Binder composition for non-aqueous secondary battery electrode, slurry composition for non-aqueous secondary battery electrode, electrode for non-aqueous secondary battery, and non-aqueous secondary battery

Abstract

Provided is a binder composition for a non-aqueous secondary battery electrode, the binder composition containing a polymer, wherein the distance between the Hansen solubility parameters of the polymer and those of a standard conductive material having Hansen solubility parameters of δd=19.2, δp=9.6, and δh=8.9 is at least 6.0 (MPa1 / 2), the distance between the Hansen solubility parameters of the polymer and those of a standard dispersant having Hansen solubility parameters of δd=16.9, δp=10.0, and δh=9.0 is at least 3.5 (MPa1 / 2), and the polymer has a weight average molecular weight of greater than 1,000,000.

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 a non-aqueous secondary battery electrode, a slurry composition for a non-aqueous secondary battery electrode, an electrode for a non-aqueous secondary battery, and a non-aqueous secondary battery.

[0002] Non-aqueous secondary batteries such as lithium ion secondary batteries (hereinafter sometimes abbreviated as "secondary batteries") are small, lightweight, have high energy density, and are capable of repeated charge and discharge, and are therefore used in a wide range of applications. Therefore, in recent years, improvements to battery components such as electrodes have been investigated with the aim of further improving the performance of non-aqueous secondary batteries.

[0003] Here, an electrode used in a secondary battery such as a lithium-ion secondary battery typically includes a current collector and an electrode mixture layer (positive electrode mixture layer or negative electrode mixture layer) formed on the current collector. The electrode mixture layer is formed, for example, by applying a slurry composition containing an electrode active material (hereinafter also simply referred to as "active material") and a binder composition containing a binding agent onto the current collector and then drying the applied slurry composition.

[0004] In recent years, attempts have been made to improve the electrode mixture layer in order to achieve further improvements in the performance of secondary batteries. For example, Patent Document 1 discloses the use of a positive electrode comprising a positive electrode active material, a positive electrode binder, and a conductive material, in order to provide a flexible, high-capacity lithium-ion secondary battery with excellent cycle characteristics, wherein the positive electrode active material is coated with a nitrile group-containing acrylic polymer having predetermined physical properties, and the positive electrode binder comprises a fluorine-containing polymer.

[0005] Patent Document 2 discloses a slurry composition for a positive electrode of a secondary battery, which aims to provide a lithium ion secondary battery having excellent cycle characteristics and rate characteristics, and which contains a conductive material having a BET specific surface area of ​​at least a certain level, and a binder containing a fluorine-containing polymer X, a polymer Y containing a predetermined amount of a nitrile group-containing monomer unit, and a polymer Z containing a predetermined amount of a (meth)acrylic acid alkyl ester monomer, and the fluorine-containing polymer X is contained in the binder in a predetermined ratio.

[0006] Patent Document 3 discloses the use of a pressure-sensitive adhesive for bonding active materials together in an electrode, in order to maintain the shape of an electrode for a lithium ion battery and to prevent the energy density of the electrode from decreasing, the pressure-sensitive adhesive being an acrylic polymer essentially containing a structural unit derived from a (meth)acrylic acid alkyl ester monomer in a predetermined proportion or more, and having a predetermined glass transition point, solubility parameter, storage shear modulus, and loss shear modulus.

[0007] International Publication No. 2014 / 088070 International Publication No. 2015 / 064099 International Publication No. 2018 / 194164

[0008] In recent years, thicker electrode films have been investigated to improve the energy density of secondary batteries. However, thicker electrodes reduce the electrode's flexibility, and in wound secondary batteries in particular, cracks can occur in the electrode when the innermost electrode is wound. Furthermore, design changes to increase electrode flexibility can sometimes increase electrode resistance.

[0009] Therefore, an object of the present invention is to provide a binder composition for a non-aqueous secondary battery electrode that can be suitably used to produce an electrode with excellent flexibility and that can reduce the internal resistance of a secondary battery equipped with the resulting electrode. Another object of the present invention is to provide a slurry composition for a non-aqueous secondary battery electrode that can form an electrode with excellent flexibility and can reduce the internal resistance of a secondary battery equipped with the resulting electrode. A further object of the present invention is to provide a non-aqueous secondary battery electrode that can reduce the internal resistance of a non-aqueous secondary battery, and a non-aqueous secondary battery with low internal resistance.

[0010] The present inventors conducted extensive research to solve the above-mentioned problems. They focused on the Hansen solubility parameter (HSP) and weight-average molecular weight of the polymer to be incorporated into the binder composition. More specifically, they discovered that by incorporating a polymer in the binder composition, in which the distance between the HSP of the polymer and the HSPs of the conductive material and the conductive material dispersant (hereinafter also simply referred to as dispersant) is equal to or greater than a predetermined value and the polymer has a weight-average molecular weight of more than 1,000,000, an electrode with excellent flexibility can be produced and the internal resistance of a secondary battery including the electrode can be reduced, thereby completing the present invention.

[0011] That is, the present invention aims to advantageously solve the above-mentioned problems, and the present invention provides [1] a binder composition containing a polymer, wherein the distance between the Hansen solubility parameter of the polymer and a standard conductive material having Hansen solubility parameters of δd = 19.2, δp = 9.6, and δh = 8.9 is 6.0 (MPa １／２ ) or more, and the distance between the Hansen solubility parameter of the polymer and the standard dispersant having Hansen solubility parameters of δd = 16.9, δp = 10.0, and δh = 9.0 is 3.5 (MPa １／２) or more, and the weight-average molecular weight of the polymer exceeds 1,000,000. When the distance between the Hansen solubility parameter (HSP) of the polymer and the HSP of the standard conductive material (hereinafter, the distance between the HSPs of different substances may be referred to as the "HSP distance") and the HSP distance between the polymer and the standard dispersant are each at or above the respective lower limits, the flexibility of the electrode formed using the binder composition for a non-aqueous secondary battery electrode can be improved, the electrode resistance of the resulting electrode can be reduced, and the internal resistance of a non-aqueous secondary battery equipped with the resulting electrode can be reduced. Furthermore, by making the molecular weight of the polymer exceed 1,000,000, the flexibility of the electrode using the binder composition can be increased and the slurry composition can be made uniform. The HSP distance between the polymer and the standard conductive material and the HSP distance between the polymer and the standard dispersant can be calculated using the method described in the Examples section of this specification. The definition and calculation method of the Hansen solubility parameter are described in the following literature: Charles M. Hansen, "Hansen Solubility Parameters: A User's Handbook", CRC Press, 2007. The weight average molecular weight can be measured by the method described in the examples of this specification.

[0012] [2] In the binder composition for a non-aqueous secondary battery electrode according to [1] above, the indentation modulus of the polymer is preferably 3 MPa or more and 30 MPa or less. If the indentation modulus of the polymer is equal to or more than the lower limit, the flexibility of the resulting electrode mixture layer against compression can be increased. If the indentation modulus is equal to or less than the upper limit, the flexibility of the resulting electrode mixture layer against tension can be increased. The indentation modulus of the polymer can be measured according to the method described in the Examples of this specification.

[0013] [3] In the binder composition for a non-aqueous secondary battery electrode according to [1] or [2] above, the polymer preferably contains a (meth)acrylic acid alkyl ester monomer unit. By including the (meth)acrylic acid alkyl ester monomer unit in the polymer, the flexibility of the resulting electrode mixture layer can be further enhanced. In the present invention, "(meth)acrylic" refers to acrylic and / or methacrylic.

[0014] The present invention also aims to advantageously solve the above-mentioned problems, and provides [4] a slurry composition for a non-aqueous secondary battery electrode, comprising at least the binder composition for a non-aqueous secondary battery electrode according to any one of [1] to [3] above, a conductive material, a dispersant, and an active material, wherein the standard conductive material and the conductive material may be the same or different, and the standard dispersant and the dispersant may be the same or different. Thus, by using the binder composition for a non-aqueous secondary battery electrode described above, it is possible to easily obtain a slurry composition for a non-aqueous secondary battery electrode that can produce an electrode with excellent flexibility, reduce the resistance of the resulting electrode, and reduce the internal resistance of a secondary battery equipped with the resulting electrode.

[0015] [5] The nonaqueous secondary battery electrode slurry composition according to [4] above preferably further contains a fluoropolymer, and the proportion of the fluoropolymer is preferably 70 mass% or less when the total of the fluoropolymer and the polymer is 100 mass%. When the content of the fluoropolymer is equal to or less than the upper limit, the flexibility of the obtained electrode mixture layer can be further improved.

[0016] [6] In the non-aqueous secondary battery electrode slurry composition according to the above [4] or [5], the conductive material has a BET specific surface area of ​​100 m ２ / g or more 300m ２ / g or less. When the BET specific surface area of ​​the conductive material is equal to or greater than the lower limit, the capacity of a secondary battery using the slurry composition of the present invention can be increased. Furthermore, when the BET specific surface area of ​​the conductive material is equal to or less than the upper limit, the dispersibility of the conductive material in the slurry composition can be increased, and the internal resistance of the resulting secondary battery can be suppressed. In the present invention, the "BET specific surface area" refers to the BET specific surface area measured by the nitrogen adsorption method, and can be measured in accordance with JIS Z8830:2013.

[0017] Another object of the present invention is to advantageously solve the above-mentioned problems, and the present invention provides [7] a non-aqueous secondary battery electrode including an electrode mixture layer formed using the non-aqueous secondary battery electrode slurry composition according to any one of [4] to [6] above. In this way, by using the above-mentioned non-aqueous secondary battery electrode slurry composition, a non-aqueous secondary battery electrode having excellent flexibility can be successfully produced, and the internal resistance of a secondary battery using the non-aqueous secondary battery electrode can be suppressed.

[0018] Another object of the present invention is to advantageously solve the above-mentioned problems, and the present invention provides [8] a nonaqueous secondary battery including the electrode for a nonaqueous secondary battery according to the above [7]. In this way, by using the electrode for a nonaqueous secondary battery described above, the internal resistance of the secondary battery can be suppressed.

[0019] According to the present invention, a binder composition for a non-aqueous secondary battery electrode can be provided that can be suitably used to produce an electrode with excellent flexibility and that can reduce the internal resistance of a secondary battery including the resulting electrode. Furthermore, according to the present invention, a slurry composition for a non-aqueous secondary battery electrode can be provided that can form an electrode with excellent flexibility and can reduce the internal resistance of a secondary battery including the resulting electrode. Furthermore, according to the present invention, a non-aqueous secondary battery electrode that can reduce the internal resistance of a non-aqueous secondary battery and a non-aqueous secondary battery with low internal resistance can be provided.

[0020] Hereinafter, embodiments of the present invention will be described in detail. The binder composition for a non-aqueous secondary battery electrode of the present invention (hereinafter also simply referred to as the "binder composition") can be suitably used, for example, when preparing a slurry composition for a non-aqueous secondary battery electrode of the present invention (hereinafter also simply referred to as the "slurry composition"). The slurry composition for a non-aqueous secondary battery electrode of the present invention can also be suitably used, for example, when manufacturing a non-aqueous secondary battery electrode of the present invention (hereinafter also simply referred to as the "electrode"). Furthermore, the non-aqueous secondary battery of the present invention is characterized by using a non-aqueous secondary battery electrode formed using the slurry composition for a non-aqueous secondary battery electrode of the present invention. The binder composition for a non-aqueous secondary battery electrode and the slurry composition for a non-aqueous secondary battery electrode of the present invention can be particularly suitably used when forming a positive electrode for a non-aqueous secondary battery.

[0021] (Binder composition for non-aqueous secondary battery electrodes) The binder composition of the present invention contains a polymer and may optionally contain other components. The binder composition of the present invention has a Hansen solubility parameter of the polymer and a standard conductive material having Hansen solubility parameters δd = 19.2, δp = 9.6, and δh = 8.9, and the distance between the Hansen solubility parameter of the polymer and the standard conductive material is 6.0 (MPa １／２ ) or more, and the distance between the Hansen solubility parameter of the polymer and the standard dispersant having Hansen solubility parameters of δd = 16.9, δp = 10.0, and δh = 9.0 is 3.5 (MPa １／２ ) or more, and the weight-average molecular weight of the polymer exceeds 1,000,000. Therefore, the flexibility of an electrode formed using the binder composition can be improved, and the electrode resistance of the resulting electrode can be reduced, thereby reducing the internal resistance of a nonaqueous secondary battery including the resulting electrode.

[0022] The reason for this is not clear, but is presumed to be as follows: That is, the HSP distance between the standard dispersant and the polymer is 3.5 (MPa １／２) or more means that the dispersant and polymer that can be used in the technical field do not aggregate, and the dispersant disperses the conductive material sufficiently, thereby suppressing the internal resistance of the resulting secondary battery. In addition, the HSP distance between the standard conductive material and the polymer is 6.0 (MPa １／２ ) or more means that conductive materials that can be used in this technical field are unlikely to be coated with the polymer. From this perspective, it is possible to prevent the electrochemical reaction of conductive materials inside secondary batteries from being inhibited. Furthermore, the fact that the polymer does not aggregate with the dispersant and is unlikely to coat the conductive material means, conversely, that polymers are likely to aggregate with each other. If the polymers aggregate when the electrode mixture layer is formed, flexibility can be imparted to the electrode mixture layer. Based on the above-mentioned estimated mechanism, it is believed that a polymer that satisfies the above-mentioned specified properties can provide an electrode with excellent flexibility and reduce the internal resistance of the resulting secondary battery.

[0023] <Polymer> In an electrode produced by applying a slurry composition prepared using a binder composition onto a current collector and drying the slurry composition, the polymer is a component that has the function of imparting flexibility to the electrode and retaining components such as an electrode active material contained in the electrode mixture layer so that they do not detach from the electrode mixture layer.

[0024] <<Properties>> [Weight-Average Molecular Weight] The weight-average molecular weight of the polymer must exceed 1,000,000, preferably 1,500,000 or more, more preferably 2,000,000 or more. A weight-average molecular weight of the polymer exceeding 1,000,000 can enhance the flexibility of an electrode using the binder composition. Furthermore, a weight-average molecular weight of the polymer exceeding 1,000,000 can impart an appropriate viscosity to the slurry composition when prepared, thereby suppressing the sedimentation of the conductive material and active material contained in the slurry composition. As a result, the uniformity of the slurry composition itself and the coating film formed using the slurry composition can be enhanced, thereby enhancing the flexibility of the electrode mixture layer. The upper limit of the weight-average molecular weight of the polymer is not particularly limited and can be, for example, 5,000,000 or less. When the average molecular weight of the polymer is equal to or less than the above upper limit, the flexibility of the resulting electrode mixture layer can be further enhanced. The weight-average molecular weight of the polymer can be adjusted by the reaction temperature, polymerization method, the addition of a polymerization initiator, the addition of a molecular weight modifier, etc.

[0025] [HSP distance between polymer and standard conductive material] The HSP distance between the polymer and the standard conductive material is 6.0 (MPa １／２ ) or more, and 8.0 (MPa １／２ It is preferable that the HSP distance between the polymer and the standard conductive material is 6.0 (MPa) or more. １／２ ) or more, the covering of the conductive material by the polymer can be reduced, and the resistance of the electrode can be suppressed. In addition, the upper limit of the HSP distance between the polymer and the standard conductive material is not particularly limited, but from the viewpoint of separation of the polymer and the standard conductive material, for example, 15.0 (MPa １／２ ) can be:

[0026] [HSP distance between polymer and standard dispersant] The HSP distance between the polymer and the standard dispersant is 3.5 (MPa １／２ ) or more, and 4.0 (MPa １／２ It is preferable that the HSP distance between the polymer and the standard dispersant is 3.5 (MPa) or more. １／２) or more, the polymer aggregates and flexibility is increased, and the dispersant and the polymer do not aggregate, and the dispersant sufficiently disperses the conductive material, thereby suppressing the internal resistance of the resulting secondary battery. Furthermore, the upper limit of the HSP distance between the polymer and the standard dispersant is not particularly limited, but from the viewpoint of the stability of the slurry, it is preferable that the upper limit be 15.0 (MPa １／２ ) can be:

[0027] The standard conductive material is a conductive material having Hansen solubility parameters (HSP) of δd = 19.2, δp = 9.6, and δh = 8.9. An example of such a conductive material is acetylene black (manufactured by Denka Co., Ltd., "Li435").

[0028] The standard dispersant is a dispersant having Hansen solubility parameters (HSP) of δd = 16.9, δp = 10.0, and δh = 9.0. Such dispersants include hydrogenated nitrile butadiene rubber (H-NBR).

[0029] [Indentation Complex Modulus] The indentation complex modulus of the polymer is preferably 3 MPa or more, more preferably 5 MPa or more. The indentation complex modulus of the polymer is preferably 30 MPa or less, more preferably 24 MPa or less. If it is 3 MPa or more, the flexibility of the resulting electrode mixture layer against compression can be increased, and for example, in a wound-type secondary battery, cracking due to compressive stress during electrode winding can be suppressed. Furthermore, if it is 30 MPa or less, the flexibility of the resulting electrode mixture layer against tension can be increased, and for example, in a wound-type secondary battery, cracking due to tensile stress during electrode winding can be suppressed. The indentation complex modulus of the polymer can be adjusted by the structure, molecular weight, molecular weight distribution, and monomer composition. The indentation complex modulus of the polymer can be measured by the method described in the Examples of this specification.

[0030] <<Composition>> The polymer is not particularly limited as long as it satisfies the above-mentioned essential properties, and a polymer of any composition can be used. The polymer may be composed of one or more substances. In the following, when a polymer is composed of two or more substances, the content ratio of the structural units and / or monomer units in the polymer refers to the total content ratio of the structural units and / or monomer units in all substances constituting the polymer. Examples of substances suitable for use as the polymer include polymers containing at least one monomer unit selected from the group consisting of (meth)acrylic acid alkyl ester monomer units, nitrile group-containing monomer units, hydrophilic group-containing monomer units, alkylene structural units, and aromatic vinyl monomers. Among these, from the viewpoint of ensuring that the HSP distance between the polymer and the dispersant and conductive material is at least as large as required, polymers containing acrylic acid alkyl ester monomer units are preferred, and polymers containing acrylic acid alkyl ester monomer units and hydrophilic group-containing monomer units are more preferred. In the present invention, "(meth)acrylic" refers to acrylic and / or methacrylic. In addition, the polymer preferably does not contain fluorine atoms.

[0031] [(Meth)acrylic acid alkyl ester monomer unit] The (meth)acrylic acid alkyl ester monomer unit is a repeating unit derived from a (meth)acrylic acid alkyl ester monomer.

[0032] Examples of the (meth)acrylic acid alkyl ester monomer include acrylic acid alkyl esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-pentyl acrylate, isopentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate, and stearyl acrylate; and alkyl methacrylates such as ethyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, isobutyl methacrylate, n-pentyl methacrylate, isopentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, lauryl methacrylate, n-tetradecyl methacrylate, and stearyl methacrylate. Among these, at least one alkyl acrylate monomer selected from the group consisting of 2-ethylhexyl acrylate, ethyl acrylate, and butyl acrylate is preferred, and a combination of ethylhexyl acrylate and butyl acrylate is more preferred.

[0033] The content of the (meth)acrylic acid alkyl ester monomer unit in the polymer is preferably 75% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, and may be 100% by mass, when the total repeating units in the polymer (the sum of structural units and monomer units) is 100% by mass. If the content of the (meth)acrylic acid alkyl ester monomer unit in the polymer is equal to or more than the above lower limit, the HSP distance between the conductive material and the dispersant can be increased, and a flexible and low-resistance electrode can be produced.

[0034] [Nitrile Group-Containing Monomer Unit] The nitrile group-containing monomer unit is a repeating unit derived from a nitrile group-containing monomer unit. Examples of nitrile group-containing monomers that can form the nitrile group-containing monomer unit include α,β-ethylenically unsaturated nitrile monomers. The α,β-ethylenically unsaturated nitrile monomer is not particularly limited as long as it is an α,β-ethylenically unsaturated compound having a nitrile group, and examples include acrylonitrile; α-halogenoacrylonitriles such as α-chloroacrylonitrile and α-bromoacrylonitrile; and α-alkylacrylonitriles such as methacrylonitrile and α-ethylacrylonitrile. Among these, acrylonitrile and methacrylonitrile are preferred as the nitrile group-containing monomer, with acrylonitrile being more preferred. These may be used alone or in combination of two or more.

[0035] [Hydrophilic Group-Containing Monomer Unit] The hydrophilic group-containing monomer unit is a repeating unit derived from a hydrophilic group-containing monomer. Examples of the hydrophilic group-containing monomer that can form the hydrophilic group-containing monomer unit include a monomer having a carboxylic acid group, a monomer having a sulfonic acid group, a monomer having a phosphoric acid group, and a monomer having a hydroxyl group.

[0036] Examples of monomers having a carboxylic acid group 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-ethylacrylic acid, isocrotonic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, α-chloro-β-E-methoxyacrylic acid, and β-diaminoacrylic acid. Examples of dicarboxylic acids include maleic acid, fumaric acid, and itaconic acid. Examples of dicarboxylic acid derivatives include methylmaleic acid, dimethylmaleic acid, phenylmaleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid, and maleic acid esters such as methylallyl maleate, diphenyl maleate, nonyl maleate, decyl maleate, dodecyl maleate, octadecyl maleate, and fluoroalkyl maleates. Examples of dicarboxylic acid anhydrides include maleic anhydride, acrylic anhydride, methyl maleic anhydride, and dimethyl maleic anhydride. Furthermore, examples of monomers having a carboxylic acid group include acid anhydrides that generate a carboxyl group upon hydrolysis. Other examples include monoesters and diesters of α,β-ethylenically unsaturated polycarboxylic acids, such as monoethyl maleate, diethyl maleate, monobutyl maleate, dibutyl maleate, monoethyl fumarate, diethyl fumarate, monobutyl fumarate, dibutyl fumarate, monocyclohexyl fumarate, dicyclohexyl fumarate, monoethyl itaconate, diethyl itaconate, monobutyl itaconate, and dibutyl itaconate.

[0037] Examples of the monomer having a sulfonic acid group include vinyl sulfonic acid, methyl vinyl sulfonic acid, (meth)allyl sulfonic acid, styrene sulfonic acid, (meth)acrylic acid-2-ethyl sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, 3-allyloxy-2-hydroxypropanesulfonic acid, etc. In the present invention, "(meth)allyl" means allyl and / or methallyl.

[0038] Examples of the monomer having a phosphate group include 2-(meth)acryloyloxyethyl phosphate, methyl-2-(meth)acryloyloxyethyl phosphate, ethyl-(meth)acryloyloxyethyl phosphate, vinylphosphonic acid, dimethyl vinylphosphonate, etc. In the present invention, "(meth)acryloyl" means acryloyl and / or methacryloyl.

[0039] Examples of the monomer having a hydroxyl group include ethylenically unsaturated alcohols such as (meth)allyl alcohol, 3-butene-1-ol, and 5-hexene-1-ol; alkanol esters of ethylenically unsaturated carboxylic acids such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, di-2-hydroxyethyl maleate, di-4-hydroxybutyl maleate, and di-2-hydroxypropyl itaconate; and compounds of the general formula: CH ２ =CR １ -COO-(C ｎ H ２ｎ O) ｍ-H (wherein m is an integer of 2 to 9, n is an integer of 2 to 4, and R1 represents hydrogen or a methyl group), and esters of (meth)acrylic acid; mono(meth)acrylic acid esters of dihydroxy esters of dicarboxylic acids such as 2-hydroxyethyl-2'-(meth)acryloyloxyphthalate and 2-hydroxyethyl-2'-(meth)acryloyloxysuccinate; vinyl ethers such as 2-hydroxyethyl vinyl ether and 2-hydroxypropyl vinyl ether; (meth)allyl-2-hydroxyethyl ether, (meth)allyl-2-hydroxypropyl ether, (meth)allyl-3-hydroxypropyl ether, (meth)allyl-2-hydroxybutyl ether, (meth)allyl-3-hydroxybutyl ether, (meth)allyl-4-hydroxybutyl ether, (meth)allyl-6-hydroxyethyl ether, mono(meth)allyl ethers of alkylene glycols such as diethylene glycol mono(meth)allyl ether and dipropylene glycol mono(meth)allyl ether; mono(meth)allyl ethers of halogen- and hydroxy-substituted (poly)alkylene glycols such as glycerin mono(meth)allyl ether, (meth)allyl-2-chloro-3-hydroxypropyl ether and (meth)allyl-2-hydroxy-3-chloropropyl ether; mono(meth)allyl ethers of polyhydric phenols such as eugenol and isoeugenol and halogen-substituted products thereof; (meth)allyl thioethers of alkylene glycols such as (meth)allyl-2-hydroxyethyl thioether and (meth)allyl-2-hydroxypropyl thioether; and the like.

[0040] The content of the hydrophilic group-containing monomer units in the polymer may be 0% by mass, but is preferably 2.0% by mass or more, more preferably 4.0% by mass or more, and preferably 10.0% by mass or less, and more preferably 7.0% by mass or less, when the total repeating units in the polymer (the sum of structural units and monomer units) is taken as 100% by mass. If the content of the hydrophilic group-containing monomer units in the polymer is within the above range, the internal resistance of the resulting secondary battery can be further reduced and the cycle characteristics can be further improved.

[0041] [Alkylene structural unit] The alkylene structural unit is represented by the general formula: -C ｎ H ２ｎ - [where n is an integer of 2 or more].

[0042] The alkylene structural unit may be linear or branched, but from the viewpoint of further improving the flexibility of the resulting electrode, the alkylene structural unit is preferably linear, i.e., a linear alkylene structural unit. The alkylene structural unit has 4 or more carbon atoms (i.e., the alkylene structural unit represented by the above-mentioned general formula -C ｎ H ２ｎ -n is an integer of 4 or more).

[0043] The method for introducing alkylene structural units into polymer A is not particularly limited, and examples thereof include the following methods (1) and (2): (1) a method of preparing a polymer from a monomer composition containing a conjugated diene monomer and hydrogenating (adding hydrogen) the polymer to convert the conjugated diene monomer units into alkylene structural units; and (2) a method of preparing a polymer from a monomer composition containing a 1-olefin monomer. Among these, method (1) is preferred because it allows for easy production of the polymer.

[0044] That is, the alkylene structural unit is preferably a structural unit (conjugated diene hydride unit) obtained by hydrogenating (hydrogenating) a conjugated diene monomer unit, more preferably a structural unit (isoprene hydride unit) obtained by hydrogenating an isoprene unit or a structural unit (1,3-butadiene hydride unit) obtained by hydrogenating a 1,3-butadiene unit, and even more preferably a structural unit (1,3-butadiene hydride unit) obtained by hydrogenating a 1,3-butadiene unit. Here, hydrogenation can be carried out using a known method as described below. Furthermore, examples of 1-olefin monomers include 1-butene and 1-hexene. These conjugated diene monomers and 1-olefin monomers can be used alone or in combination of two or more.

[0045] Examples of the conjugated diene monomer that can be used in the above method (1) include conjugated diene compounds such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, etc. Among these, isoprene and 1,3-butadiene are preferred, and 1,3-butadiene is more preferred.

[0046] In addition, when an alkylene structural unit is introduced into a polymer via the above method (1), if the conjugated diene monomer unit is not completely hydrogenated, the conjugated diene monomer unit may remain in the polymer. In other words, the polymer may optionally contain a conjugated diene monomer unit as a repeating unit.

[0047] The content ratio of the alkylene structural unit and the conjugated diene monomer unit in the polymer may be 0% by mass or may be 2% by mass or more and 30% by mass or less, when the total repeating units in the polymer (the sum of the structural units and the monomer units) is 100% by mass. If it is equal to or more than the lower limit, flexibility can be imparted to the electrode, and if it is equal to or less than the upper limit, the HSP distance between the polymer and the conductive additive can be increased.

[0048] [Aromatic vinyl monomer unit] The aromatic vinyl monomer unit is a repeating unit derived from an aromatic vinyl monomer. Examples of aromatic vinyl monomers that can form the aromatic vinyl monomer unit include styrene, α-methylstyrene, vinyltoluene, and divinylbenzene. These can be used alone or in combination of two or more.

[0049] The content of the aromatic vinyl monomer units in the polymer may be 0% by mass or may be 2% by mass or more and 30% by mass or less, where the total repeating units in the polymer (the sum of structural units and monomer units) is taken as 100% by mass. If the content is equal to or more than the lower limit, flexibility can be imparted to the electrode, and if the content is equal to or less than the upper limit, the HSP distance between the polymer and the conductive additive can be increased.

[0050] <<Method for Preparing Polymer>> The method for producing the above-mentioned polymer is not particularly limited, and any method can be used, such as solution polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, etc. Furthermore, as the polymerization method, addition polymerization such as ionic polymerization, radical polymerization, and living radical polymerization can be used.

[0051] The polymerization initiator that can be used in preparing the polymer is not particularly limited, and includes known polymerization initiators such as sodium persulfate, ammonium persulfate, potassium persulfate, and t-butylperoxy-2-ethylhexanoate. One type of polymerization initiator may be used alone, or two or more types may be used in combination at any ratio.

[0052] The emulsifier that can be used in preparing the polymer is not particularly limited, and includes known emulsifiers, such as anionic surfactants such as sodium dodecylbenzenesulfonate, sodium lauryl sulfate, and sodium dialkylsulfosuccinate; and nonionic surfactants such as polyoxyethylene nonylphenyl ether, polyethylene glycol monostearate, and sorbitan monostearate. Among these, sodium lauryl sulfate is preferably used. One type of emulsifier may be used alone, or two or more types may be used in combination at any ratio.

[0053] <Solvent> The solvent contained in the binder composition is not particularly limited, and either water or an organic solvent can be used. Examples of organic solvents include N-methylpyrrolidone (hereinafter also simply referred to as "NMP"), N,N-dimethylformamide, and acetone. From the viewpoint of enhancing the stability of the binder composition, it is preferable to use N-methylpyrrolidone as the organic solvent. Note that one type of solvent may be used alone, or two or more types may be mixed in any ratio.

[0054] <Other Components> Examples of other components that may be optionally contained in the binder composition of the present invention include dispersants, reinforcing materials, leveling agents, viscosity modifiers, electrolyte additives, etc. These are not particularly limited as long as they do not affect the battery reaction, and known components, such as those described in WO 2012 / 115096, can be used. Furthermore, these components may be used alone or in combination of two or more at any ratio.

[0055] <Method for Preparing Binder Composition> When the binder composition of the present invention contains a solvent, it can be prepared by dissolving or dispersing the above-mentioned polymer and any other components described above in the solvent. Specifically, the binder composition can be prepared by mixing the above-mentioned components and the solvent using a mixer such as a ball mill, sand mill, bead mill, pigment disperser, crusher, ultrasonic disperser, homogenizer, planetary mixer, or Filmix. Note that when the polymer is prepared in the form of an aqueous dispersion, the aqueous dispersion may be used as the binder composition as is, or the binder composition may be prepared by mixing the aqueous dispersion of the polymer with an organic solvent and then removing the water.

[0056] (Slurry composition for non-aqueous secondary battery electrode) The slurry composition of the present invention contains at least the binder composition of the present invention described above, a conductive material, a dispersant, and an active material. Since the slurry composition of the present invention contains the binder composition of the present invention described above, an electrode with excellent flexibility can be produced, and the electrode resistance of the resulting electrode can be reduced. Hereinafter, a case where the slurry composition for non-aqueous secondary battery electrode is a slurry composition for a lithium-ion secondary battery positive electrode will be described as an example, but the present invention is not limited to the following example.

[0057] <Composition> <<Binder Composition>> The binder composition is the binder composition for a non-aqueous secondary battery electrode of the present invention described above. The content of the binder composition in the slurry composition of the present invention (in terms of solid content) is, for example, preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and preferably 5% by mass or less, based on 100% by mass of the total solid content of the slurry composition.

[0058] <<Conductive Material>> The conductive material that may be contained in the slurry composition of the present invention is intended to ensure electrical contact between electrode active materials. Examples of conductive materials that can be used include carbon black (e.g., acetylene black, Ketjen Black (registered trademark), furnace black, etc.), single-walled or multi-walled carbon nanotubes (multi-walled carbon nanotubes include cup-stacked types), carbon nanohorns, vapor-grown carbon fibers, milled carbon fibers obtained by calcining and then crushing polymer fibers, and single-walled or multi-walled graphene. Of these, acetylene black is preferred. These may be used alone or in combination of two or more. The particle size of the conductive material is not particularly limited and may be the same as that of conventionally used conductive materials. The content of the conductive material in the slurry composition may be, for example, 0.1% by mass or more and 10% by mass or less, with the total solid content in the slurry composition being 100% by mass. The conductive material may be the same as or different from the standard conductive material, and may be a conductive material having an HSP distance of 6.0 (MPa １／２) or more, and 8.0 (MPa １／２ ) or more. Also, the HSP distance between the conductive material and the polymer is preferably 15.0 or less. Furthermore, when a combination of multiple conductive materials is used, it is sufficient that the above relationship at least holds between the HSP value of at least one of the multiple conductive materials and the HSP value of the polymer. Furthermore, it is preferable that the above relationship at least holds between the HSP value of the conductive material with the highest blending ratio and the HSP value of the polymer, and it is more preferable that the above relationship holds between all of the HSP values ​​of the multiple conductive materials and the HSP value of the polymer.

[0059] The conductive material in the present invention further comprises a conductive material having a BET specific surface area of ​​100 m ２ / g or more is preferred, and 120m ２ / g or more is more preferable, and 300m ２ / g or less is preferable, and 200m ２ / g or less is more preferable. ２ / g or more, a secondary battery using the slurry composition of the present invention can have a high capacity. ２ / g or less, the dispersibility of the conductive material can be improved, and the resistance of the electrode using the slurry composition of the present invention can be suppressed. Note that, in the present invention, the "BET specific surface area" refers to the BET specific surface area measured by the nitrogen adsorption method, and can be measured in accordance with JIS Z8830:2013.

[0060] [Conductive Material Dispersant] Examples of conductive material dispersants include nonionic dispersants such as polyvinylpyrrolidone and polyvinyl butyral; carboxymethyl cellulose; and polymers containing a nitrile group-containing monomer unit (e.g., acrylonitrile unit, etc.) and an alkylene structural unit (e.g., 1,3-butadiene hydride unit, etc.). These dispersants may be used alone or in combination of two or more. The content of the conductive material dispersant in the slurry composition is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and is preferably 5% by mass or less, and more preferably 3% by mass or less, based on the total solid content in the slurry composition being 100% by mass. The conductive material dispersant may be the same as or different from the standard dispersant, and is a dispersant having an HSP distance with respect to the polymer of 3.5 (MPa １／２ ) or more, and 4.0 (MPa １／２ ) or more. The HSP distance between the dispersant and the polymer is preferably 15.0 (MPa) or more. １／２ ) or less.

[0061] <<Electrode Active Material>> An electrode active material is a material that transfers electrons at an electrode of a secondary battery. As a positive electrode active material for a lithium ion secondary battery, a material that can absorb and release lithium is usually used.

[0062] Specifically, the positive electrode active material for a lithium ion secondary battery is not particularly limited, and may be a lithium-containing cobalt oxide (LiCoO ２ ), lithium manganese oxide (LiMn ２ O ４ ), lithium-containing nickel oxide (LiNiO ２ ), Co—Ni—Mn lithium-containing composite oxide (Li(Co, Mn, Ni)O ２ ), lithium-containing composite oxide of Ni-Mn-Al, lithium-containing composite oxide of Ni-Co-Al, olivine-type lithium iron phosphate (LiFePO ４ ), olivine-type lithium manganese phosphate (LiMnPO ４ ), Li ２ MnO ３ -LiNiO２ system solid solution, Li １＋ｘ Mn ２－ｘ O ４ (0<X<2) Lithium-excess spinel compound represented by Li[Ni ０．１７ Li ０．２ Co ０．０７ Mn ０．５６ ]O ２ , LiNi ０．５ Mn １．５ O ４ , NMC532 (LiNi ０．５ Mn ０．３ Co ０．２ O ２ Examples of known positive electrode active materials include ammonium nitrate, ...

[0063] <<Other Components>> Other components that can be blended into the slurry composition are not particularly limited, and examples thereof include the same components as those that can be blended into the binder composition of the present invention. Furthermore, the other components may be used singly, or two or more may be used in combination at any ratio. In particular, when the slurry composition is a slurry composition for a lithium-ion secondary battery positive electrode, it is preferable to use a binder other than a polymer (for example, a fluorine-based polymer such as polyvinylidene fluoride (PVdF) or polytetrafluoroethylene (PTFE)) in addition to the above-mentioned polymer.

[0064] [Fluorine-Based Polymer] Fluorine-based polymers include, but are not limited to, polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, perfluoroalkoxy fluororesin, tetrafluoroethylene-hexafluoropropylene copolymer, and modified products thereof. Among these, from the viewpoint of further increasing the peel strength of the electrode mixture layer, polyvinylidene fluoride (PVdF) and acid-modified polyvinylidene fluoride are preferred, and acid-modified polyvinylidene fluoride is more preferred. Commercially available PVdF and acid-modified PVdF include, for example, "W#7 200" and "W#9700" manufactured by Kureha Corporation, and "Solef 5130" and "Solef XPH-859" manufactured by Solvay.

[0065] The content of the fluoropolymer is preferably 70% by mass or less, more preferably 55% by mass or less, even more preferably 50% by mass or less, particularly preferably 45% by mass or less, and preferably 30% by mass or more, when the total of the polymer and the fluoropolymer is taken as 100% by mass. If the content of the fluoropolymer is equal to or less than the upper limit, the flexibility of the obtained electrode mixture layer can be further increased. On the other hand, if the content of the fluoropolymer is equal to or more than the lower limit, the internal resistance of the obtained secondary battery can be further suppressed.

[0066] <Preparation of Slurry Composition> The method for preparing the slurry composition is not particularly limited. The slurry composition of the present invention can be prepared, for example, by mixing at least the binder composition of the present invention described above, a conductive material, a dispersant, an active material, and optionally other components in the presence of a solvent. The solvent can be the same as the solvent described in the binder composition section. The solvent can be the same as the solvent contained in the binder composition, or it can be a newly added solvent. The mixing method used to prepare the slurry composition is not particularly limited, and mixers such as a ball mill, sand mill, bead mill, pigment disperser, crusher, ultrasonic disperser, homogenizer, planetary mixer, and Filmix can be used.

[0067] (Electrode for non-aqueous secondary battery) The electrode for a non-aqueous secondary battery of the present invention comprises a current collector and an electrode mixture layer formed on the current collector, the electrode mixture layer being formed using the above-described slurry composition of the present invention. That is, the electrode mixture layer is a dried product of the above-described slurry composition of the present invention, and contains at least a binder composition, a conductive material, a dispersant, and an active material. Note that the components contained in the electrode mixture layer are those contained in the above-described slurry composition, and the preferred abundance ratio of each component is the same as the preferred abundance ratio of each component in the slurry composition. Note that the above-described polymer may be in a particulate form or another form in the electrode mixture layer.

[0068] <Method for manufacturing electrode> The electrode for a non-aqueous secondary battery of the present invention is manufactured, for example, through a step of applying the above-described slurry composition onto a current collector (application step) and a step of drying the slurry composition applied onto the current collector to form an electrode mixture layer on the current collector (drying step).

[0069] <<Coating Step>> The method for applying the slurry composition onto the current collector is not particularly limited, and known methods can be used. Specifically, examples of the application method include a comma coater method, a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, and a brush coating method. In this case, the slurry composition may be applied to only one side or both sides of the current collector. The thickness of the slurry film on the current collector after application and before drying can be appropriately set depending on the thickness of the electrode mixture layer obtained by drying.

[0070] Here, the current collector to which the slurry composition is applied is made of a material that is electrically conductive and electrochemically durable. Specifically, the current collector may be made of, for example, iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, platinum, etc. Note that one of the above materials may be used alone, or two or more may be used in combination in any ratio.

[0071] <<Drying Step>> The method for drying the slurry composition on the current collector is not particularly limited and any known method can be used, including, for example, drying with warm air, hot air, or low-humidity air, vacuum drying, and drying by irradiation with infrared rays, electron beams, etc. By drying the slurry composition on the current collector in this manner, an electrode mixture layer can be formed on the current collector, and a secondary battery electrode including the current collector and the electrode mixture layer can be obtained.

[0072] After the drying step, the electrode mixture layer may be subjected to a pressure treatment using a mold press or a roll press. The pressure treatment can improve the adhesion between the electrode mixture layer and the current collector. In addition, when the electrode mixture layer contains a curable polymer, it is preferable to cure the polymer after the electrode mixture layer is formed.

[0073] (Nonaqueous secondary battery) The nonaqueous secondary battery of the present invention includes the nonaqueous secondary battery electrode of the present invention. More specifically, the nonaqueous secondary battery of the present invention includes a positive electrode, a negative electrode, an electrolyte, and a separator, and uses the nonaqueous secondary battery electrode of the present invention as at least one of the positive electrode and the negative electrode. Furthermore, since the nonaqueous secondary battery of the present invention includes the nonaqueous secondary battery electrode of the present invention, the nonaqueous secondary battery has low internal resistance. Note that the nonaqueous secondary battery of the present invention preferably uses the nonaqueous secondary battery electrode of the present invention as the positive electrode. Furthermore, the following description will be given of a case where the secondary battery is a lithium ion secondary battery as an example, but the present invention is not limited to the following example.

[0074] <Electrode> Electrodes other than the above-described electrodes for non-aqueous secondary batteries that can be used in the non-aqueous secondary battery of the present invention are not particularly limited, and known electrodes used in the manufacture of non-aqueous secondary batteries can be used. Specifically, electrodes other than the above-described electrodes for non-aqueous secondary batteries can be electrodes formed by forming an electrode mixture layer on a current collector using a known manufacturing method.

[0075] <Electrolyte> As the electrolyte, an organic electrolyte solution in which a supporting electrolyte is dissolved in an organic solvent is usually used. As the supporting electrolyte of a lithium ion secondary battery, for example, a lithium salt is used. As the lithium salt, for example, LiPF ６, LiAsF ６ , LiBF ４ , LiSbF ６ , LiAlCl ４ , LiClO ４ , C.F. ３ SO ３ Li, C ４ F ９ SO ３ Li, CF ３ COOLi, (CF ３ CO) ２ NLi, (CF ３ SO ２ ) ２ NLi, (C ２ F ５ SO ２ Among them, LiPF is particularly preferred because it is easily soluble in solvents and shows a high degree of dissociation. ６ , LiClO ４ , C.F. ３ SO ３ Li is preferred, and LiPF ６ is particularly preferred. Note that one type of electrolyte may be used alone, or two or more types may be used in combination in any ratio. Generally, the lithium ion conductivity tends to increase as the supporting electrolyte with a higher degree of dissociation is used, so the lithium ion conductivity can be adjusted by the type of supporting electrolyte.

[0076] The organic solvent used in the electrolyte is not particularly limited as long as it can dissolve the supporting electrolyte. For example, carbonates such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate (BC), and ethyl methyl carbonate (EMC) are suitable. Other suitable solvents include esters such as γ-butyrolactone and methyl formate, ethers such as 1,2-dimethoxyethane and tetrahydrofuran, and sulfur-containing compounds such as sulfolane and dimethyl sulfoxide. Mixtures of these solvents may also be used. Among these, carbonates are preferred because of their high dielectric constant and wide stable potential range, and a mixture of ethylene carbonate and ethyl methyl carbonate is even more preferred. The concentration of the electrolyte in the electrolyte can be adjusted as appropriate. Known additives, such as vinylene carbonate, can also be added to the electrolyte.

[0077] <Separator> The separator is not particularly limited, and for example, those described in JP 2012-204303 A can be used. Among these, a microporous film made of a polyolefin resin (polyethylene, polypropylene, polybutene, polyvinyl chloride) is preferred because it allows the thickness of the entire separator to be thin, thereby increasing the proportion of electrode active material in the secondary battery and increasing the capacity per volume.

[0078] <Method for Manufacturing Non-Aqueous Secondary Battery> The non-aqueous secondary battery of the present invention can be manufactured, for example, by stacking a positive electrode and a negative electrode with a separator interposed therebetween, rolling or folding the resulting assembly as needed according to the battery shape, placing it in a battery container, injecting an electrolyte into the battery container, and sealing it. To prevent internal pressure increases, overcharging and overdischarging, and the like, a fuse, an overcurrent protection element such as a PTC element, an expanded metal, a lead plate, or the like may be provided as needed. The shape of the secondary battery may be, for example, any of a coin type, a button type, a sheet type, a cylindrical type, a rectangular type, a flat type, and the like.

[0079] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. In the following description, "%" and "parts" representing amounts are based on mass unless otherwise specified. Furthermore, in a polymer produced by copolymerizing multiple types of monomers, the proportion of a monomer unit formed by polymerizing a certain monomer in the polymer usually coincides with the ratio (feed ratio) of that certain monomer to all monomers used in the polymerization of the polymer, unless otherwise specified. In the examples and comparative examples, various measurements and evaluations were carried out by the following methods.

[0080] (Physical Property Measurement) <Measurement of HSP Distance> <<Calculation of Hansen Solubility Parameter (HSP) of Conductive Material>> In the following Examples and Comparative Examples, a standard conductive material was used as the conductive material, and therefore the conductive material to be measured was the standard conductive material. 0.02 mg of conductive material was weighed into a 30 mL sealed container, and 20 mL of organic solvent was added thereto. The solution was subjected to ultrasonic dispersion at 20 kHz, 200 W, and 10 minutes to prepare a measurement solution. The measurement solution was allowed to stand for 1 hour, and the presence or absence of precipitate was visually confirmed. Complete dispersion without precipitate was scored as "score 1," and the presence of precipitate was scored as "score 0." The above confirmation of the presence or absence of precipitate was performed using 18 types of organic solvents listed in the table below.

[0081]

[0082] Next, an analysis was performed using HSP analysis software (Hansen Solubility Parameters in Practice (HSPiP), 5th Edition 5.4.05) so that the solvent with a solubility score of 1 was located inside the Hansen solubility sphere. The HSP of the standard conductive material was found to be δD = 19.2 MPa. １／２ , δP=9.6 MPa １／２ , δH=8.9 MPa １／２The HSP of the organic solvent was calculated using the values ​​built into the HSP analysis software (HSPiP, 5th Edition 5.4.05). The HSP analysis software (HSPiP) can determine the target HSP based on the logic described in the following document: "Hansen Solubility Parameters: A User's Handbook" by Charles M. Hansen, CRC Press, 2007.

[0083] <<Calculation of Hansen Solubility Parameters (HSP) of Dispersants>> In the following examples and comparative examples, standard dispersants were used as dispersants, and therefore the dispersants measured were standard dispersants. 0.1 g of dispersant dried at 130°C for 6 hours was added to 5 ml of each of 16 solvents (acetone, THF, hexane, toluene, ethyl acetate, MEK, DMF, NMP, DMSO, salicylaldehyde, pyridine, benzyl alcohol, 1-butanol, nitrobenzene, propylene glycol monomethyl ether, and γ-butyrolactone). The mixture was shaken at 180 rpm for 6 hours using a shaker to obtain a measurement solution. This measurement solution was visually observed and scored as follows: - Insoluble (poor solvent): 0 - Turbid and / or turbid (poor solvent): 2 - Completely soluble (good solvent): 1. Based on the obtained scores, the polarity parameter δp4, dispersion parameter δd4, and hydrogen bond parameter δh4 of HSPb were calculated using the HSPiP.

[0084] <<Calculation of the Hansen Solubility Parameter (HSP) of Polymer>> A 1 cm wide, 1 cm deep, and 2 cm high cage was created using a 200-mesh wire mesh and weighed (mass A). Approximately 100 mg of polymer was weighed into the cage (mass B). The cage was placed in a 30 mL sealed container, and 20 mL of organic solvent was added and allowed to stand for 24 hours. The above procedure was performed for 16 organic solvents (acetone, THF, hexane, toluene, ethyl acetate, MEK, DMF, NMP, dimethyl sulfoxide (DMSO), salicylaldehyde, pyridine, benzyl alcohol, 1-butanol, nitrobenzene, propylene glycol monomethyl ether, and γ-butyrolactone). After 24 hours, the cage was removed and dried in an oven at 120°C for 1 hour to completely remove the solvent. The dried cage was weighed (mass C), and the solubility was calculated using the following formula (1): Dissolution rate (%) = (1 - (mass C - mass A) / (mass B)) x 100% (1) A dissolved amount of 15% or more was assigned a score of 1, and a dissolved amount of less than 15% was assigned a score of 0. The HSP value was calculated in the same manner as in the method described in the section <<Calculation of the Hansen Solubility Parameter (HSP) of Conductive Material>>.

[0085] <<Calculation of HSP distance>> The HSP distance (R ａ ) is the HSP of substance A ａ and HSP of substance B ｂ The HSP distance (R ａ ) = {(δ ｐ１ -δ ｐ２ ) ２ + 4 × (δ ｄ１ -δ ｄ２ ) ２ + (δ ｈ１ -δ ｈ２ ) ２} １／２ ... (2) δp １ : Polar term of substance A δp ２ : Polar term of substance B δd １ : Dispersion term of material A δd ２ : Dispersion term of material B δh １ : Hydrogen bond term of substance A δh ２: Hydrogen bond term of substance B From the above, the HSP distance between the polymer and the conductive material, and the HSP distance between the polymer and the dispersant were calculated.

[0086] <Measurement of Weight-Average Molecular Weight of Polymer> 5 mL of THF was added to 0.2 g of a polymer NMP solution with a solids concentration of 8%, and the mixture was passed through a 0.45 μm filter to prepare a sample. The obtained sample was measured by gel permeation chromatography (GPC) under the following measurement conditions. Apparatus: HLC-8320GPC (manufactured by Tosoh Corporation) Separation column: TSKgel Super H2000, TSKgel Super H4000, TSKgel Super H5000 (manufactured by Tosoh Corporation) Detector: Differential refractometer detector (manufactured by Tosoh Corporation) Eluent flow rate: 0.3 mL / min Column temperature: 40°C Standard polymer: TSK standard polystyrene (manufactured by Tosoh Corporation)

[0087] <Indentation Elastic Modulus Test> An 8% by mass NMP solution of the binder composition prepared in each of the Examples and Comparative Examples was applied to an aluminum foil and dried to form a thin film having a thickness of 10 μm. The elastic modulus of the obtained sample was measured under the following conditions. Indenter used: tip radius 10 μm Measurement atmosphere: in a vacuum (10 －３ Pa or less) Measurement temperature: Room temperature Measurement conditions: Displacement control measurement of 300 nm Test conditions: Press-fitting and unloading for 3 seconds

[0088] <Flexibility of electrode> Aluminum foil having a thickness of 15 μm was prepared as a current collector, and the positive electrode slurry compositions prepared in the Examples and Comparative Examples were coated on the aluminum foil with a comma coater so that the weight per unit area after drying was 30 mg / cm. ２ The positive electrode blank was rolled by a roll press to a density of 3.6 g / cm. ３A positive electrode consisting of a positive electrode active material layer and aluminum foil was fabricated. The fabricated positive electrode was subjected to a bending test in accordance with JIS K5600-5-1. Specifically, a positive electrode cut to a width of 10 mm was attached to a mandrel tester, and the positive electrode was bent with the positive electrode active material layer facing outward. The positive electrode active material layer in the bent state was observed under a microscope to check for cracks in the positive electrode. The mandrel diameter was then gradually increased until no cracks were found in the positive electrode, and the mandrel diameter at which the positive electrode did not crack was recorded. A smaller mandrel diameter indicates better flexibility (windability) of the positive electrode. A: No cracks at a diameter of 4 mm B: No cracks at a diameter of 6 mm C: No cracks at a diameter of 8 mm D: No cracks at a diameter of 10 mm

[0089] <Internal Resistance> After injecting the electrolyte, the lithium-ion secondary batteries fabricated in the Examples and Comparative Examples were left standing at 25°C for 5 hours. Next, they were charged to a cell voltage of 3.65 V at a constant current of 0.2 C at 25°C, and then aged at 60°C for 12 hours. The batteries were charged to a cell voltage of 4.2 V at a constant current of 0.2 C and then discharged to a cell voltage of 3.0 V, repeating this charge-discharge cycle three times to measure the initial capacity. After charging to a depth of charge (SOC) of 50%, they were charged for 20 seconds and discharged for 20 seconds at 0.5 C, 1.0 C, 1.5 C, and 2.0 C, centered around 50% SOC. The battery voltage after 20 seconds (on the charge side and the discharge side) was plotted against the current value, and the slope was calculated as the IV resistance (Ω) (IV resistance during charging and IV resistance during discharging). The resulting IV resistance values ​​(Ω) were evaluated according to the following criteria. The smaller the IV resistance value, the lower the internal resistance and the better the IV characteristics. A: IV resistance value is less than 2.3Ω B: IV resistance value is 2.3Ω or more and less than 2.4Ω C: IV resistance value is 2.4Ω or more and less than 2.5Ω D: IV resistance value is 2.5Ω or more

[0090] <Cycle Characteristics> The lithium ion secondary batteries produced in the Examples and Comparative Examples were charged to 4.2 V at a constant current of 1.0 C in an atmosphere of 45° C., and then discharged to 3.0 V. This charge-discharge cycle was repeated 300 times. The cycle capacity retention rate, which is expressed as the ratio of the electric capacity at the end of 300 cycles to the initial electric capacity (= [electric capacity at the end of cycles] / [initial electric capacity]×100(%)), was then determined and evaluated according to the following criteria. A higher cycle capacity retention rate indicates better cycle characteristics. A: Cycle capacity retention rate is 93% or more B: Cycle capacity retention rate is 88% or more but less than 93% C: Cycle capacity retention rate is 83% or more but less than 88% D: Cycle capacity retention rate is less than 83%

[0091] Example 1 <Method for Producing Binder Composition> <<Production of Binder Composition of Example 1>> 90 parts of ion-exchanged water, 0.5 parts of sodium lauryl sulfate (manufactured by Kao Chemical Corporation, "EMAL 2FG") as an emulsifier, and 0.25 parts of ammonium persulfate were each supplied to a reactor equipped with a stirrer. The gas phase was replaced with nitrogen gas, and the temperature was raised to 70°C. Meanwhile, in a separate vessel, 40 parts of ion-exchanged water, 1.0 part of sodium lauryl sulfate (manufactured by Kao Chemical Corporation, "EMAL 2FG") as an emulsifier, 69 parts of butyl acrylate (BA) as (meth)acrylic acid alkyl ester monomers, 25 parts of 2-ethylhexyl acrylate (2EHA), and 6 parts of methacrylic acid (MAA) were mixed to obtain a monomer composition. This monomer composition was continuously added to the reactor over a period of 3 hours to carry out polymerization. The reaction was carried out at 70°C during the addition. After the addition was completed, 0.05 parts of ammonium persulfate was added, and the temperature was raised to 75°C. After the temperature was raised, the mixture was stirred for 3 hours to terminate the reaction, and an aqueous dispersion containing a particulate polymer was produced. Next, 600 parts of N-methylpyrrolidone was added to 100 parts of this aqueous dispersion, and all of the water and residual monomers and 60 parts of N-methylpyrrolidone were evaporated under reduced pressure to obtain an NMP solution (binder composition) with a polymer concentration of 8% by mass.

[0092] <Preparation of Slurry Composition for Positive Electrode> NMC532 (LiNi) having a layered structure was used as the positive electrode active material. ０．５ Mn ０．３ Co ０．２ O２ To 96.8 parts of the binder composition, 0.45 parts of PVdF and 0.55 parts of the binder composition (corresponding to the solid content) were added. To this, a carbon paste prepared by mixing 2.0 parts of acetylene black (represented as "AB" in the table; Li435, manufactured by Denka Co., Ltd.) as a conductive material and 0.2 parts of hydrogenated nitrile butadiene rubber (H-NBR) as a dispersant was added, and an appropriate amount of NMP was added. The resulting mixture was stirred with a planetary mixer to prepare a slurry composition (slurry composition for a positive electrode).

[0093] <Production of Positive Electrode> The obtained slurry composition for a lithium ion secondary battery positive electrode was applied to an aluminum foil (current collector) having a thickness of 15 μm using a comma coater in a coating amount of 20 mg / cm after drying. ２ The aluminum foil coated with the slurry composition for lithium ion secondary battery positive electrodes was transported at a speed of 0.5 m / min through an oven at a temperature of 100°C for 2 minutes, and then through an oven at a temperature of 120°C for 2 minutes, thereby drying the slurry composition for lithium ion secondary battery positive electrodes on the aluminum foil and obtaining a positive electrode blank. The positive electrode blank was rolled using a roll press to a density of 3.6 g / cm. ３ A positive electrode was fabricated, which consisted of a positive electrode active material layer and aluminum foil.

[0094] <Production of negative electrode> A planetary mixer with a disperser was used to prepare a negative electrode active material with a specific surface area of ​​4 m. ２ 100 parts of 1 / g artificial graphite and 1 part (solids equivalent) of a 1% aqueous solution of carboxymethyl cellulose ("BSH-12" manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as a dispersant were added, and the solids concentration was adjusted to 55% with ion-exchanged water, followed by mixing at 25°C for 60 minutes. Next, the solids concentration was adjusted to 52% with ion-exchanged water. Mixing was then continued for an additional 15 minutes to obtain a mixed solution. To the above mixed solution, 1.0 part (solids equivalent) of a 40% aqueous solution containing a styrene-butadiene copolymer and ion-exchanged water were added, and the final solids concentration was adjusted to 50%, followed by mixing for an additional 10 minutes. This was degassed to obtain a negative electrode slurry composition with good fluidity. The above negative electrode slurry composition was applied to a 15 μm-thick copper foil current collector using a comma coater in a coating amount of 11 mg / cm after drying. ２The negative electrode blank was then rolled with a roll press to a density of 1.5 g / cm. ３ Thus, a negative electrode having a negative electrode active material layer of the following formula was obtained.

[0095] <Preparation of Separator> A single-layer polypropylene separator (width 65 mm, length 500 mm, thickness 25 μm; manufactured by a dry method; porosity 55%) was prepared. This separator was cut into a 5 cm × 5 cm square and used in the following lithium-ion secondary battery.

[0096] <Preparation of Secondary Battery> An aluminum packaging material was prepared as the battery packaging. The positive electrode was cut into a 4 cm x 4 cm square and placed so that the surface on the current collector side was in contact with the aluminum packaging material. Next, the square separator was placed on the surface of the positive electrode composite layer of the positive electrode. Furthermore, the negative electrode was cut into a 4.2 cm x 4.2 cm square and placed on the separator so that the surface on the negative electrode composite layer side faced the separator. Then, LiPF 5 with a concentration of 1.0 M was used as an electrolyte. ６ The solution (the solvent was a mixed solvent of ethylene carbonate (EC) / ethyl methyl carbonate (EMC) = 3 / 7) was filled with 2 vol% vinylene carbonate as an additive. Furthermore, in order to seal the opening of the aluminum packaging material, the aluminum packaging exterior was closed by heat sealing at 150°C, thereby producing a laminate cell type lithium ion secondary battery. The cycle characteristics of the lithium ion secondary battery obtained by the above-mentioned method were evaluated.

[0097] (Examples 2 to 9) Various operations, measurements, and evaluations were carried out in the same manner as in Example 1, except that the type and amount of the monomers blended when producing the binder composition and the proportion of the polymer in the slurry composition were changed as shown in Table 2. The results are shown in Table 2.

[0098] (Comparative Examples 1 to 3) Various operations, measurements, and evaluations were carried out in the same manner as in Example 1, except that the types and amounts of monomers blended when producing the binder compositions were changed as shown in Table 2, and further, 0.1 parts of t-dodecyl mercaptan was added as a chain transfer agent to the emulsion tank in Comparative Examples 1 and 2, and 0.15 parts of t-dodecyl mercaptan was added as a chain transfer agent in Comparative Example 3. The results are shown in Table 2.

[0099]

[0100] The results in Table 2 show that in Examples 1 to 8, in which the distance between the HSP of the polymer and the HSPs of the conductive material and dispersant was equal to or greater than a predetermined value and a non-aqueous secondary battery electrode binder composition containing a polymer having a weight-average molecular weight of more than 1,000,000 was used, the resulting electrodes were excellent in flexibility and were able to suppress the internal resistance of the secondary battery.

[0101] According to the present invention, a binder composition for a non-aqueous secondary battery electrode can be provided that can be suitably used to produce an electrode with excellent flexibility and that can reduce the internal resistance of a secondary battery including the resulting electrode. Furthermore, according to the present invention, a slurry composition for a non-aqueous secondary battery electrode can be provided that can form an electrode with excellent flexibility and can reduce the internal resistance of a secondary battery including the resulting electrode. Furthermore, according to the present invention, a non-aqueous secondary battery electrode that can reduce the internal resistance of a non-aqueous secondary battery and a non-aqueous secondary battery with low internal resistance can be provided.

Claims

1. A binder composition comprising a polymer, wherein the distance between the Hansen solubility parameter of the polymer and a standard conductive material having Hansen solubility parameters of δd = 19.2, δp = 9.6, and δh = 8.9 is 6.0 (MPa １／２ ) or more, and the distance between the Hansen solubility parameter of the polymer and a standard dispersant having Hansen solubility parameters of δd = 16.9, δp = 10.0, and δh = 9.0 is 3.5 (MPa １／２ ) or more, and the weight average molecular weight of the polymer exceeds 1,000,000.

2. The binder composition for a non-aqueous secondary battery electrode according to claim 1, wherein the polymer has an indentation composite elastic modulus of 3 MPa or more and 30 MPa or less.

3. The binder composition for a non-aqueous secondary battery electrode according to claim 1 or 2, wherein the polymer contains a (meth)acrylic acid alkyl ester monomer unit.

4. A slurry composition for a non-aqueous secondary battery electrode, comprising at least the binder composition for a non-aqueous secondary battery electrode according to any one of claims 1 to 3, a conductive material, a dispersant, and an active material, wherein the standard conductive material and the conductive material may be the same or different, and the standard dispersant and the dispersant may be the same or different.

5. The slurry composition for a non-aqueous secondary battery electrode according to claim 4, further comprising a fluoropolymer, wherein the proportion of the fluoropolymer is 70 mass% or less when the total of the fluoropolymer and the polymer is 100 mass%.

6. The conductive material has a BET specific surface area of ​​100 m ２ / g or more 300m ２ The slurry composition for a non-aqueous secondary battery electrode according to claim 4 or 5, wherein the molecular weight of the non-aqueous secondary battery electrode is 100 / g or less.

7. A non-aqueous secondary battery electrode comprising an electrode mixture layer formed using the slurry composition for a non-aqueous secondary battery electrode according to any one of claims 4 to 6.

8. A non-aqueous secondary battery comprising the electrode for a non-aqueous secondary battery according to claim 7.

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