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

Abstract

A binder composition for a non-aqueous secondary battery, which contains a copolymer having a first structural unit derived from a monomer (a1) that is a nonionic compound having only one ethylenically unsaturated bond and a second structural unit derived from a monomer (a2) that is a non-ionic compound having only one ethylenically unsaturated bond, and a polyrotaxane. The monomer (a2) is a compound having a carboxyl group and only one ethylenically unsaturated bond, and the polyrotaxane has a cyclic molecule having a cyclic skeleton and a chain molecule penetrating an opening of the cyclic molecule and having a blocking group at both ends.

Description

Technical Field

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

[0002] This application claims priority based on patent application No. 2022-202379 filed in Japan on December 19, 2022, and the contents of which are incorporated herein by reference. Background Art

[0003] Non-aqueous secondary batteries, due to their ability to be miniaturized and lightweight, are widely used as power sources for laptop computers, mobile phones, power tools, and electronic and communications equipment. In recent years, they have also been used as power sources for electric vehicles and hybrid vehicles. A representative example of a non-aqueous secondary battery is the lithium-ion secondary battery.

[0004] Non-aqueous secondary batteries consist of a positive electrode containing a metal oxide or other active material, a negative electrode containing a carbon material such as graphite, and an electrolyte. Each positive and negative electrode includes a current collector and an electrode active material layer formed on the current collector. The electrode active material layer typically contains a binder that secures the electrode active material layer to the current collector by bonding the active material to each other and to the current collector.

[0005] Conventionally, as binders used in non-aqueous secondary batteries, those described in Patent Documents 1 and 2 are known.

[0006] Patent Document 1 describes a binder composition for secondary battery electrodes containing 100 parts by mass of at least one polymer aqueous dispersion selected from styrene-butadiene copolymer latex and acrylic emulsion and 1 to 20 parts by mass of a nonionic surfactant.

[0007] Patent document 2 describes a binder for lithium-ion secondary battery electrodes, which is obtained by emulsion polymerization of ethylenically unsaturated monomers containing 15 to 70% by mass of styrene, ethylenically unsaturated carboxylic acid ester, ethylenically unsaturated carboxylic acid, and an internal crosslinking agent as essential components in the presence of a surfactant, and has a glass transition temperature of 30° C. or less.

[0008] Patent Document 3 also describes a coating resin emulsion suitable for use in building exterior coatings and the like. Patent Document 3 discloses a coating resin emulsion comprising a resin having a glass transition temperature of 0°C or higher and containing 0.01 to 4% by mass of a structural unit derived from a modified polyrotaxane having a cyclic molecule and an opening penetrating the cyclic molecule and a chain molecule having blocking groups at both ends, wherein the cyclic molecule of the polyrotaxane is bonded to a functional group having a radically polymerizable group.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: Japanese Patent Application Laid-Open No. 2014-239070 (A)

[0012] Patent Document 2: Japanese Patent Application Laid-Open No. 2011-243464 (A)

[0013] Patent Document 3: Japanese Patent Application Publication No. 2019-116594 (A) Summary of the Invention

[0014] Problems to be solved by the invention

[0015] In recent years, non-aqueous secondary batteries have been strongly demanded to have higher output, higher capacity, and longer life. Binders used in non-aqueous secondary batteries are required to improve the cycle characteristics of non-aqueous secondary batteries having electrodes formed using the binders.

[0016] The present invention has been completed in view of the above situation, and its purpose is to provide a binder composition for non-aqueous secondary batteries and a method for producing the same, a slurry for non-aqueous secondary battery electrodes, a non-aqueous secondary battery electrode capable of producing a non-aqueous secondary battery with excellent cycle characteristics, and a non-aqueous secondary battery having the electrode.

[0017] Means of solving problems

[0018] The present invention includes the following aspects.

[0019] [1] A binder composition for a non-aqueous secondary battery, comprising a copolymer and a polyrotaxane, wherein the copolymer has a first structural unit derived from a monomer (a1) and a second structural unit derived from a monomer (a2),

[0020] The monomer (a1) is a nonionic compound having only one ethylenically unsaturated bond.

[0021] The monomer (a2) is a compound having a carboxyl group and only one ethylenically unsaturated bond,

[0022] The polyrotaxane includes a cyclic molecule and a chain molecule. The cyclic molecule has a cyclic skeleton, and the chain molecule penetrates the opening of the cyclic molecule and has blocking groups at both ends.

[0023] [2] The binder composition for a non-aqueous secondary battery according to [1], wherein at least one of the cyclic skeletons of the cyclic molecule is a crown ether skeleton, a cyclic siloxane skeleton, or a cyclic oligosaccharide skeleton.

[0024] [3] The binder composition for a non-aqueous secondary battery according to [1] or [2], wherein at least one of the cyclic skeletons of the cyclic molecules is an α-cyclodextrin skeleton.

[0025] [4] The binder composition for a non-aqueous secondary battery according to any one of [1] to [3], wherein at least one of the blocking groups is a dinitrophenyl group, an adamantyl group, a triphenylmethyl group, or a derivative of any of these groups.

[0026] [5] The binder composition for a non-aqueous secondary battery according to any one of [1] to [4], wherein at least one of the blocking groups is an adamantyl group.

[0027] [6] The binder composition for a non-aqueous secondary battery according to any one of [1] to [5], wherein the chain molecule is at least one selected from polyethylene glycol, polypropylene glycol, polyisoprene, polyisobutylene, polybutadiene, polytetramethylene glycol, polyacrylate, polydimethylsiloxane, polyethylene and polypropylene.

[0028] [7] The binder composition for a non-aqueous secondary battery according to any one of [1] to [6], wherein at least one of the chain molecules is polyethylene glycol.

[0029] [8] The binder composition for a non-aqueous secondary battery according to any one of [1] to [7], wherein the weight average molecular weight of the chain molecules is 5,000 to 50,000.

[0030] [9] The binder composition for a non-aqueous secondary battery according to any one of [1] to [8], wherein the polyrotaxane has an ethylenically unsaturated bond.

[0031]

[10] The binder composition for a non-aqueous secondary battery as described in [9], wherein a group containing an ethylenically unsaturated bond is bonded to the cyclic skeleton,

[0032] At least one of the groups containing an ethylenically unsaturated bond bonded to the cyclic skeleton is a (meth)acryloyl group, a vinyl group, an allyl group, or a propenyl group.

[0033]

[11] The binder composition for a non-aqueous secondary battery according to

[10] , wherein at least one of the groups containing an ethylenically unsaturated bond bonded to the cyclic skeleton is a (meth)acryloyl group.

[0034]

[12] The binder composition for a non-aqueous secondary battery according to any one of [1] to [8], wherein the polyrotaxane does not have an ethylenically unsaturated bond.

[0035]

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

[12] , wherein the content of the polyrotaxane is 0.10 parts by mass or more and 50 parts by mass or less relative to 100 parts by mass of the copolymer.

[0036]

[14] The binder composition for a non-aqueous secondary battery according to any one of [1] to

[13] , wherein the content of the second structural unit in all structural units of the copolymer is 0.10% by mass or more and 20% by mass or less.

[0037]

[15] The binder composition for a non-aqueous secondary battery according to any one of [1] to

[14] , wherein the copolymer has a third structural unit derived from monomer (a3),

[0038] The monomer (a3) is a compound having a plurality of independent ethylenically unsaturated bonds.

[0039]

[16] The binder composition for a non-aqueous secondary battery according to

[15] , wherein the content of the third structural unit in all structural units of the copolymer is 0.010% by mass or more and 10% by mass or less.

[0040]

[17] The binder composition for a non-aqueous secondary battery according to any one of [1] to

[16] , further comprising an aqueous medium.

[0041]

[18] The binder composition for a non-aqueous secondary battery as described in

[17] , wherein the emulsified particles of the copolymer and the polyrotaxane are dispersed in the aqueous medium.

[0042]

[19] . A slurry for non-aqueous secondary battery electrodes, comprising the binder composition for non-aqueous secondary batteries described in

[17] and an electrode active material.

[0043]

[20] . A non-aqueous secondary battery electrode comprising the non-volatile component of the binder composition for a non-aqueous secondary battery according to any one of [1] to

[18] .

[0044]

[21] . A non-aqueous secondary battery comprising the non-aqueous secondary battery electrode described in

[20] .

[0045] Effects of the Invention

[0046] According to the present invention, a binder composition for a non-aqueous secondary battery capable of forming an electrode capable of obtaining a non-aqueous secondary battery with excellent cycle characteristics and a method for producing the same can be provided.

[0047] Furthermore, according to the present invention, it is possible to provide a slurry for non-aqueous secondary battery electrodes that can form an electrode capable of obtaining a non-aqueous secondary battery having excellent cycle characteristics.

[0048] Furthermore, the present invention can provide a non-aqueous secondary battery electrode capable of obtaining a non-aqueous secondary battery with excellent cycle characteristics, and a non-aqueous secondary battery with excellent cycle characteristics including the non-aqueous secondary battery electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 This is a schematic cross-sectional view showing an example of a non-aqueous secondary battery electrode produced using the binder composition for a non-aqueous secondary battery of the present invention.

[0050] Figure 2 This is a schematic diagram for explaining the polyrotaxane used as a raw material for the binder composition for a non-aqueous secondary battery of the present invention. DETAILED DESCRIPTION

[0051] The present inventors have conducted intensive studies as described below to solve the above problems and realize a binder capable of forming a non-aqueous secondary battery electrode capable of obtaining a non-aqueous secondary battery with excellent cycle characteristics.

[0052] Figure 1 This is a schematic cross-sectional view showing an example of a non-aqueous secondary battery electrode produced using the binder composition for a non-aqueous secondary battery of the present invention.

[0053] Figure 1 The non-aqueous secondary battery electrode (hereinafter sometimes referred to as "electrode") 20 shown includes a current collector 23 made of copper foil or the like and an electrode active material layer 24 formed on the current collector 23. In one embodiment, the electrode active material layer 24 includes an electrode active material 22, a thickener 21, and a binder 25. The binder 25 is composed of the non-volatile component of the binder composition for a non-aqueous secondary battery of the present invention.

[0054] Regarding the discharge capacity of a non-aqueous secondary battery having an electrode 20, as the non-aqueous secondary battery is used, that is, as the electrode active material 22 expands and contracts with charge and discharge, the electrode active material layer 24 of the electrode 20 expands and contracts accordingly, and if this expands and contracts and peels off from the current collector 23, the discharge capacity decreases. Furthermore, even if the electrode active material layer 24 is not peeled off from the current collector 23, the discharge capacity of the non-aqueous secondary battery may decrease if the adhesion between the electrode active material layers 22 and between the electrode active material layers 22 and the current collector 23 becomes insufficient due to the expansion and contraction of the electrode active material 22.

[0055] Therefore, the binder 25 is preferably one that can maintain the binding properties between the electrode active materials 22 and between the electrode active materials 22 and the current collector 23 for a long period of time and can form an electrode 20 in which the electrode active material layer 24 is unlikely to be peeled off from the current collector 23 .

[0056] However, in the conventional art, since the toughness of the binder is insufficient, the binder cannot follow the expansion and contraction of the electrode active material 22 accompanying charge and discharge.

[0057] The expansion and contraction directions of the multiple electrode active materials 22 contained in the electrode active material layer 24 are random. Therefore, the binder 25 contained in the electrode active material layer 24 is mostly arranged between the electrode active materials 22 that expand and contract in different directions, and between the electrode active materials 22 that expand and contract in different directions and the current collector 23. Therefore, if the binder 25 does not have sufficient followability for each of the multiple materials that expand and contract in different directions and are connected through the binder 25, good bonding cannot be achieved.

[0058] For example, when a coating film containing a binder but not an electrode active material 22 is formed on a substrate, the binder in the coating film may be adapted as long as it can follow the direction of expansion and contraction of the substrate. Therefore, even a binder that can be used as a material for a coating film that is difficult to peel off from a substrate does not necessarily have the followability to achieve sufficient adhesion between the electrode active materials 22 and between the electrode active material 22 and the current collector 23, and the electrode active material layer 24 containing the binder and the electrode active material 22 is not necessarily difficult to peel off from the current collector 23.

[0059] Therefore, it is difficult to conventionally realize a binder that has good bonding properties between the electrode active materials 22 and between the electrode active materials 22 and the current collector 23 and that prevents the electrode active material layer 24 from being peeled off from the current collector 23 .

[0060] Therefore, as a polymer that can easily obtain an electrode active material layer 24 that is difficult to peel off from a collector 23 composed of copper foil, etc., the present inventors focused on a copolymer (P) formed by copolymerizing a monomer (a1) composed of a non-ionic compound having only one ethylenically unsaturated bond and a monomer (a2) composed of a compound having a carboxyl group and only one ethylenically unsaturated bond, and conducted in-depth research on a binder composition for non-aqueous secondary batteries containing this copolymer.

[0061] As a result, it was found that a non-aqueous secondary battery binder composition containing a copolymer (P) obtained by copolymerizing a raw material monomer (a) containing the monomers (a1) and (a2) and a polyrotaxane can be used.

[0062] Figure 2 This is a schematic diagram for explaining the polyrotaxane used as a raw material for the binder composition for a non-aqueous secondary battery of the present invention.

[0063] Figure 2 The polyrotaxane 2 shown includes a "cyclic molecule 51 having a cyclic skeleton" and a "chain molecule 53 penetrating an opening 55 of the cyclic molecule 51 and having blocking groups 52 at both ends." Figure 2 In FIG, the symbol 54 represents a modification group. The polyrotaxane 2 may not have the modification group 54.

[0064] In the use of the copolymer (P) containing "the copolymer (P) obtained by copolymerizing the raw material monomer (a) containing the above-mentioned monomer (a1) and monomer (a2)" Figure 2 In the binder 25 contained in the electrode 20 manufactured from the binder composition for a non-aqueous secondary battery containing the polyrotaxane 2″ shown in FIG. 2 , the cyclic molecules 51 contained in the polyrotaxane 2 are movable relative to the chain molecules 53. Therefore, when stress is applied to the binder 25, the cyclic molecules 51 of the polyrotaxane 2 contained in the binder 25 are movable relative to the chain molecules 53 (pulley effect), thereby dissipating the stress. Furthermore, when the cyclic molecules 51 in the binder 25 are movable due to the stress applied to the binder 25 and the distance between the cyclic molecules 51 on the chain molecules 53 is shortened, the binder 25 exhibits an air spring effect that attempts to maintain the distance between the cyclic molecules 51 on the chain molecules 53, thereby restoring the distance.

[0065] Therefore, the binder 25 has the ability to follow the expansion and contraction of the electrode active material 22 caused by the polyrotaxane 2 during use of the non-aqueous secondary battery. As a result, in the electrode active material layer 24 containing the binder 25, it is estimated that the following can be obtained: <1> and <2> function.

[0066] <1> Due to the followability caused by the polyrotaxane 2, the retention force of the electrode active material 22 brought about by the binder 25 between the electrode active materials 22 in the electrode active material layer 24 and between the electrode active material 22 and the current collector 23 is improved. Even if the electrode active material 22 expands or contracts, the adhesion between the electrode active materials 22 and between the electrode active materials 22 and the current collector 23 can be maintained for a long time.

[0067] <2> Even if the electrode active material layer 24 expands and contracts along with the expansion and contraction of the electrode active material 22, the conformability of the polyrotaxane 2 effectively enables the structural units derived from the monomers (a1) and (a2) in the copolymer (P) to effectively exert their adhesion to the current collector 23, making it difficult for the electrode active material layer 24 to peel off from the current collector 23.

[0068] Furthermore, the present inventors produced an electrode 20 using a binder composition for a non-aqueous secondary battery containing the copolymer (P) and polyrotaxane 2, and confirmed that a non-aqueous secondary battery having the electrode 20 had excellent cycle characteristics, thereby arriving at the present invention.

[0069] The following describes in detail the binder composition for aqueous secondary batteries, the slurry for nonaqueous secondary battery electrodes, the nonaqueous secondary battery electrodes, the nonaqueous secondary batteries, and the method for producing the binder composition for nonaqueous secondary batteries of the present invention. The present invention is not limited to the embodiments described below.

[0070] Here, the following terms used in this specification are explained.

[0071] "(Meth)acrylic acid" is a general term for acrylic acid and methacrylic acid. "(Meth)acrylate" is a general term for acrylate and methacrylate.

[0072] Unless otherwise specified, the term "ethylenically unsaturated bond" refers to an ethylenically unsaturated bond that is free radical polymerizable.

[0073] In a polymer formed using a compound having an ethylenically unsaturated bond, a structural unit derived from the compound having an ethylenically unsaturated bond refers to a structural unit in which the chemical structure of the portion of the compound having an ethylenically unsaturated bond other than the ethylenically unsaturated bond is identical to the chemical structure of the portion of the structural unit in the polymer other than the portion corresponding to the ethylenically unsaturated bond. The ethylenically unsaturated bond of the compound is converted to a single bond during polymer formation. For example, in a polymer of methyl methacrylate, the structural unit derived from methyl methacrylate is represented by -CH2-C(CH3)(COOCH3)-.

[0074] In the case of a polymer of a compound having an ionic functional group and an ethylenically unsaturated bond, for example, a structural unit having an ionic functional group such as a carboxyl group, as in the second structural unit described below, is considered to be a structural unit derived from the same ionic compound, even if a portion of the functional group is ion-exchanged or not. For example, a structural unit represented by -CH2-C(CH3)(COONa)- is also considered to be a structural unit derived from methacrylic acid.

[0075] In addition, for compounds having multiple independent ethylenically unsaturated bonds, the structural units of the polymers of the compounds may also have one or more ethylenically unsaturated bonds remaining within the structural units. For example, in the case of a divinylbenzene polymer, the structural unit derived from divinylbenzene may have a structure without ethylenically unsaturated bonds (a form in which the portions corresponding to both ethylenically unsaturated bonds of divinylbenzene are incorporated into the polymer chain), or a structure with one ethylenically unsaturated bond (a form in which only the portion corresponding to one ethylenically unsaturated bond is incorporated into the polymer chain). Here, multiple independent ethylenically unsaturated bonds refer to multiple ethylenically unsaturated bonds that do not form a conjugated diene with each other.

[0076] Furthermore, if, after polymerization, portions other than the chain structure corresponding to the ethylenically unsaturated bond in the polymer, such as functional groups such as carboxyl groups, become no longer corresponding to the chemical structure of the monomer due to a chemical reaction, the structural units of the polymer are regarded as structural units derived from compounds having ethylenically unsaturated bonds in the polymer. For example, if vinyl acetate is saponified after polymerization, the structural units of the polymer are regarded as structural units derived from vinyl alcohol, not structural units derived from vinyl acetate, based on the chemical structure of the polymer.

[0077] In the present embodiment, the "class" given to a compound name refers to a group of compounds containing the structure of the compound, and also includes the compound having a substituent.

[0078] <1. Binder composition for non-aqueous secondary batteries>

[0079] The binder composition for a non-aqueous secondary battery of the present embodiment (hereinafter sometimes referred to as "binder composition") comprises a copolymer (P) having a first structural unit and a second structural unit described below and Figure 2 The adhesive composition of this embodiment may contain an aqueous medium, and preferably, the copolymer (P) and the polyrotaxane 2 are separately dispersed in the aqueous medium described below. The adhesive composition of this embodiment may also contain no aqueous medium and be composed of a non-volatile component containing the copolymer (P) having the first structural unit and the second structural unit and the polyrotaxane 2.

[0080] The adhesive composition of this embodiment may contain other components together with the copolymer (P) having the first structural unit and the second structural unit and the polyrotaxane 2. Specifically, the adhesive composition of this embodiment may contain, as other components, for example, a polymer not having the first structural unit and / or the second structural unit, a surfactant, and a component for synthesizing the copolymer (P).

[0081] (Copolymer (P))

[0082] The copolymer (P) contained in the adhesive composition of this embodiment has at least a first structural unit derived from a monomer (a1) shown below and a second structural unit derived from a monomer (a2) shown below.

[0083] The copolymer (P) contained in the adhesive composition of this embodiment may contain, in addition to the first structural unit and the second structural unit, a third structural unit derived from a monomer (a3) composed of a compound having multiple independent ethylenically unsaturated bonds that does not belong to monomer (a1) or monomer (a2) and / or a fourth structural unit derived from another monomer (a4) that does not belong to any of monomers (a1) to (a3).

[0084] [First structural unit]

[0085] The first structural unit in the copolymer (P) contained in the adhesive composition of this embodiment is derived from the monomer (a1).

[0086] Monomer (a1) is a nonionic compound having only one ethylenically unsaturated bond. That is, monomer (a1) is a compound having neither anionic functional groups nor cationic functional groups. The silane compound is considered not to be included in monomer (a1). Monomer (a1) may be a single compound or a combination of two or more compounds.

[0087] As monomer (a1), at least one of a (meth)acrylate and an aromatic compound having an ethylenically unsaturated bond is preferably used, and a combination of the two compounds is more preferred. The (meth)acrylate is more preferably an alkyl (meth)acrylate. The alkyl group in the alkyl (meth)acrylate preferably has 1 to 20 carbon atoms. In this case, monomers (a1) other than the alkyl (meth)acrylate and the aromatic compound having an ethylenically unsaturated bond, as described below, may also be used in combination.

[0088] As the (meth)acrylate used as the monomer (a1), the (meth)acrylate alkyl esters included include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, tert-butyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isobornyl (meth)acrylate, lauryl (meth)acrylate, and stearyl (meth)acrylate. Among these, 2-ethylhexyl acrylate is preferably included in order to form a binder composition capable of forming an electrode active material layer 24 having excellent electrolyte resistance.

[0089] Examples of the aromatic compound having an ethylenically unsaturated bond used in monomer (a1) include styrene, tert-butylstyrene, α-methylstyrene, p-methylstyrene, and 1,1-diphenylethylene. When monomer (a1) contains an aromatic vinyl compound, it is more preferable to contain at least one of styrene and α-methylstyrene. Styrene is further preferably contained because it has excellent dispersibility in aqueous media and a non-aqueous secondary battery having the electrode 20 manufactured using the binder composition of this embodiment has even better cycle characteristics.

[0090] Examples of the monomer (a1) other than (meth)acrylates and aromatic compounds having an ethylenically unsaturated bond include compounds having an ethylenically unsaturated bond and a nonionic polar functional group, aliphatic hydrocarbon compounds having an ethylenically unsaturated bond, and alicyclic hydrocarbon compounds having an ethylenically unsaturated bond.

[0091] The polar functional group in the compound having an ethylenically unsaturated bond and a polar functional group used as the monomer (a1) preferably contains at least one of a hydroxyl group and a cyano group, and more preferably contains a hydroxyl group.

[0092] Examples of the compound having an ethylenically unsaturated bond and a polar functional group used as monomer (a1) include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and (meth)acrylonitrile. 2-hydroxyethyl methacrylate is preferably contained because good polymerization stability can be obtained when producing the copolymer (P).

[0093] [Second structural unit]

[0094] The second structural unit in the copolymer (P) contained in the adhesive composition of this embodiment is derived from the monomer (a2).

[0095] The monomer (a2) is a compound having only one ethylenically unsaturated bond and a carboxyl group. The monomer (a2) may be a single compound or a combination of two or more compounds.

[0096] As the monomer (a2), a compound having a plurality of carboxyl groups in one molecule may be used. That is, the copolymer (P) may contain a plurality of carboxyl groups in one structural unit.

[0097] Examples of the monomer (a2) having a carboxyl group include unsaturated monocarboxylic acids such as methacrylic acid, acrylic acid, and crotonic acid; and unsaturated dicarboxylic acids such as itaconic acid and fumaric acid. Among these, since the monomer (a2) can form a binder composition that can form an electrode 20 with good adhesion between the electrode active materials 22 and between the electrode active materials 22 and the current collector 23, it is preferred to use at least one of acrylic acid, methacrylic acid, and itaconic acid.

[0098] At least a portion of the structural units derived from monomer (a2) may also form a salt with an alkaline substance. Examples of monomers (a2) that form salts include metal salts and ammonium salts of monomer (a2). Examples of metals in the metal salts include alkali metals such as lithium, sodium, and potassium. Specific compounds include lithium (meth)acrylate, lithium itaconate, dilithium itaconate, sodium (meth)acrylate, sodium itaconate, disodium itaconate, ammonium (meth)acrylate, ammonium itaconate, and diammonium itaconate.

[0099] [Third structural unit]

[0100] The copolymer (P) contained in the adhesive composition of this embodiment may also have a third structural unit as an arbitrary structural unit. The third structural unit is derived from monomer (a3). Monomer (a3) is a compound having a plurality of independent ethylenically unsaturated bonds. "Independent" means that it is not a conjugated double bond like that possessed by 1,3-butadiene. Therefore, monomer (a3) is a compound that can form a cross-linked structure in free radical polymerization with monomer (a1) and monomer (a2). Monomer (a3) does not belong to any of monomer (a1) and monomer (a2). As monomer (a3), only one compound may be used, or two or more different compounds may be used.

[0101] Examples of monomer (a3) include compounds having two ethylenically unsaturated bonds, such as divinylbenzene, ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and 2-hydroxy-3-acryloyloxypropyl methacrylate, and compounds having three or more ethylenically unsaturated bonds, such as trimethylolpropane tri(meth)acrylate. Since good polymerization stability can be achieved when producing the copolymer (P), a non-aqueous secondary battery having an electrode 20 produced using a binder composition containing the copolymer (P) has lower internal resistance and excellent cycle characteristics, it is preferred to use at least one of divinylbenzene and trimethylolpropane triacrylate as the monomer (a3).

[0102] [Other monomers (a4)]

[0103] Other monomers (a4) are monomers that do not belong to any of monomers (a1) to (a3). Examples of other monomers (a4) include, but are not limited to, compounds having only one ethylenically unsaturated bond and an anionic functional group other than a carboxyl group, such as a sulfonic group or a phosphoric group, surfactants having an ethylenically unsaturated bond (hereinafter sometimes referred to as "polymerizable surfactants"), and compounds having an ethylenically unsaturated bond and functioning as a silane coupling agent.

[0104] Examples of the compound having only one ethylenically unsaturated bond and a sulfonic group include aromatic vinyl compounds having a sulfonic group and aromatic vinyl compounds having a sulfonic group in the form of salts. Among these, at least one of p-vinylbenzenesulfonic acid and p-vinylbenzenesulfonic acid salts is preferably used, and p-vinylbenzenesulfonic acid salts are more preferably used. Sodium p-vinylbenzenesulfonate is more preferably used because it provides good polymerization stability when producing the copolymer (P).

[0105] As the polymerizable surfactant as an example of other monomer (a4), a compound having an ethylenically unsaturated bond and having a function as a surfactant can be used.

[0106] Examples of the polymerizable surfactant include compounds represented by the following chemical formulas (1) to (4).

[0107]

[0108] In formula (1), R 1 is an alkyl group. p is an integer from 10 to 40. 1 An alkyl group having 10 to 40 carbon atoms is preferred, and a linear unsubstituted alkyl group having 10 to 40 carbon atoms is more preferred.

[0109]

[0110] In formula (2), R 2 is an alkyl group. q is an integer from 10 to 12. 2 It is preferably an alkyl group having 10 to 40 carbon atoms, more preferably a linear unsubstituted alkyl group having 10 to 40 carbon atoms. Examples of the compound represented by formula (2) include polyoxyethylene alkyl ether sulfate (Aqualon KH-10 manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.).

[0111]

[0112] In formula (3), R 3 M is an alkyl group. 1 It is NH4 or Na.3 An alkyl group having 10 to 40 carbon atoms is preferred, and a linear unsubstituted alkyl group having 10 to 40 carbon atoms is more preferred.

[0113]

[0114] In formula (4), R 4 M is an alkyl group. 2 It is NH4 or Na. 4 An alkyl group having 10 to 40 carbon atoms is preferred, and a linear unsubstituted alkyl group having 10 to 40 carbon atoms is more preferred.

[0115] Examples of the compound having an ethylenically unsaturated bond and functioning as a silane coupling agent as another monomer (a4) include vinyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, vinyltriethoxysilane, and γ-methacryloxypropyltriethoxysilane.

[0116] [Content of each structural unit in the copolymer (P)]

[0117] The content of each structural unit in the copolymer (P) contained in the adhesive composition of the present embodiment is considered to be the same as the content of each monomer in the total amount of monomer components used to produce the copolymer (P).

[0118] (Content ratio of the first structural unit in all structural units)

[0119] The content of the first structural unit in all the structural units of the copolymer (P) (in other words, the content of the monomer (a1) in the total amount of the monomer components used in the manufacture of the copolymer (P)) is preferably 60% by mass or more, more preferably 70% by mass or more, further preferably 75% by mass or more, and particularly preferably 80% by mass or more. This is because better polymerization stability can be obtained when manufacturing the copolymer (P). The content of the first structural unit in all the structural units is preferably 97% by mass or less, more preferably 95% by mass or less, and further preferably 94% by mass or less. This is because it can be formed into a binder composition of an electrode 20 with good bonding between the electrode active material 22 and between the electrode active material 22 and the collector 23.

[0120] Regarding the composition of the monomer (a1), it is preferred to appropriately adjust the type and amount of the compound in order to adjust the glass transition temperature of the copolymer (P) or to adjust the polymerization rate according to the molecular design.

[0121] Specifically, when monomer (a1) contains an aromatic compound having an ethylenically unsaturated bond, the content of the structural unit derived from the aromatic compound having an ethylenically unsaturated bond in all structural units is preferably 36% by mass or more, more preferably 41% by mass or more, and even more preferably 43% by mass or more. This is because the copolymer (P) has excellent dispersibility when producing a PSA composition dispersed in an aqueous medium.

[0122] (Content ratio of the second structural unit in all structural units)

[0123] The content of the second structural unit in all the structural units of the copolymer (P) (in other words, the content of the monomer (a2) in the total amount of the monomer components used in the manufacture of the copolymer (P)) is preferably 0.10% by mass or more, more preferably 1.0% by mass or more, further preferably 3.0% by mass, and particularly preferably 4.0% by mass or more. This is because it is a binder composition that can form an electrode 20 with better adhesion between the electrode active material 22 and between the electrode active material 22 and the collector 23. The content of the second structural unit in all the structural units is preferably 20% by mass or less, more preferably 15% by mass or less, and further preferably 10% by mass or less. This is because better polymerization stability can be obtained when manufacturing the copolymer (P).

[0124] (Content ratio of the third structural unit in all structural units)

[0125] In the case where the copolymer (P) contained in the adhesive composition of the present embodiment contains the third structural unit, the content of the third structural unit in all the structural units of the copolymer (P) (in other words, the content of the monomer (a3) in the total amount of the monomer components used to manufacture the copolymer (P)) is preferably 0.010% by mass or more, more preferably 0.020% by mass or more, and even more preferably 0.030% by mass or more. This is because it is possible to significantly obtain the effect of monomer (a3) as an internal crosslinking agent, suppress the degradation of the copolymer (P), and become a copolymer (P) that can be used as a binder composition material for a non-aqueous secondary battery that can obtain better cycle characteristics. The content of the third structural unit in all the structural units of the copolymer (P) is preferably 10% by mass or less, more preferably 5.0% by mass or less, further preferably 1.0% by mass or less, and particularly preferably 0.1% by mass or less. This is because it is possible to suppress the gelation of the copolymer (P).

[0126] (Content ratio of the fourth structural unit in all structural units)

[0127] The copolymer (P) contained in the adhesive composition of the present embodiment contains the 4th structural unit from other monomers (a4). When the other monomers (a4) are compounds having only one ethylenically unsaturated bond and a sulfonic group, the content of the 4th structural unit in all the structural units of the copolymer (P) (in other words, the content of the monomer (a4) in the total amount of the monomer components used to manufacture the copolymer (P)) is preferably 0.10% by mass or more, more preferably 0.20% by mass or more, and even more preferably 0.30% or more. This is because good polymerization stability can be obtained when manufacturing the copolymer (P). The content of the 4th structural unit in all the structural units of the copolymer (P) is preferably 5.0% by mass or less, more preferably 3.0% by mass or less, and further preferably 1.0% by mass or less. This is because the particle size, viscosity, etc. of the copolymer (P) can be adjusted appropriately.

[0128] The copolymer (P) of the present embodiment contains the 4th structural unit from other monomers (a4). When other monomers (a4) are polymerizable surfactants, the content of the 4th structural unit in all the structural units of the copolymer (P) (in other words, the content of the monomer (a4) in the total amount of the monomer components for manufacturing the copolymer (P)) is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and further preferably 0.08% by mass or more. This is because the effect of containing a polymerizable surfactant is made significant, and good polymerization stability is obtained when manufacturing the copolymer (P). The content of the 4th structural unit in all the structural units of the copolymer (P) is preferably 5.0% by mass or less, more preferably 3.0% by mass or less, further preferably 1.0% by mass or less, and particularly preferably 0.5% by mass. This is because it is appropriate to adjust the particle size, viscosity, etc. of the copolymer (P).

[0129] [Glass transition temperature (Tg) of copolymer (P)]

[0130] The glass transition temperature (Tg) of the copolymer (P) contained in the adhesive composition of this embodiment is measured using a differential scanning calorimetry (DSC) apparatus (EXSTAR DSC / SS7020 manufactured by Hitachi High-Tech Sciences, Ltd.) at a heating rate of 10°C / min in a nitrogen atmosphere, and is measured as the peak temperature of a DDSC chart obtained by temperature differentiation of the DSC.

[0131] The glass transition temperature (Tg) of the copolymer (P) is preferably -30°C or higher, more preferably -10°C or higher. This is because a non-aqueous secondary battery having the electrode 20 produced using the binder composition containing the copolymer (P) has excellent cycle characteristics.

[0132] The glass transition temperature (Tg) of the copolymer (P) is preferably 100° C. or lower, more preferably 50° C. or lower, and even more preferably 40° C. or lower. This is because the film-forming properties of the binder composition are improved, and a non-aqueous secondary battery including an electrode 20 manufactured using the binder composition has more excellent cycle characteristics.

[0133] [Average particle size d50 of emulsified particles containing copolymer (P)]

[0134] The copolymer (P) contained in the binder composition of this embodiment preferably contains emulsified particles (dispersed particles) of the copolymer (P) when the binder composition contains an aqueous medium described below. The average particle size d50 of the emulsified particles containing the copolymer (P) contained in the binder composition of this embodiment is preferably 0.18 μm or greater, more preferably 0.20 μm or greater. When the average particle size d50 is 0.18 μm or greater, the electrode 20 can be formed in which the electrode active material layer 24 is more difficult to peel off from the current collector 23.

[0135] The average particle size d50 of the emulsified particles containing the copolymer (P) is preferably 1.0 μm or less, more preferably 0.80 μm or less, even more preferably 0.60 μm or less, and particularly preferably 0.50 μm or less. When the average particle size d50 of the emulsified particles containing the copolymer (P) is 1.0 μm or less, when pressing an electrode sheet having an electrode active material layer 24 formed on a current collector 23 to manufacture the electrode 20 using the binder composition, the pressing can be performed under appropriate pressing conditions. As a result, the electrode active material layer 24 can be firmly connected to the current collector 23.

[0136] The average particle size d50 of the emulsified particles containing the copolymer (P) can be adjusted by known methods. For example, it can be adjusted by adjusting the amount of surfactant added when producing the copolymer (P) by emulsion polymerization, the selection of raw material monomers, etc. By using the emulsion polymerization method, it is possible to easily produce an adhesive composition containing emulsified particles containing the copolymer (P).

[0137] [Method for producing copolymer (P)]

[0138] The copolymer (P) contained in the adhesive composition of this embodiment can be produced by the method shown below, for example.

[0139] The copolymer (P) can be produced by copolymerizing raw material monomers comprising monomers (a1) and (a2), and optionally monomers (a3) composed of a compound having multiple independent ethylenically unsaturated bonds and / or other monomers (a4) (polymerization step). Hereinafter, the monomers (components (a1) to (a4)) used to synthesize the copolymer (P) may be collectively referred to as raw material monomers (a).

[0140] Examples of methods for copolymerizing the raw material monomer (a) include emulsion polymerization, in which the raw material monomer (a) is emulsion-polymerized in an aqueous medium (b). When producing the copolymer (P) by emulsion polymerization, in addition to the raw material monomer (a) and the aqueous medium (b), components such as a non-polymerizable surfactant (c), an alkaline substance (d), a radical polymerization initiator (e), and a chain transfer agent (f) may be used.

[0141] [Aqueous medium (b)]

[0142] The aqueous medium (b) is one selected from water, a hydrophilic solvent, and a mixture containing water and a hydrophilic solvent. Examples of the hydrophilic solvent include methanol, ethanol, isopropanol, and N-methylpyrrolidone. From the perspective of polymerization stability, the aqueous medium (b) is preferably water. As the aqueous medium (b), a mixture of water with a hydrophilic solvent added thereto may also be used, as long as the polymerization stability is not impaired.

[0143] [Non-polymerizable surfactant (c)]

[0144] When the copolymer (P) is manufactured by emulsion polymerization, a non-polymerizable surfactant (c) may be added to the solution containing the aqueous medium (b) and the raw monomer (a) for emulsion polymerization. The non-polymerizable surfactant (c) is a surfactant (c) that does not have a polymerizable unsaturated bond in its chemical structure. The surfactant (c) can improve the dispersion stability of the solution during the emulsion polymerization process and / or the dispersion (emulsion) obtained after polymerization. As the surfactant (c), an anionic surfactant or a nonionic surfactant is preferably used.

[0145] Examples of the anionic surfactant include alkylbenzenesulfonates, alkylsulfate ester salts, polyoxyethylene alkyl ether sulfate ester salts, and fatty acid salts.

[0146] Examples of the nonionic surfactant include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene polycyclic phenyl ethers, polyoxyalkylene alkyl ethers, sorbitan fatty acid esters, and polyoxyethylene sorbitan fatty acid esters.

[0147] The surfactant (c) may be used alone or in combination of two or more.

[0148] [Alkaline substances (d)]

[0149] When producing the copolymer (P) by emulsion polymerization, an alkaline substance (d) may be added to the solution to be emulsion-polymerized containing the aqueous medium (b) and the raw material monomer (a) and / or the dispersion after emulsion polymerization. The addition of the alkaline substance (d) neutralizes the acidic components contained in the raw material monomer (a). As a result, the pH of the solution during emulsion polymerization and / or the dispersion after emulsion polymerization is within an appropriate range, and the stability of the solution during emulsion polymerization and / or the dispersion after emulsion polymerization is good.

[0150] Examples of the alkaline substance (d) added to the solution during emulsion polymerization and / or the dispersion after emulsion polymerization include ammonia, triethylamine, sodium hydroxide, lithium hydroxide, etc. These alkaline substances (d) may be used alone or in combination of two or more.

[0151] [Radical polymerization initiator (e)]

[0152] The radical polymerization initiator (e) used when producing the copolymer (P) by emulsion polymerization is not particularly limited, and known initiators can be used. Examples of the radical polymerization initiator (e) include persulfates such as ammonium persulfate and potassium persulfate; hydrogen peroxide; azo compounds; and organic peroxides such as tert-butyl hydroperoxide, tert-butyl peroxybenzoate, and cumene hydroperoxide.

[0153] In the present embodiment, when the copolymer (P) is produced by emulsion polymerization, redox polymerization may be carried out using a reducing agent such as sodium bisulfite, rongalite, or ascorbic acid together with the radical polymerization initiator (e).

[0154] Relative to 100 parts by mass of raw monomer (a), the addition amount of free radical polymerization initiator (e) (including reducing agent when using reducing agent in combination) is preferably 0.001 parts by mass or more, more preferably 0.002 parts by mass or more. This is because when copolymer (P) is manufactured by emulsion polymerization, the conversion rate of raw monomer (a) to copolymer (P) can be increased. Relative to 100 parts by mass of raw monomer (a), the addition amount of free radical polymerization initiator (e) is preferably 10 parts by mass or less, more preferably 5 parts by mass or less. This is because the molecular weight of copolymer (P) can be increased, and the swelling rate of the electrode 20 manufactured using the adhesive composition of the present embodiment to the electrolyte can be reduced.

[0155] [Chain transfer agent (f)]

[0156] The chain transfer agent (f) used when producing the copolymer (P) by emulsion polymerization is used to adjust the molecular weight of the copolymer (P) obtained by emulsion polymerization. Examples of the chain transfer agent (f) include n-dodecyl mercaptan, t-dodecyl mercaptan, n-butyl mercaptan, 2-ethylhexyl thioglycolate, 2-mercaptoethanol, β-mercaptopropionic acid, methanol, n-propanol, isopropanol, t-butanol, and benzyl alcohol.

[0157] [Emulsion polymerization method]

[0158] As the emulsion polymerization method used when producing the copolymer (P), for example, a method in which each component used in the emulsion polymerization is continuously supplied to a reaction vessel while the emulsion polymerization is carried out can be cited. The temperature of the emulsion polymerization is not particularly limited, but is, for example, 30 to 90°C, preferably 50 to 85°C, and more preferably 55 to 80°C. The emulsion polymerization is preferably carried out while stirring. In addition, in order to make the concentrations of the raw material monomer (a) and the free radical polymerization initiator (e) in the solution during the emulsion polymerization uniform, it is preferred that the raw material monomer (a) and the free radical polymerization initiator (e) are continuously supplied to the solution during the emulsion polymerization.

[0159] (Polyrotaxane)

[0160] like Figure 2 As shown, the polyrotaxane 2 included in the adhesive composition of this embodiment includes a cyclic molecule 51 having a cyclic skeleton and a chain molecule 53 that penetrates the opening 55 of the cyclic molecule 51. The chain molecule 53 has a blocking group 52 at both ends. The polyrotaxane 2 may or may not contain an ethylenically unsaturated bond. In other words, the polyrotaxane 2 may or may not be polymerizable. One type of polyrotaxane 2 may be used alone or in combination of two or more types. Even if the polyrotaxane 2 contains an ethylenically unsaturated bond, the polyrotaxanes 2 will not polymerize to form a polymer in the adhesive composition.

[0161] The binder composition of this embodiment, when the copolymer (P) and polyrotaxane 2 are dispersed in the aqueous medium (B) described later, can be easily produced compared to, for example, particles having a structural unit derived from a polyrotaxane in the copolymer, particles obtained by copolymerizing a polyrotaxane with a raw material monomer, and binder compositions containing an aqueous medium. Furthermore, the content of polyrotaxane 2 in the binder composition has a high degree of freedom, and thus the content of polyrotaxane 2 can be appropriately adjusted depending on the intended use, etc.

[0162] like Figure 2As shown, the cyclic molecules 51 possessed by the polyrotaxane 2 have openings 55 through which the chain molecules 53 can penetrate. The cyclic molecules 51 can move along the chain molecules 53 while being penetrated by the chain molecules 53. The number of cyclic molecules 51 possessed by one molecule of the polyrotaxane 2 is not particularly limited, and may be, for example, 1 to 500, 5 to 300, or 10 to 200. In the case where the number of cyclic molecules 51 is plural, the cyclic molecules 51 possessed by the polyrotaxane 2 may be only one type, or may be two or more types. As Figure 2 As shown in FIG, a modification group 54 may also be bonded to the cyclic skeleton of the cyclic molecule 51. Figure 2 As shown, the modifying group 54 may be bonded to all of the cyclic molecules 51 or may be bonded to only a portion of the cyclic molecules 51 .

[0163] At least one of the cyclic skeletons of the cyclic molecule 51 is preferably a crown ether skeleton, a cyclic siloxane skeleton, or a cyclic oligosaccharide skeleton. Of these, the cyclic skeleton is more preferably a cyclic oligosaccharide skeleton. This is because, by reacting a predetermined compound having an epoxy group with a hydroxyl group of the cyclic skeleton, a modifying group 54 can be easily introduced into the cyclic skeleton. Among cyclic oligosaccharide skeletons, an α-cyclodextrin skeleton is particularly preferred because it can more easily introduce a modifying group 54.

[0164] Various organic groups can be exemplified as the modifying group 54 bonded to the cyclic skeleton of the cyclic molecule 51. Examples of the organic group include hydrocarbon groups having one or more carbon atoms that may have one or more substituents. Specifically, examples include acetyl groups, butyl ester groups, hexyl ester groups, octadecyl ester groups, hydroxyl groups, amino groups, amide groups, carboxyl groups, and mercapto groups.

[0165] When the polyrotaxane 2 has an ethylenically unsaturated bond, the modifying group 54 bonded to the cyclic skeleton of the cyclic molecule 51 preferably has a group containing an ethylenically unsaturated bond. At least one of the groups containing an ethylenically unsaturated bond is preferably a (meth)acryloyl group, a vinyl group, an allyl group, or an acryloyl group. Since this allows for a binder composition that can form the electrode 20 with improved adhesion between the electrode active materials 22 and between the electrode active materials 22 and the current collector 23, a (meth)acryloyl group is more preferred, and an acryloyl group is even more preferred.

[0166] The group containing an ethylenically unsaturated bond bonded to the cyclic skeleton may be bonded directly to the cyclic skeleton. Alternatively, the group containing an ethylenically unsaturated bond bonded to the cyclic skeleton may be bonded to the cyclic skeleton via an arbitrary linking group.

[0167] The polyrotaxane 2 may be a polyrotaxane having no ethylenically unsaturated bond.

[0168] The chain molecules 53 of the polyrotaxane 2 may be linear or branched.

[0169] The chain molecule 53 is preferably at least one selected from polyethylene glycol, polypropylene glycol, polyisoprene, polyisobutylene, polybutadiene, polytetramethylene glycol, polyacrylate, polydimethylsiloxane, polyethylene, polypropylene, and polycaprolactone. Polyethylene glycol is more preferable because it can function well as the chain molecule 53 enclosed in the cyclic molecule 51 of the polyrotaxane 2.

[0170] The weight average molecular weight of the chain molecule 53 is preferably 5000 to 50000, more preferably 7500 to 40000. If the weight average molecular weight of the chain molecule 53 is 5000 or more, the length of the chain molecule 53 can be sufficiently ensured. Therefore, in the adhesive composition, the distance that the cyclic molecule 51 can move relative to the chain molecule 53 becomes sufficiently long. As a result, the adhesive composition becomes better able to follow the expansion and contraction of the electrode active material 22. If the weight average molecular weight of the chain molecule 53 is 50000 or less, the copolymer (P) contained in the adhesive composition has good compatibility with the polyrotaxane 2, and therefore it is preferred.

[0171] The blocking groups 52 of the polyrotaxane 2 have the function of preventing the cyclic molecule 51 from being separated from the chain molecule 53 due to their high bulk and ionicity. The blocking groups 52 disposed at both ends of the chain molecule 53 may be the same or different.

[0172] As the blocking group 52, which prevents the cyclic molecule 51 from separating from the chain molecule 53 due to its large size, a group having a ring structure can be cited. At least one of the blocking groups 52 is preferably a dinitrophenyl group, an adamantyl group, a triphenylmethyl group, or a derivative thereof. Since the polyrotaxane 2 is easily manufactured, an adamantyl group (either 1-adamantyl or 2-adamantyl) is more preferably cited. The blocking group 52 may have one or more substituents. Examples of substituents that the blocking group 52 may have include alkyl groups, alkoxy groups, hydroxyl groups, halogen groups, cyano groups, sulfonyl groups, carboxyl groups, amino groups, and phenyl groups.

[0173] The weight-average molecular weight of polyrotaxane 2 is preferably 100,000 to 1,000,000, and more preferably 150,000 to 900,000. When the weight-average molecular weight of polyrotaxane 2 is 100,000 or greater, the elasticity of the composite particles (P) is suitable. When the weight-average molecular weight of polyrotaxane 2 is 1,000,000 or less, the compatibility between the copolymer contained in the composite particles (P) and polyrotaxane 2 is good, which is preferred.

[0174] The polyrotaxane 2 can be produced using a known method.

[0175] Commercially available products may be used as the polyrotaxane 2. Examples of commercially available polyrotaxane 2 include "Selmu (registered trademark) Super Polymer SH2400P", "Selmu (registered trademark) Super Polymer SH3400P", and "Selmu (registered trademark) Super Polymer" commercially available from Advanced Semiconductor Manufacturing Co., Ltd.ーSH1300P", "セルム(registered trademark)スーパーポリマーSM3403P", "セルム(registered trademark)スーパーポリマー"SM1313P", "セルム(registered trademark)スーパーポリマーSA3403P", "セルム(registered trademark)スーパーポリマーSA 2403P", "セルム(registered trademark)スーパーポリマーSA 1313P", "セルム(registered trademark)スーパーポリマーSM3405P", "セルム(registered trademark)キー・ミクスチャーSM3 400C", "セルム(registered trademark)スーパーポリマーSA3405P", "セルム(registered trademark)スーパーポリマーSA2405 P", "セルム(registered trademark)キー·ミクスチャーSA3400C", "セルム(registered trademark)キー·ミクスチャーSA2400C ", "セルム(registered trademark)スーパーポリマーSA3405P" and "セルム(registered trademark)スーパーポリマーSA2405P" etc.

[0176] Among these commercially available polyrotaxanes 2, SERUM (registered trademark) Super Polymer SH2400P and / or SERUM (registered trademark) Key Micro Shaker SA2400C are preferably used because they can form a binder composition that can form an electrode 20 with better adhesion between the electrode active materials 22 and between the electrode active materials 22 and the current collector 23.

[0177] The weight-average molecular weight of セルム (registered trademark) Super Polymer SH2400P is 400,000. This polyrotaxane 2 contains a cyclic molecule 51 having a cyclic skeleton composed of an α-cyclodextrin skeleton and a chain molecule 53 formed from polyethylene glycol having a weight-average molecular weight of 20,000 and having adamantyl groups as blocking groups 52 at both ends, and does not have an ethylenically unsaturated bond.

[0178] Celum (registered trademark) Key Microstructure SA2400C has an ethylenically unsaturated bond and a weight-average molecular weight of 600,000. This polyrotaxane 2 comprises a cyclic molecule 51 having a cyclic skeleton composed of an α-cyclodextrin backbone, and a chain molecule 53 formed from polyethylene glycol with a weight-average molecular weight of 20,000, having adamantyl groups as blocking groups 52 at both ends. The chain molecule 53 also has an acryloyl group bonded to the cyclic skeleton of the cyclic molecule 51.

[0179] (Content of Polyrotaxane 2 in Adhesive Composition)

[0180] The content of polyrotaxane 2 relative to the amount of copolymer (P) in the adhesive composition of this embodiment is considered to be the same as the ratio of the mass of polyrotaxane 2 used in the production of the copolymer (P) to the total mass of the monomer components. In this embodiment, the content of polyrotaxane 2 is expressed based on 100 parts by mass of the copolymer (P) contained in the adhesive composition of this embodiment (in other words, the monomer components used in the production of the copolymer (P)).

[0181] When the content of polyrotaxane 2 is 0.10 parts by mass or more relative to 100 parts by mass of the copolymer (P), the effect of the binder composition containing polyrotaxane 2 is significant, resulting in a binder composition that can form an electrode 20 with better adhesion between the electrode active materials 22 and between the electrode active materials 22 and the current collector 23, which is preferred. From this viewpoint, the content of polyrotaxane 2 is more preferably 0.20 parts by mass or more, more preferably 0.30 parts by mass or more, and particularly preferably 1.0 parts by mass or more. In addition, the content of polyrotaxane 2 can be 3.0 parts by mass or more, or 5.0 parts by mass or more.

[0182] Furthermore, when the content of the polyrotaxane 2 is 50 parts by mass or less relative to 100 parts by mass of the copolymer (P), the content of the copolymer (P) in the binder composition can be sufficiently ensured, and the non-aqueous secondary battery including the electrode 20 containing the binder composition has lower internal resistance, which is preferred. From this viewpoint, the content of the polyrotaxane 2 is more preferably 30 parts by mass or less, further preferably 15 parts by mass or less, and particularly preferably 10 parts by mass or less.

[0183] In short, the content of the polyrotaxane 2 is preferably from 0.10 to 50 parts by mass, more preferably from 0.20 to 30 parts by mass, and even more preferably from 0.30 to 15 parts by mass, relative to 100 parts by mass of the copolymer (P) contained in the binder composition of the present embodiment (in other words, the monomer component used to produce the copolymer (P)).

[0184] The adhesive composition of this embodiment may be, as one embodiment, a composition comprising a copolymer (P), a polyrotaxane 2, and an aqueous medium (B). It may be a composition in which both the copolymer (P) and the polyrotaxane 2 are dispersed in the aqueous medium (B), that is, a dispersion.

[0185] [Aqueous medium (B)]

[0186] The aqueous medium (B) is the same as that described as the aqueous medium (b). The aqueous medium (B) may be the same as or different from the aqueous medium (b) used for synthesizing the copolymer (P).

[0187] When the adhesive composition of the present embodiment contains emulsified particles obtained by manufacturing a copolymer (P) using an emulsion polymerization method, the aqueous medium (B) may also be an aqueous medium (b) used to synthesize the copolymer (P). In addition, the aqueous medium (B) may also add a new aqueous medium to the aqueous medium (b) used when synthesizing the copolymer (P). In addition, the aqueous medium (B) may also replace a portion or all of the aqueous medium (b) contained in the dispersion obtained by manufacturing the copolymer (P) using an emulsion polymerization method with a new aqueous solvent. The new aqueous medium used at this time may be the same composition as the aqueous medium (b) used to synthesize the copolymer (P), or may be a different composition.

[0188] The adhesive composition of the present embodiment may appropriately contain known additives within a range that does not impair the effects of the present invention.

[0189] (Non-volatile content of adhesive composition)

[0190] The binder 25 included in the electrode 20 manufactured using the binder composition of this embodiment is composed of a component (non-volatile component) that remains and does not volatilize even during a heating step in the non-aqueous secondary battery manufacturing method described later. Specifically, the component constituting the binder 25 is the component that remains after weighing 1 g of the binder composition, placing it on a 5 cm diameter aluminum pan, and drying it in a dryer at 1 atmosphere (1013 hPa) and 105°C for 1 hour while circulating air within the dryer.

[0191] The non-volatile component concentration of the adhesive composition of this embodiment is preferably 20% by mass or more, more preferably 25% by mass or more, and even more preferably 30% by mass or more. This is to fully increase the amount of the active ingredient contained in the adhesive composition. The non-volatile component concentration of the adhesive composition can be adjusted according to the content of the aqueous medium (B) contained in the adhesive composition.

[0192] The nonvolatile content of the binder composition is preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less. This is because the viscosity of the binder composition is suppressed from increasing, making it easier to prepare the slurry for non-aqueous secondary battery electrodes.

[0193] The total content of the copolymer (P) and the polyrotaxane 2 contained in the nonvolatile component of the adhesive composition of this embodiment is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 98% by mass or more. This is because the adhesive composition containing the copolymer (P) and the polyrotaxane 2 has a significant effect.

[0194] <2. Method for producing a binder composition for a non-aqueous secondary battery>

[0195] Next, the method for producing the adhesive composition of this embodiment will be described. The method for producing the adhesive composition of this embodiment, in one embodiment, includes a synthesis step of synthesizing the copolymer (P) and a mixing step of mixing the obtained copolymer (P) with the polyrotaxane 2. In another embodiment, the method for producing the adhesive composition of this embodiment includes preparing the copolymer (P) and mixing the copolymer (P) with the polyrotaxane 2.

[0196] In the mixing step of this embodiment, a known method can be used as a method for mixing the copolymer (P) and the polyrotaxane 2, without particular limitation. For example, methods for mixing the copolymer (P) and the polyrotaxane 2 include methods using a stirring, rotating, or vibrating mixing apparatus.

[0197] When producing a binder composition in which both the copolymer (P) and the polyrotaxane 2 are dispersed in the aqueous medium (B) as the binder composition of the present embodiment, for example, a method of mixing a dispersion obtained by producing the copolymer (P) by emulsion polymerization, the polyrotaxane 2, and the aqueous medium (B) which may be added as needed, or a method of mixing the copolymer (P) obtained by a method other than emulsion polymerization, the polyrotaxane 2, and the aqueous medium (B) can be adopted.

[0198] When a copolymer (P) obtained by a method other than emulsion polymerization is used as the copolymer (P), a known method such as a method using a surfactant can be used as a method for dispersing the copolymer (P) in the aqueous medium (B). Examples of the surfactant include the same surfactants as exemplified as the non-polymerizable surfactant (c) that can be used when producing the copolymer (P) by emulsion polymerization.

[0199] As a method for dispersing the polyrotaxane 2 in the aqueous medium (B), a known method can be used.

[0200] When using a polyrotaxane 2 that is difficult to disperse in the aqueous medium (B), such as a polyrotaxane 2 containing a cyclic molecule 51 in which a modification group 54 having a (meth)acryloyl group is bonded to a cyclic backbone, the polyrotaxane 2 can be dispersed in the aqueous medium (B) using a known method such as a method using a surfactant. Examples of the surfactant include the same surfactants as those exemplified as the non-polymerizable surfactant (c) that can be used when producing the copolymer (P) by emulsion polymerization.

[0201] <3. Non-aqueous secondary battery electrode slurry>

[0202] Next, the non-aqueous secondary battery electrode slurry of the present embodiment is described in detail. The non-aqueous secondary battery electrode slurry comprises a binder composition containing a copolymer (P), polyrotaxane 2 and an aqueous medium (B), and an electrode active material. The electrode active material contained in the non-aqueous secondary battery electrode slurry is preferably dispersed in an aqueous medium. In addition to the copolymer (P), polyrotaxane 2, the electrode active material, and the aqueous medium, the non-aqueous secondary battery electrode slurry may also contain additives such as a thickener and a conductive aid, as well as the above-mentioned components used in the manufacture of the binder composition.

[0203] [Total content of copolymer (P) and polyrotaxane 2]

[0204] The total content of the copolymer (P) and the polyrotaxane 2 contained in the non-aqueous secondary battery electrode slurry is preferably 0.50 parts by mass or more, and more preferably 1.0 parts by mass or more, relative to 100 parts by mass of the electrode active material. This is because the effects of the binder composition according to this embodiment can be fully exhibited.

[0205] The total content of the copolymer (P) and the polyrotaxane 2 contained in the non-aqueous secondary battery electrode slurry is preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, and even more preferably 3.0 parts by mass or less, relative to 100 parts by mass of the electrode active material. This is because the content of the electrode active material contained in the non-aqueous secondary battery electrode slurry can be increased.

[0206] 〔Electrode active material〕

[0207] The electrode active material contained in the slurry for non-aqueous secondary battery electrodes is a material capable of inserting and extracting ions such as lithium ions as charge carriers. The ions serving as charge carriers are preferably alkali metal ions, more preferably lithium ions, sodium ions, and potassium ions, and even more preferably lithium ions.

[0208] When the non-aqueous secondary battery electrode manufactured using the slurry for non-aqueous secondary battery electrodes is a negative electrode, the electrode active material is a negative electrode active material. As the negative electrode active material, it is preferred to contain at least one of a carbon material, a silicon-containing material, and a titanium-containing material. Examples of carbon materials used as negative electrode active materials include cokes such as petroleum coke, pitch coke, coal coke, organic polymer carbides, graphites such as artificial graphite and natural graphite. Examples of silicon-containing materials used as negative electrode active materials include silicon compounds such as silicon elemental silicon and silicon oxide. Examples of titanium-containing materials used as negative electrode active materials include lithium titanate. These materials used as negative electrode active materials may be used alone or in combination.

[0209] The negative electrode active material preferably contains at least one of a carbon material and a silicon-containing material, and more preferably contains a carbon material. This is because the copolymer (P) and the polyrotaxane 2 contained in the non-aqueous secondary battery electrode slurry can enhance the effect of improving the binding properties between the negative electrode active materials (electrode active materials) 22 and between the negative electrode active materials 22 and the current collector 23.

[0210] When the non-aqueous secondary battery electrode manufactured using the non-aqueous secondary battery electrode slurry is the positive electrode, the electrode active material is the positive electrode active material. As the positive electrode active material, a substance having a standard electrode potential that is more expensive (higher) than the negative electrode active material is used. Specifically, as the positive electrode active material, lithium composite oxides containing nickel, lithium cobaltate (LiCoO2), spinel-type lithium manganese oxide (LiMn2O4), olivine-type lithium iron phosphate, TiS2, MnO2, MoO3, V2O5 and other chalcogenides can be listed. These substances used as positive electrode active materials can be used alone or in combination of two or more.

[0211] [Aqueous medium]

[0212] The aqueous medium contained in the slurry for non-aqueous secondary battery electrodes of this embodiment is the same as that described as the aqueous medium (b). The aqueous medium may be the same as or different from the aqueous medium (b) used for synthesizing the copolymer (P).

[0213] The aqueous medium contained in the non-aqueous secondary battery electrode slurry of the present embodiment may also be only the aqueous medium (B) contained in the binder composition. In addition, a new aqueous medium may be added to the aqueous medium (B) contained in the binder composition. In addition, a part or all of the aqueous medium (B) contained in the binder composition may be replaced with a new aqueous solvent. The non-aqueous secondary battery electrode slurry of the present embodiment may appropriately use additives. For example, the following exemplified materials may be listed.

[0214] Thickener

[0215] As thickeners that can be contained in the non-aqueous secondary battery electrode slurry, celluloses such as carboxymethyl cellulose (CMC), hydroxyethyl cellulose, and hydroxypropyl cellulose, ammonium salts of celluloses, alkali metal salts of celluloses, polyvinyl alcohol, and polyvinyl pyrrolidone can be listed. As the thickener, it is preferred to contain at least one of carboxymethyl cellulose, ammonium salts of carboxymethyl cellulose, and alkali metal salts of carboxymethyl cellulose. This is because the electrode active material in the non-aqueous secondary battery electrode slurry becomes easier to disperse.

[0216] The content of the thickener contained in the non-aqueous secondary battery electrode slurry is preferably 0.50 parts by mass or more, and more preferably 0.80 parts by mass or more, relative to 100 parts by mass of the electrode active material. This is because the non-aqueous secondary battery electrode produced using the non-aqueous secondary battery electrode slurry has good adhesion between the electrode active materials 22 contained in the non-aqueous secondary battery electrode and between the electrode active materials 22 and the current collector 23.

[0217] The content of the thickener in the non-aqueous secondary battery electrode slurry is preferably 3.0 parts by mass or less, more preferably 2.0 parts by mass or less, and even more preferably 1.5 parts by mass or less, per 100 parts by mass of the electrode active material. This is because the non-aqueous secondary battery electrode slurry has good coating properties.

[0218] [Conductive additive]

[0219] As the conductive aid that can be contained in the non-aqueous secondary battery electrode slurry of the present embodiment, carbon black, carbon fiber, etc. can be listed. As carbon black, furnace black, acetylene black, Denka acetylene black (registered trademark) (manufactured by Denka Co., Ltd.), Ketjen black (registered trademark) (manufactured by Ketchen Black) and the like can be listed. As carbon fiber, carbon nanotubes, carbon nanofibers, etc. can be listed. As carbon nanotubes, as a preferred example, vapor-grown carbon fiber VGCF (registered trademark, manufactured by Showa Denko K.K.) can be listed.

[0220] (Method for producing slurry for non-aqueous secondary battery electrodes)

[0221] As a method for manufacturing a slurry for non-aqueous secondary battery electrodes of the present embodiment, for example, a method of mixing a binder composition in which a copolymer (P) and a polyrotaxane 2 are dispersed in an aqueous medium (B), an electrode active material, a thickener as needed, a conductive additive as needed, and other components as needed can be cited. The mixing order of the components of the raw material for the slurry for non-aqueous secondary battery electrodes is not particularly limited and can be appropriately determined. As a method for mixing the components, a method using a mixing device such as a stirring type, a rotating type, and a vibrating type can be cited.

[0222] <5. Non-aqueous Secondary Battery Electrodes>

[0223] Next, the non-aqueous secondary battery electrode of this embodiment will be described in detail. The electrode 20 of this embodiment includes the non-volatile component of the binder composition of this embodiment. Figure 1 As shown, the electrode 20 of this embodiment includes a current collector 23 and an electrode active material layer 24 formed on the current collector 23. Examples of the shape of the electrode 20 of this embodiment include a laminate and a wound body, but are not particularly limited.

[0224] The formation range of the electrode active material layer 24 on the current collector 23 is not particularly limited. The electrode active material layer 24 may be formed on the entire surface of the current collector 23 or on only a portion of the surface of the current collector 23. When the current collector 23 is in the shape of a plate, foil, or the like, the electrode active material layer 24 may be formed on both surfaces of the current collector 23 or on only one surface.

[0225] 〔Current Collector〕

[0226] The collector 23 is preferably a metal sheet having a thickness of 0.001 mm to 0.5 mm. Examples of metals forming the metal sheet include iron, copper, aluminum, nickel, and stainless steel. When the electrode 20 of this embodiment is the negative electrode of a lithium-ion secondary battery, the collector 23 is preferably copper foil.

[0227] (Electrode Active Material Layer)

[0228] The electrode active material layer 24 includes a binder 25, which is a nonvolatile component of the binder composition of this embodiment, and an electrode active material 22. The electrode active material layer 24 may also contain a conductive additive, a thickener 21, and the like. The electrode active material 22, the conductive additive, and the thickener 21 can all be the same as those exemplified as components of the slurry for non-aqueous secondary battery electrodes.

[0229] (Method for producing non-aqueous secondary battery electrode)

[0230] The electrode 20 of the present embodiment can be manufactured, for example, by the method shown below. First, the non-aqueous secondary battery electrode slurry of the present embodiment is applied to the collector 23. Then, the non-aqueous secondary battery electrode slurry is dried. Thus, an electrode active material layer 24 containing a binder 25 as a non-volatile component of the binder composition of the present embodiment is formed on the collector 23 to prepare an electrode sheet. Then, the electrode sheet is cut into appropriate sizes as needed. By performing the above steps, the electrode 20 of the present embodiment is obtained.

[0231] The method for coating the non-aqueous secondary battery electrode slurry on the current collector 23 is not particularly limited, and examples thereof include a reverse roll method, a direct roll method, a scraper method, a knife method, an extrusion method, a curtain method, a gravure method, a rod method, a dipping method, and an extrusion method. Among these coating methods, considering the physical properties such as the viscosity and drying properties of the non-aqueous secondary battery electrode slurry, it is preferred to use any method selected from the direct roll method, the scraper method, the knife method, or the extrusion method. This is because it can produce an electrode active material layer 24 with a smooth surface and small thickness deviation.

[0232] When the non-aqueous secondary battery electrode slurry is applied to both surfaces of the current collector 23, it can be applied sequentially one surface at a time or both surfaces can be applied simultaneously. In addition, the non-aqueous secondary battery electrode slurry can be applied to the current collector 23 continuously or intermittently.

[0233] The coating amount of the slurry for non-aqueous secondary battery electrodes can be appropriately determined according to the designed capacity of the battery, the composition of the slurry for non-aqueous secondary battery electrodes, and the like.

[0234] The method for drying the nonaqueous secondary battery electrode slurry applied on the current collector 23 is not particularly limited. For example, methods selected from hot air, reduced pressure or vacuum environment, (far) infrared rays, and low-temperature air can be used alone or in combination.

[0235] The drying temperature and drying time when drying the non-aqueous secondary battery electrode slurry can be appropriately adjusted according to the non-volatile content concentration in the non-aqueous secondary battery electrode slurry, the amount applied to the current collector 23, and the like. The drying temperature is preferably 40°C to 350°C, and more preferably 60°C to 100°C from the perspective of productivity. The drying time is preferably 1 minute to 30 minutes.

[0236] The electrode sheet having the electrode active material layer 24 formed on the current collector 23 can be cut into a size and shape suitable for the electrode 20. The cutting method of the electrode sheet is not particularly limited, and for example, slit cutting, laser cutting, wire cutting, a cutter, a Thomson knife, etc. can be used.

[0237] In this embodiment, the electrode sheet may be pressed as needed before or after cutting the electrode sheet. This allows the electrode active material 22 to be more firmly bonded to the current collector 23, and by reducing the thickness of the electrode 20, the non-aqueous secondary battery can be miniaturized.

[0238] As a method for pressing the electrode sheet, a general method can be used, and as a pressing method, a die pressing method or a roll pressing method is particularly preferably used.

[0239] When using the die pressing method, the pressing pressure is not particularly limited, but is preferably 0.5 t / cm 2 Above 5t / cm 2 the following.

[0240] When using the roller pressing method, the pressing load is not particularly limited, but is preferably 0.5 t / cm to 8 t / cm. This is because it can achieve the above-mentioned pressing effect while suppressing the reduction in the capacity of the insertion and extraction of charge carriers such as lithium ions into the electrode active material 22.

[0241] <6. Non-aqueous secondary batteries>

[0242] Hereinafter, a lithium ion secondary battery will be described as a preferred example of the nonaqueous secondary battery of this embodiment. However, the structure of the nonaqueous secondary battery of the present invention is not limited to the example shown below.

[0243] The lithium ion secondary battery of this embodiment includes a positive electrode, a negative electrode, an electrolyte solution, and, if necessary, a separator, and other known components housed in an outer casing.

[0244] The shape of the lithium ion secondary battery may be any shape such as a coin shape, a button shape, a sheet shape, a cylindrical shape, a square shape, or a flat shape.

[0245] (positive, negative)

[0246] The lithium-ion secondary battery of this embodiment includes an electrode active material layer 24 on one or both of the positive electrode and the negative electrode. The electrode active material layer 24 includes a binder 25 that is a nonvolatile component of the binder composition of this embodiment. In the lithium-ion secondary battery of this embodiment, it is preferred that at least the negative electrode of the positive electrode and the negative electrode include an electrode active material layer 24 that includes a binder 25 that is a nonvolatile component of the binder composition.

[0247] In the case where only one of the positive electrode and the negative electrode of the lithium ion secondary battery of this embodiment has an electrode active material layer 24 containing a non-volatile component of the binder composition of this embodiment, the electrode that does not contain the non-volatile component of the binder composition of this embodiment has an electrode active material layer manufactured using a well-known binder such as polyvinylidene fluoride instead of the binder composition of this embodiment.

[0248] [Electrolyte]

[0249] As the electrolyte, a non-aqueous liquid with ion conductivity is used. As the electrolyte, a solution or ionic liquid in which an electrolyte is dissolved in an organic solvent can be cited, with the former being preferred. This is because a lithium ion secondary battery with low manufacturing cost and low internal resistance can be obtained.

[0250] As the electrolyte, an alkali metal salt can be used, and it can be appropriately selected according to the type of electrode active material. Examples of the electrolyte include LiClO4, LiBF6, LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiB 10 Cl 10 , LiAlCl4, LiCl, LiBr, LiB(C2H5)4, CF3SO3Li, CH3SO3Li, LiCF3SO3, LiC4F9SO3, Li(CF3SO2)2N, aliphatic lithium carboxylate, etc. In addition, other alkali metal salts can also be used as the electrolyte.

[0251] As the organic solvent of dissolving electrolyte, it is not particularly limited, for example, carbonate compounds such as ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), fluoroethylene carbonate (FEC), vinylene carbonate (VC) can be listed, nitrile compounds such as acetonitrile, carboxylic acid esters such as ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate. These organic solvents can be used alone or in combination of more than two kinds of use. As organic solvent, the organic solvent that preferably uses the combination straight-chain carbonate solvent forms.

[0252] (outer body)

[0253] As the exterior body, for example, an aluminum laminate composed of aluminum foil and a resin film can be appropriately used, but the exterior body is not limited thereto.

[0254] Example

[0255] The present invention will be described in detail below by way of examples and comparative examples. The following examples are provided to facilitate understanding of the present invention. The present invention is not limited to these examples.

[0256] In the following examples, a negative electrode of a lithium-ion secondary battery was prepared as an example of a non-aqueous secondary battery electrode of the present invention, and a lithium-ion secondary battery was prepared as an example of a non-aqueous secondary battery. The effects of the present invention were confirmed by comparing them with the negative electrode of a lithium-ion secondary battery and the lithium-ion secondary battery of a comparative example.

[0257] In addition, water used in the following Examples and Comparative Examples was ion-exchanged water unless otherwise specified.

[0258] <1. Production of Binder Composition for Non-aqueous Secondary Batteries>

[0259] (Example 1 to Example 5)

[0260] The raw material monomers (a) listed in Tables 1 and 2 were mixed with 200 parts by mass of water as the aqueous medium (b) at the mass ratios listed in Tables 1 and 2, and emulsified to prepare monomer emulsions. Subsequently, the free radical polymerization initiators (e) listed in Tables 1 and 2 were dissolved in 50 parts by mass of water in the amounts listed in Tables 1 and 2 to prepare aqueous solutions.

[0261] 150 parts by mass of water were placed in a separable flask equipped with a cooling tube, a thermometer, a stirrer, and a dropping funnel, and the temperature was raised to 75° C. The monomer emulsion and the aqueous solution containing the radical polymerization initiator (e) were each continuously supplied to the separable flask while stirring at 75° C. for 3 hours to carry out emulsion polymerization, thereby obtaining an emulsion.

[0262] The resulting emulsion was cooled to room temperature. Then, 133 parts by mass of water and 25% by mass aqueous ammonia (17 parts by mass of ammonia, 51 parts by mass of water) in the amounts shown in Tables 1 and 2 were added to the emulsion. This yielded emulsions containing emulsified particles of the copolymer (P) of Examples 1 to 5 dispersed in water.

[0263] The emulsions containing the emulsified particles of the copolymer (P) of Examples 1 to 5 dispersed in water and the polyrotaxanes shown in Tables 1 and 2 were mixed using a homogenizer at the mass ratios shown in Tables 1 and 2 to prepare the non-aqueous secondary battery binder compositions of Examples 1 to 5 containing the copolymer (P), the polyrotaxane, and water.

[0264] In the binder compositions for non-aqueous secondary batteries of Examples 1 to 5, dispersion abnormalities such as aggregation of emulsified particles and polyrotaxane containing the copolymer (P) in the composition were not observed, and dispersion was maintained.

[0265] (Comparative Example 1)

[0266] As the binder composition for a non-aqueous secondary battery in Comparative Example 1, an emulsion in which only emulsified particles containing the copolymer (P) produced in Example 1 were dispersed in water was used.

[0267] Table 1

[0268]

[0269] *1: The numerical values in the right column of the raw material monomers (a) are the content ratios (mass %) of the respective monomers when the total amount of the raw material monomers (a) is 100 parts by mass.

[0270] The numerical value on the right side of the polyrotaxane is the mass fraction of the polyrotaxane when the total amount of the raw material monomers (a) is 100 parts by mass.

[0271] Table 2

[0272]

[0273] ※1: The values on the right column of raw material monomer (a) are calculated by setting the total amount of raw material monomer (a) to

[0274] The content (mass %) of each monomer is 100 parts by mass.

[0275] The numerical values on the right side of the polyrotaxane are based on the total amount of the raw material monomer (a) being 100 parts by mass.

[0276] The mass fraction of polyrotaxane at .

[0277] The polyoxyethylene alkyl ether sulfate salt of the monomer (a4) shown in Tables 1 and 2 (Aquacon KH-10, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) is a polymerizable surfactant.

[0278] In the polymerization initiator (e), Rongalite SFS is a trade name of Rongalite manufactured by Sumitomo Seika Chemicals, Ltd.

[0279] The SH2400P of the polyrotaxane shown in Table 1 and Table 2 is the SERUMP (registered trademark) SH2400P (manufactured by APTRON CO., LTD.).

[0280] SA2400c of the polyrotaxane shown in Tables 1 and 2 is Celsius (registered trademark) Key Midi Stria SA2400C (manufactured by Advanced Soft Materials Co., Ltd.).

[0281] The amount of ammonia as the alkaline substance (d) shown in Tables 1 and 2 is the amount (parts by mass) of ammonia contained in aqueous ammonia.

[0282] The amount of water as the aqueous medium (b) shown in Tables 1 and 2 is the total amount (parts by mass) of water contained in the binder composition for a non-aqueous secondary battery.

[0283] <2. Evaluation of Copolymer (P) and Binder Composition for Non-aqueous Secondary Batteries>

[0284] The glass transition temperature (Tg) and particle size (d50) of the copolymer (P) dispersed in an emulsion containing emulsified particles of the copolymer (P) of Examples 1 to 5 and Comparative Example 1 were measured by the following methods. The results are shown in Tables 1 and 2.

[0285] The non-volatile content of the binder compositions for non-aqueous secondary batteries of Examples 1 to 5 and Comparative Example 1 was measured by the following method.

[0286] [Glass transition temperature (Tg) of copolymer (P)]

[0287] An emulsion containing emulsified particles of the copolymer (P) dispersed in water was applied onto a release PET (polyethylene terephthalate) film and dried at 50°C for 5 hours to obtain a 2 mm thick film composed of the copolymer (P).

[0288] A square test piece measuring 2 mm in length and 2 mm in width was cut from the resulting film. The test piece was sealed in an aluminum pan and subjected to differential scanning calorimetry (DSC) at a heating rate of 10°C / minute using a differential scanning calorimeter (EXSTARDSC / SS7020, manufactured by Hitachi High-Tech Sciences) under a nitrogen atmosphere. The DSC measurement temperature range was -40°C to 200°C. The peak temperature of the DDSC chart, obtained as the temperature differential of the DSC, was then measured and used as the glass transition temperature, Tg (°C), of the copolymer (P).

[0289] [Particle size (d50) of emulsified particles containing copolymer (P)]

[0290] The particle size (d50) of the emulsion containing the copolymer (P) was measured on a volume basis using the refractive index of the particles by dynamic light scattering (DLS) using a NANOTORACWAVE II (manufactured by Microtrac Bell Co., Ltd.) in an emulsion in which the emulsion containing the copolymer (P) was dispersed in water.

[0291] (Non-volatile content concentration of the binder composition for non-aqueous secondary batteries)

[0292] 1 g of a non-aqueous secondary battery binder composition containing a copolymer (P), a polyrotaxane, and water was weighed, placed on a 5 cm diameter aluminum pan, and placed in a desiccator. Drying was performed at 1 atmosphere (1013 hPa) and 105°C for 1 hour while circulating air within the desiccator. The mass of the remaining components was measured. The mass ratio (mass %) of the above components remaining after drying relative to the mass (1 g) of the non-aqueous secondary battery binder composition before drying was calculated as the non-volatile content (mass %).

[0293] <3. Production of non-aqueous secondary batteries>

[0294] Negative electrodes were prepared by the following method using the binder compositions for nonaqueous secondary batteries of Examples 1 to 5 and Comparative Example 1, and lithium ion secondary batteries of Examples 1 to 5 and Comparative Example 1 were prepared using the negative electrodes.

[0295] [Production of positive electrode]

[0296] LiNi as the positive electrode active material 0.6 Mn 0.2 Co 0.294 parts by mass of O2, 3 parts by mass of acetylene black as a conductive additive, and 3 parts by mass of polyvinylidene fluoride as a binder were mixed to obtain a mixture. 50 parts by mass of N-methylpyrrolidone was added to the obtained mixture and further mixed to obtain a positive electrode slurry.

[0297] A 15 μm thick aluminum foil was prepared as the positive electrode current collector. The positive electrode slurry was applied to both sides of the positive electrode current collector using a direct roll method. The amount of positive electrode slurry applied to the positive electrode current collector was adjusted to a thickness of 125 μm per side after the roll press process described later.

[0298] The positive electrode slurry applied to the positive electrode current collector was dried at 120°C for 5 minutes and then rolled using a roller press (manufactured by Sank Metal, with a pressing load of 5 t / cm and a roller width of 7 cm) to produce a positive electrode sheet having a positive electrode active material layer on both sides of the positive electrode current collector. The resulting positive electrode sheet was cut into rectangles measuring 50 mm in length and 40 mm in width, and a conductive tab was attached to form the positive electrode.

[0299] [Fabrication of negative electrode (non-aqueous secondary battery electrode)]

[0300] 96.9 parts by mass of artificial graphite (G49, manufactured by Jiangxi Zichen Technology Co., Ltd.) as a negative electrode active material, 3.6 parts by mass of any one of the binder compositions for non-aqueous secondary batteries manufactured in Examples 1 to 5 and Comparative Example 1 (1.4 parts by mass of non-volatile components), and 60 parts by mass of a 2% aqueous solution of CMC (carboxymethyl cellulose-sodium salt, manufactured by Nippon Paper Chemical Co., Ltd., Sanloz (registered trademark) MAC500LC) were mixed, and 16 parts by mass of water were added, and the mixture was mixed using a rotary mixer (ARE-310, manufactured by Shinkyo Co., Ltd.) to obtain a negative electrode slurry (slurry for non-aqueous secondary battery electrodes).

[0301] A 10μm-thick copper foil was prepared as the negative electrode current collector. Negative electrode slurry was applied to both sides of the negative electrode current collector using a direct roll method. The amount of negative electrode slurry applied to the negative electrode current collector was adjusted so that the thickness of the negative electrode active material layer on one side after the roll pressing process described below would be 170μm.

[0302] The negative electrode slurry applied to the negative electrode current collector was dried at 90°C for 10 minutes and then rolled using a roller press (manufactured by Sank Metal, with a pressing load of 8 t / cm and a roller width of 7 cm). This produced a negative electrode sheet with a negative electrode active material layer on both sides of the negative electrode current collector. The resulting negative electrode sheet was cut into a rectangle measuring 52 mm in length and 42 mm in width, and a conductive tab was attached to form the negative electrode.

[0303] [Fabrication of non-aqueous secondary batteries]

[0304] A separator made of a polyolefin-based porous film (polyethylene, 25 μm thick) is sandwiched between the positive and negative electrodes. The positive and negative active material layers are stacked facing each other and housed in an outer casing (battery pack) made of aluminum laminate. The outer casing is then injected with an electrolyte, vacuum impregnated, and packaged with a vacuum heat sealant to produce a lithium-ion secondary battery.

[0305] As the electrolyte, an electrolyte solution was used which was prepared by dissolving LiPF6 at a concentration of 1.0 mol / L in a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) in a volume ratio of EC:EMC:DEC=30:50:20 and mixing 99 parts by mass of a solution and 1 part by mass of vinylene carbonate (VC).

[0306] <4. Evaluation of Non-aqueous Secondary Batteries>

[0307] The internal resistance and discharge capacity retention after 500 cycles of the lithium ion secondary batteries of Examples 1 to 5 and Comparative Example 1 were evaluated by the following methods. The results are shown in Tables 1 and 2.

[0308] [Internal resistance (DCR)]

[0309] The internal resistance (DCR (Ω)) of a lithium-ion secondary battery is measured at 25°C using the following procedure. Specifically, constant current charging is performed at 0.2C from the rest potential to a voltage of 3.6V, bringing the state of charge to 50% of the initial capacity (SOC 50%). The battery is then discharged for 60 seconds at currents of 0.2C, 0.5C, 1C, and 2C. The internal resistance (DCR (Ω)) at SOC 50% is determined based on the relationship between these four current values (values within 1 second) and voltage.

[0310] [Discharge capacity retention after 500 cycles]

[0311] The following steps (i) to (iv) were performed once at 45°C, representing one cycle, and charge and discharge were performed. The time-integrated value of the current in steps (i) and (ii) was used as the charge capacity, and the time-integrated value of the current in step (iv) was used as the discharge capacity. The discharge capacity at the first cycle and the discharge capacity at the 500th cycle were measured, and the discharge capacity retention rate after 500 cycles was calculated using the following formula.

[0312] Discharge capacity retention rate (%) = 100 × (discharge capacity at the 500th cycle / discharge capacity at the 1st cycle)

[0313] (i) Charge with a current of 1C (constant current (CC) charge) until the voltage reaches 4.2V.

[0314] (ii) Charge at 4.2 V (constant voltage (CV) charge) until the current reaches 0.05 C. (iii) Let stand for 30 minutes.

[0315] (iv) Discharge at a current of 1C (constant current (CC) discharge) until the voltage reaches 2.75V.

[0316] <5. Evaluation Results>

[0317] As shown in Tables 1 and 2, the lithium-ion secondary batteries of Examples 1 to 5 all showed higher capacity retention rates than the lithium-ion secondary battery of Comparative Example 1. This is presumably because the nonvolatile component of the binder composition for non-aqueous secondary batteries contained in the negative electrodes of the lithium-ion secondary batteries of Examples 1 to 5 contained "a copolymer (P) containing structural units derived from monomers (a1) and (a2) shown in Tables 1 and 2" and "a polyrotaxane shown in Tables 1 and 2."

[0318] More specifically, in Comparative Example 1, a negative electrode was produced using a binder composition for a non-aqueous secondary battery in which emulsified particles containing the same copolymer (P) as in Example 1 were dispersed in water but did not contain a polyrotaxane. Therefore, it is presumed that in the lithium-ion secondary battery of Comparative Example 1, insufficient binding between the electrode active materials and between the electrode active materials and the current collector resulted in poor capacity retention.

[0319] Furthermore, as shown in Tables 1 and 2, from the viewpoint of internal resistance, which is a secondary effect, the lithium ion secondary batteries of Examples 1 to 5 and Comparative Example 1 all showed sufficiently low values for practical use.

[0320] Industrial availability

[0321] The present invention provides a binder composition for a non-aqueous secondary battery that can form an electrode for a non-aqueous secondary battery having excellent cycle characteristics, and a method for producing the same.

[0322] A slurry for non-aqueous secondary battery electrodes can be provided that can form an electrode for a non-aqueous secondary battery having excellent cycle characteristics.

[0323] A non-aqueous secondary battery electrode capable of obtaining a non-aqueous secondary battery having excellent cycle characteristics, and a non-aqueous secondary battery having excellent cycle characteristics and including the non-aqueous secondary battery electrode can be provided.

[0324] Description of the accompanying drawings

[0325] 2 Polyrotaxanes

[0326] 20 electrodes

[0327] 21 Thickener

[0328] 22 Electrode active material

[0329] 23 Current Collector

[0330] 24 Electrode active material layer

[0331] 25 Adhesive

[0332] 51 cyclic molecules

[0333] 52 blocking base

[0334] 53 Chain molecules

[0335] 54 Modification groups

[0336] 55 opening

Claims

1. A binder composition for a non-aqueous secondary battery, comprising a copolymer and a polyrotaxane, wherein the copolymer has a first structural unit derived from a monomer a1 and a second structural unit derived from a monomer a2, The monomer a1 is a nonionic compound having only one ethylenically unsaturated bond. The monomer a2 is a compound having a carboxyl group and only one ethylenically unsaturated bond, The polyrotaxane includes a cyclic molecule and a chain molecule. The cyclic molecule has a cyclic skeleton, and the chain molecule penetrates the opening of the cyclic molecule and has blocking groups at both ends. 2 . The binder composition for a non-aqueous secondary battery according to claim 1 , wherein at least one of the cyclic skeletons of the cyclic molecules is a crown ether skeleton, a cyclic siloxane skeleton, or a cyclic oligosaccharide skeleton. 3 . The binder composition for a non-aqueous secondary battery according to claim 1 , wherein at least one of the cyclic skeletons of the cyclic molecules is an α-cyclodextrin skeleton. 4 . The binder composition for a non-aqueous secondary battery according to claim 1 , wherein at least one of the blocking groups is a dinitrophenyl group, an adamantyl group, a triphenylmethyl group, or a derivative of any one of these groups. 5 . The binder composition for a non-aqueous secondary battery according to claim 1 , wherein at least one of the blocking groups is an adamantyl group. 6 . The binder composition for a non-aqueous secondary battery according to claim 1 , wherein the chain molecule is at least one selected from the group consisting of polyethylene glycol, polypropylene glycol, polyisoprene, polyisobutylene, polybutadiene, polytetramethylene glycol, polyacrylate, polydimethylsiloxane, polyethylene, and polypropylene. 7 . The binder composition for a non-aqueous secondary battery according to claim 1 , wherein at least one of the chain molecules is polyethylene glycol. 8 . The binder composition for a non-aqueous secondary battery according to claim 1 , wherein the chain molecules have a weight average molecular weight of 5,000 to 50,000. 9 . The binder composition for a non-aqueous secondary battery according to claim 1 , wherein the polyrotaxane has an ethylenically unsaturated bond.

10. The binder composition for a non-aqueous secondary battery according to claim 9, wherein a group containing an ethylenically unsaturated bond is bonded to the cyclic skeleton. At least one of the groups containing an ethylenically unsaturated bond bonded to the cyclic skeleton is a (meth)acryloyl group, a vinyl group, an allyl group, or a propenyl group. 11 . The binder composition for a non-aqueous secondary battery according to claim 10 , wherein at least one of the groups containing an ethylenically unsaturated bond bonded to the cyclic skeleton is a (meth)acryloyl group. 12 . The binder composition for a non-aqueous secondary battery according to claim 1 , wherein the polyrotaxane does not have an ethylenically unsaturated bond. 13 . The binder composition for a non-aqueous secondary battery according to claim 1 , wherein the content of the polyrotaxane is 0.10 parts by mass or more and 50 parts by mass or less relative to 100 parts by mass of the copolymer. 14 . The binder composition for a non-aqueous secondary battery according to claim 1 , wherein a content of the second structural unit in all structural units of the copolymer is 0.10% by mass or more and 20% by mass or less.

15. The binder composition for a non-aqueous secondary battery according to claim 1, wherein the copolymer has a third structural unit derived from monomer a3. The monomer a3 is a compound having a plurality of independent ethylenically unsaturated bonds. 16 . The binder composition for a non-aqueous secondary battery according to claim 15 , wherein a content of the third structural unit in all structural units of the copolymer is 0.010% by mass or more and 10% by mass or less. 17 . The binder composition for a non-aqueous secondary battery according to claim 1 , further comprising an aqueous medium. 18 . The binder composition for a non-aqueous secondary battery according to claim 17 , wherein the emulsified particles containing the copolymer and the polyrotaxane are dispersed in the aqueous medium. 19 . A slurry for non-aqueous secondary battery electrodes, comprising the binder composition for non-aqueous secondary batteries according to claim 17 and an electrode active material. 20 . A non-aqueous secondary battery electrode comprising a non-volatile component of the binder composition for a non-aqueous secondary battery according to claim 1 . A non-aqueous secondary battery comprising the non-aqueous secondary battery electrode according to claim 20.

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