10 volume% or less, the formation of aggregates in the binder composition after long-term storage can be further suppressed, and the adhesion of the functional layer can be further improved.

[0111] Meanwhile, it is preferable to store the binder product obtained as described above in an environment where the temperature is 5°C or higher and 40°C or lower. Storing the binder product within this temperature range can prevent the deterioration of the binder while sufficiently suppressing the formation of aggregates within the binder composition. As a result, the adhesion of the resulting functional layer can be further improved.

[0112] (Uses of binder products)

[0113] In the binder product of the present invention, the binder composition filled in the receiving portion of the container can be used, for example, to form a functional layer such as an electrode composite layer.

[0114] Hereinafter, a case is described in which an electrode slurry composition is prepared using a binder composition included in the binder product of the present invention and an electrode is formed, but the present invention is not limited thereto.

[0115] Electrode Slurry Composition

[0116] The electrode slurry composition comprises electrode active material particles, the binder composition, and other components used as needed.

[0117] <<Electrode Active Material Particles>>

[0118] The electrode active material particles may be positive electrode active material particles or negative electrode active material particles. The electrode active material particles are materials that exchange electrons within the battery. The following describes the case where it is used in a lithium-ion secondary battery.

[0119] Positive electrode active material particles are particles composed of compounds (positive electrode active materials) capable of absorbing and releasing lithium ions. Positive electrode active materials are broadly classified into those composed of inorganic compounds and those composed of organic compounds.

[0120] Examples of positive electrode active materials composed of inorganic compounds include transition metal oxides, complex oxides of lithium and transition metals, and transition metal sulfides. The above transition metals used include Fe, Co, Ni, and Mn. Specific examples of inorganic compounds used as positive electrode active materials include lithium-containing complex metal oxides such as LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiFePO4, and LiFeVO4; transition metal sulfides such as TiS2, TiS3, and amorphous MoS2; and Cu2V2O3, amorphous V2O-P2O5, MoO3, V2O5, and V6O. 13 Examples include transition metal oxides. These compounds may be partially elementally substituted.

[0121] Examples of positive electrode active materials composed of organic compounds include polyaniline, polypyrrole, polyacene, disulfide compounds, polysulfide compounds, N-fluoropyridinium salts, etc. Meanwhile, the positive electrode active material may be a mixture of the above-mentioned inorganic compounds and organic compounds.

[0122] Meanwhile, the positive electrode active material particles may be used as a single type or in combination of two or more types.

[0123] Examples of negative electrode active materials constituting the negative electrode active material particles include allotropes of carbon such as graphite or coke. The negative electrode active material composed of the above-mentioned allotropes of carbon may also be used in the form of a mixture or coating with metals, metal salts, oxides, etc. Additionally, as negative electrode active materials, oxides or sulfates of silicon, tin, zinc, manganese, iron, nickel, etc., lithium alloys such as metallic lithium, Li-Al, Li-Bi-Cd, Li-Sn-Cd, lithium transition metal nitrides, silicon, etc. may be used.

[0124] Meanwhile, the negative electrode active material particles may be used as a single type or in combination of two or more types.

[0125] <<Binder Composition>>

[0126] As a binder composition, the above-described binder composition containing a binder may be used. The amount of binder used is preferably in the range of 0.1 parts by mass or more and 50 parts by mass or less, more preferably 0.5 parts by mass or more and 20 parts by mass or less, and even more preferably 1 part by mass or more and 10 parts by mass or less, with respect to reducing the internal resistance of the secondary battery while sufficiently ensuring the adhesion of the obtained electrode composite layer.

[0127] Other ingredients

[0128] Other components that can be incorporated into the electrode slurry composition include known components such as conductive materials and thickeners, without being specifically limited. Meanwhile, one type of other component may be used alone, or two or more types may be used in combination.

[0129] <<Preparation of Slurry Composition for Electrodes>>

[0130] The method of preparing the electrode slurry composition is not particularly limited.

[0131] For example, an electrode slurry composition can be prepared by mixing a binder composition, electrode active material particles, and other components used as needed in the presence of a dispersion medium such as water. The mixing method is not particularly limited and can be mixed using a stirrer or a disperser that can be commonly used.

[0132] Electrode

[0133] An electrode can be obtained by forming an electrode composite layer on a current collector using the electrode slurry composition described above. Specifically, the electrode composite layer can be formed using the following method.

[0134] 1) A method of applying an electrode slurry composition to the surface of a current collector and then drying it;

[0135] 2) A method of immersing a current collector in an electrode slurry composition and then drying it; and

[0136] 3) A method of applying an electrode slurry composition onto a release substrate, drying to produce an electrode composite layer, and transferring the obtained electrode composite layer onto the surface of a current collector.

[0137] Among these, the method of 1) above is particularly preferred in that it is easy to control the thickness of the electrode composite layer. Specifically, the method of 1) includes a process of applying an electrode slurry composition onto a current collector (application process) and a process of drying the electrode slurry composition applied onto the current collector to form an electrode composite layer on the current collector (drying process).

[0138] Coating Process

[0139] The method of applying the above electrode slurry composition onto the current collector is not particularly limited and known methods may be used. Specifically, the doctor blade method, dip method, reverse roll method, direct roll method, gravure method, extrusion method, brush application method, etc. may be used as the application method. At this time, the slurry composition may be applied only to one side of the current collector or to both sides. The thickness of the slurry film on the current collector after application and before drying can be appropriately set according to the thickness of the electrode composite layer obtained by drying.

[0140] Here, as the current collector to which the electrode slurry composition is applied, a material having electrical conductivity and electrochemical durability is used. Specifically, as the current collector, for example, a current collector made of iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, platinum, etc., may be used. Meanwhile, the above materials may be used as a single type or in combination of two or more types.

[0141] <<Drying Process>>

[0142] The method for drying the electrode slurry composition on the current collector is not particularly limited and any known method may be used. For example, drying methods using hot air, hot air, low humidity air, vacuum drying, or drying methods using infrared rays or electron beams may be used. By drying the slurry composition on the current collector in this way, an electrode composite layer is formed on the current collector, thereby obtaining an electrode having a current collector and an electrode composite layer.

[0143] Meanwhile, after the drying process, pressure treatment may be applied to the electrode composite layer using a mold press or a roll press. By applying pressure, the adhesion of the electrode composite layer can be further improved, and at the same time, the resulting electrode composite layer can be made denser.

[0144] The electrode obtained as described above can be suitably used as an electrode for a secondary battery, such as a lithium-ion secondary battery.

[0145] [Example]

[0146] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. Meanwhile, in the following description, "%" and "parts" indicating amounts are based on mass unless otherwise specified.

[0147] In addition, in a polymer produced by polymerizing multiple types of monomers, the proportion of a monomer unit formed by polymerizing a certain monomer in the polymer is, unless otherwise noted, usually equal to the proportion (input ratio) of that certain monomer in the total monomers used in the polymerization of the polymer.

[0148] In addition, in the examples and comparative examples, the contact angle with water of the inner wall surface of the receiving portion, the surface tension of the binder composition, the suppression of aggregate formation in the binder composition after long-term storage, the viscosity stability of the binder composition, the viscosity stability of the negative electrode slurry composition, and the adhesion of the negative electrode composite layer were evaluated by the following method.

[0149] <Contact angle with respect to water>

[0150] A contact angle meter (manufactured by Kyowa Interface Chemical Co., Ltd., product name "DMs-400") was used as a measuring device. Water was dropped onto the inner wall of the receiving section, and the contact angle was calculated by analyzing the image acquired from the horizontal direction using the contact angle meter based on the tangent method.

[0151] Surface Tension

[0152] The surface tension of the binder composition for secondary batteries was measured by the platinum plate method using an automatic surface tension meter ("DY-300" manufactured by Kyowa Interface Science Co., Ltd.) under an environment of 25°C.

[0153] Inhibition of aggregate formation

[0154] The manufactured binder product was placed in a constant temperature bath with adjustable storage temperature and stored at 60°C for 30 days. At storage days 0, 10, and 20, the binder product was subjected to shaking operations in all directions (up, down, left, and right). After 30 days of storage, aggregates in the binder composition were captured on a 200-mesh stainless steel wire mesh. The captured aggregates were washed with water and dried using a dryer at 80°C under atmospheric pressure for 1 hour to evaporate the moisture. Then, the amount of aggregates after drying (mass%) was calculated based on 100 mass% of the solid content in the binder composition before storage, and evaluated according to the following criteria. A smaller amount indicates that the formation of aggregates is suppressed.

[0155] A: Amount of aggregates less than 0.05 mass%

[0156] B: Amount of aggregates 0.05 mass% or more and less than 0.10 mass%

[0157] C: Amount of aggregates is 0.10 mass% or more

[0158] <Viscosity Stability (Binder Composition)>

[0159] The viscosity of the prepared binder composition (viscosity before storage) was measured using a Type B viscometer under conditions of 25°C and 60 rpm. Subsequently, after storing the binder product in the same manner as described in <Inhibition of Aggregate Formation> above, the viscosity of the binder composition (viscosity after storage) was measured using a Type B viscometer under the same conditions as above. A change exceeding ±5% relative to the viscosity before storage was determined to indicate a viscosity abnormality and evaluated according to the following criteria.

[0160] A: No abnormalities in viscosity

[0161] B: Viscosity abnormality

[0162] <Viscosity Stability (Negative Electrode Slurry Composition)>

[0163] The viscosity η0 of the prepared negative electrode slurry composition was measured using a Type B viscometer under conditions of 25°C and 60 rpm. Subsequently, after allowing the negative electrode slurry composition to stand at 25°C for 72 hours, the viscosity η1 was measured under the same conditions as η0. Then, the viscosity change rate defined by the equation: Δη = |η1 - η0| / η0 × 100(%) was calculated and evaluated according to the following criteria. A smaller value of the viscosity change rate Δη indicates that the negative electrode slurry composition has superior viscosity stability.

[0164] A: Viscosity change rate Δη is less than 20%

[0165] B: Viscosity change rate Δη is 20% or more and less than 50%

[0166] C: Viscosity change rate Δη is 50% or more and less than 80%

[0167] D: Viscosity change rate Δη is 80% or more

[0168] <Adhesion>

[0169] Cellophane tape (as specified in JIS Z1522) was attached to the surface of the negative electrode composite layer of the fabricated negative electrode, and the stress was measured when one end of the current collector was pulled vertically at a tensile speed of 50 mm / min and peeled off (the cellophane tape was fixed to the test table). A total of three measurements were performed, and the average value was calculated and set as the peel strength, which was evaluated according to the following criteria. A higher peel strength value indicates that the negative electrode composite layer has excellent adhesion and is firmly attached to the current collector.

[0170] A: Peel strength 12 N / m or higher

[0171] B: Peel strength 8 N / m or more and less than 12 N / m

[0172] C: Peel strength less than 8 N / m

[0173] (Example 1)

[0174] Preparation of Courage

[0175] A polyethylene container (capacity: 20 liters) consisting of a receptacle and a cap as shown in Fig. 1 was prepared. The receptacle has an opening, and the internal space can be sealed by twisting the cap into the opening to seal it. A silane coupling agent (3-glycidoxypropylmethyldimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-402") dissolved at 2% in weakly acidic water (pH = 4-6) was applied to the inner wall surface of the receptacle of this polyethylene container, and the container was prepared for use in manufacturing binder products by performing a hydrophobic treatment by drying at 80°C for 1 hour. The contact angle with water was measured on the inner wall surface of this receptacle. The results are shown in Table 1.

[0176] <Preparation of Binder Composition and Binder Product>

[0177] In a 5 MPa pressure vessel equipped with a stirrer, 30 parts of 1,3-butadiene, 40 parts of styrene, 9 parts of acrylonitrile, 17 parts of methyl methacrylate, 4 parts of methacrylic acid, 0.5 parts of t-dodecyl mercaptan as a molecular weight adjusting agent, 9 parts of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of ion-exchanged water, and 1.0 parts of potassium persulfate as a polymerization initiator were added, and after stirring sufficiently, the mixture was heated to 50°C to start polymerization, and seed particles (particulate diene-based polymers) were obtained.

[0178] In addition, 4 parts of the seed particles, 45 parts of 1,3-butadiene, 14 parts of styrene, 26 parts of acrylonitrile, 12 parts of methyl methacrylate, 1 part of acrylic acid, 1 part of itaconic acid, 1 part of acrylamide, 1 part of t-dodecyl mercaptan and 0.5 parts of α-methylstyrene dimer as molecular weight adjusters, 1 part of sodium dodecyl diphenyl oxide disulfonate and 0.1 parts of sodium salt of β-naphthalenesulfonic acid formalin condensate as emulsifiers, 150 parts of ion-exchanged water, and 1.0 part of potassium persulfate as a polymerization initiator were added to a 5 MPa pressure vessel equipped with a stirrer, and after sufficient stirring, the mixture was heated to 50°C to start polymerization. The reaction was stopped by cooling when the polymerization conversion rate reached 96%. A 5% aqueous sodium hydroxide solution was added to the aqueous dispersion containing the obtained diene-based polymer to adjust the pH to 8. Subsequently, unreacted monomers were removed by heated vacuum distillation. Afterward, the mixture was cooled to below 30°C.

[0179] To an aqueous dispersion containing a diene-based polymer after cooling, 0.05 parts of a mineral oil-based defoamer (manufactured by Seiko PMC, product name "DF6351") as a defoamer and 0.1 parts of an isothiazoline-based compound (1,2-benzisothiazolin-3-one) as a preservative were added to 100 parts of the binder, and after filtering with a 200-mesh stainless steel wire mesh, the mixture was filled into the container of the above-mentioned container to obtain a binder product containing a binder composition (18 liters). The porosity of this binder product was 10 volume%. Meanwhile, the amount of emulsifier included in the binder composition was 1.4 parts per 100 parts of the binder (the sum of sodium dodecylbenzenesulfonate introduced by the seed particles, and sodium dodecyldiphenyloxide disulfonate and sodium β-naphthalenesulfonate formalin condensate used in the second stage of polymerization). In addition, using this binder product, the inhibition of aggregate formation in the binder composition after long-term storage and the viscosity stability of the binder composition were evaluated. The results are shown in Table 1.

[0180] <Preparation of Slurry Composition for Negative Electrode>

[0181] A mixture was obtained by adding 100 parts of graphite as a negative electrode active material particle, 0.2 parts of carbon black (manufactured by Denka, product name “HS-100”) as a conductive material, and 1.0 parts of a 2% aqueous solution of carboxymethylcellulose (manufactured by Nippon Paper Chemical, product name “MAC-500LC”) as a water-soluble polymer as an equivalent solid content to a planetary mixer equipped with a disperser. The obtained mixture was adjusted to a solid content concentration of 60% with ion-exchanged water and mixed at 25°C for 60 minutes. Next, the mixture was adjusted to a solid content concentration of 53% with ion-exchanged water and mixed again at 25°C for 10 minutes to obtain a mixture. To the obtained mixture, 2.0 parts as an equivalent solid content of the binder composition contained in the binder product after long-term storage under the same conditions as the “inhibition of aggregate formation” evaluation, and ion-exchanged water were added, and the final solid content concentration was adjusted to 48%. After mixing again for 10 minutes, a negative electrode slurry composition was obtained by degassing under reduced pressure. Viscosity stability was evaluated using this negative electrode slurry composition. The results are shown in Table 1.

[0182] The Production of the Play

[0183] The above negative electrode slurry composition was applied using a comma coater onto a 15 μm thick copper foil current collector, and after drying, the mass per unit area was 9 mg / cm² 2 It was coated and dried. This drying was carried out by conveying the copper foil through a 60°C oven at a speed of 0.5 m / min for 2 minutes. Subsequently, it was heat-treated at 120°C for 2 minutes to obtain a negative electrode material. Then, the negative electrode material was rolled using a roll press, so that the density of the negative electrode composite layer was 1.70 g / cm³ 3 A negative electrode was obtained. Using this negative electrode, the adhesion of the negative electrode composite layer was evaluated. The results are shown in Table 1.

[0184] (Example 2)

[0185] A binder composition and a binder product were prepared as follows. Except for that, a container, a slurry composition for the negative electrode, and a negative electrode were prepared in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 1.

[0186] <Preparation of Binder Composition and Binder Product>

[0187] In a 5 MPa pressure vessel equipped with a stirrer, 60 parts of 1,3-butadiene, 38 parts of styrene, 2 parts of methacrylic acid, 0.2 parts of t-dodecyl mercaptan as a molecular weight adjusting agent, 4 parts of sodium dodecyl diphenyl oxide disulfonate as an emulsifier, 150 parts of ion-exchanged water, and 0.5 parts of potassium persulfate as a polymerization initiator were added, and after stirring thoroughly, the mixture was heated to 50°C to start polymerization and seed particles (particulate diene-based polymer) were obtained.

[0188] In addition, 6 parts of the seed particles, 33 parts of 1,3-butadiene, 62 parts of acrylonitrile, 4 parts of itaconic acid, 1 part of hydroxyethyl acrylate, 0.5 parts of t-dodecyl mercaptan as a molecular weight adjuster, 0.5 parts of sodium dodecyl diphenyl oxide disulfonate as an emulsifier, 150 parts of ion-exchanged water, and 1.0 parts of potassium persulfate as a polymerization initiator were added to a 5 MPa pressure vessel equipped with a stirrer, and after sufficient stirring, the mixture was heated to 50°C to start polymerization. The reaction was stopped by cooling when the polymerization conversion rate reached 96%. A 5% aqueous sodium hydroxide solution was added to the aqueous dispersion containing the obtained diene-based polymer to adjust the pH to 8. Subsequently, unreacted monomers were removed by heated vacuum distillation. Afterward, the mixture was cooled to 30°C or lower.

[0189] Subsequent operations were performed in the same manner as in Example 1 to obtain a binder composition and a binder product. Meanwhile, the amount of emulsifier included in the binder composition was 0.7 parts per 100 parts of binder (the sum of sodium dodecyl diphenyl oxide disulfonate introduced by the seed particles and sodium dodecyl diphenyl oxide disulfonate used in the second polymerization).

[0190] (Examples 3, 4)

[0191] Except for changing the amount of the mineral oil-based defoamer used as the defoamer to 0.3 parts (Example 3) and 0.02 parts (Example 4) when preparing the binder composition, the process was the same as in Example 1. A container, a binder composition, a binder product, a slurry composition for the negative electrode, and a negative electrode were prepared, and various evaluations were performed. The results are shown in Table 1.

[0192] (Example 5)

[0193] A binder composition and a binder product were prepared as follows. Except for that, a container, a slurry composition for the negative electrode, and a negative electrode were prepared in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 1.

[0194] <Preparation of Binder Composition and Binder Product>

[0195] Seed particles (particulate diene-based polymers) were obtained in the same manner as in Example 1.

[0196] In addition, 4 parts of the seed particles, 45 parts of 1,3-butadiene, 14 parts of styrene, 26 parts of acrylonitrile, 12 parts of methyl methacrylate, 1 part of acrylic acid, 1 part of itaconic acid, 1 part of acrylamide, 1 part of t-dodecyl mercaptan and 0.5 parts of α-methylstyrene dimer as molecular weight adjusters, 0.2 parts of sodium dodecyl diphenyl oxide disulfonate as an emulsifier, 150 parts of ion-exchanged water, and 1.0 part of potassium persulfate as a polymerization initiator were added to a 5 MPa pressure vessel equipped with a stirrer, and after stirring sufficiently, the mixture was heated to 50°C to start polymerization. The reaction was stopped by cooling when the polymerization conversion rate reached 96%. A 5% aqueous sodium hydroxide solution was added to the aqueous dispersion containing the obtained diene-based polymer to adjust the pH to 8. After that, unreacted monomers were removed by heated vacuum distillation. Then, the temperature was cooled to below 30°C.

[0197] Subsequent operations were performed in the same manner as in Example 1 to obtain a binder composition and a binder product. Meanwhile, the amount of emulsifier included in the binder composition was 0.5 parts per 100 parts of binder (the sum of sodium dodecylbenzenesulfonate introduced by the seed particles and sodium dodecyldiphenyloxide disulfonate used in the second polymerization).

[0198] (Example 6)

[0199] A binder composition and a binder product were prepared as follows. Except for that, a container, a slurry composition for the negative electrode, and a negative electrode were prepared in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 1.

[0200] <Preparation of Binder Composition and Binder Product>

[0201] Seed particles (particulate diene-based polymers) were obtained in the same manner as in Example 1.

[0202] In addition, 4 parts of the seed particles, 45 parts of 1,3-butadiene, 14 parts of styrene, 26 parts of acrylonitrile, 12 parts of methyl methacrylate, 1 part of acrylic acid, 1 part of itaconic acid, 1 part of acrylamide, 1 part of t-dodecyl mercaptan and 0.5 parts of α-methylstyrene dimer as molecular weight adjusters, 4 parts of sodium dodecyl diphenyl oxide disulfonate and 0.8 parts of sodium salt of β-naphthalenesulfonic acid formalin condensate as emulsifiers, 150 parts of ion-exchanged water, and 1.0 part of potassium persulfate as a polymerization initiator were added to a 5 MPa pressure vessel equipped with a stirrer, and after sufficient stirring, the mixture was heated to 50°C to start polymerization. The reaction was stopped by cooling when the polymerization conversion rate reached 96%. A 5% aqueous sodium hydroxide solution was added to the aqueous dispersion containing the obtained diene-based polymer to adjust the pH to 8. Subsequently, unreacted monomers were removed by heated vacuum distillation. Afterward, the mixture was cooled to below 30°C.

[0203] Subsequent operations were performed in the same manner as in Example 1 to obtain a binder composition and a binder product. Meanwhile, the amount of emulsifier included in the binder composition was 5 parts per 100 parts of binder (the sum of sodium dodecylbenzenesulfonate introduced by the seed particles, and sodium dodecyldiphenyloxide disulfonate and sodium β-naphthalenesulfonate formalin condensate used in the second polymerization).

[0204] (Example 7)

[0205] A binder composition, a binder product, a slurry composition for a negative electrode, and a negative electrode were prepared in the same manner as in Example 1, except that a container prepared as described below was used, and various evaluations were performed. The results are shown in Table 1.

[0206] Preparation of Courage

[0207] A fluoropolymer resin (a perfluoropolyether group-containing compound, manufactured by Fluoro Technology Co., Ltd., product name "FS-6130") dissolved in water at 10% was applied to the inner wall surface of a receptacle of a polyethylene container identical to that used in Example 1, and hydrophobization treatment was performed by drying at 80°C for 1 hour to prepare a container for use in making a binder product.

[0208] (Example 8)

[0209] A binder composition and a binder product were prepared as follows. Except for that, a container, a slurry composition for the negative electrode, and a negative electrode were prepared in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 1.

[0210] <Preparation of Binder Composition and Binder Product>

[0211] In a 5 MPa pressure vessel A equipped with a stirrer, 38 parts of styrene, 60 parts of 1,3-butadiene, 2 parts of methacrylic acid, 4 parts of sodium lauryl sulfate as an emulsifier, 270 parts of ion-exchanged water, 0.15 parts of tert-dodecyl mercaptan as a chain transfer agent, 0.15 parts of sodium bicarbonate, and 0.3 parts of potassium persulfate as a polymerization initiator were added, stirred thoroughly, and then heated to 60°C to start polymerization, and seed particles (particulate diene-based polymer) were obtained.

[0212] In addition, 6 parts of the seed particles, 82 parts of ion-exchanged water, and 0.2 parts of sodium lauryl sulfate as an emulsifier were added to a 5 MPa pressure vessel B equipped with a stirrer, and after heating to 75°C, 18 parts of ion-exchanged water and 1.8 parts of itaconic acid were added. Furthermore, a mixture of these was continuously added to pressure vessel B from another vessel C containing 44 parts of ion-exchanged water, 62 parts of styrene, 33.2 parts of 1,3-butadiene, 2 parts of itaconic acid, 0.2 parts of sodium lauryl sulfate as an emulsifier, and 0.4 parts of sodium bicarbonate, and at the same time, 0.5 parts of potassium persulfate as a polymerization initiator was added to pressure vessel B to start the second stage of polymerization.

[0213] In addition, after the start of the second stage of polymerization, 0.3 parts of tert-dodecyl mercaptan were added to vessel C as a chain transfer agent. Also, starting from the start of polymerization, a total of 0.5 parts of potassium persulfate as a polymerization initiator were continuously added to pressure vessel B. Furthermore, starting 30 minutes before the end of adding the mixture in vessel C and coinciding with the end of adding, a total of 1.0 parts of 2-hydroxyethyl acrylate were continuously added to pressure vessel B. Subsequently, pressure vessel B was heated to 90°C, and after the reaction rate of the monomer reached 96% or higher, nitrous acid was added to stop the reaction.

[0214] A 5% aqueous sodium hydroxide solution was added to the aqueous dispersion containing the obtained diene-based polymer to adjust the pH to 8. Subsequently, unreacted monomers were removed by heated vacuum distillation. Afterward, the mixture was cooled to below 30°C.

[0215] Subsequent operations were performed in the same manner as in Example 1 to obtain a binder composition and a binder product. Meanwhile, the amount of emulsifier included in the binder composition was 0.44 parts per 100 parts of binder (the sum of sodium lauryl sulfate introduced by the seed particles and sodium lauryl sulfate used in the second polymerization).

[0216] (Comparative Examples 1, 2)

[0217] Except for changing the amount of the mineral oil-based defoamer used as the defoamer to 0.01 parts (Comparative Example 1) and 0.4 parts (Comparative Example 2) when preparing the binder composition, the procedure was the same as in Example 1, and a container, binder composition, binder product, slurry composition for the negative electrode, and negative electrode were prepared and various evaluations were performed. The results are shown in Table 1.

[0218] (Comparative Example 3)

[0219] A binder composition and a binder product were prepared as follows. Except for that, a container, a slurry composition for the negative electrode, and a negative electrode were prepared in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 1.

[0220] <Preparation of Binder Composition and Binder Product>

[0221] Seed particles (particulate diene-based polymers) were obtained in the same manner as in Example 1.

[0222] In addition, 4 parts of the seed particles, 45 parts of 1,3-butadiene, 14 parts of styrene, 26 parts of acrylonitrile, 12 parts of methyl methacrylate, 1 part of acrylic acid, 1 part of itaconic acid, 1 part of acrylamide, 1 part of t-dodecyl mercaptan and 0.5 parts of α-methylstyrene dimer as molecular weight adjusters, 0.1 parts of sodium dodecyl diphenyl oxide disulfonate as an emulsifier, 150 parts of ion-exchanged water, and 1.0 parts of potassium persulfate as a polymerization initiator were added to a 5 MPa pressure vessel equipped with a stirrer, and after stirring sufficiently, the mixture was heated to 50°C to start polymerization. The reaction was stopped by cooling when the polymerization conversion rate reached 96%. A 5% aqueous sodium hydroxide solution was added to the aqueous dispersion containing the obtained diene-based polymer to adjust the pH to 8. After that, unreacted monomers were removed by heated vacuum distillation. Then, the temperature was cooled to below 30°C.

[0223] Subsequent operations were performed in the same manner as in Example 1 to obtain a binder composition and a binder product. Meanwhile, the amount of emulsifier included in the binder composition was 0.4 parts per 100 parts of binder (the sum of sodium dodecylbenzenesulfonate introduced by the seed particles and sodium dodecyldiphenyloxide disulfonate used in the second polymerization).

[0224] (Comparative Example 4)

[0225] A binder composition and a binder product were prepared as follows. Except for that, a container, a slurry composition for the negative electrode, and a negative electrode were prepared in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 1.

[0226] <Preparation of Binder Composition and Binder Product>

[0227] Seed particles (particulate diene-based polymers) were obtained in the same manner as in Example 1.

[0228] In addition, 4 parts of the seed particles, 45 parts of 1,3-butadiene, 14 parts of styrene, 26 parts of acrylonitrile, 12 parts of methyl methacrylate, 1 part of acrylic acid, 1 part of itaconic acid, 1 part of acrylamide, 1 part of t-dodecyl mercaptan and 0.5 parts of α-methylstyrene dimer as molecular weight adjusters, 5 parts of sodium dodecyl diphenyl oxide disulfonate and 0.9 parts of sodium salt of β-naphthalenesulfonic acid formalin condensate as emulsifiers, 150 parts of ion-exchanged water, and 1.0 part of potassium persulfate as a polymerization initiator were added to a 5 MPa pressure vessel equipped with a stirrer, and after sufficient stirring, the mixture was heated to 50°C to start polymerization. The reaction was stopped by cooling when the polymerization conversion rate reached 96%. A 5% aqueous sodium hydroxide solution was added to the aqueous dispersion containing the obtained diene-based polymer to adjust the pH to 8. Subsequently, unreacted monomers were removed by heated vacuum distillation. Afterward, the mixture was cooled to below 30°C.

[0229] Subsequent operations were performed in the same manner as in Example 1 to obtain a binder composition and a binder product. Meanwhile, the amount of emulsifier included in the binder composition was 6 parts per 100 parts of binder (the sum of sodium dodecylbenzenesulfonate introduced by the seed particles, and sodium dodecyldiphenyloxide disulfonate and sodium β-naphthalenesulfonate formalin condensate used in the second polymerization).

[0230] (Comparative Example 5)

[0231] A binder composition, a binder product, a slurry composition for a negative electrode, and a negative electrode were prepared in the same manner as in Example 1, except that a polyethylene container that had not undergone hydrophobization treatment was used, and various evaluations were performed. The results are shown in Table 1.

[0232] Meanwhile, among Table 1 shown below,

[0233] "Functional group" represents an amide group-containing monomer unit and a hydroxyalkyl group-containing monomer unit, and

[0234] "AAm" represents an acrylamide unit,

[0235] "HEA" represents a hydroxyethyl acrylate unit, and

[0236] "Mineral oil" refers to a mineral oil-based antifoaming agent,

[0237] "IST" represents an isothiazoline compound (1,2-benzisothiazolin-3-one), and

[0238] "SDBS" represents sodium dodecylbenzenesulfonate, and

[0239] "DSBP" represents sodium dodecyl diphenyl oxide disulfonate, and

[0240] "BETA" represents the sodium salt of the β-naphthalenesulfonic acid formalin condensate, and

[0241] "SLS" represents sodium lauryl sulfate, and

[0242] "PE" stands for polyethylene,

[0243] "Silan" indicates treatment by a silane coupling agent, and

[0244] "Fluorine" refers to treatment by fluorine resin.

[0245]

[0246] From Table 1, it can be seen that in the binder products of Examples 1 to 8, aggregation is unlikely to occur in the binder composition even after long-term storage, and a negative electrode composite layer with excellent adhesion can be formed using the binder composition after long-term storage. In addition, in Examples 1 to 8, it can be seen that a negative electrode slurry composition with excellent viscosity stability can be prepared even when the binder composition after long-term storage is used. Furthermore, in Examples 1 to 8, it can be seen that the binder composition has excellent viscosity stability.

[0247] [Industrial Applicability]

[0248] The binder product for secondary batteries according to the present invention is unlikely to cause aggregation in the binder composition even after long-term storage, and can also form a functional layer with excellent adhesion using said binder composition. Explanation of the symbols

[0249] 1 container 2. Binder composition 11 capsules 12 reception units 13 Interior wall surface 14 interior space 100 Binder Products for Secondary Batteries

Claims

Claim 1 A binder product for a secondary battery comprising a container having a receiving portion and a binder composition contained in the internal space of the receiving portion, wherein the contact angle of the inner wall surface of the receiving portion with respect to water is 100° or more, the binder composition comprises a binder, an antifoaming agent, and water, the content of the antifoaming agent is 0.02 parts by mass or more and 0.3 parts by mass or less per 100 parts by mass of the binder, and the surface tension of the binder composition is 20 mN / m or more and 60 mN / m or less. Claim 2 A binder product for a secondary battery according to claim 1, wherein the binder has at least one of an amide group and a hydroxyalkyl group. Claim 3 A binder product for a secondary battery according to claim 1, wherein the binder comprises at least one of an amide group-containing monomer unit and a hydroxyalkyl group-containing monomer unit, and the sum of the content ratio of the amide group-containing monomer unit and the content ratio of the hydroxyalkyl group-containing monomer unit in the binder is 0.05 mass% or more and 5 mass% or less. Claim 4 A binder product for a secondary battery according to claim 1, wherein the binder composition further comprises a preservative, and the content of the preservative is 0.01 parts by mass or more and 0.5 parts by mass or less per 100 parts by mass of the binder. Claim 5 A binder product for a secondary battery according to claim 1, wherein the volume ratio of the void portion, excluding the volume occupied by the binder composition in the container from the content volume of the container, is 10 volume% or less relative to the content volume of the container. Claim 6 A binder product for a secondary battery according to claim 1, wherein the solid content concentration of the binder composition is 30 mass% or more and 60 mass% or less. Claim 7 A binder product for a secondary battery according to any one of claims 1 to 6, wherein the defoaming agent comprises a mineral oil-based defoaming agent.

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