Binder composition for nonaqueous secondary battery electrodes, slurry composition for nonaqueous secondary battery electrodes, electrode for nonaqueous secondary batteries, and nonaqueous secondary battery

Abstract

The purpose of the present invention is to provide a binder composition for a nonaqueous secondary battery electrode capable of enhancing viscosity stability of a slurry composition. The present invention is a binder composition for a nonaqueous secondary battery electrode, the binder composition for a nonaqueous secondary battery electrode containing a binder, an aromatic surfactant, a polyether-modified polydimethylsiloxane, and water, wherein the binder is a polymer X containing 60-85 mass % of a (meth) acrylic acid ester monomer unit when the amount of all repeating units is 100 mass %, the aromatic surfactant has a naphthalene structure, the content of the aromatic surfactant is 1-10 parts by mass with respect to 100 parts by mass of the binder, and the content of the polyether-modified polydimethylsiloxane is 0.01-0.1 parts by mass with respect to 100 parts by mass of the binder.

Description

Binder composition for non-aqueous secondary battery electrodes, slurry composition for non-aqueous secondary battery electrodes, electrodes for non-aqueous secondary batteries and non-aqueous secondary batteries

[0001] The present invention relates to a binder composition for non-aqueous secondary battery electrodes, a slurry composition for non-aqueous secondary battery electrodes, an electrode for a non-aqueous secondary battery, and a non-aqueous secondary battery.

[0002] Non-aqueous secondary batteries, such as lithium-ion batteries (hereinafter sometimes abbreviated as "secondary batteries"), are small, lightweight, have high energy density, and can be repeatedly charged and discharged, making them suitable for a wide range of applications. Therefore, in recent years, improvements to battery components such as electrodes have been considered with the aim of further enhancing the performance of non-aqueous secondary batteries.

[0003] Here, electrodes for secondary batteries typically include an electrode composite layer. The electrode composite layer is formed by, for example, dispersing an electrode active material and a non-aqueous secondary battery electrode binder composition containing a polymer acting as a binder in a dispersion medium, and then applying a slurry composition (non-aqueous secondary battery electrode slurry composition) onto a current collector and drying it.

[0004] Therefore, in recent years, attempts have been made to improve the binder composition used in forming the electrode composite layer in order to achieve further performance improvements in secondary batteries.

[0005] For example, Patent Document 1 discloses a binder for lithium-ion secondary battery electrodes with a glass transition temperature of 30°C or lower, obtained by emulsion polymerization of a predetermined monomer in the presence of a surfactant. According to Patent Document 1, this binder has good bonding properties between active materials and between active materials and current collectors in an aqueous dispersion system, and also possesses high-temperature charge-discharge cycle characteristics.

[0006] Japanese Patent Publication No. 2011-243464

[0007] In this context, from the viewpoint of improving the productivity and performance of secondary batteries, binder compositions are required to enhance the viscosity stability of the slurry composition prepared using such binder compositions.

[0008] However, when using the binders described above in the conventional technology, there was room for improvement in the viscosity stability of the resulting slurry composition.

[0009] Therefore, the present invention aims to provide a binder composition for non-aqueous secondary battery electrodes that can improve the viscosity stability of the slurry composition. The present invention also aims to provide a slurry composition for non-aqueous secondary battery electrodes that has excellent viscosity stability. The present invention also aims to provide an electrode for a non-aqueous secondary battery comprising an electrode composite layer formed using the above-mentioned slurry composition for non-aqueous secondary battery electrodes. The present invention also aims to provide a non-aqueous secondary battery comprising the above-mentioned electrode for a non-aqueous secondary battery.

[0010] The inventors conducted diligent research to achieve the above objectives. They then discovered that the above problems can be solved by a binder composition containing a predetermined binder, a predetermined aromatic surfactant, a predetermined polyether-modified polydimethylsiloxane, and water in predetermined compositions, and thus completed the present invention.

[0011] In other words, the present invention aims to advantageously solve the above problems, and [1] the present invention is a binder composition for a non-aqueous secondary battery electrode comprising a binder, an aromatic surfactant, a polyether-modified polydimethylsiloxane, and water, wherein the binder is a polymer X containing (meth)acrylic acid ester monomer units in a proportion of 60% to 85% by mass when the total amount of repeating units is 100% by mass, the aromatic surfactant has a naphthalene structure, the content of the aromatic surfactant is 1 to 10 parts by mass per 100 parts by mass of the binder, and the content of the polyether-modified polydimethylsiloxane is 0.01 to 0.1 parts by mass per 100 parts by mass of the binder. In this specification, "monomer unit" of a polymer means "a repeating unit derived from the monomer contained in the polymer obtained using that monomer." Furthermore, the content ratio of various repeating units (monomer units and structural units) in the polymer is as follows: １ It can be measured using nuclear magnetic resonance (NMR) methods such as 1H-NMR. In this specification, (meth)acrylic means acrylic and / or methacrylic.

[0012] [2] The binder composition for non-aqueous secondary battery electrodes described in [1] above preferably has an alkyl group having 1 to 4 carbon atoms bonded to the naphthalene structure of the aromatic surfactant. Using an aromatic surfactant in which an alkyl group having 1 to 4 carbon atoms bonded to the naphthalene structure can improve the viscosity stability of the slurry composition for non-aqueous secondary battery electrodes.

[0013] [3] In the binder composition for non-aqueous secondary battery electrodes according to [1] or [2] above, it is preferable that the polymer X further contains aromatic vinyl monomer units. If the polymer X contains aromatic vinyl monomer units, the output characteristics of the secondary battery can be improved.

[0014] [4] In any of the binder compositions for non-aqueous secondary battery electrodes described in [1] to [3] above, the polymer X is particulate, and the median diameter of the polymer X is preferably 100 nm or more and 250 nm or less. If the median diameter of the particulate polymer X is within the above range, the adhesion of the electrode composite layer formed using the slurry composition for non-aqueous secondary battery electrodes to the current collector can be effectively improved. In this specification, "particulate" means a polymer that is dispersible in an aqueous medium such as water and exists in a particulate form in the aqueous medium. Typically, when 0.5 g of a particulate polymer is dissolved in 100 g of water at 25°C, the insoluble content is 90% by mass or more. In this specification, the "median diameter" of the particulate polymer X means the particle diameter (D50) at which the cumulative volume calculated from the smallest diameter side becomes 50% in the particle size distribution (volume basis) measured by laser diffraction, and can be measured in more detail using the method described in the examples of this specification.

[0015] [5] In the binder composition for non-aqueous secondary battery electrodes described in any of [1] to [4] above, it is preferable that the polymer X further contains acidic group-containing monomer units. If the polymer X contains acidic group-containing monomer units, the viscosity stability of the slurry composition for non-aqueous secondary battery electrodes can be improved.

[0016] Furthermore, this invention aims to advantageously solve the above problems, and [6] the present invention is a slurry composition for a non-aqueous secondary battery electrode, comprising an electrode active material and any of the non-aqueous secondary battery electrode binder compositions of [1] to [5] above. The above-described slurry composition for a non-aqueous secondary battery electrode has excellent viscosity stability.

[0017] [7] The slurry composition for a non-aqueous secondary battery electrode according to [6] above preferably further contains a water-soluble polymer Y containing a hydrophilic group. If the water-soluble polymer Y containing a hydrophilic group is further contained, the adhesion of the electrode composite layer formed using the slurry composition for a non-aqueous secondary battery electrode to the current collector can be improved. In this specification, when a polymer is "water-soluble", it means that when 0.5 g (in terms of solid content) of the polymer is dissolved in 100 g of water at a temperature of 25°C, the amount of insoluble matter is less than 5.0% by mass.

[0018] [8] In the slurry composition for a non-aqueous secondary battery electrode according to [7] above, the content ratio of the water-soluble polymer Y is preferably 0.1% by mass or more and 5.0% by mass or less when the total solid content contained in the slurry composition for a non-aqueous secondary battery electrode is 100% by mass. If the content ratio of the water-soluble polymer Y is at least the above lower limit, the adhesion of the electrode composite layer formed using the slurry composition for a non-aqueous secondary battery electrode to the current collector can be effectively improved. On the other hand, if the content ratio of the water-soluble polymer Y is at most the above upper limit, the output characteristics of the secondary battery can be effectively improved.

[0019] [9] In the slurry composition for a non-aqueous secondary battery electrode according to any one of [6] to [8] above, the electrode active material preferably contains a lithium-containing composite metal oxide having an olivine-type structure. If lithium iron phosphate having an olivine type is used as the electrode active material, the stability of the secondary battery against overcharging can be improved.

[0020]

[10] The slurry composition for a non-aqueous secondary battery electrode according to any one of [6] to [9] above preferably further contains a conductive material containing at least one of a particulate conductive material and carbon nanotubes. If the conductive material contains at least one of a particulate conductive material and carbon nanotubes, the output characteristics of the non-aqueous secondary battery can be improved.

[0021] Moreover, the present invention aims to advantageously solve the above problems, and

[11] the present invention is a non-aqueous secondary battery electrode comprising an electrode mixture layer formed using the slurry composition for non-aqueous secondary battery electrodes according to any one of [6] to

[10] above. For a non-aqueous secondary battery electrode as described above, excellent battery characteristics can be exhibited in the secondary battery.

[0022] Moreover, the present invention aims to advantageously solve the above problems, and

[12] the present invention is a non-aqueous secondary battery comprising the non-aqueous secondary battery electrode according to

[11] above. A non-aqueous secondary battery as described above is excellent in battery characteristics.

[0023] According to the present invention, a binder composition for non-aqueous secondary battery electrodes capable of enhancing the viscosity stability of the slurry composition can be provided. Further, according to the present invention, a slurry composition for non-aqueous secondary battery electrodes having excellent viscosity stability can be provided. Further, according to the present invention, a non-aqueous secondary battery electrode comprising an electrode mixture layer formed using the above slurry composition for non-aqueous secondary battery electrodes can be provided. Further, according to the present invention, a non-aqueous secondary battery comprising the above non-aqueous secondary battery electrode can be provided.

[0024] Each component disclosed in this specification, as well as the preferred embodiments, numerical ranges, and each threshold value defining such numerical ranges shown for each component, can be combined with each other in any manner independently.

[0025] Embodiments of the present invention will be described in detail below. Here, the binder composition for non-aqueous secondary battery electrodes of the present invention (hereinafter sometimes simply referred to as "binder composition") can be used to prepare the slurry composition for non-aqueous secondary battery electrodes of the present invention (hereinafter sometimes simply referred to as "slurry composition"). Furthermore, the slurry composition for non-aqueous secondary battery electrodes of the present invention can be used when manufacturing electrodes for non-aqueous secondary batteries such as lithium-ion secondary batteries. Moreover, the non-aqueous secondary battery of the present invention is characterized by using an electrode for a non-aqueous secondary battery (hereinafter sometimes simply referred to as "electrode") formed using the slurry composition for non-aqueous secondary battery electrodes of the present invention. It is preferable that the binder composition for non-aqueous secondary battery electrodes be a binder composition for a positive electrode of a non-aqueous secondary battery, as it can particularly enhance the viscosity stability of the slurry composition containing the positive electrode active material described later.

[0026] (Binder composition for non-aqueous secondary battery electrodes) The binder composition for non-aqueous secondary battery electrodes of the present invention comprises a binder, an aromatic surfactant, a polyether-modified polydimethylsiloxane, and water. In the binder composition of the present invention, the binder is a polymer X containing (meth)acrylic acid ester monomer units in a proportion of 60% to 85% by mass when the total amount of repeating units is 100% by mass, and the aromatic surfactant has a naphthalene structure. In the binder composition of the present invention, the content of the aromatic surfactant is 1 to 10 parts by mass per 100 parts by mass of the binder, and the content of the polyether-modified polydimethylsiloxane is 0.01 to 0.1 parts by mass per 100 parts by mass of the binder. With a binder composition as described above, the viscosity stability of the slurry composition can be improved. The reason for this is presumed to be that polymer X, aromatic surfactant, and polyether-modified polydimethylsiloxane in the binder composition adsorb to the surface of the electrode active material contained in the slurry composition, effectively covering the surface and effectively suppressing aggregation of the electrode active materials. Furthermore, with such a binder composition, the electrode composite layer formed using the resulting slurry composition can be given the desired adhesion to the current collector. Moreover, with such a binder composition, the resulting secondary battery can be given the desired output characteristics and cycle characteristics. The binder composition of the present invention may optionally further contain components other than a binder, aromatic surfactant, polyether-modified polydimethylsiloxane, and water (hereinafter sometimes referred to as "other components"). In addition, the binder composition of the present invention usually does not contain electrode active material.

[0027] <Binding agent (polymer X)> The binding agent is polymer X, which contains (meth)acrylic acid ester monomer units in a proportion of 60% to 85% by mass when the total amount of repeating units is 100% by mass, and can hold components such as electrode active material contained in the electrode mixture layer so as not to detach from the electrode mixture layer in an electrode mixture layer formed on a current collector using a slurry composition containing a binder composition.

[0028] <<Composition of Polymer X>> Polymer X contains (meth)acrylic acid ester monomer units in a proportion of 60% to 85% by mass, when the total amount of repeating units in Polymer X is taken as 100% by mass. Furthermore, Polymer X preferably further contains aromatic vinyl monomer units, which will be described later, as this can improve the output characteristics of secondary batteries. Furthermore, Polymer X preferably further contains acidic group-containing monomer units, which will be described later, as this can improve the viscosity stability of the slurry composition. Polymer X may optionally contain repeating units other than the (meth)acrylic acid ester monomer units, aromatic vinyl monomer units, and acidic group-containing monomer units described above (hereinafter referred to as "other repeating units A").

[0029] [(meth)acrylic acid monomer units] Examples of (meth)acrylic acid monomers that can form (meth)acrylic acid monomer units include alkyl acrylates such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate, and stearyl acrylate; and acrylic acrylates such as 2-methoxyethyl acrylate and 2-ethoxyethyl acrylate. Examples include methacrylate alkoxy esters; alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, isobutyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, lauryl methacrylate, n-tetradecyl methacrylate, and stearyl methacrylate; and methacrylate alkoxy esters such as 2-methoxyethyl methacrylate and 2-ethoxyethyl methacrylate. The (meth)acrylic acid ester monomer units may be used individually or in combination of two or more types. Among the above, alkyl (meth)acrylate is preferred from the viewpoint of further reducing the degree of electrolyte swelling of polymer X while improving electrode adhesion, methyl acrylate, n-butyl acrylate, isobutyl acrylate, and 2-ethylhexyl acrylate are more preferred, n-butyl acrylate and 2-ethylhexyl acrylate are even more preferred, and n-butyl acrylate is even more preferred.That is, the (meth)acrylic acid ester monomer unit is preferably an alkyl (meth)acrylic acid ester unit, more preferably at least one monomer unit selected from the group consisting of methyl acrylate units, n-butyl acrylate units, isobutyl acrylate units, and 2-ethylhexyl acrylate units, even more preferably at least one of n-butyl acrylate units and 2-ethylhexyl acrylate units, and even more preferably an n-butyl acrylate unit. In this specification, hydroxyl group-containing (meth)acrylic acid ester monomer units are not included in "(meth)acrylic acid ester monomer units" but are included in "hydroxyl group-containing monomer units" as described later.

[0030] The proportion of (meth)acrylic acid ester monomer units in polymer X must be 60.0% by mass or more, preferably 65.0% by mass or more, more preferably 70.0% by mass or more, and must be 85.0% by mass or less, preferably 82.5% by mass or less, and more preferably 80.0% by mass or less, based on the total amount of repeating units (total monomer units) in polymer X being 100% by mass. If the proportion of (meth)acrylic acid ester monomer units in polymer X is within the above range, the viscosity stability of the slurry composition can be effectively improved. Furthermore, if the proportion of (meth)acrylic acid ester monomer units in polymer X is above the lower limit, the flexibility of the electrode composite layer can be effectively improved, and the adhesion of the electrode composite layer to the current collector can be effectively improved. Moreover, if the proportion of (meth)acrylic acid ester monomer units in polymer X is below the upper limit, excessive swelling of polymer X in the electrolyte can be effectively suppressed, and the output characteristics and cycle characteristics of the secondary battery can be effectively improved.

[0031] [Aromatic vinyl monomer units] Examples of aromatic vinyl monomers that can form aromatic vinyl monomer units optionally included in polymer X include styrene, α-methylstyrene, vinyltoluene, and divinylbenzene. These may be used individually or two or more in any ratio. Among the above, styrene, α-methylstyrene, and vinyltoluene are preferred, with styrene being more preferred. That is, the aromatic vinyl monomer unit is preferably at least one monomer unit selected from the group consisting of styrene units, α-methylstyrene units, and vinyltoluene units, and is more preferably a styrene unit.

[0032] The proportion of aromatic vinyl monomer units in polymer X is preferably 10.0% by mass or more, more preferably 12.5% ​​by mass or more, even more preferably 15.0% by mass or more, preferably 30.0% by mass or less, more preferably 27.5% by mass or less, and even more preferably 25.0% by mass or less, when the total amount of repeating units (total monomer units) in polymer X is taken as 100% by mass. If the proportion of aromatic vinyl monomer units in polymer X is above the lower limit, the degree of electrolyte swelling of polymer X is effectively increased, and the output characteristics of the secondary battery can be effectively improved. On the other hand, if the proportion of aromatic vinyl monomer units in polymer X is below the upper limit, the flexibility of the electrode composite layer is effectively improved, and the adhesion of the electrode composite layer to the current collector can be effectively improved.

[0033] [Acid group-containing monomer units] Examples of acid group-containing monomers that can optionally be included in polymer X to form acid group-containing monomer units include carboxylic acid group-containing monomers, sulfonic acid group-containing monomers, phosphate group-containing monomers, etc. The acidic group of the acid group-containing monomer unit may form a salt with alkali metals, ammonia, etc.

[0034] Here, examples of carboxylic acid group-containing monomers that can form carboxylic acid group-containing monomer units include monocarboxylic acids and their derivatives, dicarboxylic acids and their acid anhydrides, and their derivatives. Examples of monocarboxylic acids include acrylic acid, methacrylic acid, and crotonic acid. Examples of monocarboxylic acid derivatives include 2-ethyl acrylic acid, isocrotonic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, and α-chloro-β-E-methoxyacrylic acid. Examples of dicarboxylic acids include maleic acid, fumaric acid, and itaconic acid. Examples of dicarboxylic acid derivatives include methyl maleic acid, dimethyl maleic acid, phenyl maleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid, and maleic acid monoesters such as nonyl maleic acid, decyl maleic acid, dodecyl maleic acid, octadecyl maleic acid, and fluoroalkyl maleic acid. Examples of acid anhydrides of dicarboxylic acids include maleic anhydride, acrylic anhydride, methyl maleic anhydride, and dimethyl maleic anhydride. Furthermore, acid anhydrides that generate carboxylic acid groups through hydrolysis can also be used as monomers containing carboxylic acid groups.

[0035] Furthermore, examples of sulfonic acid group-containing monomers that can form sulfonic acid group-containing monomer units include vinyl sulfonic acid, methyl vinyl sulfonic acid, (meth)allyl sulfonic acid, styrene sulfonic acid, ethyl (meth)acrylate-2-sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, and 3-alyloxy-2-hydroxypropanesulfonic acid. In this invention, "(meth)allyl" means allyl and / or methallyl.

[0036] Furthermore, examples of phosphate-containing monomers that can form phosphate-containing monomer units include 2-(meth)acryloyloxyethyl phosphate, methyl-2-(meth)acryloyloxyethyl phosphate, and ethyl-(meth)acryloyloxyethyl phosphate. In this invention, "(meth)acryloyl" means acryloyl and / or methacryloyl.

[0037] Here, the above-mentioned acidic group-containing monomer may be used individually or in combination of two or more types. The acidic group-containing monomer is preferably a carboxylic acid-containing monomer, more preferably itaconic acid, methacrylic acid, or acrylic acid, with itaconic acid being even more preferred. Specifically, the acidic group-containing monomer unit is preferably a carboxylic acid-containing monomer unit, more preferably at least one monomer unit selected from the group consisting of itaconic acid units, methacrylic acid units, and acrylic acid units, and even more preferably an itaconic acid unit.

[0038] When polymer X contains acidic group-containing monomer units, the proportion of acidic group-containing monomer units in polymer X is preferably 1.5% by mass or more, more preferably 1.7% by mass or more, even more preferably 1.9% by mass or more, preferably 3.0% by mass or less, more preferably 2.8% by mass or less, and even more preferably 2.6% by mass or less, based on the total amount of repeating units (total monomer units) in polymer X being 100% by mass. If the proportion of acidic group-containing monomer units in polymer X is above the lower limit above, viscosity stability can be effectively improved. On the other hand, if the proportion of acidic group-containing monomer units in polymer X is below the upper limit above, adhesion can be effectively improved.

[0039] [Other Repeating Units A] The other repeating units A that polymer X may optionally contain are not particularly limited. For example, other repeating units A include hydroxyl group-containing monomer units, amide group-containing monomer units, and so on. Polymer X may contain one type of other repeating unit A, or two or more types. It is preferable that polymer X contains hydroxyl group-containing monomer units.

[0040] Examples of hydroxyl group-containing monomers that can form hydroxyl group-containing monomer units include hydroxyl group-containing (meth)acrylic acid ester monomers and hydroxyl group-containing (meth)acrylamide monomers. Among these, hydroxyl group-containing (meth)acrylic acid ester monomers are preferred.

[0041] Examples of hydroxyl group-containing (meth)acrylic acid ester monomers include 2-hydroxymethyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, 4-hydroxybutyl acrylate, 1,4-cyclohexanedimethanol monoacrylate, 2-hydroxymethyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 4-hydroxybutyl methacrylate, and 1,4-cyclohexanedimethanol monomethacrylate. These may be used individually or in combination of two or more. Among these, 2-hydroxyethyl acrylate is preferred.

[0042] Examples of hydroxyl group-containing (meth)acrylamide monomers include N-hydroxymethylacrylamide, N-hydroxyethylacrylamide, N-hydroxypropylacrylamide, N-hydroxymethylmethacrylamide, N-hydroxyethylmethacrylamide, and N-hydroxypropylmethacrylamide. These may be used individually or in combination of two or more types. In this specification, hydroxyl group-containing (meth)acrylamide monomers are not included in the "amide group-containing monomer units" described later.

[0043] When polymer X contains hydroxyl group-containing monomer units, the proportion of hydroxyl group-containing monomer units in polymer X is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, preferably 10.0% by mass or less, more preferably 5.0% by mass or less, and even more preferably 2.5% by mass or less, based on the total amount of repeating units (total monomer units) in polymer X being 100% by mass.

[0044] Examples of amide group-containing monomers that can form amide group-containing monomer units include acrylamide and methacrylamide. These may be used individually or in combination of two or more types. Among these, acrylamide is preferred.

[0045] When polymer X contains amide group-containing monomer units, the proportion of amide group-containing monomer units in polymer X is preferably 0.5% by mass or more, more preferably 1.5% by mass or more, preferably 5.0% by mass or less, and more preferably 3.0% by mass or less, when the total amount of repeating units (total monomer units) in polymer X is taken as 100% by mass.

[0046] <<Properties of Polymer X>> Polymer X is preferably in particulate form. The median diameter of the particulate polymer X is preferably 100 nm or more, more preferably 110 nm or more, even more preferably 120 nm or more, preferably 250 nm or less, more preferably 230 nm or less, and even more preferably 210 nm or less. If the median diameter of the particulate polymer X is within the above range, the adhesion of the electrode composite layer formed using the slurry composition to the current collector can be effectively improved.

[0047] <<Method for Preparing the Polymer>> The polymer X described above is not particularly limited and can be prepared by any of the following methods, for example, solution polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, etc. Addition polymerization such as ionic polymerization, radical polymerization, and living radical polymerization can be used as the polymerization method. The polymerization initiator, polymerization accelerator, emulsifier, dispersant, chain transfer agent, etc. used during polymerization can be those that are commonly used, and the amount used should also be the amount commonly used. Among these, emulsion polymerization using water as the polymerization solvent is preferred because it does not require solvent removal and the solvent is highly safe.

[0048] Furthermore, when water is used as the polymerization solvent and the monomer composition described above is polymerized in water to prepare an aqueous solution containing polymer X, it is preferable to adjust the pH of the aqueous solution to 7 or higher and 9 or lower after polymerization. This is because neutralizing the resulting aqueous solution and adjusting the pH to the above range makes it easier to improve the viscosity stability of the slurry composition.

[0049] The polymerization initiator that can be used to prepare polymer X is not particularly limited and includes known polymerization initiators such as sodium persulfate, ammonium persulfate, potassium persulfate, and t-butylperoxy-2-ethylhexanoate. Among these, ammonium persulfate is preferred. The polymerization initiator may be used alone or in combination of two or more in any ratio. Furthermore, from the viewpoint of further improving the peel strength of the electrode and reducing the internal resistance of the secondary battery, the amount of polymerization initiator added is preferably 0.1 parts by mass or more, and more preferably 0.2 parts by mass or more, per 100 parts by mass of the total monomers used to prepare polymer X. The upper limit of the amount of polymerization initiator added is not particularly limited, but for example, it can be 2 parts by mass or less, or 1 part by mass or less, per 100 parts by mass of the total monomers used to prepare polymer X.

[0050] Furthermore, the emulsifiers that can be used in the preparation of polymer X are not particularly limited and include known emulsifiers, such as anionic surfactants such as sodium dodecylbenzenesulfonate, sodium lauryl sulfate, and sodium dialkyl sulfosuccinate; and nonionic surfactants such as polyoxyethylene nonylphenyl ether, polyethylene glycol monostearate, and sorbitan monostearate. Among these, sodium lauryl sulfate is preferred. The emulsifier may be used alone or in combination of two or more types in any ratio.

[0051] <Aromatic surfactants> The aromatic surfactant contained in the binder composition of the present invention has a naphthalene structure. Examples of aromatic surfactants having a naphthalene structure include salts of naphthalene sulfonic acid formalin condensates such as sodium salt of naphthalene sulfonic acid formalin condensate (Kao Corporation, "Demol N", "Demol RN", "Mighty 150", etc.) and ammonium salt of naphthalene sulfonic acid formalin condensate (Kao Corporation, "Demol AS", etc.); salts of methylnaphthalene sulfonic acid formalin condensate such as sodium salt of methylnaphthalene sulfonic acid formalin condensate (Kao Corporation, "Demol MS", etc.); salts of butylnaphthalene / naphthalene sulfonic acid formalin condensate such as sodium salt of butylnaphthalene / naphthalene sulfonic acid formalin condensate (Kao Corporation, "Demol SNB", etc.); and salts of naphthol methylene sulfonic acid formalin condensate such as sodium salt of naphthol methylene sulfonic acid formalin condensate (Kao Corporation, "Demol SSL", etc.). These may be used individually, or two or more may be combined in any ratio.

[0052] Here, it is preferable that the aromatic surfactant has an alkyl group having 1 to 4 carbon atoms bonded to the naphthalene structure. Using an aromatic surfactant in which an alkyl group having 1 to 4 carbon atoms bonded to the naphthalene structure can improve the viscosity stability of the slurry composition. The aromatic surfactant may optionally further have a naphthalene structure other than the naphthalene structure to which an alkyl group having 1 to 4 carbon atoms bonded (hereinafter sometimes referred to as "other naphthalene structures"). That is, the aromatic surfactant may have a naphthalene structure to which an alkyl group having 1 to 4 carbon atoms bonded and other naphthalene structures. Examples of other naphthalene structures include unsubstituted (without substituents such as alkyl groups) naphthalene structures. As aromatic surfactants having an alkyl group with 1 to 4 carbon atoms bonded to the naphthalene structure, sodium salt of methylnaphthalene sulfonic acid formalin condensate and sodium salt of butylnaphthalene / naphthalene sulfonic acid formalin condensate are preferred, and sodium salt of methylnaphthalene sulfonic acid formalin condensate is more preferred, as they can improve the adhesion of the electrode composite layer to the current collector.

[0053] The content of aromatic surfactant in the binder composition must be 1 part by mass or more, preferably 2.5 parts by mass or more, more preferably 4 parts by mass or more, and must be 10 parts by mass or less, preferably 8.5 parts by mass or less, and more preferably 7 parts by mass or less, per 100 parts by mass of binder (polymer X). If the content of aromatic surfactant is within the above range, the viscosity stability of the slurry composition can be effectively improved. In addition, the adhesion of the electrode composite layer to the current collector can be effectively improved.

[0054] <Polyether-modified polydimethylsiloxane> The polyether-modified polydimethylsiloxane contained in the binder composition of the present invention is a type of silicon-based compound and is a compound represented by the following general formula (1). In equation (1) above, R １R represents a hydrogen atom, alkyl group, carboxyl group, hydroxyl group, or ether group. ２ x represents any alkyl group, and x and y each represent any positive integer.

[0055] The viscosity of the polyether-modified polydimethylsiloxane is preferably 0.1 mPa·s or higher, more preferably 1 mPa·s or higher, preferably 10 mPa·s or lower, more preferably 5 mPa·s or lower, and even more preferably 2.5 mPa·s or lower. Hereinafter, in this specification, "viscosity of polyether-modified polydimethylsiloxane" refers to the viscosity of a 2.0% by mass aqueous solution of polyether-modified polydimethylsiloxane.

[0056] Furthermore, the surface tension of the polyether-modified polydimethylsiloxane is preferably 10 mN / m or more, more preferably 15 mN / m or more, even more preferably 20 mN / m or more, preferably 40 mN / m or less, more preferably 30 mN / m or less, and even more preferably 24 mN / m or less. Hereinafter, in this specification, "surface tension of polyether-modified polydimethylsiloxane" refers to the surface tension of an aqueous solution of polyether-modified polydimethylsiloxane with a concentration of 10.0% by mass.

[0057] Here, specific examples of the polyether-modified polydimethylsiloxanes described above include, without any particular limitations, BYK-1770, BYK1785, BYK-1789, BYK1610, etc., manufactured by BIC Chemie Japan Co., Ltd.

[0058] The content of polyether-modified polydimethylsiloxane in the binder composition must be 0.01 parts by mass or more, preferably 0.03 parts by mass or more, more preferably 0.05 parts by mass or more, required to be 0.1 parts by mass or less, preferably 0.09 parts by mass or less, and more preferably 0.08 parts by mass or less, per 100 parts by mass of the binder (polymer X). If the content of polyether-modified polydimethylsiloxane is within the above range, the viscosity stability of the slurry composition can be effectively improved. Furthermore, the adhesion of the electrode composite layer to the current collector can be effectively improved. Moreover, if the content of polyether-modified polydimethylsiloxane is above the lower limit, the output characteristics of the secondary battery can be improved.

[0059] <Solvent> The binder composition contains water as a solvent. The binder composition may further contain an organic solvent other than water. Examples of organic solvents include N-methylpyrrolidone (NMP), N,N-dimethylformamide, and acetone.

[0060] <Other Components> In addition to the components described above, the binder composition of the present invention may also contain reinforcing agents, leveling agents, wetting agents, dispersants, viscosity modifiers, electrolyte additives, preservatives, antifungal agents, defoaming agents, polymerization inhibitors, and binders other than the polymer X described above. These are not particularly limited as long as they do not affect the battery reaction, and known components can be used. Furthermore, the other components may be used individually or in combination of two or more components in any ratio.

[0061] <Preparation of Binder Composition for Non-Aqueous Secondary Battery Electrodes> The binder composition of the present invention can be prepared by mixing the above-mentioned components by known methods. Specifically, the binder composition can be prepared by mixing the above components using a mixer such as a ball mill, sand mill, bead mill, pigment disperser, lye crusher, ultrasonic disperser, homogenizer, planetary mixer, or film mixer. If polymer X is prepared by polymerizing in an aqueous solvent, the aqueous dispersion can be mixed as is to prepare a binder composition containing water as the solvent.

[0062] (Slurry composition for non-aqueous secondary battery electrodes) The slurry composition for non-aqueous secondary battery electrodes of the present invention comprises an electrode active material and the binder composition for non-aqueous secondary battery electrodes of the present invention described above. Because the slurry composition of the present invention contains the binder composition of the present invention described above, it has excellent viscosity stability. Here, the slurry composition of the present invention may optionally further contain, in addition to the electrode active material and the binder composition, a water-soluble polymer, a conductive material, a dispersion medium, and other components.

[0063] The slurry composition of the present invention may be a slurry composition for the positive electrode of a non-aqueous secondary battery containing a positive electrode active material as the electrode active material, or it may be a slurry composition for the negative electrode of a non-aqueous secondary battery containing a negative electrode active material as the electrode active material. Here, the slurry composition of the present invention is preferably a slurry composition for the positive electrode of a non-aqueous secondary battery because it has particularly excellent viscosity stability when containing a positive electrode active material.

[0064] The following describes in detail the case where the non-aqueous slurry composition for secondary battery electrodes of the present invention is a slurry composition for lithium-ion secondary battery cathodes, but the present invention is not limited to the following example.

[0065] <Electrode active material (positive electrode active material)> Here, as the positive electrode active material of the lithium ion secondary battery, known positive electrode active materials can be used without particular limitation. Specifically, as the positive electrode active material, compounds containing transition metals, for example, transition metal oxides, transition metal sulfides, composite metal oxides of lithium and transition metals, etc. can be used. Examples of the transition metal include Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, etc.

[0066] Here, examples of the transition metal oxide include MnO, MnO ２ , V ２ O ５ , V ６ O １３ , TiO ２ , Cu ２ V ２ O ３ , amorphous V [[ID={22}]] ２ O - P ２ O ５ , amorphous MoO ３ , amorphous V ２ O ５ , amorphous V ６ O １３ , etc. Examples of the transition metal sulfide include TiS ２ , TiS ３ , amorphous MoS ２ , FeS, etc. Examples of the composite metal oxide of lithium and transition metal include lithium-containing composite metal oxides having a layered structure, lithium-containing composite metal oxides having a spinel structure, lithium-containing composite metal oxides having an olivine structure, etc. Among them, it is preferable that the electrode active material contains a lithium-containing composite metal oxide having an olivine structure. If the electrode active material contains a lithium-containing composite metal oxide having an olivine structure, the stability of the secondary battery against overcharging can be improved.

[0067] Examples of the lithium-containing composite metal oxide having an olivine structure include, for example, olivine-type lithium iron phosphate (LiFePO ４ ), olivine-type lithium manganese phosphate (LiMnPO ４ ), olivine-type lithium manganese iron phosphate (LiMn １－ｘ Fe ｘPO ４ Li such as 0 < x < 1 ｙ MdPO ４ Examples of olivine-type lithium phosphate compounds are given by the formula: Here, Md represents one or more transition metals with an average oxidation state of 3+, such as Mn, Fe, Co, etc. Also, y represents a number satisfying 0 ≤ y ≤ 2. Furthermore, Li ｙ MdPO ４ The olivine-type lithium phosphate compound represented by may have Md partially substituted with another metal. Examples of substituted metals include Cu, Mg, Zn, V, Ca, Sr, Ba, Ti, Al, Si, B, and Mo. Here, as the olivine-type lithium iron phosphate, carbon-coated olivine-type lithium iron phosphate particles can also be used, in which at least a portion of the surface of the olivine-type lithium iron phosphate particles is coated with a carbon coating layer.

[0068] The particle size of the positive electrode active material is not particularly limited and can be adjusted as appropriate within the range in which the desired effects of the present invention can be obtained. However, for example, it is preferable that the median diameter of the positive electrode active material is 2 μm or less. In the present invention, the median diameter of the positive electrode active material refers to the particle size D50 at which the cumulative volume calculated from the smallest diameter side in the particle size distribution (volume basis) measured by a laser diffraction particle size analyzer manufactured by Malvern Corporation becomes 50%.

[0069] Furthermore, the content ratio of the electrode active material in the slurry composition is preferably 90% by mass or more and 99% by mass or less, for example, when the total solid content in the slurry composition is taken as 100% by mass.

[0070] <Binder Composition> The binder composition of the present invention described above can be used as the binder composition.

[0071] The amount of binder composition added when preparing the slurry composition can be appropriately adjusted within the range in which the desired effects of the present invention can be obtained. For example, when the total solid content in the slurry composition is 100% by mass, the amount of binder composition added can be adjusted so that the content of polymer X is preferably 0.1% by mass or more and 5% by mass or less, more preferably 0.1% by mass or more and 3% by mass or less, and even more preferably 0.1% by mass or more and 2% by mass or less. The slurry composition contains polymer X and optionally a water-soluble polymer, but the total content of polymer X and the optional water-soluble polymer in the slurry composition can satisfy the same preferred content range as above, specifically, preferably 0.1% by mass or more, preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 2% by mass or less.

[0072] <Conductive Material> The conductive material that may be optionally included in the slurry composition is a component that has the function of contributing to electrical contact between electrode active materials in the electrode composite layer.

[0073] The conductive material preferably contains at least one of carbon nanotubes and particulate conductive material, and more preferably contains both carbon nanotubes and particulate conductive material, as this can improve the output characteristics of the secondary battery. However, conductive materials other than carbon nanotubes and particulate conductive material (other conductive materials) may also be used. Examples of other conductive materials include fibrous conductive materials other than carbon nanotubes.

[0074] <<Carbon Nanotubes>> Carbon nanotubes can improve the output characteristics of secondary batteries by forming conductive paths in the electrode composite layer. Furthermore, the use of carbon nanotubes can also improve the cycle characteristics and low-temperature characteristics of secondary batteries. The carbon nanotubes are not particularly limited as long as they are carbon nanotubes that can obtain the desired effects of the present invention (hereinafter sometimes abbreviated as "CNT"). Depending on the type of layer, examples of carbon nanotubes include single-walled (SW) carbon nanotubes and multi-walled (MW) carbon nanotubes. The carbon nanotubes that can be used as conductive materials may be single-walled carbon nanotubes, multi-walled carbon nanotubes, or a combination thereof.

[0075] The average number of layers of the CNT is preferably 10 or less, more preferably 9 or less, even more preferably 8 or less, even more preferably 2 or less, and even more preferably 1.5 or less. If the average number of layers of the CNT is below the above upper limit, the cycle characteristics of the secondary battery can be further improved. The lower limit of the average number of layers of the CNT is not particularly limited, and is usually 1 or more.

[0076] The average diameter of the CNTs is preferably 0.5 nm or more, more preferably 1 nm or more, even more preferably 1.5 nm or more, even more preferably 2 nm or more, even more preferably 2.5 nm or more, preferably 20 nm or less, more preferably 12 nm or less, even more preferably 8 nm or less, even more preferably 6 nm or less, and even more preferably 4 nm or less. If the average diameter of the CNTs is above the lower limit, the aggregation of CNTs can be sufficiently suppressed, and the dispersibility of the CNTs as a conductive material can be improved. On the other hand, if the average diameter of the CNTs is below the upper limit, good conductive paths can be formed in the electrode composite layer, further improving the output characteristics of the secondary battery and further improving the cycle characteristics of the secondary battery.

[0077] The ratio of the G-band peak intensity to the D-band peak intensity in the Raman spectrum of CNTs (G / D ratio) is preferably 0.6 or higher, more preferably 1.2 or higher, even more preferably 2.1 or higher, even more preferably 3.0 or higher, and even more preferably 3.6 or higher. If the G / D ratio of the CNTs is above the lower limit mentioned above, the cycle characteristics of the secondary battery can be further improved. The upper limit of the G / D ratio of the CNTs is not particularly limited, but for example, it is 200 or lower.

[0078] The BET specific surface area of ​​CNT is 100 m². ２ Preferably, it is 1 / g or more, and 200m ２ It is more preferable that the amount is 250m or more per gram. ２ It is even more preferable that the amount is 1200m or more. ２ It is preferable that the amount is less than or equal to 1100m ２ It is more preferable that it be less than or equal to 1000m ２ It is even more preferable that the amount is less than or equal to / g. If the BET specific surface area of ​​the CNT is within the above predetermined range, the output characteristics of the secondary battery can be further improved. In this invention, the "BET specific surface area" of the CNT refers to the nitrogen adsorption specific surface area measured using the BET method.

[0079] [Method for Manufacturing Carbon Nanotubes] CNTs having the above-described properties can be manufactured using known methods such as arc discharge, laser ablation, and supergrowth, without any particular limitations.

[0080] [Carbon Nanotube Content] The content of any CNT in the slurry composition can be adjusted as appropriate within the range in which the desired effects of the present invention can be obtained. For example, when the total solid content in the slurry composition is 100% by mass, it is preferable to have a content of 0.01% by mass or more and 0.5% by mass or less. If the content of CNT in the slurry composition is above the lower limit, the internal resistance of the secondary battery can be effectively reduced, and the output characteristics of the secondary battery can be further improved. On the other hand, if the content of CNT in the slurry composition is below the upper limit, the flexibility of the electrode composite layer can be increased.

[0081] <<Particulate Conductive Material>> Particulate conductive material is a component that can function as a conductive material in the electrode composite layer and can also improve the flexibility of the electrode composite layer. The particulate conductive material is not particularly limited as long as it is a conductive material having a shape other than fibrous (for example, spherical, plate-shaped, etc.), and examples include carbon black (for example, acetylene black, Ketjenblack®, Farnest Black, etc.) and graphene. These particulate conductive materials may be used individually or in combination of two or more types in any ratio.

[0082] [Content ratio of particulate conductive material] The content ratio of any particulate conductive material in the slurry composition can be appropriately adjusted within the range in which the desired effects of the present invention can be obtained. For example, when the total solid content in the slurry composition is 100% by mass, it is preferable to have a content ratio of 0.1% by mass or more and 5% by mass or less. If the content ratio of particulate conductive material in the slurry composition is above the lower limit above, the flexibility of the electrode composite layer can be further improved. On the other hand, if the content ratio of particulate conductive material in the slurry composition is below the upper limit above, the adhesion of the electrode composite layer to the current collector can be improved.

[0083] <<Mixing ratio of CNTs and particulate conductive material>> The mixing ratio of CNTs and particulate conductive material is not particularly limited, but for example, the proportion of CNTs in the total content of CNTs and particulate conductive material in the slurry composition is preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 3% by mass or more, preferably 30% by mass or less, and more preferably 25% by mass or less. If the proportion of CNTs in the total content of CNTs and particulate conductive material is above the lower limit above, the internal resistance of the secondary battery can be effectively reduced and the output characteristics of the secondary battery can be further improved. On the other hand, if the proportion of CNTs in the total content of CNTs and particulate conductive material is below the upper limit above, the flexibility of the electrode composite layer can be improved.

[0084] <Water-soluble polymer> The water-soluble polymer that may be optionally contained in the slurry composition of the present invention is a component that can effectively disperse the compounding components such as the polymer X mentioned above in an aqueous medium. Therefore, by including a water-soluble polymer in the slurry composition, the dispersibility of the slurry composition is improved, the structure of the electrode composite layer formed using the slurry composition is optimized, and the adhesion of the electrode composite layer to the current collector can be effectively improved. The water-soluble polymer may also be in the form of a salt (salt of the water-soluble polymer). That is, in the present invention, "water-soluble polymer" also includes salts of the water-soluble polymer.

[0085] Here, the water-soluble polymer is preferably a water-soluble polymer Y containing hydrophilic groups (hereinafter sometimes simply referred to as "water-soluble polymer Y"), as it can improve the adhesion of the electrode composite layer formed using the slurry composition to the current collector. Examples of hydrophilic groups include carboxylic acid groups, sulfonic acid groups, phosphoric acid groups, and hydroxyl groups. Water-soluble polymer Y may have only one of these hydrophilic groups, or it may have two or more. Water-soluble polymer Y preferably has at least one of a carboxylic acid group and a hydroxyl group, and more preferably has both a carboxylic acid group and a hydroxyl group. In the following description, water-soluble polymer Y is given as an example, but the water-soluble polymers that may be included in the slurry composition of the present invention are not limited to this.

[0086] Here, as the water-soluble polymer Y, for example, cellulosic polymers, synthetic polymers, etc., can be used. Examples of cellulosic polymers include cellulose compounds such as carboxymethylcellulose (CMC), carboxyethylcellulose, ethylcellulose, hydroxymethylcellulose, hydroxypropylcellulose, and carboxyethylmethylcellulose, and salts thereof such as ammonium salts and alkali metal salts. Examples of synthetic polymers include polycarboxylic acids such as polyacrylic acid, polymethacrylic acid, and alginic acid; polyvinyl alcohol; and polymers containing hydrophilic group-containing monomer units. These water-soluble polymers Y may be used individually or in combination of two or more types in any ratio. Among these, carboxymethylcellulose and polymers containing hydrophilic group-containing monomer units are preferred, and polymers containing hydrophilic group-containing monomer units are more preferred.

[0087] Below, an example of the composition of a polymer containing hydrophilic group-containing monomer units is described in detail as the water-soluble polymer Y, but the water-soluble polymer Y is not limited to this example.

[0088] <<Hydrophilic Group-Containing Monomer Units>> A polymer containing hydrophilic group-containing monomer units is a polymer containing hydrophilic group-containing monomer units and optionally other repeating units B. Examples of hydrophilic group-containing monomer units include the "acidic group-containing monomer units" and "hydroxyl group-containing monomer units" mentioned in the "Polymer X" section. Note that one type of hydrophilic group-containing monomer unit may be used alone, or two or more types may be used in any ratio, but it is preferable to include both hydroxyl group-containing monomer units and acidic group-containing monomer units.

[0089] In a polymer containing a hydrophilic group-containing monomer unit, the hydroxyl group-containing monomer unit is preferably at least one monomer unit selected from the group consisting of 2-hydroxyethyl acrylate unit, 2-hydroxyethyl methacrylate unit, 4-hydroxybutyl acrylate unit, and 4-hydroxybutyl methacrylate unit, more preferably at least one of 2-hydroxyethyl methacrylate unit and 4-hydroxybutyl acrylate unit, and even more preferably both 2-hydroxyethyl methacrylate unit and 4-hydroxybutyl acrylate unit.

[0090] In a polymer containing hydrophilic group-containing monomer units, the acidic group-containing monomer unit is preferably a carboxylic acid group-containing monomer unit, more preferably at least one monomer unit selected from the group consisting of itaconic acid units, methacrylic acid units, and acrylic acid units, and even more preferably a methacrylic acid unit.

[0091] The proportion of hydrophilic group-containing monomer units in a polymer containing hydrophilic group-containing monomer units is preferably 40% by mass or more, more preferably 50% by mass or more, preferably 80% by mass or less, and more preferably 70% by mass or less, when the total amount of repeating units in the polymer containing hydrophilic group-containing monomer units is taken as 100% by mass.

[0092] The proportion of hydroxyl group-containing monomer units in a polymer containing hydrophilic group-containing monomer units is preferably 15% by mass or more, more preferably 25% by mass or more, preferably 45% by mass or less, and more preferably 40% by mass or less, when the total amount of repeating units in the polymer containing hydrophilic group-containing monomer units is taken as 100% by mass.

[0093] The proportion of acidic group-containing monomer units in a polymer containing hydrophilic group-containing monomer units is preferably 15% by mass or less, more preferably 20% by mass or less, more preferably 35% by mass or less, and more preferably 30% by mass or less, when the total amount of repeating units in the polymer containing hydrophilic group-containing monomer units is taken as 100% by mass.

[0094] <<Other Repeating Units B>> The other repeating units B that a polymer containing hydrophilic group-containing monomer units may optionally contain are not particularly limited. Examples of other repeating units B include conjugated diene monomer units and (meth)acrylic acid ester monomer units. The polymer containing hydrophilic group-containing monomer units may contain one type of other repeating unit, or two or more types.

[0095] Here, examples of arbitrary (meth)acrylic acid ester monomer units include those mentioned above in the "polymer X" section. Among these, the n-butyl acrylate unit is preferred.

[0096] The proportion of (meth)acrylic acid ester monomer units in a polymer containing hydrophilic group-containing monomer units is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, preferably 5% by mass or less, and more preferably 2% by mass or less, when the total amount of repeating units in the polymer containing hydrophilic group-containing monomer units is taken as 100% by mass.

[0097] Furthermore, any conjugated diene monomer unit can be formed from conjugated diene monomers. Examples of conjugated diene monomers include conjugated diene compounds such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, and 1,3-pentadiene. These can be used individually or in combination of two or more. Among these, 1,3-butadiene is preferred.

[0098] The proportion of conjugated diene monomer units in a polymer containing hydrophilic group-containing monomer units is preferably 15% by mass or more, more preferably 25% by mass or more, preferably 55% by mass or less, and more preferably 45% by mass or less, when the total amount of repeating units in the polymer containing hydrophilic group-containing monomer units is taken as 100% by mass.

[0099] <<Method for preparing water-soluble polymer Y>> Here, the method for preparing water-soluble polymer Y is not particularly limited. It may be prepared by modifying a natural polymer such as cellulose using a chemical reaction, or by polymerizing a monomer composition containing the above-mentioned monomers in an aqueous solvent such as water. In this case, the content ratio of each monomer in the monomer composition can be determined in accordance with the content ratio of each monomer unit in water-soluble polymer Y. The method for introducing hydrophilic groups into the synthetic polymer water-soluble polymer Y is not particularly limited. A polymer may be prepared by addition polymerization of the above-mentioned hydrophilic group-containing monomers to obtain a polymer containing hydrophilic group-containing monomer units as water-soluble polymer Y, or water-soluble polymer Y may be obtained by modifying any addition polymer (for example, by terminal modification), but the former is preferred. The polymerization method is not particularly limited, and any method such as solution polymerization, suspension polymerization, bulk polymerization, or emulsion polymerization can be used. In addition, any polymerization reaction such as ionic polymerization, radical polymerization, or living radical polymerization can be used. Furthermore, commonly used additives such as emulsifiers, dispersants, polymerization initiators, polymerization accelerators, and molecular weight modifiers can be used in polymerization. The amounts of these additives used can also be the amounts commonly used. Polymerization conditions can be adjusted as appropriate depending on the polymerization method and the type of polymerization initiator.

[0100] <Content of water-soluble polymer Y> The content of water-soluble polymer Y in the slurry composition is preferably 0.1% by mass or more, more preferably 0.25% by mass or more, even more preferably 0.5% by mass or more, preferably 5.0% by mass or less, more preferably 2.0% by mass or less, even more preferably 1.75% by mass or less, and even more preferably 1.5% by mass or less, based on the total solid content in the slurry composition being 100% by mass. If the content of water-soluble polymer Y is above the lower limit above, the adhesion of the electrode composite layer formed using the slurry composition to the current collector can be effectively improved. On the other hand, if the content of water-soluble polymer Y is below the upper limit above, the output characteristics of the secondary battery can be effectively improved.

[0101] <Dispersion medium> Water and the organic solvents listed in the <Solvent> section above can be used as the dispersion medium.

[0102] <Other Components> Other components that can be incorporated into the slurry composition are not particularly limited and include those similar to the other components that can be incorporated into the binder composition of the present invention. In addition, one type of other component may be used alone, or two or more types may be used in any ratio.

[0103] <Method for Producing Slurry Composition> The slurry composition described above can be prepared by dissolving or dispersing each of the above components in a dispersion. For example, it is preferable to prepare the slurry composition of the present invention by adding a positive electrode active material, a solvent, and optional components to the binder composition described above and mixing them using the known method described above. In particular, when CNTs are incorporated as a conductive material, it is preferable to prepare a CNT dispersion by mixing CNTs with a dispersant such as carboxymethylcellulose and a dispersion medium, and then perform a multi-stage mixing process in which the CNT dispersion is further mixed with the positive electrode active material, etc.

[0104] (Electrodes for non-aqueous secondary batteries) The electrode of the present invention comprises an electrode composite layer formed using the slurry composition of the present invention described above, and usually has a structure in which the electrode composite layer is formed on a current collector. Therefore, the electrode composite layer contains at least an electrode active material and polymer X, and optionally further contains a water-soluble polymer, a conductive material, etc.

[0105] Here, since the electrode composite layer of the electrode of the present invention is formed using the slurry composition of the present invention, it can enable secondary batteries to exhibit excellent battery characteristics. More specifically, since the electrode composite layer of the electrode of the present invention is formed using the slurry composition of the present invention, which has excellent viscosity stability, it has a uniform structure and can reduce the internal resistance of secondary batteries. Furthermore, since the slurry composition of the present invention exhibits particularly excellent viscosity stability when it contains a positive electrode active material, and can enable secondary batteries to exhibit excellent battery characteristics, it is preferable that the electrode of the present invention is a positive electrode.

[0106] The electrode active material, polymer X, water-soluble polymer, conductive material, and other components contained in the electrode composite layer are those that were contained in the slurry composition described above, and the preferred content ratio of each component is the same as the preferred content ratio of each component when the total solid content in the slurry composition is taken as 100% by mass.

[0107] Furthermore, the electrode of the present invention may further include a conductive adhesive layer between the current collector and the electrode composite layer, the adhesive layer comprising at least a conductive material and an adhesive.

[0108] <Current Collector> The current collector is made of a material that is electrically conductive and electrochemically durable. Specifically, the current collector can be made of metal materials such as iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, or platinum. These materials may be used individually or in combination of two or more materials in any ratio.

[0109] Furthermore, for example, when manufacturing an electrode further comprising the conductive adhesive layer described above between the electrode composite layer and the current collector, a current collector with a conductive adhesive layer can be used, wherein the conductive adhesive layer is formed on a current collector substrate. As the current collector substrate, for example, a current collector made of the metal material described above can be used. The method for forming the conductive adhesive layer on the current collector substrate is not particularly limited. For example, a slurry composition (also referred to as "conductive adhesive") in which a conductive material and an adhesive are dispersed or dissolved in a dispersion medium or solvent such as water, and optionally a dispersant is further dispersed or dissolved, can be applied to the current collector substrate and then dried to form the conductive adhesive layer. The conductive material is not particularly limited, and for example, a conductive material that may be included in the slurry composition described above can be used. Also, the adhesive is not particularly limited, and a polymer X that may be included in the slurry composition described above can be used. Furthermore, the dispersant is not particularly limited, and for example, known dispersants such as carboxymethylcellulose and its salts, or a water-soluble polymer Y that may be included in the slurry composition described above can be used. Furthermore, the method for applying the conductive adhesive onto the substrate for the current collector and the method for drying the applied conductive adhesive are not particularly limited, and known methods can be used.

[0110] <Electrode Mixture Layer> The electrode mixture layer is formed, for example, through a process of applying a slurry composition onto the current collector (coating process) and a process of drying the slurry composition applied onto the current collector (drying process). The electrode mixture layer formed in this way can usually take the form of a dried film.

[0111] <<Coating Process>> The method for coating the slurry composition onto the current collector is not particularly limited, and known methods can be used. Specifically, the coating methods can include the doctor blade method, dip method, reverse roll method, direct roll method, gravure method, extrusion method, brush coating method, etc. In this case, the slurry composition may be coated on only one side of the current collector or on both sides. Furthermore, the thickness of the slurry composition film on the current collector before drying after coating can be appropriately set according to the thickness of the electrode composite layer obtained after drying.

[0112] <<Drying Process>> The method for drying the slurry composition applied to the current collector is not particularly limited and known methods can be used, such as drying with hot air, hot air, or low-humidity air, vacuum drying, or drying by irradiation with infrared rays or electron beams. By drying the slurry composition applied to the current collector in this way, an electrode composite layer is formed on the current collector, and an electrode having a current collector and an electrode composite layer can be obtained. After the drying process, the electrode composite layer may be subjected to pressure treatment using a die press or roll press or the like. Pressure treatment can improve the peel strength of the electrode.

[0113] (Non-aqueous secondary battery) The secondary battery of the present invention is equipped with the electrodes of the present invention as described above. For example, the secondary battery of the present invention is equipped with a positive electrode, a negative electrode, a separator, and an electrolyte, and at least one of the positive electrode and the negative electrode is the electrode of the present invention as described above. In other words, the secondary battery of the present invention may have the electrode of the present invention as the positive electrode and a known negative electrode as the negative electrode, or the electrode of the present invention and a known positive electrode as the negative electrode, or both the positive electrode and the negative electrode may be the electrode of the present invention. However, the slurry composition of the present invention is particularly excellent in viscosity stability and excellent in battery characteristics when it contains a positive electrode active material, so it is preferable that at least the positive electrode of the secondary battery of the present invention is the electrode of the present invention. Furthermore, since the secondary battery of the present invention is equipped with the electrodes of the present invention as described above, the internal resistance is reduced, the output characteristics are excellent, and the cycle characteristics are excellent. In the following, the case in which the non-aqueous secondary battery is a lithium-ion secondary battery will be described as an example, but the present invention is not limited to the following example.

[0114] <Positive Electrode> The positive electrode is not particularly limited and can be the electrode of the present invention as described above. That is, for example, the positive electrode can be a positive electrode comprising a positive electrode composite layer formed from the slurry composition of the present invention and a current collector. Also, if the electrode of the present invention is not used as the positive electrode, a known positive electrode can be used.

[0115] <Negative Electrode> The negative electrode is not particularly limited and can be the electrode of the present invention as described above. That is, for example, the negative electrode can be a negative electrode comprising a negative electrode composite layer formed from the slurry composition of the present invention and a current collector. If the electrode of the present invention is not used for the negative electrode, a known negative electrode can be used.

[0116] <Separator> The separator is not particularly limited, but examples include microporous membranes using polyolefin resins (polyethylene, polypropylene, polybutene, polyvinyl chloride), microporous membranes using resins such as polyethylene terephthalate, polycycloolefin, polyethersulfone, polyamide, polyimide, polyimidamide, polyaramid, polycycloolefin, nylon, and polytetrafluoroethylene, woven or nonwoven fabrics using polyolefin fibers, and aggregates of particles made of insulating materials. Among these, microporous membranes using polyolefin resins (polyethylene, polypropylene, polybutene, polyvinyl chloride) are preferred because they allow for a thinner overall film thickness of the separator, thereby increasing the ratio of the electrode composite layer in the secondary battery and thus increasing the capacity per unit volume.

[0117] <Electrolyte> As the electrolyte, an electrolyte solution obtained by dissolving an electrolyte in a solvent can be used. Here, an organic solvent capable of dissolving the electrolyte can be used as the solvent. Specifically, suitable solvents include carbonates such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate (BC), and ethyl methyl carbonate (EMC); esters such as γ-butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; sulfur-containing compounds such as sulfolane and dimethyl sulfoxide; etc. A mixture of these solvents may also be used. In addition, known additives, such as vinylene carbonate (VC), fluoroethylene carbonate (FEC), and ethyl methyl sulfone, may be added to the solvent. As the electrolyte, a lithium salt can be used. As a lithium salt, for example, the compound described in Japanese Patent Publication No. 2012-204303 can be used. Among these lithium salts, LiPF is preferred as an electrolyte due to its easy solubility in organic solvents and high degree of dissociation. ６ LiClO ４ CF 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 any ratio. Generally, lithium ion conductivity tends to increase as the degree of dissociation of the supporting electrolyte increases; therefore, lithium ion conductivity can be adjusted by the type of supporting electrolyte.

[0118] Furthermore, the secondary battery of the present invention can be manufactured using known assembly methods without particular limitations. Specifically, the secondary battery of the present invention can be manufactured, for example, by winding, folding, etc., the negative electrode, positive electrode, and separator obtained above into a battery shape as needed, placing them in a battery container, injecting electrolyte into the battery container, and sealing it. Here, in order to prevent the occurrence of an increase in the internal pressure of the secondary battery, overcharging and discharging, etc., an overcurrent prevention element such as a fuse or PTC element, expanded metal, lead plates, etc. may be provided as needed. The shape of the secondary battery may be, for example, coin type, button type, sheet type, cylindrical type, rectangular type, flat type, etc. The battery components such as the positive electrode, negative electrode, and separator of the secondary battery are usually arranged so that the positive electrode is in contact with one side of the separator and the negative electrode is in contact with the other side of the separator. More specifically, the positive electrode composite layer is arranged so that it is in contact with one side of the separator and the negative electrode composite layer is in contact with the other side of the separator.

[0119] (Exemplary Embodiments) The present invention is further illustrated by the following exemplary embodiments [1] to

[20] . However, the present invention is not limited to the following embodiments [1] to

[20] .

[0120] [1] A binder composition for non-aqueous secondary battery electrodes comprising a binder, an aromatic surfactant, a polyether-modified polydimethylsiloxane, and water, wherein the binder is a polymer X containing (meth)acrylic acid ester monomer units in a proportion of 60.0% by mass or more and 85.0% by mass or less when the total amount of repeating units is 100% by mass, the aromatic surfactant has a naphthalene structure, the content of the aromatic surfactant is 1 part by mass or more and 10 parts by mass or less per 100 parts by mass of the binder, and the content of the polyether-modified polydimethylsiloxane is 0.01 parts by mass or more and 0.1 parts by mass or less per 100 parts by mass of the binder.

[0121] [2] The binder composition for non-aqueous secondary battery electrodes according to [1], wherein the content of the polyether-modified polydimethylsiloxane is 0.03 parts by mass or more and 0.09 parts by mass or less per 100 parts by mass of the binder.

[0122] [3] The binder composition for non-aqueous secondary battery electrodes according to [1] or [2], wherein the content of the polyether-modified polydimethylsiloxane is 0.05 parts by mass or more and 0.08 parts by mass or less per 100 parts by mass of the binder.

[0123] [4] The binder composition for non-aqueous secondary battery electrodes according to any one of [1] to [3], wherein the content of the aromatic surfactant is 2.5 parts by mass or more and 8.5 parts by mass or less with respect to 100 parts by mass of the binder.

[0124] [5] The binder composition for non-aqueous secondary battery electrodes according to any one of [1] to [4], wherein the content of the aromatic surfactant is 4 parts by mass or more and 7 parts by mass or less per 100 parts by mass of the binder.

[0125] [6] The binder composition for non-aqueous secondary battery electrodes according to any one of [1] to [5], wherein the proportion of the (meth)acrylic acid ester monomer units in the polymer X is 65.0% by mass or more and 82.5% by mass or less, when the total amount of repeating units in the polymer X is 100% by mass.

[0126] [7] The binder composition for non-aqueous secondary battery electrodes according to any one of [1] to [6], wherein the proportion of the (meth)acrylic acid ester monomer units in the polymer X is 70.0% by mass or more and 80.0% by mass or less, when the total amount of repeating units in the polymer X is 100% by mass.

[0127] [8] A binder composition for non-aqueous secondary battery electrodes according to any one of [1] to [7], wherein an alkyl group having 1 to 4 carbon atoms is bonded to the naphthalene structure of the aromatic surfactant.

[0128] [9] The binder composition for non-aqueous secondary battery electrodes according to any one of [1] to [8], wherein the aromatic surfactant is at least one selected from the group consisting of the sodium salt of methylnaphthalene sulfonic acid formalin condensate and the sodium salt of butylnaphthalene / naphthalene sulfonic acid formalin condensate.

[0129]

[10] A binder composition for non-aqueous secondary battery electrodes according to any one of [1] to [9], wherein the aromatic surfactant is the sodium salt of methylnaphthalene sulfonic acid formalin condensate.

[0130]

[11] A binder composition for non-aqueous secondary battery electrodes according to any one of [1] to

[10] , wherein the polymer X further contains aromatic vinyl monomer units.

[0131]

[12] A binder composition for non-aqueous secondary battery electrodes according to any one of [1] to

[11] , wherein the polymer X is particulate and the median diameter of the polymer X is 100 nm or more and 250 nm or less.

[0132]

[13] A binder composition for non-aqueous secondary battery electrodes according to any one of [1] to

[12] , wherein the polymer X further contains an acidic group-containing monomer unit.

[0133]

[14] A slurry composition for non-aqueous secondary battery electrodes, comprising an electrode active material and a binder composition for non-aqueous secondary battery electrodes described in any of [1] to

[13] .

[0134]

[15] The slurry composition for non-aqueous secondary battery electrodes according to

[14] , further comprising a water-soluble polymer Y containing a hydrophilic group.

[0135]

[16] The non-aqueous secondary battery electrode slurry composition according to

[15] , wherein the content of the water-soluble polymer Y is 0.1% by mass or more and 5.0% by mass or less when the total solid content contained in the non-aqueous secondary battery electrode slurry composition is 100% by mass.

[0136]

[17] A slurry composition for non-aqueous secondary battery electrodes according to any one of

[14] to

[16] , wherein the electrode active material contains a lithium-containing composite metal oxide having an olivine-type structure.

[0137]

[18] A slurry composition for non-aqueous secondary battery electrodes according to any one of

[14] to

[17] , further comprising a conductive material containing at least one of particulate conductive material and carbon nanotubes.

[0138] An electrode for a non-aqueous secondary battery comprising an electrode composite layer formed using the slurry composition for non-aqueous secondary battery electrodes described in any of

[19] ,

[14] , to

[18] .

[0139] A non-aqueous secondary battery comprising electrodes for non-aqueous secondary batteries as described in

[20] and

[19] .

[0140] 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 quantities refer to mass unless otherwise specified. In addition, in polymers produced by copolymerizing multiple types of monomers, the proportion of monomer units formed by polymerization of a certain monomer in the polymer is usually equal to the ratio of that certain monomer to the total monomers used in the polymerization of the polymer (starting ratio), unless otherwise specified. Various measurements and evaluations were performed in the examples and comparative examples using the following methods.

[0141] <Median diameter D50 of polymer X> For each polymer X produced in the examples and comparative examples, the median diameter D50 of polymer X was determined by measuring the particle size distribution (volume basis) of an aqueous dispersion solution adjusted to a solid content concentration of 0.1% by mass using a laser diffraction particle size distribution analyzer (Beckman Coulter, product name "LS-230"), and calculating from the smallest diameter side, the cumulative volume at which 50% was obtained (nm).

[0142] <Viscosity Stability> The viscosity of the positive electrode slurry composition was measured using a Brookfield B-type viscometer (60 rpm, 25°C), and the viscosity η0 immediately after preparation was measured. Next, the slurry composition whose viscosity was measured was stored standing for 24 hours, and the viscosity η1 after 24 hours of storage was measured using the same B-type viscometer (rotation speed: 60 rpm). The viscosity retention rate Δη of the slurry composition before and after storage was calculated as η1 / η0 × 100 (%), and the viscosity stability of the slurry composition was evaluated according to the following criteria. The closer the viscosity retention rate Δη is to 100%, the better the viscosity stability of the slurry composition. A: Viscosity retention rate Δη is 100% or more and less than 150% B: Viscosity retention rate Δη is 150% or more and less than 250% C: Viscosity retention rate Δη is 250% or more and less than 350% D: Viscosity retention rate Δη is 350% or more

[0143] <Adhesion of Electrode Mixture Layer to Current Collector> The positive electrodes manufactured in the examples and comparative examples were cut into rectangles measuring 1.0 cm wide x 10 cm long to serve as test specimens. Cellophane tape (as specified in JIS Z1522) was attached to the positive electrode mixture layer side surface of these test specimens. The stress was measured when the cellophane tape was peeled off from one end of the test specimen at a speed of 50 mm / min in a 90° direction. The measurement was performed a total of three times, and the average value was calculated and defined as the peel strength (N / m). A higher peel strength indicates that the positive electrode mixture layer has excellent adhesion and is firmly attached to the current collector.

[0144] <Output Characteristics> The lithium-ion secondary batteries prepared in the examples and comparative examples were left to stand for 5 hours at 25°C after electrolyte injection. Next, they were charged to a State of Charge (SOC) of 20% using a constant current method at 25°C and 0.1C, and then aged for 12 hours at 60°C. Then, they were discharged to a cell voltage of 2.6V using a constant current method at 25°C and 0.2C. After that, CC-CV charging (upper limit cell voltage 3.6V) was performed with a constant current of 0.2C, and CC discharge was performed to a cell voltage of 2.6V with a constant current of 0.2C. This charging and discharging at 0.2C was repeated three times. The discharge capacity of the third discharge at 0.2C was defined as the initial capacity CX. Subsequently, CC-CV charging was performed at a constant current of 0.2C (maximum cell voltage 3.6V), and CC discharge was performed at a constant current of 2.0C until the cell voltage reached 2.6V. The discharge capacity at this time was defined as CY. The 2.0C / 0.2C discharge capacity retention rate, expressed as (CY / CX) × 100 (%), was calculated. Note that a higher discharge capacity retention rate indicates better output characteristics of the lithium-ion secondary battery.

[0145] <Cycle Characteristics> The lithium-ion secondary batteries prepared in the examples and comparative examples were left standing at 25°C for 5 hours after electrolyte injection. Next, they were charged to a State of Charge (SOC) of 20% using a constant current method at 0.1C at 25°C, and then aged for 12 hours at 60°C. Then, they were discharged to a cell voltage of 2.6V using a constant current method at 0.2C at 25°C. After that, CC-CV charging (upper limit cell voltage 3.6V) was performed with a constant current of 0.2C, and CC discharge was performed to a cell voltage of 2.6V with a constant current of 0.2C. This charging and discharging at 0.2C was repeated three times. After that, under conditions of 45°C, the charging and discharging operation was performed 100 times with a cell voltage of 3.60-2.60V, a constant current of 0.2C, CC-CV charging (upper limit cell voltage 3.6V), and a discharge rate of 1.0C. In this process, the discharge capacity of the first cycle was defined as X1, and the discharge capacity of the 100th cycle was defined as X2. Using the discharge capacities X1 and X2, the capacity retention rate, expressed as ΔC = (X2 / X1) × 100 (%), was calculated. A larger value of this capacity retention rate ΔC indicates that the lithium-ion secondary battery has superior cycle characteristics.

[0146] (Example 1) <Preparation of Polymer X> Polymer X was prepared as a binder according to the following procedure. 90 parts of deionized water and 0.5 parts of sodium lauryl sulfate as an emulsifier were added to a 1 L flask with a septum equipped with a stirrer (reaction vessel), the gas phase was replaced with nitrogen gas, and the temperature was raised to 60°C. Then, 0.3 parts of ammonium persulfate (APS) was dissolved in 20.0 parts of deionized water and added as a polymerization initiator. Meanwhile, in a separate container (emulsion container), 30 parts of deionized water, 0.5 parts of sodium lauryl sulfate as an emulsifier, 77.0 parts of n-butyl acrylate as a (meth)acrylic acid ester monomer, 2.5 parts of itaconic acid as an acidic group-containing monomer, 1.5 parts of 2-hydroxyethyl acrylate as a monomer that forms other repeating units A, and 19.0 parts of styrene as an aromatic vinyl monomer were mixed to obtain a monomer composition. Polymerization was carried out by continuously adding this monomer composition to a 1 L flask with a septum over 3 hours. The reaction was carried out at 60°C during the addition. After the addition was complete, the mixture was stirred at 80°C for 2 hours to obtain an aqueous dispersion of polymer X. To the aqueous dispersion of polymer X thus obtained, an 8% sodium hydroxide aqueous solution was added to adjust the pH to 8 to obtain an aqueous dispersion of polymer X. The obtained polymer X was particulate in the aqueous dispersion and was water-insoluble according to the definition herein. The median diameter of polymer X was measured according to the above procedure. The results are shown in Table 1.

[0147] <Preparation of Binder Composition> To the aqueous dispersion of polymer X after neutralization obtained above, 0.07 parts of polyether-modified polydimethylsiloxane (manufactured by BIC Chemie Japan Co., Ltd., product name "BYK-1789") was added to 100 parts of the binder (polymer X), and the mixture was stirred for 30 minutes. Then, 5 parts of sodium salt of methylnaphthalene sulfonic acid formalin condensate (manufactured by Kao Corporation, product name "Demol MS"), an aromatic surfactant having a naphthalene structure, was added to 100 parts of the binder (polymer X), and the mixture was stirred for 30 minutes to obtain the binder composition.

[0148] <Water-soluble polymer Y> In the reactor, 200 parts of deionized water, 8.5 parts of a 30% aqueous solution of sodium dodecyldiphenyl ethersulfonate, 10.0 parts of 2-hydroxyethyl methacrylate, 25.0 parts of 4-hydroxybutyl acrylate, 24.0 parts of methacrylic acid, 1.0 part of n-butyl acrylate, and 2.5 parts of t-dodecyl mercaptan as a molecular weight modifier (chain transfer agent) were charged in order. Next, the gas inside was replaced with nitrogen three times, and then 40.0 parts of 1,3-butadiene was charged. The reactor was then kept at 18°C, and 0.3 parts of cumene hydroperoxide as a polymerization initiator, appropriate amounts of a reducing agent and a chelating agent were charged. The polymerization reaction was continued while stirring, and when the polymerization conversion rate reached 85%, 0.1 parts of a 10% aqueous solution of hydroquinone as a polymerization arrestor was added to stop the polymerization reaction. Next, residual monomers were removed using an evaporator at a water temperature of 80°C to obtain an aqueous dispersion of the polymer precursor. Then, the dispersion was concentrated using an evaporator until the solid content concentration reached 40%. Subsequently, an 8.0% NaOH aqueous solution and deionized water were added to the concentrated aqueous dispersion of the polymer to adjust the pH to 8.5 and the solid content concentration to 8% to obtain the water-soluble polymer Y.

[0149] <Preparation of slurry composition for positive electrode> Lithium iron phosphate (LiFePO) olivine type as positive electrode active material ４96.5 parts of (median diameter: 1 μm) and 1.5 parts of acetylene black as a conductive material were mixed in a planetary mixer (15 rpm, 15 minutes). Then, 1.0 part of an aqueous solution of water-soluble polymer Y (equivalent to solid content) and deionized water were added to adjust the solid content concentration to 78%, and the mixture was mixed in a planetary mixer (60 rpm, 50 minutes). Next, water was added to adjust the viscosity of the slurry composition to be in the range of 3000 mPa·s to 4000 mPa·s. Next, 1.0 part of an aqueous dispersion of polymer X as a binder composition (equivalent to solid content) was added and mixed in a planetary mixer (40 rpm, 10 minutes) to prepare the slurry composition for the positive electrode. Finally, water was added to adjust the viscosity of the slurry composition to be in the range of 1000 mPa·s to 2000 mPa·s. The viscosity stability of the obtained cathode slurry composition was evaluated according to the above. The results are shown in Table 1. During the preparation of the cathode slurry composition, the viscosity of the obtained cathode slurry composition was measured using a single-cylinder rotational viscometer (Brookfield B-type viscometer) in accordance with JIS Z8803:1991. The measurement conditions were a temperature of 25°C and a rotational speed of 60 rpm.

[0150] <Preparation of Current Collector with Conductive Adhesive Layer> A current collector with a conductive adhesive layer prepared by the following method was used as the current collector for the manufacture of the positive electrode. 70 parts of conductive carbon (graphite / acetylene black = 70 / 30 (mass ratio)) and 8 parts of carboxymethylcellulose (Daicel 1220, manufactured by Daicel Corporation) as a dispersant were added, and the mixture was stirred at 3000 rpm for 60 minutes using a disperser. Then, 22 parts of an aqueous dispersion of polymer X equivalent to the solid content were added, and the mixture was further stirred at 1500 rpm for 10 minutes using a disperser to prepare a conductive adhesive. The conductive adhesive was applied to aluminum foil, which was to be used as the substrate for the current collector, using a casting method with a roll bar at a molding speed of 20 m / min, and dried at 80°C to form a conductive adhesive layer with a thickness of 1 μm. This obtained a current collector with a conductive adhesive layer formed on the substrate for the current collector.

[0151] <Preparation of positive electrode for lithium-ion secondary battery> The positive electrode slurry composition obtained as described above is applied to the conductive adhesive layer side of the current collector with a conductive adhesive layer, and the basis weight after drying is 25 mg / cm² using a comma coater. 2 The material was applied to obtain a cathode base by drying at 90°C for 20 minutes, then at 120°C for another 20 minutes, and finally at 60°C for 10 hours. This cathode base was rolled using a roll press to obtain a density of 2.5 g / cm³. 3 A sheet-like positive electrode was fabricated consisting of a positive electrode composite layer, a conductive adhesive layer, and aluminum foil. The sheet-like positive electrode was then cut to a width of 48.0 mm and a length of 47 cm to be used as a positive electrode for a lithium-ion secondary battery. The adhesion of the positive electrode composite layer to the current collector was evaluated using the obtained lithium-ion secondary battery positive electrode, and the adhesion was found to be good.

[0152] <Preparation of anode for lithium-ion secondary battery> In a 5 MPa pressure vessel equipped with a stirrer, 65.0 parts of styrene as an aromatic vinyl monomer, 35.0 parts of 1,3-butadiene as an aliphatic conjugated diene monomer, 2.0 parts of itaconic acid as an acidic group-containing monomer, 1.0 part of 2-hydroxyethyl acrylate as a hydroxyl group-containing monomer, 0.3 parts of t-dodecyl mercaptan as a molecular weight modifier, 5 parts of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of deionized water as a solvent, and 1 part of potassium persulfate as a polymerization initiator were added and thoroughly stirred. Polymerization was started by heating to 55°C. When the monomer consumption reached 95.0%, the mixture was cooled and the reaction was stopped. To the aqueous dispersion containing the polymer thus obtained, a 5% sodium hydroxide aqueous solution was added to adjust the pH to 8. Subsequently, unreacted monomers were removed by heated vacuum distillation. The mixture was then cooled to below 30°C to obtain an aqueous dispersion of particulate polymer to be used as a binder for the negative electrode. 48.75 parts of artificial graphite and 48.75 parts of natural graphite as negative electrode active materials, along with 1 part of carboxymethylcellulose (equivalent to solid content) as a thickener, were added to a planetary mixer. The mixture was then diluted with deionized water to a solid content concentration of 60%, and kneaded at a rotation speed of 45 rpm for 60 minutes. Subsequently, 1.5 parts (equivalent to solid content) of the aqueous dispersion of particulate polymer obtained as a binder for the negative electrode was added, and the mixture was kneaded at a rotation speed of 40 rpm for 40 minutes. Finally, deionized water was added to achieve a viscosity of 3000 ± 500 mPa·s (measured with a B-type viscometer at 25°C and 60 rpm) to prepare the slurry composition for the negative electrode. The above-mentioned negative electrode slurry composition was applied to the surface of a 15 μm thick copper foil current collector using a comma coater, at a rate of 12.5 ± 0.5 mg / cm². ２ The material was applied in this manner. Subsequently, the copper foil coated with the negative electrode slurry composition was transported at a speed of 400 mm / min in an oven at 80°C for 2 minutes, and then in an oven at 110°C for another 2 minutes, thereby drying the negative electrode slurry composition on the copper foil and obtaining a negative electrode base roll with a negative electrode composite layer formed on the current collector. This negative electrode base roll was rolled in a roll press to obtain a density of 1.6 g / cm³. 3A sheet-like negative electrode was fabricated consisting of a negative electrode composite layer and copper foil. The sheet-like negative electrode was then cut to a width of 50.0 mm and a length of 52 cm to be used as a negative electrode for a lithium-ion secondary battery.

[0153] <Fabrication of Lithium-ion Secondary Battery> The fabricated positive electrode and negative electrode for the lithium-ion secondary battery were placed with their electrode composite layers facing each other, and a 15 μm thick separator (microporous polyethylene membrane) was interposed between them. The materials were then wound around a 20 mm diameter core to obtain a wound body. The resulting wound body was then compressed from one direction at a speed of 10 mm / second until its thickness reached 4.5 mm. The compressed wound body was elliptical in plan view, and its ratio of major axis to minor axis (major axis / minor axis) was 7.7. A 1.0 M LiPF 4 solution was used as the electrolyte. ６ A solution (solvent: mixed solvent of ethylene carbonate (EC) / ethyl methyl carbonate (EMC) = 3 / 7 (volume ratio), additive: containing 2 vol% vinylene carbonate (solvent ratio)) was prepared. Then, the compressed coil was placed in an aluminum laminate case along with 3.2 g of electrolyte. Nickel lead wires were connected to the designated locations on the negative electrode for the secondary battery, and aluminum lead wires were connected to the designated locations on the positive electrode for the lithium-ion secondary battery. The opening of the case was then sealed with heat to obtain a lithium-ion secondary battery. This lithium-ion secondary battery was a pouch type with a width of 35 mm, a height of 60 mm, and a thickness of 5 mm, and the nominal capacity of the battery was 700 mAh. The output characteristics of the obtained lithium-ion secondary battery were evaluated, and the output characteristics were good. The cycle characteristics of the obtained lithium-ion secondary battery were also evaluated, and the cycle characteristics were good.

[0154] (Example 2) In preparing the binder composition, the same operations, measurements, and evaluations as in Example 1 were performed, except that 0.07 parts of polyether-modified polydimethylsiloxane (manufactured by BIC Chemie Japan Co., Ltd., product name "BYK-1789") were replaced with 0.07 parts of polyether-modified polydimethylsiloxane (manufactured by BIC Chemie Japan Co., Ltd., product name "BYK-1770"). The results are shown in Table 1. The adhesion of the positive electrode composite layer to the current collector was evaluated using the obtained lithium-ion secondary battery positive electrode, and the adhesion was good. The output characteristics of the obtained lithium-ion secondary battery were evaluated, and the output characteristics were good. The cycle characteristics of the obtained lithium-ion secondary battery were also evaluated, and the cycle characteristics were good.

[0155] (Example 3) In preparing the binder composition, the same operations, measurements, and evaluations as in Example 1 were performed, except that the amount of polyether-modified polydimethylsiloxane (manufactured by BIC Chemie Japan Co., Ltd., product name "BYK-1789") was changed from 0.07 parts to 0.02 parts. The results are shown in Table 1. The adhesion of the positive electrode composite layer to the current collector was evaluated using the obtained lithium-ion secondary battery positive electrode, and the adhesion was good. The output characteristics of the obtained lithium-ion secondary battery were evaluated, and the output characteristics were good. The cycle characteristics of the obtained lithium-ion secondary battery were also evaluated, and the cycle characteristics were good.

[0156] (Example 4) In preparing the binder composition, the same operations, measurements, and evaluations as in Example 1 were performed, except that the amount of polyether-modified polydimethylsiloxane (manufactured by BIC Chemie Japan Co., Ltd., product name "BYK-1789") was changed from 0.07 parts to 0.1 parts. The results are shown in Table 1. The adhesion of the positive electrode composite layer to the current collector was evaluated using the obtained lithium-ion secondary battery positive electrode, and the adhesion was good. The output characteristics of the obtained lithium-ion secondary battery were evaluated, and the output characteristics were good. The cycle characteristics of the obtained lithium-ion secondary battery were also evaluated, and the cycle characteristics were good.

[0157] (Example 5) In preparing the binder composition, the same operations, measurements, and evaluations as in Example 1 were performed, except that 5 parts of sodium salt of methylnaphthalene sulfonic acid formalin condensate (manufactured by Kao Corporation, product name "Demol MS") were replaced with 5 parts of sodium salt of butylnaphthalene / naphthalene sulfonic acid formalin condensate (manufactured by Kao Corporation, "Demol SNB"). The results are shown in Table 1. The adhesion of the positive electrode composite layer to the current collector was evaluated using the obtained lithium-ion secondary battery positive electrode, and the adhesion was good. The output characteristics of the obtained lithium-ion secondary battery were evaluated, and the output characteristics were good. The cycle characteristics of the obtained lithium-ion secondary battery were also evaluated, and the cycle characteristics were good.

[0158] (Example 6) In preparing the binder composition, the same operations, measurements, and evaluations as in Example 1 were performed, except that 5 parts of sodium salt of methylnaphthalene sulfonic acid formalin condensate (manufactured by Kao Corporation, product name "Demol MS") were replaced with 5 parts of Na salt of naphthalene sulfonic acid formalin condensate (manufactured by Kao Corporation, "Demol N"). The results are shown in Table 1. The adhesion of the positive electrode composite layer to the current collector was evaluated using the obtained lithium-ion secondary battery positive electrode, and the adhesion was good. The output characteristics of the obtained lithium-ion secondary battery were evaluated, and the output characteristics were good. The cycle characteristics of the obtained lithium-ion secondary battery were also evaluated, and the cycle characteristics were good.

[0159] (Example 7) In preparing the binder composition, the same operations, measurements, and evaluations as in Example 1 were performed, except that the sodium salt of methylnaphthalene sulfonic acid formalin condensate (manufactured by Kao Corporation, product name "Demol MS") was changed from 5 parts to 3 parts. The results are shown in Table 1. The adhesion of the positive electrode composite layer to the current collector was evaluated using the obtained lithium-ion secondary battery positive electrode, and the adhesion was good. The output characteristics of the obtained lithium-ion secondary battery were evaluated, and the output characteristics were good. The cycle characteristics of the obtained lithium-ion secondary battery were also evaluated, and the cycle characteristics were good.

[0160] (Example 8) In preparing the binder composition, the same operations, measurements, and evaluations as in Example 1 were performed, except that the sodium salt of methylnaphthalene sulfonic acid formalin condensate (manufactured by Kao Corporation, product name "Demol MS") was changed from 5 parts to 9 parts. The results are shown in Table 1. The adhesion of the positive electrode composite layer to the current collector was evaluated using the obtained lithium-ion secondary battery positive electrode, and the adhesion was good. The output characteristics of the obtained lithium-ion secondary battery were evaluated, and the output characteristics were good. The cycle characteristics of the obtained lithium-ion secondary battery were also evaluated, and the cycle characteristics were good.

[0161] (Example 9) In preparing polymer X, the same operations, measurements, and evaluations as in Example 1 were performed, except that a monomer composition was used which consisted of 30 parts ion-exchanged water, 0.5 parts sodium lauryl sulfate as an emulsifier, 68.0 parts n-butyl acrylate as a (meth)acrylic acid ester monomer, 2.5 parts itaconic acid as an acidic group-containing monomer, 1.5 parts 2-hydroxyethyl acrylate and 3.0 parts acrylamide as monomers forming other repeating units A, and 25.0 parts styrene as an aromatic vinyl monomer. The results are shown in Table 1. The adhesion of the positive electrode composite layer to the current collector was evaluated using the obtained lithium-ion secondary battery positive electrode, and the adhesion was good. The output characteristics of the obtained lithium-ion secondary battery were evaluated, and the output characteristics were good. The cycle characteristics of the obtained lithium-ion secondary battery were also evaluated, and the cycle characteristics were good.

[0162] (Example 10) In preparing polymer X, the same operations, measurements, and evaluations as in Example 1 were performed, except that a monomer composition was used which consisted of 30 parts ion-exchanged water, 0.5 parts sodium lauryl sulfate as an emulsifier, 83.0 parts n-butyl acrylate as a (meth)acrylic acid ester monomer, 2.0 parts itaconic acid as an acidic group-containing monomer, and 15.0 parts styrene as an aromatic vinyl monomer. The results are shown in Table 1. The adhesion of the positive electrode composite layer to the current collector was evaluated using the obtained lithium-ion secondary battery positive electrode, and the adhesion was good. The output characteristics of the obtained lithium-ion secondary battery were evaluated, and the output characteristics were good. The cycle characteristics of the obtained lithium-ion secondary battery were also evaluated, and the cycle characteristics were good.

[0163] (Example 11) In preparing polymer X, the same operations, measurements, and evaluations as in Example 1 were performed, except that a monomer composition was used which consisted of 30 parts ion-exchanged water, 0.5 parts sodium lauryl sulfate as an emulsifier, 83.0 parts n-butyl acrylate as a (meth)acrylic acid ester monomer, 2.5 parts itaconic acid as an acidic group-containing monomer, 1.5 parts 2-hydroxyethyl acrylate and 8.0 parts acrylamide as monomers forming other repeating units A, and 5.0 parts styrene as an aromatic vinyl monomer. The results are shown in Table 1. The adhesion of the positive electrode composite layer to the current collector was evaluated using the obtained positive electrode for lithium-ion secondary batteries, and the adhesion was good. The output characteristics of the obtained lithium-ion secondary battery were evaluated, and the output characteristics met a certain level. The cycle characteristics of the obtained lithium-ion secondary battery were also evaluated, and the cycle characteristics met a certain level.

[0164] (Example 12) In preparing polymer X, the same operations, measurements, and evaluations as in Example 1 were performed, except that a monomer composition was used which consisted of 30 parts ion-exchanged water, 0.5 parts sodium lauryl sulfate as an emulsifier, 80.0 parts n-butyl acrylate as a (meth)acrylic acid ester monomer, 2.5 parts itaconic acid as an acidic group-containing monomer, 2.0 parts 2-hydroxyethyl acrylate and 2.0 parts acrylamide as monomers forming other repeating units A, and 13.5 parts styrene as an aromatic vinyl monomer. The results are shown in Table 1. The adhesion of the positive electrode composite layer to the current collector was evaluated using the obtained lithium-ion secondary battery positive electrode, and the adhesion was good. The output characteristics of the obtained lithium-ion secondary battery were evaluated, and the output characteristics were good. The cycle characteristics of the obtained lithium-ion secondary battery were also evaluated, and the cycle characteristics were good.

[0165] (Example 13) In preparing polymer X, the same operations, measurements, and evaluations as in Example 1 were performed, except that a monomer composition was used which consisted of 30 parts ion-exchanged water, 0.5 parts sodium lauryl sulfate as an emulsifier, 70.0 parts n-butyl acrylate as a (meth)acrylic acid ester monomer, 2.0 parts itaconic acid as an acidic group-containing monomer, 1.0 part 2-hydroxyethyl acrylate as a monomer that forms other repeating units A, and 27.0 parts styrene as an aromatic vinyl monomer. The results are shown in Table 1. The adhesion of the positive electrode composite layer to the current collector was evaluated using the obtained lithium-ion secondary battery positive electrode, and the adhesion was good. The output characteristics of the obtained lithium-ion secondary battery were evaluated, and the output characteristics were good. The cycle characteristics of the obtained lithium-ion secondary battery were also evaluated, and the cycle characteristics were good.

[0166] (Example 14) In preparing polymer X, the same operations, measurements, and evaluations as in Example 1 were performed, except that a monomer composition was used which consisted of 30 parts ion-exchanged water, 0.5 parts sodium lauryl sulfate as an emulsifier, 65.0 parts n-butyl acrylate as a (meth)acrylic acid ester monomer, 2.5 parts itaconic acid as an acidic group-containing monomer, and 32.5 parts styrene as an aromatic vinyl monomer. The results are shown in Table 1. When the positive electrode for the obtained lithium-ion secondary battery was evaluated, the adhesion of the positive electrode composite layer to the current collector was found to be at a certain level. Furthermore, when the output characteristics of the obtained lithium-ion secondary battery were evaluated, the output characteristics were good. Furthermore, when the cycle characteristics of the obtained lithium-ion secondary battery were evaluated, the cycle characteristics were at a certain level.

[0167] (Example 15) In preparing the slurry composition for the positive electrode, a CNT dispersion was prepared as described below, and then this CNT dispersion was used to prepare the slurry composition for the positive electrode. Otherwise, the same operations, measurements, and evaluations as in Example 1 were performed. The results are shown in Table 1. The adhesion of the positive electrode composite layer to the current collector was evaluated using the obtained lithium-ion secondary battery positive electrode, and the adhesion was good. The output characteristics of the obtained lithium-ion secondary battery were evaluated, and the output characteristics were good. The cycle characteristics of the obtained lithium-ion secondary battery were also evaluated, and the cycle characteristics were good.

[0168] <Preparation of CNT dispersion> Carbon nanotubes as conductive material (BET specific surface area: 250 m²) 2 A CNT dispersion with a solid content of 1% by mass was prepared by stirring 0.4 parts ( / g) of carboxymethylcellulose (Daicel 1220, manufactured by Daicel Corporation) and 99 parts of deionized water using a disperser (3000 rpm, 10 minutes), and then mixing for 1 hour at a peripheral speed of 8 m / s using a bead mill with 1 mm diameter zirconia beads.

[0169] <Preparation of slurry composition for positive electrode> Lithium iron phosphate (LiFePO) olivine type as positive electrode active material ４96.5 parts of polymer X (median diameter: 1 μm) and 1.5 parts of acetylene black as a conductive material were mixed in a planetary mixer (15 rpm, 15 minutes). Then, 1.0 part (equivalent to solid content) of an aqueous solution of polymer X as a binder composition and ion-exchanged water were added to adjust the solid content concentration to 78%, and the mixture was mixed in a planetary mixer (60 rpm, 50 minutes). Next, a CNT dispersion was added so that the amount of carbon nanotubes added was 0.1 parts, and the mixture was mixed in a planetary mixer (60 rpm, 10 minutes). Next, water was added to adjust the viscosity of the slurry composition so that it was in the range of 3000 mPa·s to 4000 mPa·s. Next, 1.0 part (equivalent to solid content) of an aqueous dispersion of polymer X was added, and the mixture was mixed in a planetary mixer (40 rpm, 10 minutes) to prepare the slurry composition for the positive electrode. Finally, water was added to adjust the viscosity of the slurry composition to a range of 1000 mPa·s to 2000 mPa·s. The viscosity stability of the obtained cathode slurry composition was evaluated. The results are shown in Table 1. During the preparation of the cathode slurry composition, the viscosity of the obtained cathode slurry composition was measured using a single-cylinder rotational viscometer (Brookfield B-type viscometer) in accordance with JIS Z8803:1991. The measurement conditions were a temperature of 25°C and a rotational speed of 60 rpm.

[0170] (Comparative Example 1) In preparing the binder composition, the same operations, measurements, and evaluations as in Example 1 were performed, except that polyether-modified polydimethylsiloxane (manufactured by BIC Chemie Japan Co., Ltd., product name "BYK-1789") was not used. The results are shown in Table 1.

[0171] (Comparative Example 2) In preparing the binder composition, the same operations, measurements, and evaluations as in Example 1 were performed, except that the amount of polyether-modified polydimethylsiloxane (manufactured by BIC Chemie Japan Co., Ltd., product name "BYK-1789") was changed from 0.07 parts to 0.2 parts. The results are shown in Table 1.

[0172] (Comparative Example 3) In preparing the binder composition, the same operations, measurements, and evaluations as in Example 1 were performed, except that 0.07 parts of polyether-modified polydimethylsiloxane (manufactured by BIC Chemie Japan Co., Ltd., product name "BYK-1789") were replaced with 0.07 parts of non-polyether-modified polydimethylsiloxane (manufactured by BIC Chemie Japan Co., Ltd., product name "BYK-1616"). The results are shown in Table 1.

[0173] (Comparative Example 4) In preparing the binder composition, the same operations, measurements, and evaluations as in Example 1 were performed, except that the sodium salt of methylnaphthalene sulfonic acid formalin condensate (manufactured by Kao Corporation, product name "Demol MS") was not used. The results are shown in Table 1.

[0174] (Comparative Example 5) In preparing the binder composition, the same operations, measurements, and evaluations as in Example 1 were performed, except that the amount of sodium salt of methylnaphthalene sulfonic acid formalin condensate (manufactured by Kao Corporation, product name "Demol MS") was changed from 5 parts to 12 parts. The results are shown in Table 1.

[0175] (Comparative Example 6) In preparing the binder composition, the same operations, measurements, and evaluations as in Example 1 were performed, except that 5 parts of the sodium salt of methylnaphthalene sulfonic acid formalin condensate (manufactured by Kao Corporation, product name "Demol MS") were replaced with 5 parts of the sodium salt of polystyrene sulfonic acid without a naphthalene structure (manufactured by Toyo Soda Co., Ltd., "PS-1"). The results are shown in Table 1.

[0176] (Comparative Example 7) In preparing polymer X, the same operations, measurements, and evaluations as in Example 1 were performed, except that a monomer composition was used which consisted of 30 parts ion-exchanged water, 0.5 parts sodium lauryl sulfate as an emulsifier, 58.0 parts n-butyl acrylate as a (meth)acrylic acid ester monomer, 2.5 parts itaconic acid as an acidic group-containing monomer, 1.5 parts 2-hydroxyethyl acrylate and 8.0 parts acrylamide as monomers that form other repeating units A, and 30.0 parts styrene as an aromatic vinyl monomer. The results are shown in Table 1.

[0177] (Comparative Example 8) In preparing polymer X, the same operations, measurements, and evaluations as in Example 1 were performed, except that a monomer composition was used which consisted of 30 parts ion-exchanged water, 0.5 parts sodium lauryl sulfate as an emulsifier, 86.0 parts n-butyl acrylate as a (meth)acrylic acid ester monomer, 2.5 parts itaconic acid as an acidic group-containing monomer, and 11.5 parts styrene as an aromatic vinyl monomer. The results are shown in Table 1.

[0178] In the table below, "BA" represents the n-butyl acrylate unit, "St" represents the styrene unit, "IA" represents the itaconic acid unit, "2HEA" represents the 2-hydroxyethyl acrylate unit, "AAm" represents the acrylamide unit, "2HEMA" represents the 2-hydroxyethyl methacrylate unit, "4HBA" represents the 4-hydroxybutyl acrylate unit, "MAA" represents the methacrylic acid unit, "BD" represents the 1,3-butadiene unit, "Siloxane A" represents polyether-modified polydimethylsiloxane (manufactured by BIC Chemie Japan Co., Ltd., product name "BYK-1789"), and "Siloxane B" represents polyether-modified polydimethylsiloxane (manufactured by BIC Chemie Japan Co., Ltd., product name "BYK-1770"), "Siloxane C" refers to polydimethylsiloxane that has not been modified with polyether (manufactured by BIC Chemie Japan Co., Ltd., product name "BYK-1616"), "Surfactant A" refers to the sodium salt of methylnaphthalene sulfonic acid formalin condensate (manufactured by Kao Corporation, product name "Demol MS"), "Surfactant B" refers to the sodium salt of butylnaphthalene / naphthalene sulfonic acid formalin condensate (manufactured by Kao Corporation, "Demol SNB"), "Surfactant C" refers to the sodium salt of naphthalene sulfonic acid formalin condensate (manufactured by Kao Corporation, "Demol N"), "Surfactant D" refers to the sodium salt of polystyrene sulfonic acid that does not have a naphthalene structure (manufactured by Toyo Soda Co., Ltd., "PS-1"), "LFP" refers to olivine-type lithium iron phosphate, "AcB" refers to acetylene black, and "CNT" refers to carbon nanotubes.

[0179]

[0180] As is clear from Table 1, the binder composition of the example can be used to improve the viscosity stability of the slurry composition.

[0181]

[0182] As is clear from Table 2, it can be seen that the viscosity stability of the slurry composition can be effectively improved by keeping the content of polyether-modified polydimethylsiloxane within a predetermined range relative to 100 parts by mass of polymer X (binding agent).

[0183]

[0184] As is clear from Table 3, it can be seen that the viscosity stability of the slurry composition can be effectively improved by keeping the content of aromatic surfactants having a naphthalene structure within a predetermined range relative to 100 parts by mass of polymer X (binding agent).

[0185]

[0186] As is clear from Table 4, it can be seen that the viscosity stability of the slurry composition can be effectively improved by keeping the proportion of (meth)acrylic acid ester monomer units in polymer X (binding agent) within a predetermined range.

[0187]

[0188] As is clear from Table 5, it can be seen that the viscosity stability of the slurry composition can be effectively improved by using an aromatic surfactant in which a predetermined alkyl group is bonded to the naphthalene structure of the aromatic surfactant.

[0189] The present invention provides a binder composition for non-aqueous secondary battery electrodes that can improve the viscosity stability of the slurry composition. Furthermore, the present invention provides a slurry composition for non-aqueous secondary battery electrodes that exhibits excellent viscosity stability. Furthermore, the present invention provides an electrode for a non-aqueous secondary battery comprising an electrode composite layer formed using the above-mentioned slurry composition for non-aqueous secondary battery electrodes. Furthermore, the present invention provides a non-aqueous secondary battery comprising the above-mentioned electrode for non-aqueous secondary battery.

Claims

1. A binder composition for non-aqueous secondary battery electrodes comprising a binder, an aromatic surfactant, a polyether-modified polydimethylsiloxane, and water, wherein the binder is a polymer X containing (meth)acrylic acid ester monomer units in a proportion of 60.0% to 85.0% by mass when the total amount of repeating units is 100% by mass, the aromatic surfactant has a naphthalene structure, the content of the aromatic surfactant is 1 to 10 parts by mass per 100 parts by mass of the binder, and the content of the polyether-modified polydimethylsiloxane is 0.01 to 0.1 parts by mass per 100 parts by mass of the binder.

2. The binder composition for non-aqueous secondary battery electrodes according to claim 1, wherein an alkyl group having 1 to 4 carbon atoms is bonded to the naphthalene structure of the aromatic surfactant.

3. The binder composition for non-aqueous secondary battery electrodes according to claim 1 or 2, wherein the polymer X further contains aromatic vinyl monomer units.

4. A binder composition for non-aqueous secondary battery electrodes according to any one of claims 1 to 3, wherein the polymer X is in particulate form and the median diameter of the polymer X is 100 nm or more and 250 nm or less.

5. The binder composition for non-aqueous secondary battery electrodes according to any one of claims 1 to 4, wherein the polymer X further contains an acidic group-containing monomer unit.

6. A slurry composition for a non-aqueous secondary battery electrode, comprising an electrode active material and a binder composition for a non-aqueous secondary battery electrode according to any one of claims 1 to 5.

7. The slurry composition for non-aqueous secondary battery electrodes according to claim 6, further comprising a water-soluble polymer Y containing a hydrophilic group.

8. The non-aqueous secondary battery electrode slurry composition according to claim 7, wherein the content of the water-soluble polymer Y is 0.1% by mass or more and 5.0% by mass or less, when the total solid content contained in the non-aqueous secondary battery electrode slurry composition is taken as 100% by mass.

9. The slurry composition for non-aqueous secondary battery electrodes according to any one of claims 6 to 8, wherein the electrode active material contains a lithium-containing composite metal oxide having an olivine-type structure.

10. A slurry composition for non-aqueous secondary battery electrodes according to any one of claims 6 to 9, further comprising a conductive material containing at least one of particulate conductive material and carbon nanotubes.

11. An electrode for a non-aqueous secondary battery comprising an electrode composite layer formed using the slurry composition for non-aqueous secondary battery electrodes described in any one of claims 6 to 10.

12. A non-aqueous secondary battery comprising an electrode for a non-aqueous secondary battery as described in claim 11.

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