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 nonaqueous secondary battery electrodes, wherein the binder composition can be suitably used for manufacturing an electrode having excellent flexibility and can improve static storage stability of a slurry composition. A binder composition for nonaqueous secondary battery electrodes according to the present invention contains a polymer A. In a hydrodynamic radius distribution obtained by a dynamic light scattering method using an N-methylpyrrolidone solution having a concentration of 0.5 mass% of the polymer A, D10 is 100 nm or more and D90 is 4000 nm or less, where D10 is a hydrodynamic radius at which the cumulative frequency of light scattering intensity calculated from the small diameter side is 10% and D90 is a hydrodynamic radius at which the cumulative frequency of light scattering intensity calculated from the small diameter side is 90%.

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 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 an electrode binder composition that has good binding properties and is capable of producing electrodes with excellent charge / discharge characteristics, the electrode binder composition containing 5 to 40 parts by mass of (A) structural units derived from an α,β-unsaturated nitrile compound and 0.3 to 10 parts by mass of (B) structural units derived from an unsaturated carboxylic acid, polymer particles having a number average particle size of 50 to 400 nm, a gel content of 90 to 99%, and an electrolyte swelling rate of 110 to 400%.

[0005] Japanese Patent Application Laid-Open No. 2012-209258

[0006] In recent years, thickening of electrodes has been investigated to improve the energy density of secondary batteries. However, thickening of electrodes reduces the flexibility of the electrodes, and in particular in wound secondary batteries, cracks may occur in the electrodes when the innermost electrode is wound up. Furthermore, increasing the amount of binder to improve the flexibility of the electrodes may result in separation of the electrode active material and the solvent when the slurry composition is stored statically (i.e., the static storage stability of the slurry composition may be deteriorated).

[0007] Therefore, an object of the present invention is to provide a binder composition for non-aqueous secondary battery electrodes that can be suitably used to produce electrodes with excellent flexibility and that can improve the static storage stability of the slurry composition. Another object of the present invention is to provide a slurry composition for non-aqueous secondary battery electrodes that can form electrodes with excellent flexibility and that has excellent static storage stability. A further object of the present invention is to provide a non-aqueous secondary battery electrode with excellent flexibility, and a non-aqueous secondary battery including the non-aqueous secondary battery electrode.

[0008] The present inventors conducted extensive research to solve the above-mentioned problems. The inventors then focused on the hydrodynamic radius distribution of the polymer incorporated into the binder composition. More specifically, in a hydrodynamic radius distribution obtained by dynamic light scattering using a 0.5% by mass N-methylpyrrolidone solution of the polymer, where D10 is the hydrodynamic radius at which the cumulative frequency of the light scattering intensity calculated from the smallest diameter side is 10%, and D90 is the hydrodynamic radius at which the cumulative frequency of the light scattering intensity calculated from the smallest diameter side is 90%, the inventors newly discovered that by incorporating into the binder composition a polymer having D10 and D90 within respective predetermined ranges, it is possible to produce an electrode with excellent flexibility and improve the static storage stability of the slurry composition, thereby completing the present invention.

[0009] The present invention aims to advantageously solve the above-mentioned problems. [1] The present invention provides a binder composition for a non-aqueous secondary battery electrode containing a polymer A. In a hydrodynamic radius distribution obtained by dynamic light scattering of a 0.5% by mass solution of the polymer A in N-methylpyrrolidone, the polymer A has a hydrodynamic radius D10 of 100 nm or more and a hydrodynamic radius D90 of 4000 nm or less, where D10 is the hydrodynamic radius at which the cumulative frequency of the light scattering intensity calculated from the smallest diameter side reaches 10% and D90 is the hydrodynamic radius at which the cumulative frequency of the light scattering intensity calculated from the smallest diameter side reaches 90%. By incorporating a polymer A having hydrodynamic radii D10 and D90 each within the above-mentioned ranges into the binder composition for a non-aqueous secondary battery electrode, an electrode with excellent flexibility can be produced and the static storage stability of the slurry composition can be improved. In the present invention, the hydrodynamic radius of the polymer A can be measured by the method described in the Examples.

[0010] [2] In the binder composition for an aqueous secondary battery electrode according to [1] above, the polymer A preferably has a D10 of 100 nm or more and 1,000 nm or less. When the D10 of the polymer A is within the above range, the flexibility of the electrode can be further improved, and the static storage stability of the slurry composition can be further improved.

[0011] [3] In the binder composition for an aqueous secondary battery electrode according to [1] above, the polymer A preferably has a D10 of 140 nm or more and 500 nm or less. When the D10 of the polymer A is within the above range, the flexibility of the electrode can be further improved, and the static storage stability of the slurry composition can be further improved.

[0012] [4] In the binder composition for an aqueous secondary battery electrode according to [1] above, the polymer A preferably has a D10 of 200 nm or more and 500 nm or less. When the D10 of the polymer A is within the above range, the flexibility of the electrode can be further improved, and the static storage stability of the slurry composition can be further improved.

[0013] [5] In the aqueous secondary battery electrode binder composition according to any one of [1] to [4] above, the polymer A preferably has a D90 of more than 500 nm and not more than 4,000 nm. When the D90 of the polymer A is within the above range, the flexibility of the electrode can be further improved, and the static storage stability of the slurry composition can be further improved.

[0014] [6] In the binder composition for an aqueous secondary battery electrode according to any one of [1] to [4] above, the polymer A preferably has a D90 of 600 nm or more and 3500 nm or less. When the D90 of the polymer A is within the above range, the flexibility of the electrode can be further improved, and the static storage stability of the slurry composition can be further improved.

[0015] [7] In the aqueous secondary battery electrode binder composition according to any one of [1] to [4] above, the polymer A preferably has a D90 of 800 nm or more and 3000 nm or less. When the D90 of the polymer A is within the above range, the flexibility of the electrode can be further improved, and the static storage stability of the slurry composition can be further improved.

[0016] [8] In the binder composition for aqueous secondary battery electrodes according to any one of [1] to [7] above, the polymer A preferably contains 80% by mass or more of (meth)acrylic acid alkyl ester monomer units. If the polymer A contains 80% by mass or more of (meth)acrylic acid alkyl ester monomer units, the electrode can be imparted with even greater flexibility. In the present invention, the presence or absence and content of the monomer units (repeating units) in the polymer can be determined, for example, by: １ It can be determined or measured by H-NMR.

[0017] [9] In the binder composition for an aqueous secondary battery electrode according to any one of [1] to [7] above, the polymer A preferably contains 90% by mass or more of (meth)acrylic acid alkyl ester monomer units. When the polymer A contains 90% by mass or more of (meth)acrylic acid alkyl ester monomer units, the electrode can be imparted with even greater flexibility.

[0018]

[10] In the binder composition for an aqueous secondary battery electrode according to any one of [1] to [9] above, the polymer A preferably has an electrolyte swelling degree of 300% by mass or less. When the electrolyte swelling degree of the polymer A is equal to or less than the upper limit, the cycle characteristics of the resulting secondary battery can be improved. In the present invention, the electrolyte swelling degree of the polymer A can be measured by the method described in the Examples.

[0019]

[11] In the binder composition for a non-aqueous secondary battery electrode according to any one of [1] to

[10] above, it is preferable that the polymer A contains (meth)acrylic acid alkyl ester monomer units having an alkyl chain with 6 or more carbon atoms in a proportion of 20% by mass to 60% by mass. As described above, when the content of (meth)acrylic acid alkyl ester monomer units having an alkyl chain with 6 or more carbon atoms in the polymer A is within the above range, the static storage stability of the obtained slurry composition can be further improved.

[0020]

[12] In the binder composition for a non-aqueous secondary battery electrode according to any one of [1] to

[11] above, it is preferable that the polymer A contains hydroxyl group-containing monomer units in a proportion of more than 0 mass % and not more than 10 mass %. When the polymer A contains hydroxyl group-containing monomer units in the above range, the flexibility of the resulting electrode and the static storage stability of the resulting slurry composition can be further improved.

[0021]

[13] In the binder composition for a non-aqueous secondary battery electrode according to any one of [1] to

[12] above, it is preferable that the polymer A does not contain a crosslinkable monomer unit. If the polymer A does not contain a crosslinkable monomer unit, the static storage stability of the slurry composition can be further improved.

[0022] Another object of the present invention is to advantageously solve the above-mentioned problems, and the present invention provides

[14] a slurry composition for a non-aqueous secondary battery electrode, comprising the binder composition for a non-aqueous secondary battery electrode according to any one of [1] to

[13] above and an electrode active material. In this way, by using any one of the binder compositions described above, it is possible to form an electrode having excellent flexibility, and it is also possible to easily obtain a slurry composition for a non-aqueous secondary battery electrode having excellent static storage stability.

[0023]

[15] The nonaqueous secondary battery electrode slurry composition according to

[14] above preferably further contains a fluoropolymer. When the slurry composition contains a fluoropolymer in this way, the static storage stability of the slurry composition can be further improved.

[0024]

[16] In the slurry composition for a nonaqueous secondary battery electrode according to

[15] above, the proportion of the fluoropolymer is preferably 70 mass% or less when the total of the fluoropolymer and the polymer A is taken as 100 mass%. In this way, when the content of the fluoropolymer is not more than the above upper limit, the static storage stability of the slurry composition can be further improved.

[0025]

[17] The nonaqueous secondary battery electrode slurry composition according to any one of

[14] to

[16] above preferably further contains a conductive material. When the slurry composition further contains a conductive material, an increase in the resistance of an electrode obtained using the slurry composition can be suppressed.

[0026]

[18] In the non-aqueous secondary battery electrode slurry composition according to

[17] , the conductive material has a BET specific surface area of ​​100 m ２ / g or more 300m ２ / g or less. Thus, when the BET specific surface area of ​​the conductive material is equal to or greater than the above lower limit, the capacity of a secondary battery obtained using the slurry composition can be increased. Furthermore, when the BET specific surface area of ​​the conductive material is equal to or less than the above upper limit, the dispersibility of the conductive material can be improved, and the resistance of an electrode obtained using the slurry composition can be further 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.

[0027] Another object of the present invention is to advantageously solve the above-mentioned problems, and the present invention provides

[19] a non-aqueous secondary battery electrode comprising an electrode mixture layer formed using the non-aqueous secondary battery electrode slurry composition of any one of

[14] to

[18] above. In this way, by using any one of the above-mentioned non-aqueous secondary battery electrode slurry compositions, a non-aqueous secondary battery electrode with excellent flexibility can be successfully produced.

[0028] Another object of the present invention is to advantageously solve the above-mentioned problems, and the present invention provides

[20] a nonaqueous secondary battery including the electrode for a nonaqueous secondary battery according to

[19] . In this way, by using the electrode for a nonaqueous secondary battery described above, a secondary battery having excellent electrode flexibility can be obtained.

[0029] According to the present invention, a binder composition for a non-aqueous secondary battery electrode can be provided that can be suitably used for producing an electrode with excellent flexibility and can improve the static storage stability of the slurry composition. 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 has excellent static storage stability. Furthermore, according to the present invention, a non-aqueous secondary battery electrode with excellent flexibility and a non-aqueous secondary battery including the non-aqueous secondary battery electrode can be provided.

[0030] Embodiments of the present invention will be described in detail below. The binder composition for a non-aqueous secondary battery electrode of the present invention (hereinafter 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 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 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. The non-aqueous secondary battery of the present invention preferably uses the non-aqueous secondary battery electrode of the present invention as the positive electrode.

[0031] (Binder Composition for Nonaqueous Secondary Battery Electrodes) The binder composition of the present invention contains polymer A and may optionally further contain a solvent and / or other components. The binder composition of the present invention is characterized in that, in a hydrodynamic radius distribution obtained by measuring the hydrodynamic radius of polymer A by dynamic light scattering when the polymer A is dissolved in N-methylpyrrolidone at a concentration of 0.5% by mass, D10 is the hydrodynamic radius at which the cumulative frequency of the light scattering intensity calculated from the smallest diameter side is 10%, and D90 is the hydrodynamic radius at which the cumulative frequency of the light scattering intensity calculated from the smallest diameter side is 90%, D10 is 100 nm or more, and D90 is 4000 nm or less. Because the binder composition of the present invention contains polymer A having the above-described properties, it is possible to improve the flexibility of an electrode formed using the binder composition and to improve the static storage stability of a slurry composition.

[0032] Here, the reason why the flexibility of the electrode and the static storage stability of the slurry composition can be highly achieved by controlling the D10 and D90 of polymer A is not entirely clear, but it is presumed to be as follows. That is, in order to impart flexibility to the electrode, a polymer with a relatively large aggregate size must be present between the electrode active materials. However, such a polymer has a small adsorption area to the electrode active material, making it difficult to disperse the electrode active material well in the slurry composition, and it is difficult to ensure the static storage stability of the slurry composition. Therefore, in order to achieve both the flexibility of the electrode and the static storage stability of the slurry composition, it is necessary to appropriately control the degree of aggregation of the polymer in the solvent. It is presumed that when D10 is equal to or greater than a predetermined value, the polymer is moderately aggregated to ensure the flexibility of the electrode, while when D90 is equal to or less than a predetermined value, the polymer is not excessively aggregated to ensure the static storage stability of the slurry composition.

[0033] <Polymer A> In an electrode produced by applying a slurry composition prepared using a binder composition onto a current collector and drying the slurry composition, polymer A is a component that has the function of imparting flexibility to the electrode while retaining components such as an electrode active material contained in the electrode mixture layer so as not to be detached from the electrode mixture layer. Furthermore, polymer A is a component that has the function of dispersing the electrode active material in a solvent in the slurry composition.

[0034] <<Properties>> [Hydrodynamic Radius] In the hydrodynamic radius distribution of polymer A obtained by dynamic light scattering when polymer A is dissolved in N-methylpyrrolidone at a concentration of 0.5% by mass, where D10 is the hydrodynamic radius at which the cumulative frequency of the light scattering intensity calculated from the small diameter side is 10% and D90 is the hydrodynamic radius at which the cumulative frequency of the light scattering intensity calculated from the small diameter side is 90%, it is necessary that D10 is 100 nm or more and D90 is 4000 nm or less.

[0035] If the D10 of polymer A is less than 100 nm, the electrode active material can be well dispersed in the slurry composition, ensuring the static storage stability of the slurry composition, but not ensuring the flexibility of the electrode. From the viewpoint of further improving the flexibility of the electrode, the D10 of polymer A is preferably 140 nm or more, more preferably 200 nm or more, and even more preferably 300 nm or more. On the other hand, from the viewpoint of ensuring the static storage stability of the slurry composition, the D10 of polymer A is preferably 1000 nm or less, more preferably 500 nm or less.

[0036] If D90 exceeds 4000 nm, although the flexibility of the electrode is improved by the aggregated polymer A, the electrode active material in the slurry composition cannot be sufficiently dispersed, and the static storage stability of the slurry composition cannot be ensured. From the viewpoint of further improving the static storage stability of the slurry composition, D90 of polymer A is preferably 3500 nm or less, and more preferably 3000 nm or less. On the other hand, from the viewpoint of ensuring the flexibility of the electrode, D90 of polymer A is preferably greater than 500 nm, more preferably 600 nm or more, and even more preferably 800 nm or more.

[0037] From the viewpoint of achieving both the flexibility of the electrode and the static storage stability of the slurry composition at an even higher level, it is preferable that the polymer A has a D10 of 140 nm or more, 200 nm or more, or 300 nm or more, and a D90 of 3500 nm or less or 3000 nm or less, and it is more preferable that the D10 is 200 nm or more, and a D90 of 3000 nm or less.

[0038] Furthermore, when the polymer A is dissolved in N-methylpyrrolidone at a concentration of 0.5% by mass, the hydrodynamic radius D50 is the hydrodynamic radius at which the cumulative frequency of light scattering intensity calculated from the smallest diameter side reaches 50% in a hydrodynamic radius distribution obtained by dynamic light scattering. The D50 is preferably 500 nm or more, more preferably 700 nm or more, and preferably 2000 nm or less, and more preferably 1500 nm or less. When the D50 of the polymer A is equal to or greater than the lower limit, the polymer A can contribute to electrode flexibility. When the D50 of the polymer A is equal to or less than the upper limit, the polymer A can dissolve well in N-methylpyrrolidone.

[0039] The hydrodynamic radii (D10, D50, D90, etc.) of polymer A can be adjusted by, for example, changing the composition of polymer A (type and / or content ratio of monomer units), production conditions of polymer A (amount of emulsifier used, etc.), etc. Specifically, for example, the hydrodynamic radius distribution of polymer A can be adjusted by appropriately adding a chain transfer agent such as t-dodecyl mercaptan to the monomer composition when preparing polymer A.

[0040] [Electrolyte Swelling Degree] The electrolyte swelling degree of the polymer A is preferably 300% by mass or less. If the electrolyte swelling degree of the polymer A is 300% by mass or less, the cycle characteristics of the obtained secondary battery can be improved. From the viewpoint of further improving the cycle characteristics of the secondary battery, the electrolyte swelling degree of the polymer A is preferably 250% by mass or less, more preferably 200% by mass or less, and even more preferably 150% by mass or less.

[0041] The degree of swelling of polymer A in an electrolyte solution can be adjusted, for example, by changing the composition of polymer A (the type and / or content ratio of monomer units).

[0042] [Weight-Average Molecular Weight] The weight-average molecular weight of polymer A is preferably greater than 1,000,000, more preferably greater than 1,500,000, and even more preferably greater than 2,000,000. When the weight-average molecular weight of polymer A is greater than 1,000,000, the flexibility of an electrode using the binder composition can be further enhanced. Furthermore, when the weight-average molecular weight of polymer A is greater than 1,000,000, the slurry composition can be imparted with an appropriate viscosity when prepared, thereby suppressing the sedimentation of the conductive material and electrode 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 improved, and ultimately the flexibility of the electrode mixture layer can be further enhanced. The upper limit of the weight-average molecular weight of polymer A is not particularly limited and can be, for example, 5,000,000 or less. When the average molecular weight of polymer A is equal to or less than the above upper limit, the flexibility of the resulting electrode can be further enhanced. In the present invention, the weight-average molecular weight of polymer A can be measured by gel permeation chromatography (GPC). The weight average molecular weight of polymer A can be adjusted by the reaction temperature, polymerization method, blending of a polymerization initiator, blending of a molecular weight modifier, and the like.

[0043] <<Composition>> Polymer A is not particularly limited as long as it satisfies the above-mentioned essential properties, and a polymer of any composition can be used. The substance constituting polymer A may be one type or two or more types. Furthermore, hereinafter, when polymer A is composed of two or more types of substances, the content of monomer units (repeating units) in polymer A refers to the total content of monomer units (repeating units) in all substances constituting polymer A. Polymer A is usually water-insoluble. Here, "water-insoluble" means that when 0.5 g of polymer A is dissolved in 100 g of water at a temperature of 50°C, the insoluble content is 90.0 mass % or more.

[0044] Examples of polymer A include polymers containing at least one monomer unit selected from the group consisting of (meth)acrylic acid alkyl ester monomer units, hydroxyl group-containing monomer units, and nitrile group-containing monomer units. Among these, from the viewpoint of further improving the flexibility of the resulting electrode, polymer A preferably contains (meth)acrylic acid alkyl ester monomer units. Furthermore, from the viewpoint of further improving the flexibility of the resulting electrode and the static storage stability of the slurry composition, polymer A preferably contains (meth)acrylic acid alkyl ester monomer units and hydroxyl group-containing monomer units, and more preferably consists solely of (meth)acrylic acid alkyl ester monomer units and hydroxyl group-containing monomer units. In the present invention, "(meth)acrylic" refers to acrylic and / or methacrylic.

[0045] Here, from the viewpoint of further improving the static storage stability of the slurry composition, it is preferable that polymer A does not contain a crosslinkable monomer unit. When polymer A does not contain a crosslinkable monomer unit, aggregation of polymer A due to crosslinking is suppressed, and the electrode active material can be well dispersed in the slurry composition, resulting in further improving the static storage stability of the slurry composition. Examples of crosslinkable monomers that can form crosslinkable monomer units include polyfunctional monomers having two or more polymerization reactive groups in the monomer. Examples of such polyfunctional monomers include divinyl monomers such as divinylbenzene, 1,3-butadiene, isoprene, and allyl methacrylate; di(meth)acrylic acid ester monomers such as ethylene dimethacrylate, diethylene glycol dimethacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, and 1,3-butylene glycol diacrylate; tri(meth)acrylic acid ester monomers such as trimethylolpropane trimethacrylate and trimethylolpropane triacrylate; ethylenically unsaturated monomers containing an epoxy group such as allyl glycidyl ether and glycidyl methacrylate; and monomers having an ethylenically unsaturated bond and an alkoxysilyl group such as vinyltriethoxysilane and vinyltrimethoxysilane.

[0046] [(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. Examples of the (meth)acrylic acid alkyl ester monomer that can form the (meth)acrylic acid alkyl ester monomer unit include 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. Examples of the methacrylic acid alkyl ester include methyl 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, from the viewpoint of further improving the flexibility of the resulting electrode, at least one acrylic acid alkyl ester monomer selected from the group consisting of (meth)acrylic acid alkyl esters having an alkyl chain carbon number of 6 or more (i.e., hexyl acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate, stearyl acrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, lauryl methacrylate, n-tetradecyl methacrylate, stearyl methacrylate, etc.), ethyl acrylate, and butyl acrylate is preferred, and at least one acrylic acid alkyl ester monomer selected from the group consisting of 2-ethylhexyl acrylate, ethyl acrylate, and butyl acrylate is preferred. More preferred are (meth)acrylic acid alkyl ester monomers, and a combination of a (meth)acrylic acid alkyl ester having an alkyl chain of 6 or more carbon atoms with a (meth)acrylic acid alkyl ester having an alkyl chain of 5 or less carbon atoms (i.e., methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-pentyl acrylate, isopentyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, isobutyl methacrylate, n-pentyl methacrylate, isopentyl methacrylate, etc.) is even more preferred, a combination of butyl acrylate or ethyl acrylate with 2-ethylhexyl acrylate is even more preferred, and a combination of butyl acrylate with 2-ethylhexyl acrylate is particularly preferred. Note that in the present invention, monomers included in the (meth)acrylic acid alkyl ester monomer are not included in the hydroxyl group-containing monomer described below.

[0047] The content of the (meth)acrylic acid alkyl ester monomer units in polymer A 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, based on 100% by mass of all repeating units in polymer A. When the content of the acrylic acid alkyl ester monomer units in polymer A is equal to or more than the above lower limit, even better flexibility can be imparted to the electrode.

[0048] Furthermore, the content of (meth)acrylic acid alkyl ester monomer units having an alkyl chain with 6 or more carbon atoms in polymer A is preferably 20% by mass or more, more preferably 25% by mass or more, and preferably 60% by mass or less, and more preferably 40% by mass or less, when the total amount of repeating units in polymer A is taken as 100% by mass. When the content of acrylic acid alkyl ester monomer units having an alkyl chain with 6 or more carbon atoms in polymer A is within the above range, the static storage stability of the resulting slurry composition can be further improved.

[0049] [Hydroxyl group-containing monomer unit] The hydroxyl group-containing monomer unit is a repeating unit derived from a hydroxyl group-containing monomer. Examples of hydroxyl group-containing monomers that can form the hydroxyl group-containing monomer unit include hydroxymethyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxymethyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, and hydroxybutyl methacrylate. These may be used alone or in combination of two or more in any ratio. Among these, hydroxyethyl methacrylate or hydroxypropyl methacrylate is preferred, and hydroxyethyl methacrylate is more preferred.

[0050] The content of the hydroxyl group-containing monomer units in polymer A may be 0% by mass, but is preferably more than 0% by mass, more preferably 4% by mass or more, and preferably 10% by mass or less, and more preferably 7% by mass or less, when the total amount of repeating units in polymer A is taken as 100% by mass. If polymer A contains the hydroxyl group-containing monomer units in the above range, the flexibility of the resulting electrode and the static storage stability of the resulting slurry composition can be further improved.

[0051] [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.

[0052] The content of the nitrile group-containing monomer unit in polymer A may be 0% by mass, but is preferably 3% by mass or more, more preferably 10% by mass or less, and more preferably 7% by mass or less, when the total amount of all repeating units in polymer A is 100% by mass.

[0053] <<Method for Preparing Polymer A>> The method for producing Polymer A 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.

[0054] The polymerization initiator that can be used in the preparation of polymer A is not particularly limited, and examples thereof include 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.

[0055] The emulsifier that can be used in the preparation of polymer A is not particularly limited, and examples thereof include 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. Of 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.

[0056] <Solvent> The solvent that may be optionally contained in the binder composition of the present invention is not particularly limited, and examples thereof include organic solvents such as 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 solvent. Note that, as the solvent, one type may be used alone, or two or more types may be mixed at any ratio.

[0057] <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 types in any ratio.

[0058] <Method for Preparing Binder Composition> The binder composition of the present invention can be prepared, for example, by dissolving or dispersing the above-described polymer A and any other components described above in a solvent. Specifically, the binder composition can be prepared by mixing the above-described components with a solvent using a mixer such as a ball mill, sand mill, bead mill, pigment disperser, crusher, ultrasonic disperser, homogenizer, planetary mixer, or Filmix. When polymer A is prepared in the form of an aqueous dispersion, a binder composition containing polymer A and an organic solvent can be suitably obtained by mixing the aqueous dispersion of polymer A with an organic solvent and then removing the water to obtain a binder composition. For example, water can be removed by placing the aqueous dispersion of polymer A and an organic solvent in a rotary evaporator, reducing the pressure, and performing solvent exchange and dehydration at a predetermined temperature. Here, the water content in the organic solvent containing polymer A after solvent exchange (water content of the binder composition) is preferably less than 2000 ppm, more preferably less than 1000 ppm, even more preferably less than 800 ppm, and most preferably 500 ppm or less.

[0059] (Slurry composition for non-aqueous secondary battery electrode) The slurry composition of the present invention contains the binder composition of the present invention described above and an electrode active material, and may optionally further contain at least one component selected from a conductive material and other components. Furthermore, since the slurry composition of the present invention contains the binder composition of the present invention described above, it is possible to produce an electrode with excellent flexibility and also has excellent static storage stability. 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.

[0060] <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) can be, for example, 0.1 mass % or more and 5 mass % or less, where the total solid content of the slurry composition is 100 mass %.

[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 -LiNiO ２ system solid solution, Li １＋ｘ Mn ２－ｘ O ４ Examples of known positive electrode active materials include lithium-excess spinel compounds represented by (0<X<2). The particle size of the positive electrode active material is not particularly limited and can be the same as that of conventionally used positive electrode active materials. The content of the positive electrode active material in the slurry composition can be, for example, 90% by mass or more and 99% by mass or less, where the total solid content in the slurry composition is 100% by mass.

[0063] <<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.), multi-walled carbon nanotubes, carbon nanohorns, vapor-grown carbon fibers, milled carbon fibers obtained by calcining and then crushing polymer fibers, and multi-walled graphene. Among these, acetylene black is preferred. These materials can be used alone or in combination of two or more. The particle size of the conductive material is not particularly limited and can be the same as that of conventionally used conductive materials. The content of the conductive material in the slurry composition can be, for example, 0.1% by mass or more and 8% by mass or less, based on 100% by mass of the total solid content of the slurry composition.

[0064] The conductive material in the present invention is a 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 If the content is 0.01 to 0.1g, the dispersibility of the conductive material can be increased, and the resistance of the electrode using the slurry composition of the present invention can be suppressed.

[0065] <<Other Components>> Other components that can be incorporated into the slurry composition are not particularly limited, and examples thereof include the same components as those that can be incorporated 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, in addition to the above-mentioned polymer A, a binder other than polymer A (e.g., a fluoropolymer such as polyvinylidene fluoride (PVdF) or polytetrafluoroethylene (PTFE)). If the slurry composition contains a fluoropolymer, the static storage stability of the slurry composition can be further improved. Furthermore, it is preferable that the slurry composition contains a conductive material dispersant to improve the dispersibility of the conductive material.

[0066] [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, with acid-modified polyvinylidene fluoride being 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.

[0067] 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, based on 100% by mass of the total of polymer A and the fluoropolymer. When the content of the fluoropolymer is equal to or less than the upper limit, the static storage stability of the slurry composition can be further improved. When 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.

[0068] [Conductive Material Dispersant] Examples of conductive material dispersants include nonionic dispersants such as polyvinylpyrrolidone and polyvinyl butyral; carboxymethyl cellulose; and polymers containing nitrile group-containing monomer units (e.g., acrylonitrile units) and alkylene structural units (e.g., 1,3-butadiene hydride units). 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, and more preferably 0.1% by mass or more, and preferably 5% by mass or less, and more preferably 3% by mass or less, based on 100% by mass of the total solids content in the slurry composition.

[0069] <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 the binder composition of the present invention and the electrode active material described above, and optionally, a conductive material and / or 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.

[0070] (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, and the electrode mixture layer is formed using the above-mentioned slurry composition of the present invention. That is, the electrode mixture layer is a dried product of the above-mentioned slurry composition of the present invention, and contains at least a binder composition and an electrode active material. Note that the components contained in the electrode mixture layer are those contained in the above-mentioned 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-mentioned polymer A may be in a particulate form or another form in the electrode mixture layer.

[0071] <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).

[0072] <<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.

[0073] 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.

[0074] <<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.

[0075] After the drying step, the electrode mixture layer may be subjected to pressure treatment using a mold press, a roll press, etc. Pressure treatment can improve the adhesion between the electrode mixture layer and the current collector.

[0076] (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 electrode has excellent flexibility. 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.

[0077] <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.

[0078] <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 ２Among 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.

[0079] 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.

[0080] <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.

[0081] <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.

[0082] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. In the following description, "%" and "parts" representing amounts are based on mass unless otherwise specified. Furthermore, in a polymer produced by copolymerizing multiple types of monomers, the proportion of a structural unit formed by polymerizing a certain monomer in the polymer usually coincides with the ratio (feed ratio) of that certain monomer to all monomers used in the polymerization of the polymer, unless otherwise specified. In the examples and comparative examples, various measurements and evaluations were carried out by the following methods.

[0083] <Hydrodynamic Radius of Polymer A Measured by Dynamic Light Scattering> NMP was added to the NMP solution containing 8% by mass of polymer A prepared in the Examples and Comparative Examples to prepare a binder solution containing 0.5% by mass of polymer A. The particle size distribution (hydrodynamic radius distribution) of polymer A in the binder solution obtained above was measured using a particle size distribution analyzer (manufactured by Otsuka Electronics Co., Ltd., model "nanoSAQLA") that uses dynamic light scattering as its measurement principle. In the measured particle size distribution, the hydrodynamic radii (particle diameters) at which the cumulative frequency of the light scattering intensity calculated from the small diameter side reached 10%, 50%, and 90%, respectively, were determined as D10, D50, and D90. The measurement conditions for the dynamic light scattering method were as follows: Dispersion medium: NMP Measurement temperature: 25±1°C Measurement concentration (solid content concentration): 0.5 mass% Scattering angle: 168.8° Light source laser wavelength: 660 nm <Electrolyte swelling degree of polymer A> The NMP solution with a polymer concentration of 8 mass% prepared in the Examples and Comparative Examples was dropped into a petri dish so that the solid content was 1.5 g. The dropped NMP solution was dried in an environment of 22 to 25°C for 24 hours, and further dried in vacuum at 100°C for 10 hours to obtain a film. The mass of the film piece obtained by cutting the film was designated as w0, and this film piece was then immersed in a 1.0 M LiPF6 solution, which was the electrolyte. ６ The film was immersed in a solution (a mixed solvent of ethylene carbonate (EC) / ethyl methyl carbonate (EMC) = 3 / 7 (volume ratio), with 2 wt % vinylene carbonate added as an additive) at 60°C for 72 hours. After immersion, the film piece was pulled out of the electrolyte, the droplets were wiped off, and the film piece was left to stand under a draft for 1 minute. The mass of the film piece was then measured and recorded as mass w1. The electrolyte swelling degree (mass %) of Polymer A was then calculated according to the following formula: Electrolyte swelling degree (mass %) = (w1 / w0) × 100 <Electrode flexibility> Aluminum foil with 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 using a comma coater so that the basis weight 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 was fabricated, consisting of an electrode (positive electrode) composite layer and aluminum foil. 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 electrode (positive electrode) composite layer facing outward. The electrode (positive electrode) composite 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 <Static Storage Stability of Slurry Compositions> The slurry compositions prepared in the examples and comparative examples were poured into test tubes with a diameter of 1 cm to a height of 5 cm to prepare test samples (5 in total). The test sample was placed vertically on a desk. The state of the placed slurry composition was observed for 10 days, and the static storage stability of the slurry composition was evaluated according to the following criteria. The longer the time after placing the test sample on the desk during which two-phase separation was not observed, the better the static storage stability of the slurry composition. A: No two-phase separation observed after 10 days B: Two-phase separation observed after 5 days but before 10 days C: Two-phase separation observed before 5 days <Viscosity Stability of Slurry Composition> The viscosity η0 of the slurry compositions obtained in the examples and comparative examples was measured using a B-type viscometer (manufactured by Toki Sangyo Co., Ltd., product name "TVB-10", rotation speed: 60 rpm). Next, the slurry compositions whose viscosity had been measured were stirred for 24 hours using a planetary mixer (rotation speed: 60 rpm), and the viscosity η1 of the slurry composition after stirring was measured using the same B-type viscometer (rotation speed: 60 rpm) as above. The viscosity retention rate Δη of the slurry composition before and after stirring was calculated as Δη=η1 / η0×100(%), and the viscosity stability of the slurry composition was evaluated according to the following criteria. The temperature during viscosity measurement was 25° C. The closer the value of the viscosity retention rate Δη is to 100%, the better the viscosity stability of the slurry composition is.A: Viscosity retention rate Δη is 90% or more and 110% or less. B: Viscosity retention rate Δη is 80% or more and less than 90%. C: Viscosity retention rate Δη is less than 80%. <Cycle characteristics of secondary batteries> The lithium ion secondary batteries manufactured 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 discharged to 3.0 V. This cycle was repeated for 300 cycles. The cycle capacity retention rate, 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 of the secondary battery. A: Cycle capacity retention rate is 93% or more. B: Cycle capacity retention rate is 88% or more and less than 93%. C: Cycle capacity retention rate is less than 88%.

[0084] Example 1 Production of Binder Composition 90 parts of ion-exchanged water and 0.5 parts of sodium lauryl sulfate ("EMAL 2FG" manufactured by Kao Chemical Co., Ltd.) as an emulsifier were 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, 0.5 parts of sodium lauryl sulfate ("EMAL 2FG" manufactured by Kao Chemical Co., Ltd.) as an emulsifier, 68 parts of butyl acrylate (BA) and 25 parts of 2-ethylhexyl acrylate (2-EHA) as (meth)acrylic acid alkyl ester monomers, and 7 parts of 2-hydroxyethyl methacrylate (HEMA) as a hydroxyl group-containing monomer were mixed to obtain a monomer composition. An amount equivalent to 4 parts of the above monomer composition was added to the reactor, and then 0.25 parts of ammonium persulfate was added and the mixture was stirred for 20 minutes. Thereafter, the remaining monomer composition was continuously added to the reactor over 3 hours to carry out polymerization. During the addition, the reaction was carried out at 70°C. 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, producing an aqueous dispersion containing a particulate polymer. Next, 600 parts of N-methylpyrrolidone was added to 100 parts of this aqueous dispersion, and all of the water, 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. The electrolyte swelling degree and hydrodynamic radius (D10, D50, D90) of polymer A were then measured. The results are shown in Table 1. <Preparation of Positive Electrode Slurry Composition> NMC (LiNi) having a layered structure was used as the positive electrode active material. ０．9 Mn ０．05 Co ０．05 O ２ To 96.8 parts of the fluoropolymer, 0.5 parts of PVdF and 0.5 parts of the binder composition (solid content equivalent) were added. ２A carbon paste prepared by mixing 2.0 parts of acetylene black (Li435: manufactured by Denka Co., Ltd.) with 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 positive electrode). This slurry composition was used to measure the static storage stability and viscosity stability of the slurry composition. The results are shown in Table 1. <Production of positive electrode> The obtained slurry composition for positive electrode was coated on a 15 μm-thick aluminum foil (current collector) with a comma coater so that the coating amount after drying was 20 mg / cm. 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 from a positive electrode active material layer having a specific surface area of ​​4 m2 and aluminum foil. 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. ２ The negative electrode blank was then rolled with a roll press to a density of 1.5 g / cm. ３A negative electrode having a negative electrode active material layer of the formula (1) was obtained. <Preparation of Separator> A single-layer polypropylene separator (width 65 mm, length 500 mm, thickness 25 μm; manufactured by a dry process; porosity 55%) was prepared. This separator was cut into a 5 cm x 5 cm square and used in the following lithium-ion secondary battery. <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. Thereafter, 1.0 M LiPF 6 was used as the electrolyte. ６ A solution (a mixed solvent of ethylene carbonate (EC) / ethyl methyl carbonate (EMC) = 3 / 7, with 2% by volume of vinylene carbonate as an additive) was filled into the battery. Furthermore, in order to seal the opening of the aluminum packaging, the exterior of the aluminum packaging was closed by heat sealing at 150°C, thereby producing a laminate cell type lithium ion secondary battery. The cycle characteristics of the obtained lithium ion secondary battery were evaluated. The results are shown in Table 1.

[0085] (Examples 2 to 8, 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 1. The results are shown in Table 1.

[0086] The results shown in Table 1 show that the binder compositions of Examples 1 to 8 containing polymer A having D10 and D90 of 100 nm or more and 4000 nm or less, respectively, can produce electrodes with excellent flexibility and can improve the static storage stability of the slurry composition.

[0087] According to the present invention, a binder composition for a non-aqueous secondary battery electrode can be provided that can be suitably used for producing an electrode with excellent flexibility and can improve the static storage stability of the slurry composition. 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 has excellent static storage stability. Furthermore, according to the present invention, a non-aqueous secondary battery electrode with excellent flexibility and a non-aqueous secondary battery including the non-aqueous secondary battery electrode can be provided.

Claims

1. A binder composition for a non-aqueous secondary battery electrode, comprising polymer A, wherein polymer A has a hydrodynamic radius distribution obtained by dynamic light scattering when the polymer A is dissolved in N-methylpyrrolidone at a concentration of 0.5% by mass, where D10 is the hydrodynamic radius at which the cumulative frequency of light scattering intensity calculated from the small diameter side is 10%, and D90 is the hydrodynamic radius at which the cumulative frequency of light scattering intensity calculated from the small diameter side is 90%, and D10 is 100 nm or more, and D90 is 4000 nm or less.

2. The binder composition for a non-aqueous secondary battery electrode according to claim 1, wherein the polymer A has a D10 of 100 nm or more and 1000 nm or less.

3. The binder composition for a non-aqueous secondary battery electrode according to claim 1, wherein the polymer A has a D10 of 140 nm or more and 500 nm or less.

4. The binder composition for a non-aqueous secondary battery electrode according to claim 1, wherein the polymer A has a D10 of 200 nm or more and 500 nm or less.

5. The binder composition for a non-aqueous secondary battery electrode according to any one of claims 1 to 4, wherein the polymer A has a D90 of more than 500 nm and not more than 4000 nm.

6. The binder composition for a non-aqueous secondary battery electrode according to any one of claims 1 to 4, wherein the polymer A has a D90 of 600 nm or more and 3500 nm or less.

7. The binder composition for a non-aqueous secondary battery electrode according to any one of claims 1 to 4, wherein the polymer A has a D90 of 800 nm or more and 3000 nm or less.

8. The binder composition for a non-aqueous secondary battery electrode according to any one of claims 1 to 7, wherein the polymer A contains 80 mass % or more of alkyl (meth)acrylate monomer units.

9. The binder composition for a non-aqueous secondary battery electrode according to any one of claims 1 to 7, wherein the polymer A contains 90 mass % or more of alkyl (meth)acrylate monomer units.

10. A binder composition for a non-aqueous secondary battery electrode according to any one of claims 1 to 9, wherein the polymer A has an electrolyte swelling degree of 300 mass % or less.

11. The binder composition for a non-aqueous secondary battery electrode according to any one of claims 1 to 10, wherein polymer A contains 20% by mass or more and 60% by mass or less of (meth)acrylic acid alkyl ester monomer units having an alkyl chain with 6 or more carbon atoms.

12. The binder composition for a non-aqueous secondary battery electrode according to any one of claims 1 to 11, wherein the polymer A contains hydroxyl group-containing monomer units in a proportion of more than 0 mass % and not more than 10 mass %.

13. The binder composition for a non-aqueous secondary battery electrode according to any one of claims 1 to 12, wherein the polymer A does not contain a crosslinkable monomer unit.

14. A slurry composition for a non-aqueous secondary battery electrode, comprising the binder composition for a non-aqueous secondary battery electrode according to any one of claims 1 to 13 and an electrode active material.

15. The non-aqueous secondary battery electrode slurry composition according to claim 14, further comprising a fluoropolymer.

16. A slurry composition for a non-aqueous secondary battery electrode according to claim 15, wherein the proportion of the fluoropolymer is 70 mass% or less when the total of the fluoropolymer and polymer A is 100 mass%.

17. The slurry composition for a non-aqueous secondary battery electrode according to any one of claims 14 to 16, further comprising a conductive material.

18. 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 17, wherein the SiO2 content is 0.01g or less.

19. 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 14 to 18.

20. A non-aqueous secondary battery comprising the electrode for a non-aqueous secondary battery according to claim 19.

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