Nonaqueous secondary battery electrode binder composition, nonaqueous secondary battery electrode slurry composition, nonaqueous secondary battery electrode, and nonaqueous secondary battery

Abstract

The purpose of the present invention is to provide a nonaqueous secondary battery electrode binder composition from which it is possible to form a nonaqueous secondary battery electrode that exhibits excellent peel strength during high‑speed coating. A nonaqueous secondary battery electrode binder composition according to the present invention contains a particulate polymer. The particulate polymer contains a random copolymer having an isoprene unit or a block copolymer having an isoprene unit.

Description

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

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

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

[0003] Here, electrodes used in secondary batteries such as lithium-ion secondary batteries typically comprise a current collector and an electrode composite layer (positive electrode composite layer or negative electrode composite layer) formed on the current collector. This electrode composite layer is formed, for example, by coating the current collector with a slurry composition containing an electrode active material and a binder composition containing a binder, and then drying the coated slurry composition.

[0004] Binder compositions used in slurry compositions are being developed to improve the performance of secondary batteries. For example, Patent Document 1 proposes a binder composition capable of forming electrodes for non-aqueous secondary batteries with excellent peel strength, which includes a particulate polymer, in which the content ratios of aromatic monovinyl monomer units, aliphatic conjugated diene monomer units, and carboxyl group-containing monomer units in the particulate polymer are each within predetermined ranges, the ratio (Da / Db) of the average particle diameter Da of the particulate polymer measured by dynamic light scattering to the volume average particle diameter Db of the particulate polymer measured by laser diffraction scattering is within predetermined ranges, and the volume average particle diameter Db of the particulate polymer is within predetermined ranges.

[0005] International Publication No. 2023 / 008582

[0006] Here, in recent years, from the perspective of improving the productivity of electrodes, it has been required to coat a slurry composition on a current collector at high speed to increase the production rate of the electrode mixture layer. In addition, for secondary batteries, it has been required to exhibit excellent cycle characteristics even when the amount of the binder contained in the electrode mixture layer is reduced. Further, for the slurry composition, it has been required that the viscosity does not change significantly over time (i.e., excellent viscosity stability).

[0007] However, when the slurry composition obtained using the above conventional binder composition is subjected to high-speed coating, the peel strength of the resulting electrode may not be sufficiently ensured. In addition, there has been room for improvement in the above conventional binder composition in terms of improving the cycle characteristics of secondary batteries when the amount of the binder in the electrode mixture layer is reduced.

[0008] Therefore, an object of the present invention is to provide a binder composition for non-aqueous secondary battery electrodes and a slurry composition for non-aqueous secondary battery electrodes that can form non-aqueous secondary battery electrodes having excellent peel strength during high-speed coating. Another object of the present invention is to provide a non-aqueous secondary battery electrode having excellent peel strength during high-speed coating. And an object of the present invention is to provide a non-aqueous secondary battery provided with the above non-aqueous secondary battery electrode.

[0009] The present inventor has intensively studied for the purpose of solving the above problems. And the present inventor has found that a non-aqueous secondary battery having excellent peel strength during high-speed coating can be formed by using a binder composition containing a particulate polymer containing a random copolymer containing isoprene units or a block copolymer containing isoprene units, and has completed the present invention.

[0010] That is, this invention is intended to advantageously solve the above problems. According to the present invention, there are provided a binder composition for non-aqueous secondary battery electrodes of the following [1] to

[14] , a slurry composition for non-aqueous secondary battery electrodes of the following

[15] , a non-aqueous secondary battery electrode of the following

[16] , and a non-aqueous secondary battery of the following

[17] .

[0011] [1] A binder composition for non-aqueous secondary battery electrodes comprising a particulate polymer, wherein the particulate polymer comprises a random copolymer containing isoprene units or a block copolymer containing isoprene units. Using the above binder composition, the electrodes for non-aqueous secondary batteries can exhibit excellent peel strength during high-speed coating. In this invention, the "monomer unit" of a polymer means "a repeating unit derived from the monomer contained in the polymer obtained using the monomer."

[0012] [2] The particulate polymer is the binder composition for non-aqueous secondary battery electrodes described in [1] above, wherein the particulate polymer contains isoprene units and crosslinkable monomer units. A slurry composition obtained using a binder composition containing a particulate polymer containing isoprene units and crosslinkable monomer units can be used to produce electrodes with excellent peel strength. Furthermore, electrodes produced in this manner can enable non-aqueous secondary batteries to exhibit excellent cycle characteristics.

[0013] [3] The particulate polymer comprises the random copolymer, wherein the binder composition for non-aqueous secondary battery electrodes is as described in [1] or [2], preferably [2] above. If the particulate polymer includes the random copolymer, the peel strength of the electrode can be further increased and the cycle characteristics of the non-aqueous secondary battery can be further improved.

[0014] [4] The particulate polymer further comprises aromatic monovinyl monomer units, and is any of the above [1] to [3], preferably the binder composition for non-aqueous secondary battery electrodes described in [2] or [3]. If the particulate polymer further comprises aromatic monovinyl monomer units, the viscosity stability of the slurry composition can be improved.

[0015] [5] The particulate polymer further comprises (meth)acrylic acid ester monomer units, the binder composition for non-aqueous secondary battery electrodes according to any of [1] to [4] above, preferably any of [2] to [4] above. If the particulate polymer further comprises (meth)acrylic acid ester monomer units, the internal resistance of the non-aqueous secondary battery can be reduced. In this invention, "(meth)acrylic" means acrylic and / or methacrylic.

[0016] [6] The crosslinkable monomer unit is derived from a monomer having two or more crosslinkable reactive groups per molecule, and is a binder composition for non-aqueous secondary battery electrodes according to any of [1] to [5] above, preferably any of [2] to [5] above. If the crosslinkable monomer unit is a repeating unit derived from a monomer having two or more crosslinkable reactive groups per molecule, the cycle characteristics of the secondary battery can be further improved.

[0017] [7] The binder composition for non-aqueous secondary battery electrodes according to [6] above, wherein the crosslinkable reactive group is selected from the group consisting of epoxy groups, hydroxyl groups, N-methylolamide groups, oxetanyl groups, oxazoline groups, and vinyl groups. If the crosslinkable reactive group is selected from the functional groups described above, the cycle characteristics of the secondary battery can be further improved.

[0018] [8] A binder composition for non-aqueous secondary battery electrodes according to any of [1] to [7] above, preferably any of [2] to [7] above, wherein the content ratio of the crosslinkable monomer units in the particulate polymer is 0.01% by mass or more and 10% by mass or less. If the content ratio of the crosslinkable monomer units in the particulate polymer is within the above range, the internal resistance can be reduced while further improving the cycle characteristics of the non-aqueous secondary battery.

[0019] [9] A binder composition for non-aqueous secondary battery electrodes according to any of [1] to [8] above, preferably any of [2] to [8] above, wherein the ratio (Da / Db) of the average particle diameter Da of the particulate polymer measured by dynamic light scattering to the median diameter Db of the particulate polymer measured by laser diffraction scattering is 1.05 or more and 2.00 or less, and the median diameter Db is 100 nm or more and 170 nm or less. If Db and Da / Db are within the above ranges, the pourability of the electrolyte of the secondary battery can be improved and the internal resistance of the secondary battery can be reduced. In addition, the handling properties of the binder composition can be improved and the peel strength of the electrode can be further increased. In this invention, the "average particle diameter Da" of the particulate polymer means "the cumulant average particle diameter obtained by cumulant analysis of the particle size distribution (volume basis) measured by dynamic light scattering," and can be measured using the method described in the examples of this specification. Furthermore, in the present invention, the "median diameter Db" of the particulate polymer means "the particle diameter (D50) at which the cumulative volume calculated from the smallest diameter side in the particle size distribution (volume basis) measured by laser diffraction scattering method becomes 50%", and can be measured using the method described in the examples of this specification.

[0020]

[10] A binder composition for non-aqueous secondary battery electrodes according to [1] above, comprising the particulate polymer and two or more antioxidants, wherein the particulate polymer comprises a random copolymer containing isoprene units. A binder composition comprising a particulate polymer and two or more antioxidants, wherein the particulate polymer comprises a random copolymer containing isoprene units, can be used to prepare a slurry composition with excellent viscosity stability. Furthermore, a slurry composition prepared in this manner can enable a non-aqueous secondary battery to exhibit excellent cycle characteristics.

[0021]

[11] The particulate polymer further comprises aromatic monovinyl monomer units, wherein the binder composition for non-aqueous secondary battery electrodes is as described in [1] or

[10] , preferably as described in

[10] . If the particulate polymer further comprises aromatic monovinyl monomer units, the viscosity stability of the slurry composition can be further improved.

[0022]

[12] The binder composition for non-aqueous secondary battery electrodes according to

[10] or

[11] above, wherein the two or more antioxidants include an antioxidant having a molecular weight of 200 or more and 500 or less. If the binder composition includes an antioxidant having a molecular weight within the above range, the viscosity stability of the slurry composition can be further enhanced while further improving the cycle characteristics of the secondary battery. In this invention, the "molecular weight" of the antioxidant can be measured, for example, in accordance with JIS K7252.

[0023]

[13] The two or more antioxidants have a specific gravity of 1.0 g / cm³. ３ A binder composition for non-aqueous secondary battery electrodes according to any one of

[10] to

[12] above, comprising the antioxidant described above. If the binder composition contains an antioxidant having a specific gravity greater than or equal to the above value, the viscosity stability of the slurry composition can be further enhanced while further improving the cycle characteristics of the secondary battery. In this invention, "specific gravity" means the specific gravity measured at 25°C, and can be measured, for example, in accordance with JIS K:8804.

[0024]

[14] The binder composition for non-aqueous secondary battery electrodes according to

[12] or

[13] above, wherein the two or more antioxidants further include antioxidants having a melting point of 0°C or higher and 90°C or lower. If the binder composition further includes antioxidants having a melting point within the above range, the viscosity stability of the slurry composition can be further enhanced while further improving the cycle characteristics of the secondary battery. In this invention, the "melting point" of the antioxidant can be measured, for example, in accordance with JIS K0064.

[0025]

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

[14] above, preferably any of [2] to

[14] above. The slurry composition comprising the electrode active material and any of the above-described binder compositions exhibits excellent viscosity stability. Furthermore, the slurry composition comprising the electrode active material and any of the above-described binder compositions makes it possible to produce electrodes with excellent peel strength. In addition, electrodes produced in this manner can enable non-aqueous secondary batteries to exhibit excellent cycle characteristics.

[0026]

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

[15] above. An electrode comprising an electrode composite layer obtained using a slurry composition containing an electrode active material and any of the above-described binder compositions can exhibit excellent cycle characteristics in a non-aqueous secondary battery.

[0027]

[17] A non-aqueous secondary battery having a positive electrode, a negative electrode, a separator, and an electrolyte, wherein at least one of the positive electrode and the negative electrode is the electrode for a non-aqueous secondary battery described in

[16] above. By using the above-described electrode for a non-aqueous secondary battery, a non-aqueous secondary battery with excellent cycle characteristics can be manufactured.

[0028] According to the present invention, it is possible to provide a binder composition and a slurry composition for non-aqueous secondary battery electrodes that can form electrodes for non-aqueous secondary batteries with excellent peel strength during high-speed coating. Furthermore, according to the present invention, it is possible to provide electrodes for non-aqueous secondary batteries with excellent peel strength during high-speed coating. And according to the present invention, it is possible to provide a non-aqueous secondary battery equipped with the above-mentioned electrodes for non-aqueous secondary batteries.

[0029] Embodiments of the present invention will be described in detail below. Herein, the binder composition for non-aqueous secondary battery electrodes of the present invention can be used to prepare the slurry composition for non-aqueous secondary battery electrodes of the present invention. The slurry composition for non-aqueous secondary battery electrodes of the present invention can be used to form electrodes (electrodes for non-aqueous secondary batteries) of non-aqueous secondary batteries such as lithium-ion secondary batteries. Furthermore, the electrode for non-aqueous secondary battery of the present invention is characterized by comprising an electrode composite layer formed from the slurry composition for non-aqueous secondary battery electrodes of the present invention. Furthermore, the non-aqueous secondary battery of the present invention is characterized by comprising an electrode for non-aqueous secondary battery made using the slurry composition for non-aqueous secondary battery electrodes of the present invention. The binder composition and slurry composition for non-aqueous secondary battery electrodes of the present invention can be particularly suitably used when forming the negative electrode of a non-aqueous secondary battery. Each component disclosed herein, as well as preferred embodiments, numerical ranges, and thresholds defining such numerical ranges shown with respect to each component, can be independently combined with each other in any manner.

[0030] (Binder composition for non-aqueous secondary battery electrodes) The binder composition for non-aqueous secondary battery electrodes of the present invention comprises a particulate polymer and may further contain a solvent. Herein, the binder composition of the present invention is characterized in that the particulate polymer described above comprises a random copolymer containing isoprene units or a block copolymer containing isoprene units.

[0031] Here, the first and second forms described below are preferred as the binder composition. The first and second forms can be combined.

[0032] <First Embodiment> The binder composition for non-aqueous secondary battery electrodes according to the first embodiment will be described in detail below. The binder composition for non-aqueous secondary battery electrodes according to the first embodiment of the present invention contains a particulate polymer and may further contain a solvent. Herein, the binder composition of the present invention is characterized in that the above-mentioned particulate polymer contains isoprene units and crosslinkable monomer units. Note that the binder composition of the present invention does not usually contain conductive material and electrode active material.

[0033] Furthermore, since the binder composition of the present invention contains particulate polymers containing isoprene units and crosslinkable monomer units, it is possible to produce electrodes with excellent peel strength and excellent cycle characteristics for secondary batteries using this binder composition. The reason why the above effects are obtained by using the binder composition of the present invention is not clear, but it is presumed to be as follows.

[0034] In electrodes for non-aqueous secondary batteries, it is generally considered preferable to reduce the amount of binder contained in the electrode composite layer from the viewpoint of reducing the internal resistance of the secondary battery while maintaining the peel strength of the electrode. However, the inventors' research has newly revealed that when a polymer containing isoprene units (e.g., styrene-isoprene copolymer) is used as a binder, reducing the amount of binder degrades the cycle characteristics of the secondary battery. Here, the particulate polymer contained in the binder composition of the present invention contains both isoprene units and crosslinkable monomer units. The crosslinkable monomer units contained in the particulate polymer undergo a crosslinking reaction and can reinforce the interior of the particulate polymer. In addition, the isoprene units contained in the particulate polymer can contribute to improving the peel strength of the electrode by imparting flexibility to the polymer. For the reasons above, it is believed that by using the binder composition of the present invention, it is possible to produce electrodes that have excellent peel strength and can exhibit excellent cycle characteristics in secondary batteries.

[0035] <<Particulate Polymer>> Particulate polymers are components that function as binders and, in an electrode composite layer formed on a current collector using a slurry composition containing a binder composition, they retain components such as electrode active materials contained in the electrode composite layer so that they do not detach from the electrode composite layer. Particulate polymers are water-insoluble particles formed from a predetermined polymer. In this invention, "water-insoluble" particles mean that when 0.5 g of polymer is dissolved in 100 g of water at a temperature of 25°C, the insoluble content is 90% by mass or more.

[0036] Here, the particulate polymer contains at least isoprene units and crosslinkable monomer units, and optionally further contains one or more monomer units selected from aromatic monovinyl monomer units, (meth)acrylic acid ester monomer units, and acid group-containing monomer units. The particulate polymer may also contain monomer units other than isoprene units, crosslinkable monomer units, aromatic monovinyl monomer units, (meth)acrylic acid ester monomer units, and acid group-containing monomer units (other monomer units). In particular, from the viewpoint of further increasing the peel strength of the electrode and further improving the cycle characteristics of the secondary battery, it is preferable that the particulate polymer contains isoprene units, crosslinkable monomer units, styrene units, acrylic acid units and / or methacrylic acid units.

[0037] [Isoprene Unit] The isoprene unit is a structural unit derived from isoprene. In this invention, the isoprene unit does not include structural units obtained by hydrogenating isoprene units (isoprene hydride units).

[0038] The isoprene unit content in the particulate polymer is preferably 20% by mass or more, more preferably 25% by mass or more, even more preferably 40% by mass or more, preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less. Furthermore, the isoprene unit content in the particulate polymer is preferably 20% by mass or more and 90% by mass or less, more preferably 25% by mass or more and 85% by mass or less, and even more preferably 40% by mass or more and 80% by mass or less. If the isoprene unit content in the particulate polymer is 20% by mass or more, the peel strength of the electrode can be further increased. On the other hand, if the isoprene unit content in the particulate polymer is 90% by mass or less, the viscosity stability of the slurry composition can be improved. In this invention, the monomer unit content in the particulate polymer is １ It can be measured using nuclear magnetic resonance (NMR) methods such as 1H-NMR.

[0039] [Crosslinkable Monomer Units] Crosslinkable monomers that can form crosslinkable monomer units are monomers that can form a crosslinked structure by polymerization. Preferred examples of crosslinkable monomers include monomers having two or more crosslinkable reactive groups per molecule. In this invention, aliphatic conjugated diene monomers are not included in the crosslinkable monomers.

[0040] Examples of crosslinkable reactive groups possessed by a crosslinkable monomer include epoxy groups, hydroxyl groups, N-methylolamide groups, oxetanyl groups, oxazoline groups, vinyl groups, allyl groups, (meth)acryloyl groups, and halogen atoms. Among these, epoxy groups, hydroxyl groups, N-methylolamide groups, oxetanyl groups, oxazoline groups, and vinyl groups are preferred, epoxy groups, vinyl groups, and N-methylolamide groups are more preferred, and N-methylolamide groups are even more preferred. A crosslinkable monomer may have only one type of crosslinkable reactive group, or it may have two or more types of crosslinkable reactive groups. In this invention, "(meth)acryloyl" means acryloyl and / or methacryloyl.

[0041] Examples of crosslinkable monomers having epoxy groups include monomers containing a carbon-carbon double bond and an epoxy group, and monomers containing a halogen atom and an epoxy group. Examples of monomers containing a carbon-carbon double bond and an epoxy group include unsaturated glycidyl ethers such as vinyl glycidyl ether, allyl glycidyl ether, butenyl glycidyl ether, and o-allylphenyl glycidyl ether; monoepoxides of dienes or polyenes such as butadiene monoepoxide, chloroprene monoepoxide, 4,5-epoxy-2-pentene, 3,4-epoxy-1-vinylcyclohexene, and 1,2-epoxy-5,9-cyclododecadiene; and 3,4-epoxy-1- Examples include alkenyl epoxides such as tene, 1,2-epoxy-5-hexene, and 1,2-epoxy-9-decene; glycidyl esters of unsaturated carboxylic acids such as glycidyl acrylate, glycidyl methacrylate, glycidyl crotonate, glycidyl-4-heptenoate, glycidyl sorbate, glycidyl linoleate, glycidyl-4-methyl-3-pentenoate, glycidyl esters of 3-cyclohexenecarboxylic acid, and glycidyl esters of 4-methyl-3-cyclohexenecarboxylic acid. Examples of monomers having halogen atoms and epoxy groups include epihalohydrins such as epichlorohydrin, epibromohydrin, epiiodohydrin, epifluorohydrin, and β-methylepichlorohydrin; p-chlorostyrene oxide; and dibromophenyl glycidyl ether.

[0042] Examples of crosslinkable monomers having a hydroxyl group include unsaturated alcohols such as (meth)allyl alcohol, 3-buten-1-ol, and 5-hexen-1-ol; alkanol esters of 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 with the general formula CH ２ =CR １ -COO- (C ｎ H2 ｎ O)ｍ -H(m is an integer from 2 to 9, n is an integer from 2 to 4, R １ Polyalkylene glycols represented by (where represents hydrogen or a methyl group) and (meth)acrylic acid esters; mono(meth)acrylic acid esters of dihydroxy esters of dicarboxylic acids such as 2-hydroxyethyl-2'-(meth)acryloyl oxyphthalate and 2-hydroxyethyl-2'-(meth)acryloyl oxysuccinate; vinyl ethers such as 2-hydroxyethyl vinyl ether and 2-hydroxypropyl vinyl ether; alkyl groups such as (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, and (meth)allyl-6-hydroxyhexyl ether Examples include mono(meth)allyl ethers of alkylene glycol; polyoxyalkylene glycol (meth) monoallyl ethers 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 their halogen-substituted derivatives; and (meth)allyl thioethers of alkylene glycols such as (meth)allyl-2-hydroxyethyl thioether and (meth)allyl-2-hydroxypropyl thioether. In this invention, "(meth)allyl" means allyl and / or methallyl.

[0043] Examples of crosslinkable monomers having an N-methylolamide group include (meth)acrylamides having a methylol group, such as N-methylol(meth)acrylamide.

[0044] Examples of crosslinkable monomers having an oxetanyl group include 3-((meth)acryloyloxymethyl)oxetane, 3-((meth)acryloyloxymethyl)-2-trifluoromethyloxetane, 3-((meth)acryloyloxymethyl)-2-phenyloxetane, 2-((meth)acryloyloxymethyl)oxetane, and 2-((meth)acryloyloxymethyl)-4-trifluoromethyloxetane.

[0045] Examples of crosslinkable monomers having an oxazoline group include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-methyl-2-oxazoline, and 2-isopropenyl-5-ethyl-2-oxazoline.

[0046] Examples of crosslinkable monomers containing multiple crosslinkable vinyl groups include divinylbenzene. Divinylbenzene has three isomers: o-divinylbenzene, m-divinylbenzene, and p-divinylbenzene, all of which can be used as crosslinkable monomers.

[0047] Among those mentioned above, N-methylolacrylamide, allyl glycidyl ether, glycidyl methacrylate, and divinylbenzene are preferred from the viewpoint of further improving the cycle characteristics of secondary batteries, N-methylolacrylamide, allyl glycidyl ether, and glycidyl methacrylate are more preferred, and N-methylolacrylamide is even more preferred.

[0048] The number of crosslinkable reactive groups in a crosslinkable monomer is usually two or more, preferably six or fewer, more preferably four or fewer, even more preferably three or fewer, and particularly preferably two.

[0049] The content of crosslinkable monomer units in particulate polymers is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less. Furthermore, the content of crosslinkable monomer units in particulate polymers is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.05% by mass or more and 5% by mass or less, and even more preferably 0.1% by mass or more and 3% by mass or less. If the content of crosslinkable monomer units in particulate polymers is 0.01% by mass or more, the cycle characteristics of secondary batteries can be further improved. On the other hand, if the content of crosslinkable monomer units in particulate polymers is 10% by mass or less, the internal resistance of secondary batteries can be reduced.

[0050] [Aromatic Monovinyl Monomer Units] Examples of aromatic monovinyl monomers that can form aromatic monovinyl monomer units include aromatic monovinyl compounds such as styrene, α-methylstyrene, p-t-butylstyrene, butoxystyrene, vinyltoluene, chlorostyrene, and vinylnaphthalene. Among these, styrene is preferred. These can be used individually or in combination of two or more.

[0051] The content of aromatic monovinyl monomer units in the particulate polymer is preferably 5% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, preferably 60% by mass or less, more preferably 55% by mass or less, and even more preferably 50% by mass or less. Furthermore, the content of aromatic monovinyl monomer units in the particulate polymer is preferably 5% by mass or more and 60% by mass or less, more preferably 15% by mass or more and 55% by mass or less, and even more preferably 20% by mass or more and 50% by mass or less. If the content of aromatic monovinyl monomer units in the particulate polymer is 5% by mass or more, the viscosity stability of the slurry composition can be improved. On the other hand, if the content of aromatic monovinyl monomer units in the particulate polymer is 60% by mass or less, the peel strength of the electrode can be further increased.

[0052] [(meth)acrylic acid ester monomer units] Examples of (meth)acrylic acid ester monomers that can form (meth)acrylic acid ester monomer units include alkyl acrylates such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, and 2-ethylhexyl acrylate; and alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, and 2-ethylhexyl methacrylate. In particular, from the viewpoint of reducing the internal resistance of secondary batteries, methyl methacrylate, ethyl acrylate, and n-butyl acrylate are preferred, methyl methacrylate and ethyl acrylate are more preferred, and methyl methacrylate is even more preferred. The above monomers may be used individually or in combination of two or more in any ratio.

[0053] The content of (meth)acrylic acid ester monomer units in the particulate polymer is preferably 0.1% by mass or more, more preferably 1% by mass or more, even more preferably 2% by mass or more, preferably 10% by mass or less, more preferably 7% by mass or less, and even more preferably 5% by mass or less. Furthermore, the content of (meth)acrylic acid ester monomer units in the particulate polymer is preferably 0.1% by mass or more and 10% by mass or less, more preferably 1% by mass or more and 7% by mass or less, and even more preferably 2% by mass or more and 5% by mass or less. If the content of (meth)acrylic acid ester monomer units in the particulate polymer is 0.1% by mass or more, the internal resistance of the secondary battery can be reduced. On the other hand, if the content of (meth)acrylic acid ester monomer units in the particulate polymer is 10% by mass or less, the peel strength of the electrode can be further increased.

[0054] [Acid Group-Containing Monomer Units] Examples of acid group-containing monomers that can form acid group-containing monomer units include carboxylic acid group-containing monomer units, sulfonic acid group-containing monomer units, and phosphate group-containing monomer units. The acid group of an acid group-containing monomer unit may form a salt with an alkali metal or ammonia.

[0055] Here, examples of carboxylic acid group-containing monomers that can form carboxylic acid group-containing monomer units include monocarboxylic acids and their derivatives, dicarboxylic acids and their acid anhydrides, and their derivatives. Examples of monocarboxylic acids include acrylic acid, methacrylic acid, and crotonic acid. Examples of monocarboxylic acid derivatives include 2-ethylacrylic acid, isocrotonic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, and α-chloro-β-E-methoxyacrylic acid. Examples of dicarboxylic acids include maleic acid, fumaric acid, and itaconic acid. Examples of dicarboxylic acid derivatives include methylmaleic acid, dimethylmaleic acid, phenylmaleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid, and maleic acid monoesters such as butyl maleate, nonyl maleate, decyl maleate, dodecyl maleate, octadecyl maleate, and fluoroalkyl maleate. Examples of dicarboxylic acid acid anhydrides include maleic anhydride, acrylic anhydride, methyl maleic anhydride, dimethyl maleic anhydride, and citraconic anhydride. Acid anhydrides that generate carboxylic acid groups through hydrolysis can also be used as monomers containing carboxylic acid groups. Furthermore, ethylenically unsaturated polycarboxylic acids such as butentricarboxylic acid, and partial esters of ethylenically unsaturated polycarboxylic acids such as monobutyl fumarate and mono-2-hydroxypropyl maleate can also be used as monomers containing carboxylic acid groups.

[0056] Furthermore, examples of sulfonic acid group-containing monomers that can form sulfonic acid group-containing monomer units include styrene sulfonic acid, vinyl sulfonic acid (ethylene sulfonic acid), methyl vinyl sulfonic acid, (meth)allyl sulfonic acid, and 3-alyloxy-2-hydroxypropane sulfonic acid.

[0057] Furthermore, examples of phosphate group-containing monomers that can form phosphate group-containing monomer units include 2-(meth)acryloyloxyethyl phosphate, methyl-2-(meth)acryloyloxyethyl phosphate, and ethyl-(meth)acryloyloxyethyl phosphate.

[0058] Here, the monomers described above may be used individually or in combination of two or more. Furthermore, from the viewpoint of improving the viscosity stability of the slurry composition and further increasing the peel strength of the electrode, carboxylic acid group-containing monomers are preferred as acid group-containing monomers that can form acid group-containing monomer units, methacrylic acid, acrylic acid, and itaconic acid are more preferred, methacrylic acid and itaconic acid are even more preferred, and methacrylic acid is particularly preferred.

[0059] The content of acid group-containing monomer units in the particulate polymer is preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 3% by mass or more, preferably 10% by mass or less, more preferably 7% by mass or less, and even more preferably 5% by mass or less. Furthermore, the content of acid group-containing monomer units in the particulate polymer is preferably 1% by mass or more and 10% by mass or less, more preferably 2% by mass or more and 7% by mass or less, and even more preferably 3% by mass or more and 5% by mass or less. If the content of acid group-containing monomer units in the particulate polymer is 1% by mass or more, the viscosity stability of the slurry composition can be improved and the peel strength of the electrode can be further increased. On the other hand, if the content of acid group-containing monomer units in the particulate polymer is 10% by mass or less, the internal resistance of the secondary battery can be reduced.

[0060] [Other monomer units] Monomers that can form other monomer units are not particularly limited, but include, for example, aliphatic conjugated diene monomers other than isoprene, vinyl cyanide monomers, etc. The particulate polymer may contain only one type of other monomer unit, or it may contain two or more types of other monomer units.

[0061] The content of other monomer units in the particulate polymer is preferably 5% by mass or less, more preferably 1% by mass or less, even more preferably 0.1% by mass or less, and particularly preferably 0% by mass or less (i.e., the particulate polymer does not contain other monomer units), when the total repeating units (total monomer units) in the particulate polymer are taken as 100% by mass.

[0062] [Structure of particulate polymer] The polymer forming the particulate polymer may be a random copolymer, a block copolymer, or any other type. From the viewpoint of improving the viscosity stability of the slurry composition, it is preferable that the particulate polymer contains a random copolymer. Here, a random copolymer refers to a polymer in which more than 90% consists of random regions. The particulate polymer may also further contain polymers other than random copolymers (other polymers). Other polymers are not particularly limited and include block copolymers, etc. Furthermore, from the viewpoint of further improving the viscosity stability of the slurry composition, it is more preferable that the particulate polymer contains only a random copolymer. The particulate polymer may contain only one type of other polymer, or it may contain two or more types of other polymers.

[0063] Here, the particulate polymer may be a particulate polymer having a uniform monomer unit composition (type and content ratio of monomer units), or it may be a particulate polymer having a heterogeneous monomer unit composition. Examples of particulate polymers having a heterogeneous monomer unit composition include a particulate polymer having a core-shell structure comprising a core portion and a shell portion covering at least a part of the outer surface of the core portion, wherein the monomer unit composition of the core portion and the shell portion are different, and a particulate polymer having a monomer unit composition in which only the core portion is different. In the present invention, the core-shell structure also includes a structure in which the composition of the particle center and the composition of the outermost layer of the particle are different from each other. For example, when the particulate polymer has a core-shell structure, the polymer forming the core portion and the polymer forming the shell portion have different compositions, and it is preferable that at least one of the core portion and the shell portion is made of a random copolymer, and it is more preferable that both the core portion and the shell portion are made of a random copolymer. Particulate polymers having a core-shell structure can be obtained, for example, by two-step polymerization as described later.

[0064] Furthermore, the particulate polymer preferably has a core-shell structure comprising a core portion made of a copolymer containing isoprene units, crosslinkable monomer units and acid group-containing monomer units, and optionally containing aromatic monovinyl monomer units, and a shell portion made of a copolymer containing two or more monomer units selected from the group consisting of acid group-containing monomer units, aromatic monovinyl monomer units and (meth)acrylic acid ester monomer units. The core-shell structure of the particulate polymer may further contain components other than the core portion and the shell portion, but it is preferable that it consists only of the core portion and the shell portion.

[0065] [Content of particulate polymer] The content of particulate polymer in the binder composition is preferably 20% by mass or more, more preferably 25% by mass or more, preferably 60% by mass or less, and more preferably 50% by mass or less, on a solid content basis.

[0066] [Method for preparing particulate polymers] Particulate polymers can be polymerized according to known polymerization methods such as solution polymerization, suspension polymerization, bulk polymerization, and emulsion polymerization. As the polymerization reaction, addition polymerization such as ionic polymerization, radical polymerization, and living radical polymerization can be used.

[0067] During polymerization reactions, commonly used additives such as molecular weight modifiers, emulsifiers, dispersants, polymerization initiators, and polymerization aids may be used. The amounts of these additives used can be those commonly used.

[0068] The preparation of particulate polymers is not particularly limited, but can be carried out, for example, by the following procedure.

[0069] First, the monomers described above are mixed with water, an emulsifier, and a polymerization initiator, and the mixture (emulsion) is heated to carry out the polymerization reaction. When the predetermined polymerization conversion rate is reached, the reaction is stopped by cooling to obtain a mixture containing particulate polymer. Unreacted monomers are removed from the mixture. The pH of the mixture is adjusted as appropriate to obtain an aqueous dispersion of particulate polymer. Here, particulate polymers having a core-shell structure can be obtained by adding monomers in steps. For example, when using isoprene, a crosslinkable monomer, an aromatic monovinyl monomer, a (meth)acrylic acid ester monomer, and an acid group-containing monomer to prepare a particulate polymer having a core-shell structure, the entire amount of isoprene and the crosslinkable monomer, as well as a portion of the aromatic monovinyl monomer and the acid group-containing monomer, may be added first to carry out the polymerization reaction, and then the remaining aromatic monovinyl monomer, the acid group-containing monomer, and the entire amount of the (meth)acrylic acid ester monomer may be added to carry out the polymerization reaction (two-step polymerization).

[0070] Here, when preparing a particulate polymer by two-step polymerization, the total amount of monomer added in the first step is preferably 85 parts by mass or more, more preferably 90 parts by mass or more, even more preferably 92 parts by mass or more, preferably 98 parts by mass or less, more preferably 96 parts by mass or less, and even more preferably 94 parts by mass or less, based on a total monomer added in the preparation of the particulate polymer of 100 parts by mass. If the total amount of monomer added in the first step is above the lower limit, the peel strength of the resulting electrode can be improved. On the other hand, if the total amount of monomer added in the first step is below the upper limit, the internal resistance of the resulting secondary battery can be effectively reduced.

[0071] The amount of isoprene added in the first step is preferably 35 parts by mass or more, more preferably 50 parts by mass or more, even more preferably 70 parts by mass or more, preferably 98 parts by mass or less, more preferably 88 parts by mass or less, and even more preferably 80 parts by mass or less, based on 100 parts by mass of the total monomer added in the first step. If the amount of isoprene added in the first step is within the above range, the peel strength of the resulting electrode can be improved.

[0072] The amount of crosslinkable monomer added in the first step is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, even more preferably 0.5 parts by mass or more, preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 2 parts by mass or less, based on 100 parts by mass of total monomer added in the first step. If the amount of crosslinkable monomer added in the first step is within the above range, the peel strength of the resulting electrode can be improved.

[0073] The amount of aromatic monovinyl monomer added in the first stage is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 15 parts by mass or more, preferably 65 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 25 parts by mass or less, based on 100 parts by mass of the total monomer added in the first stage. If the amount of aromatic monovinyl monomer added in the first stage is within the above range, the internal resistance of the resulting secondary battery can be effectively reduced.

[0074] The amount of acid group-containing monomer added in the first step is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, preferably 5 parts by mass or less, more preferably 2 parts by mass or less, and even more preferably 1.5 parts by mass or less, based on 100 parts by mass of the total monomer added in the first step. If the amount of acid group-containing monomer added in the first step is within the above range, the peel strength of the resulting electrode can be improved.

[0075] Furthermore, when preparing particulate polymers by two-step polymerization, the total amount of monomers added in the second step is preferably 2 parts by mass or more, more preferably 4 parts by mass or more, even more preferably 6 parts by mass or more, preferably 15 parts by mass or less, more preferably 12 parts by mass or less, and even more preferably 10 parts by mass or less, based on 100 parts by mass of total monomers added in the preparation of the particulate polymer. If the total amount of monomers added in the second step is above the lower limit, the internal resistance of the resulting secondary battery can be effectively reduced. On the other hand, if the total amount of monomers added in the second step is below the upper limit, the peel strength of the resulting electrode can be improved.

[0076] The amount of aromatic monovinyl monomer added in the second stage is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, preferably 70 parts by mass or less, and more preferably 60 parts by mass or less, when the total amount of monomer added in the second stage is 100 parts by mass. If the amount of aromatic monovinyl monomer added in the second stage is within the above range, the internal resistance of the resulting secondary battery can be effectively reduced.

[0077] The amount of acid group-containing monomer added in the second step is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, even more preferably 20 parts by mass or more, preferably 60 parts by mass or less, more preferably 45 parts by mass or less, and even more preferably 30 parts by mass or less, based on 100 parts by mass of the total monomer added in the second step. If the amount of acid group-containing monomer added in the second step is within the above range, the peel strength of the resulting electrode can be improved.

[0078] The amount of (meth)acrylic acid ester monomer added in the second stage is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, even more preferably 20 parts by mass or more, preferably 60 parts by mass or less, more preferably 45 parts by mass or less, and even more preferably 30 parts by mass or less, based on 100 parts by mass of the total monomer added in the second stage. If the amount of (meth)acrylic acid ester monomer added in the second stage is within the above range, the internal resistance of the resulting secondary battery can be effectively reduced.

[0079] [Properties of Particulate Polymers] -Average particle diameter Da measured by dynamic light scattering- The average particle diameter Da of the particulate polymer is preferably 150 nm or more, more preferably 190 nm or more, even more preferably 210 nm or more, preferably 400 nm or less, more preferably 300 nm or less, and even more preferably 250 nm or less. Furthermore, the average particle diameter Da of the particulate polymer is preferably 150 nm or more and 400 nm or less, more preferably 190 nm or more and 300 nm or less, and even more preferably 210 nm or more and 250 nm or less. Note that the value of the average particle diameter Da measured by dynamic light scattering can be adjusted, for example, by changing the type and amount of monomers used to form the particulate polymer, the polymerization method and conditions, and the structure of the particulate polymer.

[0080] ―Median diameter Db measured by laser diffraction scattering method― The median diameter Db of the particulate polymer is preferably 100 nm or more, more preferably 110 nm or more, even more preferably 120 nm or more, preferably 170 nm or less, more preferably 160 nm or less, even more preferably 150 nm or less, and particularly preferably 140 nm or less. Furthermore, the median diameter Db of the particulate polymer is preferably 100 nm or more and 170 nm or less, more preferably 110 nm or more and 160 nm or less, even more preferably 120 nm or more and 150 nm or less, and particularly preferably 120 nm or more and 140 nm or less. If the median diameter Db of the particulate polymer is above the lower limit above, the pourability of the electrolyte of the secondary battery can be improved and the internal resistance of the secondary battery can be reduced. On the other hand, if the median diameter Db of the particulate polymer is below the upper limit above, the surface area of ​​the particulate polymer increases and the contact area between the particulate polymer and the electrode active material increases, so the peel strength of the electrode can be further increased. Furthermore, the median diameter Db value measured by laser diffraction scattering can be adjusted, for example, by changing the type and amount of monomers used to form the particulate polymer, the polymerization method and conditions, and the structure of the particulate polymer.

[0081] ―Da / Db― The ratio of the average particle diameter Da to the median diameter Db of the particulate polymer (Da / Db) is preferably 1.05 or more, more preferably 1.20 or more, even more preferably 1.40 or more, particularly preferably 1.60 or more, preferably 2.00 or less, more preferably 1.90 or less, even more preferably 1.80 or less, and particularly preferably 1.75 or less. Furthermore, the ratio of the average particle diameter Da to the median diameter Db of the particulate polymer (Da / Db) is preferably 1.05 or more and 2.00 or less, more preferably 1.20 or more and 1.90 or less, even more preferably 1.40 or more and 1.80 or less, and particularly preferably 1.60 or more and 1.75 or less. If Da / Db is above the lower limit, when forming an electrode composite layer on a current collector using a slurry composition containing the binder composition, migration of particulate polymers is suppressed, and the peel strength of the electrode can be further increased by ensuring that the particulate polymers are well dispersed in the electrode composite layer. On the other hand, if Da / Db is below the upper limit, the handling properties of the binder composition can be improved.

[0082] <<Solvent>> Examples of solvents that the binder composition of the present invention may contain include water, water-soluble organic solvents, etc. Among these, water is preferred. These solvents may be used individually or in combination of two or more. Here, the proportion of water in the solvent is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, even more preferably 99% by mass or more, and particularly preferably 100% by mass (i.e., the binder composition of the present invention contains only water as the solvent).

[0083] <<Other Components>> The binder composition of the present invention may contain other components as long as they do not impair the purpose of the present invention. Examples of other components include polymers other than the particulate polymers described above, antioxidants, preservatives, defoamers, dispersants, pH adjusters, etc. Other components may be used individually or in combination of two or more in any ratio.

[0084] The binder composition of the present invention preferably contains an antioxidant as another component. Including an antioxidant in the binder composition can further increase the peel strength of the electrodes and further improve the cycle characteristics of the secondary battery.

[0085] The antioxidant is not particularly limited, and examples include phenolic antioxidants, amine antioxidants, phosphorus antioxidants, sulfur-based antioxidants, and metal deactivators. These may be used individually or in combination of two or more in any ratio.

[0086] The antioxidant content in the binder composition is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 2 parts by mass or more, preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 6 parts by mass or less, per 100 parts by mass of particulate polymer. If the antioxidant content in the binder composition is 0.1 parts by mass or more per 100 parts by mass of particulate polymer, the cycle characteristics of the secondary battery can be further improved. On the other hand, if the antioxidant content in the binder composition is 10 parts by mass or less per 100 parts by mass of particulate polymer, the viscosity stability of the slurry composition can be improved.

[0087] Examples of known preservatives include isothiazolinoline compounds and 2-bromo-2-nitro-1,3-propanediol. The isothiazolinoline compounds are not particularly limited and include those described in Japanese Patent Publication No. 2013-211246, Japanese Patent Publication No. 2005-097474, and Japanese Patent Publication No. 2013-206624. The preservative may be used alone or in combination of two or more. Preferred preservatives are 1,2-benzoisothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one, and 2-bromo-2-nitro-1,3-propanediol, with 1,2-benzoisothiazolin-3-one being more preferred.

[0088] <<Method for preparing a binder composition for non-aqueous secondary battery electrodes>> The binder composition of the present invention is not particularly limited and can be prepared by mixing a particulate polymer with other components that can be optionally used in the presence of a solvent. When preparing the binder composition using an aqueous dispersion of a particulate polymer, the liquid components contained in the aqueous dispersion may be used as the solvent for the binder composition.

[0089] <Second Form> The binder composition for non-aqueous secondary battery electrodes according to the second form will be described in detail below. The binder composition for non-aqueous secondary battery electrodes according to the second form of the present invention comprises a particulate polymer and two or more antioxidants, and usually further comprises a solvent. Herein, the binder composition of the present invention is characterized in that the above-mentioned particulate polymer comprises a random copolymer containing isoprene units. Note that the binder composition of the present invention usually does not contain conductive material and electrode active material.

[0090] Furthermore, since the binder composition of the present invention contains a particulate polymer including a random copolymer containing isoprene units and two or more antioxidants, using this binder composition makes it possible to prepare a slurry composition with excellent viscosity stability and to produce electrodes that can exhibit excellent cycle characteristics in secondary batteries. The reason why the above effects are obtained by using the binder composition of the present invention is not clear, but it is presumed to be as follows.

[0091] In electrodes for non-aqueous secondary batteries, it is generally considered preferable to reduce the amount of binder contained in the electrode composite layer from the viewpoint of reducing the internal resistance of the secondary battery while maintaining the peel strength of the electrode. However, the inventors' research has newly revealed that when a polymer containing isoprene units (e.g., styrene-isoprene copolymer) is used as a binder, reducing the amount of binder degrades the cycle characteristics of the secondary battery. Here, the binder composition of the present invention contains two or more antioxidants, and a high synergistic effect can be obtained by using two or more antioxidants in combination, which can contribute to improving the cycle characteristics of the secondary battery. Furthermore, the particulate polymer contained in the binder composition of the present invention includes a random copolymer containing isoprene units, and random copolymers are less prone to excessive aggregation compared to, for example, block copolymers, which can contribute to improving the viscosity stability of the slurry composition. For the reasons above, it is believed that by using the binder composition of the present invention, a slurry composition with excellent viscosity stability can be prepared, and electrodes that can exhibit excellent cycle characteristics in secondary batteries can be manufactured.

[0092] <<Particulate Polymer>> Particulate polymers are components that function as binders and, in an electrode composite layer formed on a current collector using a slurry composition containing a binder composition, they retain components such as electrode active materials contained in the electrode composite layer so that they do not detach from the electrode composite layer. Particulate polymers are water-insoluble particles formed from a predetermined polymer. In this invention, "water-insoluble" particles mean that when 0.5 g of polymer is dissolved in 100 g of water at a temperature of 25°C, the insoluble content is 90% by mass or more.

[0093] Here, the particulate polymer includes a random copolymer containing isoprene units, and optionally further includes polymers other than random copolymers containing isoprene units (other polymers). The other polymers are not particularly limited and may be block polymers, random copolymers that do not contain isoprene units, etc. From the viewpoint of further improving the viscosity stability of the slurry composition, it is preferable that the other polymers are random copolymers that do not contain isoprene units, that is, that the particulate polymer consists only of random copolymers. The particulate polymer may contain only one type of other polymer, or it may contain two or more types of other polymers.

[0094] The particulate polymer contains at least isoprene units and optionally further contains one or more monomer units selected from crosslinkable monomer units, aromatic monovinyl monomer units, (meth)acrylic acid ester monomer units, and acid group-containing monomer units. The particulate polymer may also contain monomer units other than isoprene units, crosslinkable monomer units, aromatic monovinyl monomer units, (meth)acrylic acid ester monomer units, and acid group-containing monomer units (other monomer units). In particular, from the viewpoint of further improving the viscosity stability of the slurry composition and further improving the cycle characteristics of the secondary battery, it is preferable that the particulate polymer contains isoprene units, styrene units, and acrylic acid units and / or methacrylic acid units.

[0095] [Isoprene units] These can be the same as those in the binder composition according to the first embodiment described above, so the explanation is omitted.

[0096] [Cross-linkable monomer units] These can be the same as the binder composition according to the first embodiment described above, so the explanation is omitted.

[0097] [Aromatic monovinyl monomer units] These can be the same as the binder composition according to the first embodiment described above, so the explanation is omitted.

[0098] [(meth)acrylic acid ester monomer units] These can be the same as the binder composition according to the first embodiment described above, so the explanation is omitted.

[0099] [Acid group-containing monomer units] These can be the same as the binder composition according to the first embodiment described above, so the explanation is omitted.

[0100] [Other monomer units] These can be the same as the binder composition according to the first embodiment described above, so the explanation is omitted.

[0101] [Structure of particulate polymer] The particulate polymer contains a random copolymer containing isoprene units. If the particulate polymer does not contain a random copolymer containing isoprene units, the viscosity stability of the slurry composition will decrease. Here, a random copolymer refers to a polymer in which more than 90% consists of random regions.

[0102] Here, the particulate polymer may be a particulate polymer having a uniform monomer unit composition (type and content ratio of monomer units), or it may be a particulate polymer having a heterogeneous monomer unit composition. Examples of particulate polymers having a heterogeneous monomer unit composition include a particulate polymer having a core-shell structure comprising a core portion and a shell portion covering at least a part of the outer surface of the core portion, where the monomer unit composition of the core portion and the shell portion differs, and a particulate polymer having a monomer unit composition where only the core portion differs. In the present invention, the core-shell structure also includes a structure in which the composition of the particle center and the composition of the outermost layer of the particle are different from each other. For example, when the particulate polymer has a core-shell structure, the polymer forming the core portion and the polymer forming the shell portion have different compositions, and it is preferable that at least one of the core portion and the shell portion is made of a random copolymer containing isoprene units, and the core portion is made of a random copolymer containing isoprene units. Particulate polymers having a core-shell structure can be obtained, for example, by two-step polymerization as described later.

[0103] Furthermore, it is preferable that the particulate polymer has a core-shell structure comprising a core portion made of a random copolymer containing isoprene units and acid group-containing monomer units, and optionally containing crosslinkable monomer units and aromatic monovinyl monomer units, and a shell portion made of a polymer containing acid group-containing monomer units, and optionally containing aromatic monovinyl monomer units and (meth)acrylic acid ester monomer units. The core-shell structure of the particulate polymer may further include components other than the core portion and the shell portion, but it is preferable that it consists only of the core portion and the shell portion.

[0104] [Content ratio of particulate polymer] This can be the same as that of the binder composition according to the first embodiment described above, so the explanation is omitted.

[0105] [Method for preparing particulate polymers] Particulate polymers can be polymerized according to known polymerization methods such as solution polymerization, suspension polymerization, bulk polymerization, and emulsion polymerization. As the polymerization reaction, addition polymerization such as ionic polymerization, radical polymerization, and living radical polymerization can be used.

[0106] During polymerization reactions, commonly used additives such as molecular weight modifiers, emulsifiers, dispersants, polymerization initiators, and polymerization aids may be used. The amounts of these additives used can be those commonly used.

[0107] The preparation of particulate polymers is not particularly limited, but can be carried out, for example, by the following procedure.

[0108] First, the monomers described above are mixed with water, an emulsifier, and a polymerization initiator, and the mixture (emulsion) is heated to carry out the polymerization reaction. When the predetermined polymerization conversion rate is reached, the reaction is stopped by cooling to obtain a mixture containing particulate polymer. Unreacted monomers are removed from the mixture. The pH of the mixture is adjusted as appropriate to obtain an aqueous dispersion of particulate polymer. Here, particulate polymers having a core-shell structure can be obtained by adding monomers in steps. For example, when using isoprene, a crosslinkable monomer, an aromatic monovinyl monomer, a (meth)acrylic acid ester monomer, and an acid group-containing monomer to prepare a particulate polymer having a core-shell structure, the entire amount of isoprene and the crosslinkable monomer, as well as a portion of the aromatic monovinyl monomer and the acid group-containing monomer, may be added first to carry out the polymerization reaction, and then the remaining aromatic monovinyl monomer, the acid group-containing monomer, and the entire amount of the (meth)acrylic acid ester monomer may be added to carry out the polymerization reaction (two-step polymerization).

[0109] Here, when preparing a particulate polymer by two-step polymerization, the total amount of monomer added in the first step is preferably 85 parts by mass or more, more preferably 90 parts by mass or more, even more preferably 92 parts by mass or more, preferably 98 parts by mass or less, more preferably 96 parts by mass or less, and even more preferably 94 parts by mass or less, based on a total monomer added in the preparation of the particulate polymer of 100 parts by mass. If the total amount of monomer added in the first step is above the lower limit, the peel strength of the resulting electrode can be improved. On the other hand, if the total amount of monomer added in the first step is below the upper limit, the internal resistance of the resulting secondary battery can be effectively reduced.

[0110] The amount of isoprene added in the first step is preferably 50 parts by mass or more, more preferably 70 parts by mass or more, preferably 98 parts by mass or less, more preferably 88 parts by mass or less, and even more preferably 80 parts by mass or less, based on 100 parts by mass of the total monomers added in the first step. If the amount of isoprene added in the first step is within the above range, the viscosity stability of the slurry composition can be further enhanced, and the peel strength of the resulting electrode can be improved.

[0111] The amount of crosslinkable monomer added in the first stage is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, even more preferably 0.5 parts by mass or more, preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 3 parts by mass or less, based on 100 parts by mass of total monomer added in the first stage. If the amount of crosslinkable monomer added in the first stage is within the above range, the internal resistance can be effectively reduced while further improving the cycle characteristics of the resulting secondary battery.

[0112] The amount of aromatic monovinyl monomer added in the first step is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, preferably 40 parts by mass or less, and more preferably 25 parts by mass or less, based on 100 parts by mass of the total monomer added in the first step. If the amount of aromatic monovinyl monomer added in the first step is within the above range, the viscosity stability of the slurry composition can be further enhanced, and the peel strength of the resulting electrode can be improved.

[0113] The amount of acid group-containing monomer added in the first step is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, preferably 5 parts by mass or less, and more preferably 2 parts by mass or less, based on 100 parts by mass of the total monomer added in the first step. If the amount of acid group-containing monomer added in the first step is within the above range, the viscosity stability of the slurry composition can be further enhanced, and the peel strength of the resulting electrode can be improved. In addition, the internal resistance of the resulting secondary battery can be effectively reduced.

[0114] Furthermore, when preparing particulate polymers by two-step polymerization, the total amount of monomers added in the second step is preferably 2 parts by mass or more, more preferably 4 parts by mass or more, even more preferably 6 parts by mass or more, preferably 15 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 8 parts by mass or less, based on 100 parts by mass of total monomers added in the preparation of the particulate polymer. If the total amount of monomers added in the second step is above the lower limit, the internal resistance of the resulting secondary battery can be effectively reduced. On the other hand, if the total amount of monomers added in the second step is below the upper limit, the peel strength of the resulting electrode can be improved.

[0115] The amount of aromatic monovinyl monomer added in the second step is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, even more preferably 25 parts by mass or more, preferably 80 parts by mass or less, more preferably 70 parts by mass or less, and even more preferably 60 parts by mass or less, based on 100 parts by mass of the total monomer added in the second step. If the amount of aromatic monovinyl monomer added in the second step is within the above range, the viscosity stability of the slurry composition can be further improved, and the peel strength of the resulting electrode can be enhanced.

[0116] The amount of acid group-containing monomer added in the second stage is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 20 parts by mass or more, preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less, based on 100 parts by mass of the total monomer added in the second stage. If the amount of acid group-containing monomer added in the second stage is within the above range, the viscosity stability of the slurry composition can be further enhanced, and the peel strength of the resulting electrode can be improved. In addition, the internal resistance of the resulting secondary battery can be effectively reduced.

[0117] The amount of (meth)acrylic acid ester monomer added in the second stage is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 20 parts by mass or more, preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less, based on 100 parts by mass of the total monomer added in the second stage. If the amount of (meth)acrylic acid ester monomer added in the second stage is within the above range, the peel strength of the electrode can be improved and the internal resistance of the resulting secondary battery can be effectively reduced.

[0118] [Properties of Particulate Polymers] -Average Particle Diameter Da Measured by Dynamic Light Scattering- The average particle diameter Da of the particulate polymer, as measured by dynamic light scattering, is preferably 150 nm or more, more preferably 190 nm or more, even more preferably 210 nm or more, preferably 400 nm or less, more preferably 300 nm or less, and even more preferably 250 nm or less. Furthermore, the average particle diameter Da of the particulate polymer is preferably 150 nm or more and 400 nm or less, more preferably 190 nm or more and 300 nm or less, and even more preferably 210 nm or more and 250 nm or less. Note that the value of the average particle diameter Da measured by dynamic light scattering can be adjusted, for example, by changing the type and amount of monomers used to form the particulate polymer, the polymerization method and conditions, and the structure of the particulate polymer.

[0119] ―Median diameter Db measured by laser diffraction scattering method― The median diameter Db of the particulate polymer, as measured by laser diffraction scattering method, is preferably 100 nm or more, more preferably 110 nm or more, even more preferably 120 nm or more, preferably 170 nm or less, more preferably 160 nm or less, even more preferably 150 nm or less, and particularly preferably 140 nm or less. Furthermore, the median diameter Db of the particulate polymer is preferably 100 nm or more and 170 nm or less, more preferably 110 nm or more and 160 nm or less, even more preferably 120 nm or more and 150 nm or less, and particularly preferably 120 nm or more and 140 nm or less. If the median diameter Db of the particulate polymer is above the above lower limit, the pourability of the electrolyte of the secondary battery can be improved and the internal resistance of the secondary battery can be reduced. On the other hand, if the median diameter Db of the particulate polymer is below the above upper limit, the surface area of ​​the particulate polymer increases, and the contact area between the particulate polymer and the electrode active material increases, thereby increasing the peel strength of the electrode. The value of the median diameter Db measured by laser diffraction scattering can be adjusted, for example, by changing the type and amount of monomer used to form the particulate polymer, the polymerization method and conditions, and the structure of the particulate polymer.

[0120] ―Da / Db― The ratio of the average particle diameter Da to the median diameter Db of the particulate polymer (Da / Db) is preferably 1.05 or more, more preferably 1.20 or more, even more preferably 1.40 or more, particularly preferably 1.60 or more, preferably 2.00 or less, more preferably 1.90 or less, even more preferably 1.80 or less, and particularly preferably 1.75 or less. Furthermore, the ratio of the average particle diameter Da to the median diameter Db of the particulate polymer (Da / Db) is preferably 1.05 or more and 2.00 or less, more preferably 1.20 or more and 1.90 or less, even more preferably 1.40 or more and 1.80 or less, and particularly preferably 1.60 or more and 1.75 or less. If Da / Db is above the lower limit, when forming an electrode composite layer on a current collector using a slurry composition containing the binder composition, migration of particulate polymers can be suppressed, and the peel strength of the electrode can be increased by ensuring that the particulate polymers are well dispersed in the electrode composite layer. On the other hand, if Da / Db is below the upper limit, the handling properties of the binder composition can be improved.

[0121] <<Antioxidants>> The binder composition of the present invention contains two or more antioxidants. As antioxidants, for example, primary antioxidants such as phenolic antioxidants and amine antioxidants, and secondary antioxidants such as phosphorus antioxidants and sulfur antioxidants can be used. In addition, metal deactivators can be used as antioxidants. A primary antioxidant is an antioxidant that scavenges radicals and prevents auto-oxidation, and a secondary antioxidant is an antioxidant that decomposes hydroperoxides into harmless substances.

[0122] Examples of phenolic antioxidants include 2,6-di-tert-butyl-4-methylphenol (BHT; the compound represented by formula (I) below; hereinafter referred to as compound (I)), pentaerythritol tetrakis[3-[3,5-di(tert-butyl)-4-hydroxyphenyl]propionate] (Irganox® 1010; the compound represented by formula (II) below; hereinafter referred to as compound (II)), octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid (Irganox 1076; the compound represented by formula (III) below; hereinafter referred to as compound (III)), and 2,5,7,8-tetramethyl-2-(4,8,12-trimethyltridecyl)-2H-1-benzopyran-6-ol (Irganox E201; Compound represented by the following formula (IV); hereinafter referred to as compound (IV): 4-[[4,6-bis(octylthio)-1,3,5-triazine-2-yl]amino]-2,6-di-tert-butylphenol, 2,6-di-tert-butyl-p-cresol, 3-(3,5-di-tert-butyl-4-hydroxyphenyl)stearyl propionate, 2,4,6-tris(3',5'-di-tert-butyl-4'-hydroxybenzyl)mesitylene, 3,5-di-t-butyl-4-hydroxytoluene, dibutylhydroxytoluene, 2,2'-methylenebis(6-t-butyl-4-methylene) Examples include phenol compounds such as methylphenol, 4,4'-butylidenebis(3-t-butyl-3-methylphenol), 4,4'-thiobis(6-t-butyl-3-methylphenol), and α-tocopherol; hydroquinone compounds such as 2,2,4-trimethyl-6-hydroxy-7-t-butylchroman, 2,5-di-t-butylhydroquinone, 2,5-di-t-octylhydroquinone, 2,6-di-n-dodecylhydroquinone, 2-n-dodecyl-5-chlorohydroquinone, and 2-t-octyl-5-methylhydroquinone; and polymer-type phenol compounds such as compound (V) (WINGSTAY® L) represented by the following formula (V). Among these, compounds (I) to (V) are preferred, and compounds (III) to (V) are more preferred, from the viewpoint of further improving the cycle characteristics of secondary batteries. In the formula, n is an integer greater than or equal to 1.

[0123] Examples of amine-based antioxidants include N-phenyl-N'-isopropyl-p-phenylenediamine and compound (VI) (WINGSTAY T) represented by the following formula (VI). Among these, compound (VI) is preferred from the viewpoint of further improving the cycle characteristics of secondary batteries.

[0124] Examples of phosphorus-based antioxidants include triphenylated phosphorus, tris(dinonylphenyl)ated phosphorus, tricresolated phosphorus, 3,9-bis(octadecyloxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, 2,2-methylenebis(4,6-di-t-butylphenyl)2-ethylhexyl phosphite, and tris(2,4-di-tert-butylphenyl) phosphite.

[0125] Examples of sulfur-based antioxidants include compound (VII) represented by the following formula (VII) (dilauryl-3,3'-thiodipropionate; NOCRAC400), distearyl-3,3'-toidipropionate, and didodecyl-3,3'-thiodipropionate. Among these, compound (VII) is preferred from the viewpoint of further improving the cycle characteristics of secondary batteries.

[0126] Examples of metal deactivators include N,N'-bis{3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl}hydrazine, and [2,2-oxamidobisethyl, 3(3,5-di-tert-butyl-hydroxyphenyl)propionate].

[0127] From the perspective of further improving the cycle characteristics of a secondary battery, the binder composition of the present invention preferably contains a combination of a primary antioxidant and a secondary antioxidant, or a combination of primary antioxidants having different chemical structures. More preferably, it contains a combination of a phenolic antioxidant and a sulfur-based antioxidant, or a combination of phenolic antioxidants having different chemical structures.

[0128] As the combination of a phenolic antioxidant and a sulfur-based antioxidant, the combination of compound (V) and compound (VII) is preferable. As the combination of phenolic antioxidants having different chemical structures, the combination of compound (III) and compound (V), and the combination of compound (IV) and compound (V) are preferable.

[0129] From the perspective of further improving the cycle characteristics of a secondary battery while further enhancing the viscosity stability of the slurry composition, the binder composition of the present invention preferably contains antioxidant A described below as an antioxidant, and more preferably contains both antioxidant A and antioxidant B described below.

[0130] Hereinafter, the properties and the like of antioxidant A and B will be described in detail.

[0131] [Antioxidant A] - Molecular weight - The molecular weight of antioxidant A is preferably 200 or more, more preferably 250 or more, preferably 500 or less, more preferably 400 or less, and even more preferably 350 or less. If the molecular weight of antioxidant A is within the above range, the cycle characteristics of the secondary battery can be further improved while further enhancing the viscosity stability of the slurry composition.

[0132] - Specific gravity - The specific gravity of antioxidant A is preferably 1.0 g / cm ３ or more, more preferably 1.05 g / cm ３ or more, preferably 1.5 g / cm ３ or less, more preferably 1.2 g / cm ３ or less. If the specific gravity of antioxidant A is within the above range, the cycle characteristics of the secondary battery can be further improved while further enhancing the viscosity stability of the slurry composition.

[0133] ―Melting Point― The melting point of antioxidant A is preferably above 90°C, more preferably 100°C or higher, even more preferably 110°C or higher, preferably 150°C or lower, more preferably 140°C or lower, and even more preferably 130°C or lower. If the melting point of antioxidant A is within the above range, the viscosity stability of the slurry composition can be further enhanced while further improving the cycle characteristics of the secondary battery.

[0134] Antioxidant A having the properties described above is, for example, the compound (V) (WINGSTAY L; molecular weight 296.45; specific gravity 1.1 g / cm³) described above. ３ A melting point of 118°C is preferred.

[0135] [Antioxidant B] - Molecular Weight - The molecular weight of antioxidant B is preferably 300 or more, more preferably 400 or more, even more preferably more than 500, preferably 1000 or less, more preferably 800 or less, and even more preferably 600 or less. If the molecular weight of antioxidant B is within the above range, the viscosity stability of the slurry composition can be further enhanced while further improving the cycle characteristics of the secondary battery.

[0136] ―Specific Gravity― The specific gravity of antioxidant B is preferably 0.8 g / cm³. ３ More preferably, 0.9 g / cm³ ３ More preferably 0.95 g / cm³ ３ The above is preferable, and preferably 1.5 g / cm³. ３ More preferably, 1.2 g / cm³ ３ More preferably, 1.1 g / cm³ ３ The following applies: If the specific gravity of antioxidant B is within the above range, the viscosity stability of the slurry composition can be further enhanced while also improving the cycle characteristics of the secondary battery.

[0137] ―Melting Point― The melting point of antioxidant B is preferably 0°C or higher, more preferably 20°C or higher, even more preferably 40°C or higher, preferably 90°C or lower, more preferably 75°C or lower, and even more preferably 60°C or lower. If the melting point of antioxidant B is within the above range, the viscosity stability of the slurry composition can be further enhanced while further improving the cycle characteristics of the secondary battery.

[0138] Antioxidant B having the above-described properties is, for example, the above-described compound (III) (Irganox 1076; molecular weight 531; specific gravity 1.02 g / cm³). ３ (Melting point 50-55°C) and compound (VII) (NOCRAC400; molecular weight 514.85; specific gravity 0.92 g / cm³) ３ A melting point of 37°C is preferred. Furthermore, "Irgastab IS 3066L" and "Irgastab STYL11" (both manufactured by BASF Japan Ltd.) are also mentioned.

[0139] The total content of antioxidants in the binder composition is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 2 parts by mass or more, preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 6 parts by mass or less, per 100 parts by mass of particulate polymer. If the total content of antioxidants in the binder composition is 0.1 parts by mass or more per 100 parts by mass of particulate polymer, the cycle characteristics of the secondary battery can be further improved. On the other hand, if the total content of antioxidants in the binder composition is 10 parts by mass or less per 100 parts by mass of particulate polymer, the viscosity stability of the slurry composition can be further enhanced.

[0140] Furthermore, when the binder composition contains both antioxidant A and antioxidant B, the proportion of antioxidant A in the total of antioxidant A and antioxidant B is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less.

[0141] <<Solvent>> Examples of solvents that the binder composition of the present invention may contain include water, water-soluble organic solvents, etc. Among these, water is preferred. These solvents may be used individually or in combination of two or more. Here, the proportion of water in the solvent is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, even more preferably 99% by mass or more, and particularly preferably 100% by mass (i.e., the binder composition of the present invention contains only water as the solvent).

[0142] <<Other Components>> The binder composition of the present invention may contain other components as long as they do not impair the purpose of the present invention. Examples of other components include polymers other than the particulate polymers described above, preservatives, defoaming agents, dispersants, pH adjusters, etc. Other components may be used individually or in combination of two or more in any ratio.

[0143] Examples of known preservatives include isothiazolinoline compounds and 2-bromo-2-nitro-1,3-propanediol. The isothiazolinoline compounds are not particularly limited and include those described in Japanese Patent Publication No. 2013-211246, Japanese Patent Publication No. 2005-097474, and Japanese Patent Publication No. 2013-206624. The preservative may be used alone or in combination of two or more. Preferred preservatives are 1,2-benzoisothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one, and 2-bromo-2-nitro-1,3-propanediol, with 1,2-benzoisothiazolin-3-one being more preferred.

[0144] <<Method for preparing a binder composition for non-aqueous secondary battery electrodes>> The binder composition of the present invention is not particularly limited and can be prepared by mixing a particulate polymer, an antioxidant, and other optional components in the presence of a solvent. When preparing the binder composition using an aqueous dispersion of a particulate polymer, the liquid components contained in the aqueous dispersion may be used as the solvent for the binder composition.

[0145] (Slurry composition for non-aqueous secondary battery electrodes) The slurry composition of the present invention is a composition used for forming the electrode composite layer of an electrode, and comprises the binder composition described above and an electrode active material. That is, if the binder composition of the present invention is the binder composition according to the first embodiment described above, the slurry composition of the present invention contains the particulate polymer and electrode active material described above, and optionally further comprises a solvent and other components. On the other hand, if the binder composition of the present invention is the binder composition according to the second embodiment described above, the slurry composition of the present invention contains the particulate polymer and antioxidant and electrode active material described above, and optionally further comprises a solvent and other components. Furthermore, since the slurry composition of the present invention contains the binder composition of the present invention described above, the peel strength during high-speed coating of electrodes can be increased.

[0146] <Binder Composition> As the binder composition, the binder composition of the present invention described above, which includes a particulate polymer, is used. For example, as the binder composition, the binder composition according to the first embodiment described above, which includes a particulate polymer and optionally further includes a solvent and other components, can be used. Alternatively, as the binder composition, the binder composition according to the second embodiment described above, which includes a particulate polymer and an antioxidant and optionally further includes a solvent and other components, can be used. The amount of binder composition blended in the slurry composition is not particularly limited. For example, the amount of binder composition blended can be such that, on a solid content basis, the amount of particulate polymer is 0.5 parts by mass or more and 15 parts by mass or less per 100 parts by mass of electrode active material.

[0147] <Electrode Active Material> As the electrode active material, there are no particular limitations, and known electrode active materials used in secondary batteries can be used. Specifically, for example, as the electrode active material that can be used in the electrode composite layer of a lithium-ion secondary battery, which is an example of a secondary battery, the following electrode active materials can be used without particular limitations.

[0148] <<Positive Electrode Active Material>> As the positive electrode active material to be incorporated into the positive electrode composite layer of the positive electrode of a lithium-ion secondary battery, for example, compounds containing transition metals, such as transition metal oxides, transition metal sulfides, and composite metal oxides of lithium and transition metals can be used. Examples of transition metals include Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Mo. Specifically, the positive electrode active material is not particularly limited, but can also include lithium-containing cobalt oxide (LiCoO). ２ ), lithium manganese (LiMn ２ O ４ ), lithium-containing nickel oxide (LiNiO ２ ), Co-Ni-Mn lithium-containing composite oxide, Ni-Mn-Al lithium-containing composite oxide, Ni-Co-Al lithium-containing composite oxide, olivine-type lithium iron phosphate (LiFePO) ４ ), olivine-type lithium manganese phosphate (LiMnPO ４ ), Li １＋ｘ Mn ２－ｘ O ４ Lithium-rich spinel compounds represented by (0 < X ​​< 2), Li[Ni ０．１７ Li ０．２ Co ０．０７ Mn ０．５６ ]O ２ LiNi ０．５ Mn １．５ O ４ These are some examples. The positive electrode active material described above may be used individually or in combination of two or more types.

[0149] <<Negative Electrode Active Material>> Examples of negative electrode active materials used in the negative electrode composite layer of a lithium-ion secondary battery include carbon-based negative electrode active materials, metal-based negative electrode active materials, and negative electrode active materials that combine these. Here, carbon-based negative electrode active materials refer to active materials with a carbon-based main skeleton that can be inserted (also called "doped") with lithium. Specifically, carbon-based negative electrode active materials include carbonaceous materials such as coke, mesocarbon microbeads (MCMB), mesophase pitch carbon fibers, pyrolysis vapor-grown carbon fibers, phenolic resin calcined bodies, polyacrylonitrile carbon fibers, pseudoisotropic carbon, furfuryl alcohol resin calcined bodies (PFA), and hard carbon, as well as graphite materials such as natural graphite and artificial graphite. Furthermore, a metallic anode active material is an active material containing a metal, which typically contains an element in its structure that allows for lithium insertion, and has a theoretical electrical capacity of 500 mAh / g or more per unit mass when lithium is inserted. Examples of metallic active materials include lithium metal, elemental metals that can form lithium alloys (e.g., Ag, Al, Ba, Bi, Cu, Ga, Ge, In, Ni, P, Pb, Sb, Si, Sn, Sr, Zn, Ti, etc.), and their oxides, sulfides, nitrides, silicides, carbides, phosphides, etc. In addition, oxides such as lithium titanate can be mentioned. The above-mentioned anode active materials may be used individually or in combination of two or more types.

[0150] <Solvent> The solvent that the slurry composition may contain is the same as the solvents listed in the "Non-aqueous Binder Composition for Secondary Battery Electrodes" above.

[0151] <Other Components> Other components that can be incorporated into the slurry composition are not particularly limited and include thickeners, conductive materials, and other components similar to those that can be incorporated into the binder composition of the present invention. Note that these other components may be used individually or in combination of two or more components in any ratio.

[0152] <Preparation of Slurry Composition for Non-Aqueous Secondary Battery Electrodes> The method for preparing the slurry composition is not particularly limited. For example, the slurry composition can be prepared by mixing the binder composition, the electrode active material, and other components used as needed, in the presence of a solvent. The solvent used in preparing the slurry composition may include those contained in the binder composition. The mixing method is not particularly limited, but it can be mixed using commonly used stirrers and dispersers.

[0153] (Electrodes for Non-Aqueous Secondary Batteries) The electrode for non-aqueous secondary batteries of the present invention comprises an electrode composite layer formed using the slurry composition for non-aqueous secondary battery electrodes described above. Therefore, when the binder composition of the present invention is the binder composition according to the first embodiment described above, the electrode composite layer consists of the dried slurry composition described above and usually contains an electrode active material and a component derived from particulate polymer, and optionally further contains other components. On the other hand, when the binder composition of the present invention is the binder composition according to the second embodiment described above, the electrode composite layer consists of the dried slurry composition described above and usually contains an electrode active material, a component derived from particulate polymer, and two or more antioxidants, and optionally further contains other components. Note that each component contained in the electrode composite layer is the same as that contained in the slurry composition for non-aqueous secondary battery electrodes described above, and the preferred ratio of each component is the same as the preferred ratio of each component in the slurry composition. Furthermore, while particulate polymers exist in particle form in the slurry composition, they may be in particle form or any other arbitrary shape in the electrode composite layer formed using the slurry composition. The electrode for non-aqueous secondary batteries of the present invention has excellent peel strength during high-speed coating because the electrode composite layer is formed using the above-described non-aqueous secondary battery electrode slurry composition.

[0154] <Manufacturing of electrodes for non-aqueous secondary batteries> Here, the electrode composite layer of the electrode for the non-aqueous secondary battery of the present invention can be formed by, for example, the following methods: 1) applying the slurry composition of the present invention to the surface of a current collector and then drying it; 2) immersing a current collector in the slurry composition of the present invention and then drying it; and 3) applying the slurry composition of the present invention onto a release substrate, drying it to produce an electrode composite layer, and transferring the obtained electrode composite layer to the surface of a current collector. Among these, method 1) is particularly preferred because it allows for easy control of the thickness of the electrode composite layer. Method 1) more specifically includes a step of applying the 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 composite layer on the current collector (drying step).

[0155] <<Coating Process>> The method for coating the slurry composition onto the current collector is not particularly limited and known methods can be used. Specifically, the coating method can be the doctor blade method, dip method, reverse roll method, direct roll method, gravure method, extrusion method, brush coating method, etc. In this case, the slurry composition may be coated on only one side of the current collector or on both sides. The thickness of the slurry film on the current collector before drying after coating can be appropriately set according to the thickness of the electrode composite layer obtained after drying.

[0156] 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 can be made of, for example, iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, platinum, etc. One of the above materials may be used alone, or two or more may be used in any ratio.

[0157] <<Drying Process>> The method for drying the slurry composition on the current collector is not particularly limited and known methods can be used, such as drying with hot air, hot air, or low-humidity air, vacuum drying, or drying by irradiation with infrared rays or electron beams. By drying the slurry composition on the current collector in this way, an electrode composite layer is formed on the current collector, and an electrode for a non-aqueous secondary battery comprising a current collector and an electrode composite layer can be obtained.

[0158] Furthermore, after the drying process, the electrode composite layer may be subjected to pressure treatment using a die press or roll press. Pressure treatment improves the adhesion between the electrode composite layer and the current collector and can increase the density of the resulting electrode composite layer. In addition, if the electrode composite layer contains a curable polymer, it is preferable to cure the polymer after the formation of the electrode composite layer.

[0159] (Non-aqueous secondary battery) The non-aqueous secondary battery of the present invention comprises a positive electrode, a negative electrode, an electrolyte, and a separator, and uses the above-described non-aqueous secondary battery electrode as at least one of the positive electrode and the negative electrode. Furthermore, since the non-aqueous secondary battery of the present invention is manufactured using the above-described non-aqueous secondary battery electrode as at least one of the positive electrode and the negative electrode, it has excellent properties. In the following description, the case in which the secondary battery is a lithium-ion secondary battery will be described as an example, but the present invention is not limited to the following example.

[0160] <Electrodes> In addition to the electrodes for the non-aqueous secondary battery of the present invention described above, electrodes 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 secondary batteries can be used. Specifically, in addition to the electrodes for the non-aqueous secondary battery of the present invention described above, electrodes formed by forming an electrode composite layer on a current collector using a known manufacturing method can be used.

[0161] <Electrolyte> Typically, an organic electrolyte is used as the electrolyte, which is obtained by dissolving a supporting electrolyte in an organic solvent. For example, lithium salts are used as the supporting electrolytes in lithium-ion secondary batteries. Examples of lithium salts include LiPF4. ６ LiAsF ６ LiBF ４ LiSbF６ LiAlCl ４ LiClO ４ CF 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 Examples include NLi. Among them, LiPF is highly soluble in solvents and exhibits a high degree of dissociation. ６ LiClO ４ CF ３ SO ３ Li is preferred. Note that one type of electrolyte may be used alone, or two or more types may be used in any ratio. Generally, the lithium ion conductivity tends to increase as the degree of dissociation of the supporting electrolyte increases; therefore, the lithium ion conductivity can be adjusted by the type of supporting electrolyte.

[0162] The organic solvent used in the electrolyte is not particularly limited as long as it can dissolve the supporting electrolyte, but suitable examples include carbonates such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate (BC), ethyl methyl carbonate (EMC), and vinylene carbonate (VC); 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. A mixture of these solvents may also be used. Among these, carbonates are preferred because they have a high dielectric constant and a wide stable potential range. Generally, lithium ion conductivity tends to increase as the viscosity of the solvent used decreases, so lithium ion conductivity can be adjusted by the type of solvent. The concentration of the electrolyte in the electrolyte can be adjusted as appropriate. In addition, known additives can be added to the electrolyte.

[0163] <Separator> The separator is not particularly limited, and for example, those described in Japanese Patent Application Publication No. 2012-204303 can be used. Among these, a microporous membrane made of polyolefin resin (polyethylene, polypropylene, polybutene, polyvinyl chloride) is preferred because it allows for a thinner overall film thickness of the separator, thereby increasing the ratio of electrode active material in the secondary battery and thus increasing the capacity per unit volume.

[0164] Furthermore, the secondary battery of the present invention can be manufactured, for example, by stacking a positive electrode and a negative electrode with a separator in between, winding or folding them as needed according to the battery shape, placing them in a battery container, injecting an electrolyte into the battery container, and sealing it. In the non-aqueous secondary battery of the present invention, at least one of the positive electrode and the negative electrode, preferably the negative electrode, is the above-mentioned electrode for non-aqueous secondary batteries. In addition, the non-aqueous secondary battery of the present invention may be provided with an overcurrent prevention element such as a fuse or PTC element, expanded metal, lead plate, etc., as needed, to prevent pressure rise inside the secondary battery, overcharging and overdischarging, etc. The shape of the secondary battery may be, for example, coin type, button type, sheet type, cylindrical type, rectangular type, flat type, etc.

[0165] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. In the following description, "%" and "parts" representing quantities refer to mass unless otherwise specified. In the examples and comparative examples, various measurements and evaluations were performed using the following methods.

[0166] <Average Particle Size Da> The particle size distribution (volume-based) of the negative electrode binder compositions prepared in the examples and comparative examples 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. The average particle size Da was defined as the average particle size obtained by cumulant analysis. The measurement conditions for the dynamic light scattering method are as follows. Dispersion medium: Ion-exchanged water Measurement temperature: 25±1℃ Measurement concentration (solid content concentration): 0.5% Scattering angle: 168.8° Light source laser wavelength: 660nm <Median diameter Db> Using a particle size distribution analyzer (Shimadzu Corporation, product name "SALD-2300") that uses laser diffraction scattering as its measurement principle, the particle size distribution of the obtained binder composition (aqueous dispersion of particulate polymer, solid content concentration adjusted to 0.1 mass%) was measured in accordance with JIS Z 8825, and the particle size (D50) at which the cumulative volume calculated from the smallest diameter side becomes 50% in the measured particle size distribution was defined as the median diameter Db. <Viscosity stability of slurry composition> The viscosity η0 of the negative electrode slurry composition 1 obtained in the examples and comparative examples was measured using a B-type viscometer (Toki Sangyo Co., Ltd., product name "TVB-10", rotation speed: 60 rpm). Next, the anode slurry composition 1, whose viscosity η0 was measured, was stirred for 24 hours using a planetary mixer (rotation speed: 60 rpm). The viscosity η1 of the anode slurry composition 1 after stirring was measured using the same B-type viscometer (rotation speed: 60 rpm) as described above. The viscosity retention rate Δη = (η1 / η0) × 100 (%) of the anode slurry composition 1 before and after stirring was calculated, and the viscosity stability of the anode slurry composition 1 was evaluated according to the following criteria. The temperature during viscosity measurement was 25°C. The closer the viscosity retention rate Δη is to 100%, the better the viscosity stability of the anode slurry composition 1.[Examples 1A to 22A, Comparative Example 1A] 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% [Examples 1B to 20B] 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 70% or more and less than 80% D: Viscosity retention rate Δη is less than 70% or greater than 110% <Peel strength of electrode (negative electrode)> Negative electrode 1 prepared in the examples and comparative examples was cut into a rectangle with a length of 100 mm and a width of 10 mm to make a test piece. This test piece was placed with the surface of the negative electrode composite layer facing downwards, and cellophane tape was attached to the surface of the negative electrode composite layer. At this time, the cellophane tape used was the one specified in JIS Z1522. Furthermore, the cellophane tape was fixed to the test stand. Then, the stress was measured when one end of the current collector was pulled vertically upward at a speed of 50 mm / min and peeled off. This measurement was performed three times, and the average value was calculated. This average value was used as the peel strength and evaluated according to the following criteria: A: Peel strength of 14 N / m or more B: Peel strength of 11 N / m or more and less than 14 N / m C: Peel strength less than 11 N / m <Peel strength of electrode (negative electrode) during high-speed coating> The negative electrode slurry composition 1 prepared in the examples and comparative examples was coated onto a 15 μm thick copper foil, which is the current collector, using a comma coater at a speed of 3.6 m / min, with a basis weight of 10.5 mg / cm after drying. ２The material was applied in such a manner. The copper foil coated with the negative electrode slurry composition 1 was dried by transporting it in a 120°C oven for 20 seconds and then in a 150°C oven for 20 seconds to obtain a negative electrode (negative electrode for high-speed coating). Using the obtained negative electrode for high-speed coating, the peel strength of the electrode (negative electrode) during high-speed coating was measured in the same manner as described in "Peel Strength of Electrode (Negative Electrode)" above and evaluated according to the following criteria. [Examples 1A to 22A, Comparative Example 1A] A: Peel strength of 13 N / m or more during high-speed coating B: Peel strength of 10 N / m or more and less than 13 N / m during high-speed coating C: Peel strength of 7 N / m or more and less than 10 N / m during high-speed coating D: Peel strength of less than 7 N / m during high-speed coating [Examples 1B to 20B] A: Peel strength of 13 N / m or more during high-speed coating B: Peel strength of 10 N / m or more and less than 13 N / m during high-speed coating C: Peel strength of less than 10 N / m during high-speed coating <Powder shedding suppression> The negative electrode 1 was cut to 5 cm x 5 cm, and the weight W1 of the obtained test piece was measured using an electronic balance (5 decimal places). Next, using a 1 mm wide cross-cut jig (a jig conforming to JIS K5400) and a 9 mm wide cutter, the test specimen was placed with the copper foil (current collector) side facing outwards, and 11 cuts (slits) were made from the copper foil side in a direction parallel to the coating direction (the direction in which the negative electrode composite slurry was applied when forming the negative electrode composite layer). The cutter blade was broken off and replaced before use. Then, both sides of the test specimen were lightly brushed with a brush to remove the powder, and the weight W2 of the test specimen was measured using an electronic balance (5 decimal places). From the obtained W1 and W2, the powder removal rate = (W1 - W2) / W1 × 100 (%) was calculated and evaluated according to the following criteria. A smaller value for the powder removal rate indicates that powder removal from the negative electrode can be suppressed. A: Powder shedding rate is less than 0.15% B: Powder shedding rate is 0.15% or more and less than 0.25% C: Powder shedding rate is 0.25% or more <Internal resistance of lithium-ion secondary battery> To evaluate the internal resistance of lithium-ion secondary battery 1, the IV resistance was measured as follows. A conditioning treatment was performed by charging at a charge rate of 0.1C at a temperature of 25°C until the voltage reached 4.2V, then resting for 10 minutes, and finally discharging at a constant current (CC) at a discharge rate of 0.1C to 3.0V, repeating this operation three times.Subsequently, the battery was charged to 3.75V at 1C (where C is the rated capacity (mA) / 1 hour (h)) in a -10°C atmosphere. Then, charging and discharging were performed for 20 seconds at 0.5C, 1.0C, 1.5C, and 2.0C, centered around 3.75V. For each case, the battery voltage after 15 seconds on the charging side was plotted against the current value, and the slope was determined as the IV resistance (Ω). The obtained IV resistance values ​​(Ω) were evaluated by comparing them with the IV resistance of Comparative Example 1 according to the following criteria. Note that a smaller IV resistance value indicates a lower internal resistance of the secondary battery. [Examples 1A to 22A, Comparative Example 1A] A: Less than 85% of the IV resistance of Example 14A B: 85% or more and less than 95% of the IV resistance of Example 14A C: 95% or more of the IV resistance of Example 14A [Examples 1B to 20B] A: Less than 85% of the IV resistance of Example 12B B: 85% or more and less than 95% of the IV resistance of Example 12B C: 95% or more of the IV resistance of Example 12B <Cycle characteristics of lithium-ion secondary batteries> After the electrolyte was injected, lithium-ion secondary batteries 1 prepared in the examples and comparative examples were left to stand at 25°C for 5 hours. Next, they were charged to a cell voltage of 3.65V using a constant current method at 25°C and 0.2C, and then aged at 60°C for 12 hours. Then, they were discharged to a cell voltage of 3.00V using a constant current method at 25°C and 0.2C. Subsequently, constant current (CC) - constant voltage (CV) charging (upper cell voltage 4.20V) was performed using the 0.2C constant current method, and CC discharge was performed to 3.00V using the 0.2C constant current method. This 0.2C charge / discharge cycle was repeated three times. Then, under a temperature of 25°C, 100 charge / discharge cycles were performed with a cell voltage of 4.20-3.00V and a charge / discharge rate of 1.0C. At that time, the discharge capacity of the first cycle was defined as X1, and the discharge capacity of the 200th cycle was defined as X2. Using these discharge capacities X1 and X2, the capacity change rate, expressed as ΔC' = (X2 / X1) × 100 (%), was calculated and evaluated according to the following criteria. A larger value of this capacity change rate ΔC' indicates better cycle characteristics.A: ΔC' is 93% or more B: ΔC' is 90% or more and less than 93% C: ΔC' is less than 90% <Cycle characteristics of lithium-ion secondary batteries (at low additive level)> Using lithium-ion secondary batteries 2 prepared in the examples and comparative examples, the capacity change rate ΔC' was measured in the same manner as in "Cycle characteristics of lithium-ion secondary batteries" above and evaluated according to the following criteria. A: ΔC' is 93% or more B: ΔC' is 90% or more and less than 93% C: ΔC' is 87% or more and less than 90% D: ΔC' is less than 87%.

[0167] (Example 1A) <Preparation of Binder Composition for Non-Aqueous Secondary Battery Anode> First, in the first polymerization stage, 20 parts styrene as an aromatic monovinyl monomer, 70 parts isoprene, 1 part methacrylic acid as a carboxylic acid group-containing monomer, 1 part N-methylolacrylamide as a crosslinkable monomer, 1.0 part alkyldiphenyl ether disulfonate as an emulsifier, 143 parts ion-exchanged water, 0.1 part tert-dodecyl mercaptan as a chain transfer agent, and 0.3 parts potassium persulfate as a polymerization initiator were placed in a 5 MPa pressure vessel equipped with a stirrer, and after thorough stirring, the mixture was heated to 55°C to start polymerization and carry out the polymerization reaction. Next, in the second polymerization stage, 4 parts styrene as an aromatic monovinyl monomer and 2 parts methyl methacrylate as a (meth)acrylic acid ester monomer were added to the same pressure vessel under stirring, and then 2 parts methacrylic acid as a carboxylic acid group-containing monomer were added and carried out the polymerization reaction. Subsequently, unreacted monomers were removed by heated vacuum distillation to obtain an aqueous dispersion of particulate polymer. A 1% aqueous ammonia solution was added to this aqueous dispersion of particulate polymer to adjust the pH to 7. After further cooling, 2 parts of an oligomeric phenolic antioxidant (Good Year Co., Ltd., product name "WINGSTAY® L") and 2 parts of a hindered phenolic antioxidant (BASF Japan Ltd., product name "Irganox® 1076") were added as antioxidants to obtain an aqueous dispersion containing the desired particulate polymer as a binder composition for the negative electrode of a non-aqueous secondary battery. The particulate polymer obtained as described above had different compositions in the center of the particles and in the outermost layer of the particles. <Preparation of slurry composition for the negative electrode of a non-aqueous secondary battery> Artificial graphite (tap density: 0.85 g / cm³) as the negative electrode active material was added to a planetary mixer with a disperser. ３A mixture was obtained by adding 100 parts of (capacity: 360 mAh / g), 1 part of carbon black (manufactured by TIMCAL, product name "Super C65") as a conductive material, and 1.2 parts (in terms of solid content) of a 2% aqueous solution of carboxymethylcellulose (manufactured by Daicel, product name "Daicel 2200") as a thickener. The obtained mixture was adjusted to a solid content of 60% with deionized water and then mixed at 25°C for 60 minutes. Next, the solid content was adjusted to 52% with deionized water and then mixed further at 25°C for 15 minutes to obtain a mixed solution. To the obtained mixed solution, 2.0 parts (in terms of solid content) of the binder composition prepared above and deionized water were added and adjusted to a final solid content of 48%. After mixing for a further 10 minutes, a defoaming treatment was performed under reduced pressure to obtain a smooth negative electrode slurry composition 1. The peel strength and viscosity stability of the electrode (negative electrode) during high-speed coating were evaluated using the obtained negative electrode slurry composition 1. The results are shown in Table 1. Furthermore, negative electrode slurry composition 2 was obtained in the same manner as above, except that the amount of binder composition added was changed from 2.0 parts to 1.5 parts in terms of solid content. <Formation of negative electrode> The negative electrode slurry composition 1 obtained above was coated onto a 15 μm thick copper foil, which is the current collector, using a comma coater at a speed of 1.2 m / min, with a basis weight of 10.5 mg / cm² after drying. ２ The material was applied and dried. This drying was performed by transporting the copper foil at a speed of 1.2 m / min in a 120°C oven for 1 minute, and then in a 130°C oven for 1 minute. The resulting negative electrode base was rolled in a roll press to obtain a negative electrode composite layer with a density of 1.70 g / cm³. ３ A negative electrode 1 was obtained. Using the obtained negative electrode 1, the peel strength and powder shedding suppression of the electrode (negative electrode) were evaluated. The results are shown in Table 1. Furthermore, a negative electrode 2 was obtained in the same manner as above, except that a negative electrode slurry composition 2 was used instead of a negative electrode slurry composition 1. <Formation of positive electrode> LiCoO with a median diameter of 12 μm was used as the positive electrode active material. ２100 parts of [the material], 2 parts of acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd., product name "HS-100") as a conductive material, 2 parts of polyvinylidene fluoride (manufactured by Kureha Corporation, product name "#7208") in terms of solid content as a binder, and N-methylpyrrolidone as a solvent were mixed to obtain a total solid content concentration of 70%. These were mixed using a planetary mixer to obtain a slurry composition for the positive electrode. The obtained slurry composition for the positive electrode was coated onto a 20 μm thick aluminum foil current collector using a comma coater, with a basis weight of 23 mg / cm² after drying. ２ The material was coated and dried. This drying was performed by transporting aluminum foil at a speed of 0.5 m / min in a 60°C oven for 2 minutes. After that, it was heat-treated at 120°C for 2 minutes to obtain a cathode base. The cathode base was then rolled in a roll press to obtain a cathode composite layer with a density of 4.0 g / cm³. ３ A positive electrode was obtained. <Preparation of Separator> A single-layer polypropylene separator (manufactured by Cellguard, product name "Cellguard 2500") was prepared as a separator made of a separator substrate. This polypropylene separator is a 25 μm thick microporous film made of polypropylene. <Fabrication of Lithium-ion Secondary Battery> A laminate was obtained by interposing the pressed positive electrode, the pressed negative electrode 1, and the separator, which were prepared as described above, in the order of separator / positive electrode / separator / negative electrode. Next, a wound body comprising a positive electrode, a separator, and a negative electrode was obtained by winding the laminate of electrodes and separators around a core with a diameter of 20 mm. Subsequently, a flattened body was obtained by compressing the obtained wound body from one direction at a speed of 10 mm / second until it reached a thickness of 4.5 mm. The obtained flattened body was elliptical in plan view, and its ratio of major axis to minor axis (major axis / minor axis) was 7.7. Also, a non-aqueous electrolyte (LiPF with a concentration of 1.0 M) ６A solution was prepared (a mixed solvent of ethylene carbonate (EC) / ethyl methyl carbonate (EMC) = 3 / 7 (mass ratio), to which 2% by volume of vinylene carbonate (VC) was further added as an additive). Next, the flattened body was placed in an aluminum laminate case together with the non-aqueous electrolyte. After connecting the negative electrode lead and positive electrode lead to the designated locations, the opening of the laminate case was sealed with heat to manufacture a laminate-type lithium-ion secondary battery 1 as a non-aqueous secondary battery. The obtained lithium-ion secondary battery 1 was a pouch type with dimensions of 35 mm wide x 48 mm high x 5 mm thick, and its nominal capacity was 700 mAh. The internal resistance and cycle characteristics of the lithium-ion secondary battery 1 were evaluated using the obtained lithium-ion secondary battery 1. The results are shown in Table 1. A lithium-ion secondary battery 2 was also manufactured in the same manner as above, except that negative electrode 2 was used instead of negative electrode 1. The cycle characteristics of lithium-ion secondary batteries (at low additive levels) were evaluated using this lithium-ion secondary battery 2. The results are shown in Table 1.

[0168] (Examples 2A to 19A, Comparative Example 1A) Except for changing the type and amount of monomers used in the preparation of the binder composition for the negative electrode of a non-aqueous secondary battery as shown in Tables 1 and 2, various operations, measurements, and evaluations were performed in the same manner as in Example 1A. The results are shown in Tables 1 and 2. In all of the particulate polymers in Examples 2A to 19A and Comparative Example 1A, the composition of the core of the particle and the composition of the outermost layer of the particle were different from each other.

[0169] (Example 20A) Various operations, measurements, and evaluations were carried out in the same manner as in Example 1A, except that a binder composition for a non-aqueous secondary battery anode prepared as follows was used. The results are shown in Table 2. <Preparation of Binder Composition for Non-Aqueous Secondary Battery Anode> [Preparation of Cyclohexane Solution of Block Copolymer] 233.3 kg of cyclohexane, 54.2 mmol of N,N,N',N'-tetramethylethylenediamine (TMEDA), and 24.0 kg of styrene as an aromatic monovinyl monomer were added to a pressure reactor. These were stirred at 40°C, and 1806.5 mmol of n-butyllithium as a polymerization initiator was added, and polymerization was carried out for 1 hour while raising the temperature to 50°C. The polymerization conversion rate of styrene was 100%. Subsequently, 70.0 kg of isoprene was continuously added to the pressure reactor over 1 hour while controlling the temperature to maintain 50-60°C. After the addition of isoprene was completed, the polymerization reaction was continued for another hour. The polymerization conversion rate of isoprene was 100%. Next, 740.6 mmol of dichlorodimethylsilane as a coupling agent was added to the pressure reactor and the coupling reaction was carried out for 2 hours. After that, in order to deactivate the active ends, 3612.9 mmol of methanol was added to the reaction solution and mixed well to obtain a block copolymer solution. [Emulsification] Sodium alkylbenzene sulfonate was dissolved in deionized water to prepare a 5% aqueous solution. Then, 500 g of the obtained block copolymer solution and 500 g of the obtained aqueous solution were added to a tank and stirred to perform premixing. Subsequently, the premix was transferred from the tank to a continuous high-efficiency emulsifying disperser (manufactured by Taiheiyo Kiko Co., Ltd., product name "Milder MDN303V") at a rate of 100 g / min using a metering pump, and the premix was stirred at a rotation speed of 15,000 rpm to obtain an emulsion. Next, cyclohexane in the obtained emulsion was removed by vacuum distillation using a rotary evaporator. Subsequently, the evaporated emulsion was allowed to stand and separate for one day in a chromatography column equipped with a stopcock, and the lower layer was removed to concentrate the solution. Finally, the upper layer was filtered through a 100-mesh wire mesh to obtain an aqueous dispersion (block copolymer latex) containing particulate block copolymer (core particles).[Graft Polymerization and Crosslinking] 675 parts of deionized water were added to a polymerization reaction vessel equipped with a stirrer, followed by the addition of 3 parts of methacrylic acid, 2 parts of methyl methacrylate, and 1 part of N-methylolacrylamide. While stirring with the stirring blades of the polymerization reactor, 94 parts of the resulting block copolymer latex (in terms of block copolymer) were added to the polymerization reactor and the mixture was purged with nitrogen. The diluted block polymer latex was then heated to 30°C while being stirred. In addition, a solution was prepared in a separate container containing 7 parts of deionized water, 0.01 parts of ferrous sulfate (manufactured by Chubu Kirest Co., Ltd., product name "Frost Fe") as a reducing agent, and 0.32 parts of sodium formaldehyde sulfoxylate (manufactured by Sumitomo Seika Co., Ltd., product name "SFS"). After adding the obtained solution to a polymerization reaction vessel, 0.35 parts of tert-butyl hydroperoxide (manufactured by Nippon Oil & Fats Co., Ltd., product name "Perbutyl H") as an oxidizing agent were added, and the reaction was carried out at 30°C for 1 hour, followed by a further reaction at 70°C for 2 hours. The polymerization conversion rate was 99%. Then, an aqueous dispersion of particulate polymer consisting of graft polymers obtained by graft polymerization and crosslinking of core particles containing block copolymers was obtained. A 1% aqueous ammonia solution was added to this mixture containing particulate polymer to adjust the pH to 7. After further cooling, 2 parts of Wingstay L and 2 parts of Irganox 1076 were added as antioxidants, and the aqueous dispersion containing particulate polymer was obtained as a binder composition for lithium-ion secondary battery negative electrodes. In the particulate polymer obtained as described above, the composition of the core of the particle and the composition of the outermost layer of the particle were different from each other.

[0170] (Example 21A) Various operations, measurements, and evaluations were performed in the same manner as in Example 1A, except that no antioxidant was added during the preparation of the binder composition for the negative electrode of a non-aqueous secondary battery. The results are shown in Table 2. In Example 21A, the composition of the center of the particle and the composition of the outermost layer of the particle were different from each other.

[0171] (Example 22A) In the preparation of the binder composition for the negative electrode of a non-aqueous secondary battery, the type and amount of monomers used were changed as shown in Table 2, and no antioxidant was added. Except for these changes, various operations, measurements, and evaluations were carried out in the same manner as in Example 1A. The results are shown in Table 2. Note that in Example 22A, the composition of the center of the particle and the composition of the outermost layer of the particle were different from each other.

[0172] (Example 1B) <Preparation of Binder Composition for Non-Aqueous Secondary Battery Anode> First, in the first polymerization stage, 20 parts styrene as an aromatic monovinyl monomer, 70 parts isoprene, 1 part methacrylic acid as a carboxylic acid group-containing monomer, 1 part N-methylolacrylamide as a crosslinkable monomer, 1.0 part alkyldiphenyl ether disulfonate as an emulsifier, 143 parts ion-exchanged water, 0.1 part tert-dodecyl mercaptan as a chain transfer agent, and 0.3 parts potassium persulfate as a polymerization initiator were placed in a 5 MPa pressure vessel equipped with a stirrer, and after thorough stirring, the mixture was heated to 55°C to start polymerization and carry out the polymerization reaction. Next, in the second polymerization stage, 4 parts styrene as an aromatic monovinyl monomer and 2 parts methyl methacrylate as a (meth)acrylic acid ester monomer were added to the same pressure vessel under stirring, and then 2 parts methacrylic acid as a carboxylic acid group-containing monomer were added and carried out the polymerization reaction. Subsequently, unreacted monomers were removed by heated vacuum distillation to obtain an aqueous dispersion of particulate polymer. A 1% aqueous ammonia solution was added to this aqueous dispersion of particulate polymer to adjust the pH to 7. After further cooling, two parts of compound (V) (Good Year Co., Ltd., product name "WINGSTAY L; oligomeric phenolic antioxidant") and two parts of compound (III) (BASF Japan Ltd., product name "Irganox 1076; hindered phenolic antioxidant") were added as antioxidants to obtain an aqueous dispersion containing the desired particulate polymer as a binder composition for the negative electrode of a non-aqueous secondary battery. The particulate polymer obtained as described above had different compositions in the center of the particles and in the outermost layer of the particles. <Preparation of slurry composition for the negative electrode of a non-aqueous secondary battery> Artificial graphite (tap density: 0.85 g / cm³) as the negative electrode active material was added to a planetary mixer with a disperser.３ A mixture was obtained by adding 100 parts of (capacity: 360 mAh / g), 1 part of carbon black (manufactured by TIMCAL, product name "Super C65") as a conductive material, and 1.2 parts (in terms of solid content) of a 2% aqueous solution of carboxymethylcellulose (manufactured by Daicel, product name "Daicel 2200") as a thickener. The obtained mixture was adjusted to a solid content of 60% with deionized water and then mixed at 25°C for 60 minutes. Next, the solid content was adjusted to 52% with deionized water and then mixed further at 25°C for 15 minutes to obtain a mixed solution. To the obtained mixed solution, 2.0 parts (in terms of solid content) of the binder composition prepared above and deionized water were added and adjusted to a final solid content of 48%. After mixing for a further 10 minutes, a defoaming treatment was performed under reduced pressure to obtain a smooth negative electrode slurry composition 1. The peel strength and viscosity stability of the electrode (negative electrode) during high-speed coating were evaluated using the obtained negative electrode slurry composition 1. The results are shown in Table 3. Furthermore, negative electrode slurry composition 2 was obtained in the same manner as above, except that the amount of binder composition added was changed from 2.0 parts to 1.5 parts in terms of solid content. <Formation of negative electrode> The negative electrode slurry composition 1 obtained above was coated onto a 15 μm thick copper foil, which is the current collector, using a comma coater at a speed of 1.2 m / min, with a basis weight of 10.5 mg / cm² after drying. ２ The material was applied and dried. This drying was performed by transporting the copper foil at a speed of 1.2 m / min in a 120°C oven for 1 minute, and then in a 130°C oven for 1 minute. The resulting negative electrode base was rolled in a roll press to obtain a negative electrode composite layer with a density of 1.70 g / cm³. ３ A negative electrode 1 was obtained. Using the obtained negative electrode 1, the peel strength and powder shedding suppression of the electrode (negative electrode) were evaluated. The results are shown in Table 3. Furthermore, a negative electrode 2 was obtained in the same manner as above, except that a negative electrode slurry composition 2 was used instead of a negative electrode slurry composition 1. <Formation of positive electrode> LiCoO with a median diameter of 12 μm was used as the positive electrode active material. ２100 parts of [the material], 2 parts of acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd., product name "HS-100") as a conductive material, 2 parts of polyvinylidene fluoride (manufactured by Kureha Corporation, product name "#7208") in terms of solid content as a binder, and N-methylpyrrolidone as a solvent were mixed to obtain a total solid content concentration of 70%. These were mixed using a planetary mixer to obtain a slurry composition for the positive electrode. The obtained slurry composition for the positive electrode was coated onto a 20 μm thick aluminum foil current collector using a comma coater, with a basis weight of 23 mg / cm² after drying. ２ The material was coated and dried. This drying was performed by transporting aluminum foil at a speed of 0.5 m / min in a 60°C oven for 2 minutes. After that, it was heat-treated at 120°C for 2 minutes to obtain a cathode base. The cathode base was then rolled in a roll press to obtain a cathode composite layer with a density of 4.0 g / cm³. ３ A positive electrode was obtained. <Preparation of Separator> A single-layer polypropylene separator (manufactured by Cellguard, product name "Cellguard 2500") was prepared as a separator made of a separator substrate. This polypropylene separator is a 25 μm thick microporous film made of polypropylene. <Fabrication of Lithium-ion Secondary Battery> A laminate was obtained by interposing the pressed positive electrode, the pressed negative electrode 1, and the separator, which were prepared as described above, in the order of separator / positive electrode / separator / negative electrode. Next, a wound body comprising a positive electrode, a separator, and a negative electrode was obtained by winding the laminate of electrodes and separators around a core with a diameter of 20 mm. Subsequently, a flattened body was obtained by compressing the obtained wound body from one direction at a speed of 10 mm / second until it reached a thickness of 4.5 mm. The obtained flattened body was elliptical in plan view, and its ratio of major axis to minor axis (major axis / minor axis) was 7.7. Also, a non-aqueous electrolyte (LiPF with a concentration of 1.0 M) ６A solution was prepared (a mixed solvent of ethylene carbonate (EC) / ethyl methyl carbonate (EMC) = 3 / 7 (mass ratio), to which 2% by volume of vinylene carbonate (VC) was further added as an additive). Next, the flattened body was placed in an aluminum laminate case together with the non-aqueous electrolyte. After connecting the negative electrode lead and positive electrode lead to the designated locations, the opening of the laminate case was sealed with heat to produce a laminate-type lithium-ion secondary battery 1 as a non-aqueous secondary battery. The obtained lithium-ion secondary battery 1 was a pouch type with dimensions of 35 mm wide x 48 mm high x 5 mm thick, and had a nominal capacity of 700 mAh. The internal resistance and cycle characteristics of the lithium-ion secondary battery 1 were evaluated using the obtained lithium-ion secondary battery 1. The results are shown in Table 3. A lithium-ion secondary battery 2 was also prepared in the same manner as above, except that negative electrode 2 was used instead of negative electrode 1. The cycle characteristics of lithium-ion secondary batteries (at low additive levels) were evaluated using this lithium-ion secondary battery 2. The results are shown in Table 3.

[0173] (Examples 2B-10B and 14B-20B) Except for changing the type and amount of antioxidant during the preparation of the binder composition for the negative electrode of a non-aqueous secondary battery as shown in Tables 3-4, various operations, measurements, and evaluations were performed in the same manner as in Example 1B. The results are shown in Tables 3-4. In all of the particulate polymers in Examples 2B-10B and 14B-20B, the composition of the core of the particle and the composition of the outermost layer of the particle were different from each other.

[0174] (Examples 11B to 13B) Except for changing the type and amount of monomers used in the preparation of the binder composition for the negative electrode of a non-aqueous secondary battery as shown in Table 4, various operations, measurements, and evaluations were performed in the same manner as in Example 1B. The results are shown in Table 4. In all of the particulate polymers in Examples 11B to 13B, the composition of the particle center and the composition of the outermost layer of the particle were different from each other.

[0175] In Tables 1-4 below, "random" indicates a random copolymer, "block" indicates a block copolymer, "NMA" indicates N-methylolacrylamide, "AGE" indicates allyl glycidyl ether, "GMA" indicates glycidyl methacrylate, "DVB" indicates divinylbenzene, "ST" indicates styrene, "MAA" indicates methacrylic acid, "AA" indicates acrylic acid, "IA" indicates itaconic acid, "BD" indicates 1,3-butadiene, "MMA" indicates methyl methacrylate, "EA" indicates ethyl acrylate, "BA" indicates n-butyl acrylate, "IP" indicates isoprene, "WL" indicates WINGSTAY L, and "IRG" indicates Irganox 1076. "Compounds (I) to (VII)" refer to the compounds represented by formulas (I) to (VII) above, respectively. In Tables 1 to 4, "Da / Db" is expressed as a value rounded to the third decimal place.

[0176]

[0177]

[0178]

[0179]

[0180] As is clear from Tables 1 to 4, the binder compositions of Examples 1A to 22A and 1B to 20B can increase the peel strength during high-speed coating of electrodes compared to the binder composition of Comparative Example 1A.

[0181] According to the present invention, it is possible to provide a binder composition and a slurry composition for non-aqueous secondary battery electrodes that can form electrodes for non-aqueous secondary batteries with excellent peel strength during high-speed coating. Furthermore, according to the present invention, it is possible to provide electrodes for non-aqueous secondary batteries with excellent peel strength during high-speed coating. And according to the present invention, it is possible to provide a non-aqueous secondary battery equipped with the above-mentioned electrodes for non-aqueous secondary batteries.

Claims

A binder composition for non-aqueous secondary battery electrodes containing particulate polymer, The particulate polymer comprises a random copolymer containing isoprene units or a block copolymer containing isoprene units, and is a binder composition for non-aqueous secondary battery electrodes. 　 The particulate polymer comprises isoprene units and crosslinkable monomer units, wherein the binder composition for non-aqueous secondary battery electrodes is as described in claim 1. 　 The binder composition for non-aqueous secondary battery electrodes according to claim 2, wherein the particulate polymer comprises the random copolymer. 　 The binder composition for non-aqueous secondary battery electrodes according to claim 2, wherein the particulate polymer further comprises aromatic monovinyl monomer units. 　 The binder composition for non-aqueous secondary battery electrodes according to claim 2, wherein the particulate polymer further comprises (meth)acrylic acid ester monomer units. 　 The binder composition for non-aqueous secondary battery electrodes according to claim 2, wherein the crosslinkable monomer unit is derived from a monomer having two or more crosslinkable reactive groups per molecule. 　 The binder composition for non-aqueous secondary battery electrodes according to claim 6, wherein the crosslinkable reactive group is selected from the group consisting of epoxy groups, hydroxyl groups, N-methylolamide groups, oxetanyl groups, oxazoline groups, and vinyl groups. 　 The binder composition for non-aqueous secondary battery electrodes according to claim 2, wherein the content ratio of the crosslinkable monomer units in the particulate polymer is 0.01% by mass or more and 10% by mass or less. 　 The ratio (Da / Db) of the average particle diameter Da of the particulate polymer measured by dynamic light scattering to the median diameter Db of the particulate polymer measured by laser diffraction scattering is 1.05 or more and 2.00 or less. The binder composition for non-aqueous secondary battery electrodes according to claim 2, wherein the median diameter Db is 100 nm or more and 170 nm or less. 　 The particulate polymer and two or more antioxidants are included. The binder composition for non-aqueous secondary battery electrodes according to claim 1, wherein the particulate polymer comprises a random copolymer containing the isoprene units. 　 The binder composition for non-aqueous secondary battery electrodes according to claim 10, wherein the particulate polymer further comprises aromatic monovinyl monomer units. 　 The binder composition for non-aqueous secondary battery electrodes according to claim 10, wherein the two or more antioxidants include antioxidants having a molecular weight of 200 or more and 500 or less. 　 The two or more antioxidants mentioned above have a specific gravity of 1.0 g / cm³. ３ A binder composition for non-aqueous secondary battery electrodes according to claim 10, comprising the antioxidant described above. 　 The binder composition for non-aqueous secondary battery electrodes according to claim 12, wherein the two or more antioxidants further include antioxidants having a melting point of 0°C or higher and 90°C or lower. 　 A slurry composition for a non-aqueous secondary battery electrode, comprising an electrode active material and a binder composition for a non-aqueous secondary battery electrode according to any one of claims 1 to 14. 　 An electrode for a non-aqueous secondary battery, comprising an electrode composite layer formed using the slurry composition for non-aqueous secondary battery electrodes described in claim 15. 　 It comprises a positive electrode, a negative electrode, a separator, and an electrolyte. A non-aqueous secondary battery in which at least one of the positive electrode and the negative electrode is an electrode for a non-aqueous secondary battery as described in claim 16.

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