Composition for insulating layer of current collector for lithium-ion secondary battery and method for manufacturing the same, current collector with insulating layer for lithium-ion secondary battery, electrode for lithium-ion secondary battery and lithium-ion secondary battery

Abstract

To provide an insulating layer composition that can form an insulating layer with excellent adhesion to the current collector and blocking resistance for current collectors in lithium-ion secondary batteries. [Solution] An insulating layer composition for a lithium-ion secondary battery current collector, comprising a resin (A) having at least one binder group selected from the group consisting of urethane groups, urea groups, amide groups, and imide groups, and a non-aqueous solvent, wherein the total concentration of the binder groups in the resin (A) is 500 to 10000 mmol / kg.

Description

[Technical Field]

[0001] This disclosure relates to a composition for the insulating layer of a current collector for a lithium-ion secondary battery and a method for manufacturing the same, a current collector with an insulating layer for a lithium-ion secondary battery, an electrode for a lithium-ion secondary battery, and a lithium-ion secondary battery. [Background technology]

[0002] The electrodes (positive and negative electrodes) of a lithium-ion secondary battery typically consist of a current collector made of metal foil or the like, and an electrode active material layer formed on the current collector by pressing or other means. While a region where the electrode active material layer is not formed is provided on the electrode's current collector to ensure a current path, various technologies are being considered to prevent short circuits caused by the current collector being exposed in this region.

[0003] One of the technologies mentioned above is, for example, a method of covering the exposed part of the current collector with insulating tape. However, insulating tape has drawbacks in terms of workability (productivity), peeling over time, and concerns about reduced battery performance due to excessive tape thickness. In particular, when the electrode active material layer is formed in a long length, such as with electrodes using current collectors without current collecting tabs (so-called tabless current collectors), the area to be insulated becomes long, making it difficult to apply insulating tape.

[0004] In response to this, a technique has been proposed to form an insulating layer on the exposed portion of the current collector using a composition such as an insulating paste (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2021 / 193286 [Overview of the project] [Problems that the invention aims to solve]

[0006] While polyvinylidene fluoride (PVDF) is used in the above-mentioned Patent Document 1, there is a demand for materials other than PVDF due to stricter legal regulations on fluorine-based compounds. In this context, materials other than PVDF are being considered, but there is room for improvement in terms of adhesion to current collectors. Furthermore, insulating layers formed with conventional compositions may experience blocking (adhesion to other current collectors, etc.) during storage, and there is also room for improvement in terms of resistance to blocking.

[0007] Therefore, the present disclosure aims to provide an insulating layer composition that can form an insulating layer with excellent adhesion to the current collector and blocking resistance on a current collector for a lithium-ion secondary battery. Furthermore, the present disclosure aims to provide a method for manufacturing the insulating layer composition, a current collector with an insulating layer for a lithium-ion secondary battery using the insulating layer composition, and an electrode and a lithium-ion secondary battery equipped with the current collector with the insulating layer. [Means for solving the problem]

[0008] This disclosure provides at least the following [1] to

[17] . [1] A composition for the insulating layer of a current collector for lithium-ion secondary batteries, A resin (A) having at least one bonding group selected from the group consisting of urethane groups, urea groups, amide groups, and imide groups, and a non-aqueous solvent, An insulating layer composition wherein the total concentration of the bonding groups in the resin (A) is 500 to 10000 mmol / kg. [2] The insulating layer composition according to [1], wherein the total concentration of the bonding groups in the resin (A) is 1000 to 8000 mmol / kg. [3] The insulating layer composition according to [1] or [2], wherein the resin (A) comprises at least one resin selected from the group consisting of polyurethane resin, polyurea resin, and polyurethane urea resin. [4] The insulating layer composition according to any one of [1] to [3], wherein the resin (A) has an aromatic ring. [5] The insulating layer composition according to [4], wherein the aromatic ring concentration in the resin (A) is 1000 to 8000 mmol / kg. [6] The insulating layer composition according to any one of [1] to [5], wherein the resin (A) comprises a polyolefin structure. [7] The insulating layer composition according to [6], wherein the polyolefin structure comprises the structure of at least one polyolefin selected from the group consisting of polybutadiene, polyisoprene, and hydrogenated versions thereof. [8] The insulating layer composition according to [6] or [7], wherein the content of the polyolefin structure is 10 to 80% by mass, based on the total mass of the resin (A). [9] The insulating layer composition according to any one of [1] to [8], wherein the weight-average molecular weight of the resin (A) is 10,000 to 1,000,000.

[10] The insulating layer composition according to any one of [1] to [9], wherein the non-aqueous solvent comprises at least one solvent selected from the group consisting of N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide.

[11] An insulating layer composition according to any one of [1] to

[10] , further containing an inorganic filler.

[12] The insulating layer composition according to any one of [1] to

[11] , wherein the insulating layer is formed along the boundary between a region on the current collector where the electrode active material layer is formed and a region where the electrode active material layer is not formed.

[13] A method for producing an insulating layer composition according to any one of [1] to

[12] , A manufacturing method comprising at least one of the following steps (1) to (5). (1) A step of reacting a polyol with a polyisocyanate. (2) A step of reacting a polyamine with a polyisocyanate. (3) Step of reacting a polyol, a polyisocyanate, and a polyamine (4) Step of reacting a polycarboxylic acid and a polyamine (5) Step of reacting an acid anhydride having a carboxy group and a polyisocyanate

[14] A current collector with an insulating layer for a lithium-ion secondary battery, comprising an insulating layer formed from the insulating layer composition according to any one of [1] to

[12] .

[15] The current collector with an insulating layer for a lithium-ion secondary battery according to

[14] , which is for a positive electrode.

[16] An electrode for a lithium-ion secondary battery, comprising the current collector according to

[14] or

[15] and an electrode active material layer.

[17] A lithium-ion secondary battery, comprising the electrode according to

[16] . [Advantages of the Invention]

[0009] According to the present disclosure, it is possible to provide an insulating layer composition capable of forming an insulating layer excellent in adhesion to a current collector and blocking resistance with respect to the current collector for a lithium-ion secondary battery. Further, according to the present disclosure, it is possible to provide a method for producing the insulating layer composition, a current collector with an insulating layer for a lithium-ion secondary battery using the insulating layer composition, and an electrode and a lithium-ion secondary battery including the current collector with the insulating layer. [Embodiments for Carrying Out the Invention]

[0010] Hereinafter, exemplary embodiments of the present disclosure will be described. However, the present disclosure is not limited to the following embodiments. In this specification, a numerical range indicated by using "~" indicates a range including the numerical values described before and after "~" as the minimum value and the maximum value, respectively. Further, unless specifically specified, the units of the numerical values described before and after "~" are the same. Also, the individually described upper limit values and lower limit values can be arbitrarily combined.

[0011] [Insulating Layer Composition] One embodiment of the present disclosure is an insulating layer composition for a lithium-ion secondary battery current collector, comprising a resin (hereinafter referred to as "resin (A)") having at least one bonding group selected from the group consisting of urethane groups, urea groups, amide groups, and imide groups (hereinafter these bonding groups are collectively referred to as "bonding group (X)"), and a non-aqueous solvent, wherein the total concentration of bonding group (X) in resin (A) is 500 to 10000 mmol / kg, and is an insulating layer composition (hereinafter referred to as "composition (I)").

[0012] Composition (I) is used to form an insulating layer on a current collector for a lithium-ion secondary battery. The insulating layer is provided in a region of the current collector for a lithium-ion secondary battery where the electrode active material layer is not formed, and by covering the exposed portion of the current collector in that region, the current collector is insulated and short circuits are prevented. Since the short circuit can occur due to contact between lithium deposited at the edge of the negative electrode active material layer and the positive electrode current collector, the insulating layer is formed, for example, along the boundary between the region where the electrode active material layer is formed and the region where the electrode active material layer is not formed (particularly the boundary on the positive electrode side). A portion of the insulating layer may also be formed beyond the boundary onto the electrode active material layer (for example, on the surface of the portion along the boundary).

[0013] According to composition (I), an insulating layer with excellent adhesion to the current collector and blocking resistance can be formed on the current collector for a lithium-ion secondary battery.

[0014] The fact that the layer formed from composition (I) is an insulating layer (i.e., the layer has insulating properties) can be confirmed by measuring the cell capacity using the method described in the examples. If the cell capacity measured using the method described in the examples is 20 mAh / g or less, it can be said that the layer formed from composition (I) has insulating properties. The evaluation layer is formed by coating composition (I) onto aluminum foil to a thickness of 20 μm after drying, and drying it at 140°C for 2 hours.

[0015] Composition (I) may be liquid, paste, or slurry. Liquid means that the viscosity of composition (I) at 25°C is 10,000 mPa·s or less. The viscosity of composition (I) at 25°C may be, for example, 1,500 to 8,000 mPa·s.

[0016] (Resin (A)) The resin (A) has at least one bonding group (bonding group (X)) selected from the group consisting of a urethane group (-OC(=O)-NH-), a urea group (-NH-C(=O)-NH-), an amide group (-C(=O)-N<), and an imide group (-C(=O)-NC(=O)-).

[0017] The total concentration of the bonding group (X) of resin (A) is 500 to 10000 mmol / kg. From the viewpoint of further improving the adhesion of the insulating layer to the current collector, the above total concentration may be 1000 mmol / kg or more, 1500 mmol / kg or more, 2000 mmol / kg or more, 3000 mmol / kg or more, 4000 mmol / kg or more, or 5000 mmol / kg or more. From the viewpoint of increasing the flexibility of the insulating layer and suppressing damage during winding, the above total concentration may be 8000 mmol / kg or less, or 7000 mmol / kg or less. From the viewpoint of the above, the above total concentration may be 1000 to 8000 mmol / kg, 1500 to 7000 mmol / kg, 2000 to 7000 mmol / kg, 3000 to 7000 mmol / kg, 4000 to 7000 mmol / kg, or 5000 to 7000 mmol / kg.

[0018] The total concentration of the binding group (X) in resin (A) can be calculated from the amount of each raw material used in resin (A), and the concentration of the functional groups (binding group (X) and groups that react with other raw materials to form binding group (X)) contained in the raw materials. The composition of the raw materials for resin (A) can be determined by NMR measurement or the like. If resin (A) is composed of multiple types of resins, the total concentration mentioned above refers to the total concentration of the binding group (X) in the mixture of all the resins that make up resin (A).

[0019] In one embodiment, the concentration of urethane groups in resin (A) may be 500 to 10000 mmol / kg, the concentration of urea groups may be 500 to 10000 mmol / kg, and the total concentration of urethane groups and urea groups may be 500 to 10000 mmol / kg. When the above concentration is 500 mmol / kg or more, the adhesion of the insulating layer to the current collector is more easily improved, and when the above concentration is 10000 mmol / kg or less, the flexibility of the insulating layer is increased, and damage during winding is more easily suppressed. From the above viewpoint, the above concentration may be 1000 mmol / kg or more, 1500 mmol / kg or more, 2000 mmol / kg or more, 3000 mmol / kg or more, 4000 mmol / kg or more, or 5000 mmol / kg or more, or 8000 mmol / kg or less, or 7000 mmol / kg or less, or 1000 to 8000 mmol / kg, 1500 to 7000 mmol / kg, 2000 to 7000 mmol / kg, 3000 to 7000 mmol / kg, 4000 to 7000 mmol / kg, or 5000 to 7000 mmol / kg.

[0020] In one embodiment, the molar ratio of the concentration of urethane groups to the total concentration of bonding groups (X) in resin (A) may be 0.8 to 1.0, the molar ratio of the concentration of urea groups to the total concentration of bonding groups (X) in resin (A) may be 0.8 to 1.0, and the molar ratio of the total concentration of urethane groups and urea groups to the total concentration of bonding groups (X) in resin (A) may be 0.8 to 1.0. When the above molar ratio is 0.8 or higher, the insulating properties of the insulating layer, adhesion to the current collector, and blocking resistance tend to be further improved. From the above viewpoint, the above molar ratio may be 0.9 to 1.0 or 0.99 to 1.0.

[0021] In one embodiment, resin (A) may have aromatic rings. If resin (A) is composed of multiple types of resins, having aromatic rings in resin (A) means that resin (A) includes resins that have aromatic rings. In this case, it is sufficient if some of the resins included in resin (A) have aromatic rings, but all of the resins may also have aromatic rings.

[0022] The aromatic ring may be monocyclic or polycyclic. The aromatic ring may be aromatic hydrocarbon ring or aromatic heterocyclic. Examples of aromatic rings include benzene rings, naphthalene rings, phenanthrene rings, anthracene rings, furan rings, pyrrole rings, pyran rings, and pyridine rings. Resin (A) may have one of these, or two or more.

[0023] The aromatic ring concentration in resin (A) may be 1000 mmol / kg or more, 1500 mmol / kg or more, 2000 mmol / kg or more, 3000 mmol / kg or more, 4000 mmol / kg or more, or 5000 mmol / kg or more, from the viewpoint of further improving the adhesion, insulation, and blocking resistance of the insulating layer. The aromatic ring concentration in resin (A) may be 8000 mmol / kg or less or 7000 mmol / kg or less, from the viewpoint of improving the flexibility of the insulating layer and suppressing damage during winding. From the above viewpoint, the aromatic ring concentration may be 1000 to 8000 mmol / kg, 1500 to 7000 mmol / kg, 2000 to 7000 mmol / kg, 3000 to 7000 mmol / kg, 4000 to 7000 mmol / kg, or 5000 to 7000 mmol / kg.

[0024] The aromatic ring concentration of resin (A) can be calculated from the proportions of the raw materials used in resin (A) and the aromatic ring concentrations of the raw materials. If resin (A) is composed of multiple types of resins, the above aromatic ring concentration refers to the aromatic ring concentration of the mixture of all resins that make up resin (A).

[0025] In one embodiment, resin (A) may contain a polyolefin structure. That is, resin (A) may contain a structure obtained by removing two or more hydrogen atoms from a polyolefin. When resin (A) is composed of multiple types of resins, resin (A) containing a polyolefin structure means that resin (A) contains a resin that contains a polyolefin structure. In this case, it is sufficient if some of the resins contained in resin (A) contain a polyolefin structure, but all of the resins may contain a polyolefin structure.

[0026] The polyolefin structure may be a structure based on a monomer containing a polyolefin structure (e.g., polyolefin polyol), or a structure obtained by removing a functional group (e.g., a hydroxyl group) from the monomer. The polyolefin structure may be a structure of a saturated polyolefin such as polyethylene, polypropylene, polybutene, or polyisobutylene, or an unsaturated polyolefin such as polybutadiene or polyisoprene, or a structure of a hydrogenated version of these unsaturated polyolefins. The polyolefin structure may be composed of a combination of these structures. In particular, when the polyolefin structure includes the structure of at least one polyolefin selected from the group consisting of polybutadiene and polyisoprene, and their hydrogenated versions (hydrogenated polybutadiene and hydrogenated polyisoprene), the insulating properties and blocking resistance of the insulating layer tend to be further improved, and when the polyolefin structure includes the structure of polybutadiene, the insulating properties and blocking resistance of the insulating layer tend to be further improved.

[0027] The resin (A) may contain one type of polyolefin structure, or it may contain two or more types of polyolefin structures.

[0028] From the viewpoint of further improving the insulating properties and blocking resistance of the insulating layer, the content of the polyolefin structure may be 10% by mass or more, 30% by mass or more, 50% by mass or more, or 70% by mass or more, based on the total mass of resin (A). From the viewpoint of further improving the adhesion of the insulating layer to the current collector, the content of the polyolefin structure may be 80% by mass or less, 70% by mass or less, 60% by mass or less, 50% by mass or less, 30% by mass or less, or 15% by mass or less, based on the total mass of resin (A). From the above viewpoint, the content of the polyolefin structure may be 10-80% by mass, 30-70% by mass, 50-60% by mass, 70-80% by mass, 10-50% by mass, 10-30% by mass, or 10-15% by mass, based on the total mass of resin (A). The content of the polyolefin structure may be 0.1-90% by mass, based on the total mass of resin (A).

[0029] The polyolefin structure content can be calculated from the blending ratio of the raw materials of resin (A) and the amount of polyolefin structure contained in the raw materials. If resin (A) is composed of multiple types of resins, the above polyolefin structure content refers to the polyolefin structure content (based on the total mass of the mixture) in the mixture of all resins corresponding to resin (A).

[0030] Examples of resin (A) include polyurethane resin, polyurea resin, polyurethane urea resin, polyamide resin, polyimide resin, and polyamide-imide resin. These resins may be resins having the aromatic ring described above, resins containing the polyolefin structure described above, or resins having the aromatic ring described above and containing the polyolefin structure described above. Resin (A) may be used alone or in combination of two or more types.

[0031] Resin (A) may be at least one resin selected from the group consisting of polyurethane resin, polyurea resin, polyurethane urea resin, polyamide resin, and polyamide-imide resin, from the viewpoint of further improving the insulating properties of the insulating layer, adhesion to the current collector, and blocking resistance. In particular, when resin (A) contains at least one resin selected from the group consisting of polyurethane resin, polyurea resin, and polyurethane urea resin, the insulating properties of the insulating layer, adhesion to the current collector, and blocking resistance tend to be further improved. This tendency is more pronounced when resin (A) contains at least one resin selected from the group consisting of polyurethane resin and polyurethane urea resin, and is even more pronounced when resin (A) contains polyurethane resin.

[0032] The total content of polyurethane resin, polyurea resin, and polyurethane urea resin may be 80% by mass or more, 90% by mass or more, or 99% by mass or more, based on the total mass of resin (A), from the viewpoint of further improving the insulating properties of the insulating layer, adhesion to the current collector, and blocking resistance. From a similar viewpoint, the total content of polyurethane resin and polyurethane urea resin may be 80% by mass or more, 90% by mass or more, or 99% by mass or more, based on the total mass of resin (A), and the content of polyurethane resin may be 80% by mass or more, 90% by mass or more, or 99% by mass or more, based on the total mass of resin (A). Resin (A) may consist only of polyurethane resin, polyurea resin, and polyurethane urea resin, or only of polyurethane resin and polyurethane urea resin, or only of polyurethane resin.

[0033] From the viewpoint of further improving the insulating properties of the insulating layer, adhesion to the current collector, and blocking resistance, resin (A) does not have to contain resins having amide bonds (e.g., polyamide resins and polyamide-imide resins), does not have to contain resins having imide bonds (e.g., polyimide resins and polyamide-imide resins), and does not have to contain either of these resins. In other words, composition (I) does not have to contain resins having amide bonds, does not have to contain resins having imide bonds, and does not have to contain either of these resins.

[0034] [Polyurethane resin] Polyurethane resin is a resin having multiple urethane groups. Polyurethane resin may also have bonding groups other than urethane groups as bonding groups (X). However, resins having multiple urethane groups and urea groups are classified as polyurethane urea resins. The amount of urethane groups relative to the total number of bonding groups (X) in a polyurethane resin may be 60 mol% or more, or 80 mol% or more. Polyurethane resin does not need to have bonding groups other than urethane groups as bonding groups (X). For example, polyurethane resin does not need to have amide groups, does not need to have imide groups, or does not need to have both. When polyurethane resin does not have imide groups and amide groups, the insulating properties of the insulating layer, adhesion to current collectors, and blocking resistance tend to be further improved.

[0035] The urethane group concentration of the polyurethane resin may be 500 mmol / kg or more, 1000 mmol / kg or more, 1500 mmol / kg or more, 2000 mmol / kg or more, 3000 mmol / kg or more, 4000 mmol / kg or more, or 5000 mmol / kg or more, from the viewpoint of further improving the adhesion of the insulating layer to the current collector. The urethane group concentration of the polyurethane resin may be 10000 mmol / kg or less, 8000 mmol / kg or less, or 7000 mmol / kg or less, from the viewpoint of improving the flexibility of the insulating layer and suppressing damage during winding. From the above viewpoint, the urethane group concentration of the polyurethane resin may be 500-10000 mmol / kg, 1000-8000 mmol / kg, 1500-7000 mmol / kg, 2000-7000 mmol / kg, 3000-7000 mmol / kg, 4000-7000 mmol / kg, or 5000-7000 mmol / kg.

[0036] The polyurethane resin may have the aromatic rings described above, and may also have a polyolefin structure. If the polyurethane resin has aromatic rings, the concentration of aromatic rings in the polyurethane resin may be within the range of the concentration of aromatic rings in resin (A) described above. Similarly, if the polyurethane resin contains a polyolefin structure, the content of the polyolefin structure in the polyurethane resin (based on the total mass of the polyurethane resin) may be within the range of the content of the polyolefin structure in resin (A) described above (based on the total mass of resin (A)). The same applies to the polyurea resin, polyurethane urea resin, polyamide resin, and polyamide-imide resin described later.

[0037] Polyurethane resins include, for example, structural units based on polyols and structural units based on polyisocyanates. In this specification, "based on polyols" means that the structural unit has a structure obtained by removing functional groups (e.g., hydroxyl groups) from a polyol. Furthermore, "based on polyisocyanates" means that the structural unit has a structure obtained by removing functional groups (e.g., isocyanate groups) from a polyisocyanate.

[0038] The polyol may be a polyol with a molecular weight of 500 or more (hereinafter referred to as "high molecular weight polyol"), or a polyol with a molecular weight of less than 500 (hereinafter referred to as "low molecular weight polyol"). The polyol may contain both of these. In particular, when the polyol contains a low molecular weight polyol, adhesion to the current collector and blocking resistance tend to be improved, and when the polyol contains both high molecular weight polyols and low molecular weight polyols, insulation, flexibility, and electrolyte resistance tend to be improved.

[0039] High molecular weight polyols may be polyols having a polymer structure. Examples of high molecular weight polyols include polyolefin polyols, polyester polyols, polycarbonate polyols, polyether polyols, and polyether ester polyols. High molecular weight polyols may be used individually or in combination of two or more.

[0040] The high molecular weight polyol may include polyolefin polyols and polyester polyols from the viewpoint of further improving the insulating properties of the insulating layer, adhesion to the current collector, and blocking resistance.

[0041] Polyolefin polyols may be polyols containing the polyolefin structure described above. Specific examples of polyolefin polyols include polyethylene polyols, polypropylene polyols, polyisobutenoriols, hydrogenated polybutadiene polyols (e.g., hydrogenated polybutadiene containing hydroxyl groups at both ends), and hydrogenated polyisoprene polyols. From the viewpoint of further improving the insulating properties of the insulating layer, adhesion to the current collector, and blocking resistance, polyolefin polyols may include at least one selected from the group consisting of polybutadiene polyols, polyisoprene polyols, hydrogenated polybutadiene polyols, and hydrogenated polyisoprene polyols.

[0042] Examples of polyester polyols include condensed polyester polyols and lactone-based polyester polyols. Condensed polyester polyols are reaction products of low molecular weight polyhydric alcohols (such as ethylene glycol, propylene glycol, butanediol, pentanediol, neopentyl glycol, hexanediol, cyclohexanedimethanol, glycerin, 1,1,1-trimethylolpropane, 1,2,5-hexanetriol, pentaerythritol, 1,4-cyclohexanedimethanol, 1,3-propanediol, and sugars such as sorbitol) and polyhydric basic carboxylic acids (such as glutaric acid, adipic acid, azelaic acid, fumaric acid, maleic acid, pimelic acid, suberic acid, sebacic acid, phthalic acid, terephthalic acid, isophthalic acid, dimer acid, trimellitic acid, pyromellitic acid, oligomeric acid, hexahydrophthalic anhydride, 1,4-cyclohexanedicarboxylic acid, etc.) or their anhydrides or ester-forming derivatives. Examples of lactone-based polyester polyols include polycaprolactone polyols obtained by ring-opening polymerization of lactones such as ε-caprolactone, α-methyl-ε-caprolactone, and ε-methyl-ε-caprolactone. From the viewpoint of further improving the insulating properties of the insulating layer, adhesion to the current collector, and blocking resistance, the polyester polyol may contain a reaction product between a low molecular weight polyhydric alcohol and a polyhydric basic carboxylic acid or its anhydride or ester-forming derivative.

[0043] Examples of polycarbonate polyols include those obtained by the reaction of a carbonate (carbonate ester) with a diol such as a glycol. Examples of carbonates (carbonate esters) include dialkyl carbonates (dimethyl carbonate, diethyl carbonate, etc.), ethylene carbonate, and diphenyl carbonate. Examples of diols include diethylene glycol, ethylene glycol, triethylene glycol, propanediol, propanediol, butanediol, neopentyl glycol, pentanediol, 3-methyl-1,5-pentanediol, octanediol, 1,4-butynediol, dipropylene glycol, tripropylene glycol, polytetramethylene ether glycol, 2-methyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, 1,4-cyclohexanediglycol, and 1,4-cyclohexanedimethanol.

[0044] Examples of polyether polyols include polytetramethylene glycol obtained by ring-opening polymerization of tetrahydrofuran; modified polytetramethylene glycol obtained by copolymerizing tetrahydrofuran with alkyl-substituted tetrahydrofuran or neopentyl glycol; polyether polyols having an alicyclic structure; and products obtained by addition polymerization of one or more alkylene oxides such as ethylene oxide, propylene oxide, and butylene oxide to compounds having two or more active hydrogens, such as ethylene glycol, diethylene glycol, trimethylene glycol, propanediol, butanediol, hexanediol, neopentyl glycol, octanediol, glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, and sorbitol.

[0045] The molecular weight of the high molecular weight polyol is 500 or more, and may be 800 or more or 1000 or more from the viewpoint of improving the flexibility of the insulating layer, and may be 5000 or less, 4000 or less, or 3000 or less from the viewpoint of improving the electrolyte resistance of the insulating layer. From the above viewpoint, the molecular weight of the high molecular weight polyol may be 500 to 5000, 800 to 4000, or 1000 to 3000. The above molecular weights are the number average molecular weights on a standard polystyrene basis, obtained using gel permeation chromatography (GPC).

[0046] Examples of low molecular weight polyols include ethylene glycol, 1,2-propanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 3,3'-dimethylolheptane, 1,4-cyclohexanedimethanol, neopentyl glycol, 3,3-bis(hydroxymethyl)heptane, diethylene glycol, dipropylene glycol, glycerin, trimethylolpropane, sorbitol, hydroquinone diethylol ether, etc. Polyolefin polyols, polyester polyols, polycarbonate polyols, polyether polyols, polyether ester polyols, etc., may also be used as low molecular weight polyols. When using both high molecular weight polyols and low molecular weight polyols, a different type of low molecular weight polyol (e.g., a polyol without a polymer structure) may be used as the low molecular weight polyol. Low molecular weight polyols may be used individually or in combination of two or more types.

[0047] The low molecular weight polyol may be a diol compound, from the viewpoint of easily controlling the weight-average molecular weight of the urethane resin, and may be at least one diol selected from the group consisting of ethylene glycol, 1,4-butanediol, 1,6-hexanediol, and 1,4-cyclohexanedimethanol.

[0048] The molecular weight of the low molecular weight polyol is less than 500, and may be 50 or more, 100 or more, or 200 or more from the viewpoint of further improving the adhesion of the insulating layer to the current collector, and may be 400 or less or 300 or less from the viewpoint of further improving the blocking resistance of the insulating layer. From the above viewpoint, the molecular weight of the low molecular weight polyol may be 50 or more but less than 500, 100 to 400, or 200 to 300. If the low molecular weight polyol contains multiple types of polyols, the number average molecular weight in terms of standard polystyrene, obtained by gel permeation chromatography (GPC), may be within the above range.

[0049] The content of polyol-based constituent units may be 10-90% by mass, 15-85% by mass, or 20-80% by mass, based on the total mass of the polyurethane resin, from the viewpoint of further improving the insulating properties of the insulating layer.

[0050] The content of structural units based on high molecular weight polyols may be 0.5% by mass or more, 5% by mass or more, or 10% by mass or more, based on the total mass of the polyurethane resin, and may also be 90% by mass or less, 85% by mass or less, 80% by mass or less, 60% by mass or less, 40% by mass or less, or 20% by mass or less. From the viewpoint of achieving both flexibility and electrolyte resistance of the insulating layer, the content of structural units based on high molecular weight polyols may be 0.5 to 90% by mass, 0.5 to 85% by mass, 0.5 to 80% by mass, 0.5 to 60% by mass, 0.5 to 40% by mass, 0.5 to 20% by mass, 5 to 85% by mass, or 10 to 80% by mass, based on the total mass of the polyurethane resin.

[0051] The content of constituent units based on low molecular weight polyols may be 0% by mass or more, 5% by mass or more, 8% by mass or more, 10% by mass or more, or 15% by mass or more, based on the total mass of the polyurethane resin, and may also be 30% by mass or less, 25% by mass or less, or 20% by mass or less. From the viewpoint of achieving a higher level of compatibility between the adhesion of the insulating layer to the current collector and the blocking resistance, the content of constituent units based on low molecular weight polyols may be 0-30% by mass, 5-30% by mass, 8-30% by mass, 10-30% by mass or 15-30% by mass, 5-25% by mass or 10-20% by mass, based on the total mass of the polyurethane resin.

[0052] The mass ratio of the content of high molecular weight polyol-based constituent units to the content of low molecular weight polyol-based constituent units may be 0.001 or higher, 0.01 or higher, or 0.02 or higher, from the viewpoint of achieving a higher level of compatibility between adhesion to the current collector and blocking resistance. The mass ratio of the content of high molecular weight polyol-based constituent units to the content of low molecular weight polyol-based constituent units may be 50 or less, 20 or less, 10 or less, 5 or less, or 1 or less, from the viewpoint of improving the insulating properties, flexibility, and electrolyte resistance of the insulating layer. From the above viewpoint, the mass ratio of the content of high molecular weight polyol-based constituent units to the content of low molecular weight polyol-based constituent units may be 0.001 to 50, 0.001 to 20, 0.001 to 10, 0.01 to 5, or 0.02 to 1.

[0053] The polyisocyanate may be an aromatic polyisocyanate or a non-aromatic polyisocyanate. That is, the polyurethane resin may contain at least one selected from the group consisting of constituent units based on aromatic polyisocyanates and constituent units based on non-aromatic polyisocyanates. An aromatic polyisocyanate means a polyisocyanate having an aromatic ring skeleton, and a non-aromatic polyisocyanate means a polyisocyanate not having an aromatic ring skeleton. Examples of aromatic rings in aromatic polyisocyanates are the same as examples of aromatic rings in resin (A) above.

[0054] Examples of aromatic polyisocyanates include phenylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, xylylene diisocyanate, and tetramethylxylylene diisocyanate. Aromatic polyisocyanates may be used individually or in combination of two or more.

[0055] Aromatic polyisocyanates may be polyisocyanates having a structure in which isocyanate groups are directly bonded to carbon atoms constituting an aromatic ring, from the viewpoint of being easy to control the weight-average molecular weight and improving resistance to electrolytes. In particular, the above effects are easily obtained when using diisocyanates having a structure in which isocyanate groups are directly bonded to carbon atoms constituting an aromatic ring. Examples of diisocyanates having a structure in which isocyanate groups are directly bonded to carbon atoms constituting an aromatic ring include diphenylmethane diisocyanate, naphthalene diisocyanate, phenylene diisocyanate, and toluene diisocyanate.

[0056] Aromatic polyisocyanates may be isomer mixtures. For example, when using toluene diisocyanate, an isomer mixture containing 2,4-toluene diisocyanate and 2,6-toluene diisocyanate may be used. The ratio of the amount of 2,4-toluene diisocyanate to the amount of 2,6-toluene diisocyanate (2,4-toluene diisocyanate / 2,6-toluene diisocyanate) may be 60 / 40 to 90 / 10 or 70 / 30 to 85 / 15 in molar ratio.

[0057] Examples of non-aromatic polyisocyanates include dicyclohexylmethane 4,4'-diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate. Non-aromatic polyisocyanates may be used individually or in combination of two or more.

[0058] Non-aromatic polyisocyanates may be polyisocyanates having an aliphatic ring, from the viewpoint of easier control of weight-average molecular weight and improved resistance to electrolytes. In particular, the above effects are easily obtained when using polyisocyanates having a structure in which isocyanate groups are directly bonded to carbon atoms constituting the aliphatic ring, and the above effects are even easier to obtain when using diisocyanates having a structure in which isocyanate groups are directly bonded to carbon atoms constituting the aliphatic ring. An example of a diisocyanate having a structure in which isocyanate groups are directly bonded to carbon atoms constituting the aliphatic ring is dicyclohexylmethane 4,4'-diisocyanate.

[0059] The content of polyisocyanate-based structural units may be 10-90% by mass, 20-85% by mass, or 30-80% by mass, based on the total mass of the polyurethane resin, from the viewpoint of achieving both blocking resistance and electrolyte resistance of the insulating layer. If the polyisocyanate includes aromatic polyisocyanate, the content of structural units based on aromatic polyisocyanate may be within the above range. If the polyisocyanate includes non-aromatic polyisocyanate, the content of structural units based on non-aromatic polyisocyanate may be within the above range.

[0060] The polyurethane resin may be a reaction product of the polyol and polyisocyanate described above.

[0061] The reaction between polyols and polyisocyanates may be carried out in a non-aqueous solvent at a temperature of 50 to 150°C. The same non-aqueous solvents described later can be used. Other reaction conditions may be set according to known methods.

[0062] [Polyurea resin] Polyurea resin is a resin having multiple urea groups. Polyurea resin may have bonding groups other than urea groups as bonding groups (X). However, resins having multiple urea groups and urethane groups are classified as polyurethane urea resins. The amount of urea groups relative to the total number of bonding groups (X) in polyurea resin may be 60 mol% or more, or 80 mol% or more. Polyurea resin does not need to have bonding groups other than urea groups as bonding groups (X). For example, polyurea resin does not need to have amide groups, does not need to have imide groups, or does not need to have both. When polyurea resin does not have imide groups, the flexibility of the insulating layer tends to be improved, and when polyurea resin does not have amide groups, the adhesion to the current collector tends to be improved.

[0063] The urea group concentration of the polyurea resin may be 500 mmol / kg or more, 1000 mmol / kg or more, 1500 mmol / kg or more, 2000 mmol / kg or more, 3000 mmol / kg or more, 4000 mmol / kg or more, or 5000 mmol / kg or more, from the viewpoint of further improving the adhesion of the insulating layer to the current collector. The urea group concentration of the polyurea resin may be 10000 mmol / kg or less, 8000 mmol / kg or less, or 7000 mmol / kg or less, from the viewpoint of improving the flexibility of the insulating layer and suppressing damage during winding. From the above perspective, the urea group concentration of the polyurea resin may be 500-10000 mmol / kg, 1000-8000 mmol / kg, 1500-7000 mmol / kg, 2000-7000 mmol / kg, 3000-7000 mmol / kg, 4000-7000 mmol / kg, or 5000-7000 mmol / kg.

[0064] Polyurea resins include, for example, structural units based on polyamines and structural units based on polyisocyanates. In this specification, "based on polyamines" means that the structural unit has a structure obtained by removing functional groups (e.g., amine groups) from a polyamine.

[0065] The polyamine may be a polyamine with a molecular weight of 500 or more (hereinafter referred to as "high molecular weight polyamine"), or a polyamine with a molecular weight of less than 500 (hereinafter referred to as "low molecular weight polyamine"). The polyamine may contain both of these.

[0066] High molecular weight polyamines may be polyamines having a polymer structure. Examples of high molecular weight polyamines include polyether polyamines such as polyethylene glycol polypropylene glycol diamine. High molecular weight polyamines may be used individually or in combination of two or more.

[0067] The molecular weight of the high molecular weight polyamine is 500 or more, and may be 800 or more or 1000 or more from the viewpoint of improving the flexibility of the insulating layer, and may be 5000 or less, 4000 or less, or 3000 or less from the viewpoint of improving the electrolyte resistance of the insulating layer. From the above viewpoint, the molecular weight of the high molecular weight polyamine may be 500 to 5000, 800 to 4000, or 1000 to 3000. The above molecular weights are the number average molecular weights on a standard polystyrene basis, obtained using gel permeation chromatography (GPC).

[0068] Examples of low molecular weight polyamines include ethylenediamine, propylenediamine, hexamethylenediamine, trimethylhexamethylenediamine, isophoronediamine, 4,4'-dicyclohexylmethanediamine, diaminocyclohexane, methyldiaminocyclohexane, norbornenediamine, 4,4'-diaminodiphenylmethane, piperazine, adipic acid dihydrazide, sebacate acid dihydrazide, isophthalic acid dihydrazide, and the like. As low molecular weight polyols, polyether polyamines may also be used. When both high molecular weight polyamines and low molecular weight polyamines are used, the low molecular weight polyamine may be of a different type from the high molecular weight polyamine (for example, a polyamine without a polymer structure). Low molecular weight polyamines may be used alone or in combination of two or more types.

[0069] The molecular weight of the low molecular weight polyamine is less than 500, and may be 50 or more, 100 or more, or 200 or more from the viewpoint of further improving the adhesion of the insulating layer to the current collector, and may be 400 or less or 300 or less from the viewpoint of further improving the blocking resistance of the insulating layer. From the above viewpoint, the molecular weight of the low molecular weight polyamine may be 50 or more but less than 500, 100 to 400, or 200 to 300. If the low molecular weight polyamine contains multiple types of polyamines, the number average molecular weight on a standard polystyrene basis, obtained by gel permeation chromatography (GPC), may be within the above range.

[0070] The content of polyamine-based structural units may be 10-90% by mass, 15-85% by mass, or 20-80% by mass, based on the total mass of the polyurea resin, from the viewpoint of further improving the insulating properties of the insulating layer.

[0071] The content of the structural units based on high molecular weight polyamine may be 0.5 to 90% by mass, 5 to 85% by mass, or 10 to 80% by mass, based on the total mass of the polyurea resin, from the viewpoint of achieving both flexibility and electrolyte resistance of the insulating layer.

[0072] The content of the constituent units based on low molecular weight polyamine may be 0-30% by mass, 5-25% by mass, or 10-20% by mass, based on the total mass of the polyurea resin, from the viewpoint of achieving a higher level of both adhesion of the insulating layer to the current collector and resistance to blocking.

[0073] The polyisocyanate may be any of the polyisocyanates exemplified as monomers for polyurethane resins. One type of polyisocyanate may be used alone, or two or more types may be used in combination.

[0074] The content of the polyisocyanate-based structural units may be 5-90% by mass, 10-80% by mass, or 15-70% by mass, based on the total mass of the polyurea resin, from the viewpoint of achieving both blocking resistance and electrolyte resistance of the insulating layer.

[0075] The polyurea resin may be a reaction product of the polyamine and polyisocyanate described above.

[0076] The reaction between polyamines and polyisocyanates may be carried out in the range of 0 to 70°C. Other reaction conditions may be set according to known methods.

[0077] [Polyurethane urea resin] Polyurethane urea resin is a resin having multiple urethane groups and urea groups. Polyurethane urea resin may also have bonding groups other than urethane groups and urea groups as bonding groups (X). The total amount of urethane groups and urea groups relative to the total amount of bonding groups (X) in polyurethane urea resin may be, for example, 60 mol% or more or 80 mol% or more. The amount of urethane groups relative to the total amount of urethane groups and urea groups in polyurethane urea resin may be, for example, 20 mol% or more, 40 mol% or more or 60 mol% or more, 80 mol% or less, 60 mol% or less or 40 mol% or less, 20 to 80 mol%, 40 to 60 mol%, 60 to 80 mol%, or 20 to 40 mol%. Polyurethane urea resin does not have to have bonding groups other than urethane groups and urea groups as bonding groups (X). For example, polyurethane urea resin does not have to have amide groups, does not have to have imide groups, or does not have to have both. When polyurethane urea resin does not contain imide groups, the flexibility of the insulating layer tends to improve, and when polyurethane urea resin does not contain amide groups, the adhesion to the current collector tends to improve further.

[0078] The urethane group concentration of the polyurethane urea resin may be 500 mmol / kg or more, 1000 mmol / kg or more, 1500 mmol / kg or more, 2000 mmol / kg or more, 3000 mmol / kg or more, 4000 mmol / kg or more, or 5000 mmol / kg or more, from the viewpoint of further improving the adhesion of the insulating layer to the current collector. The urethane group concentration of the polyurethane urea resin may be 10000 mmol / kg or less, 8000 mmol / kg or less, or 7000 mmol / kg or less, from the viewpoint of improving the flexibility of the insulating layer and suppressing damage during winding. From the above viewpoint, the urethane group concentration of the polyurethane resin may be 500-10000 mmol / kg, 1000-8000 mmol / kg, 1500-7000 mmol / kg, 2000-7000 mmol / kg, 3000-7000 mmol / kg, 4000-7000 mmol / kg, or 5000-7000 mmol / kg.

[0079] The urea group concentration of the polyurethane urea resin may be 500 mmol / kg or more, 1000 mmol / kg or more, 1500 mmol / kg or more, 2000 mmol / kg or more, 3000 mmol / kg or more, 4000 mmol / kg or more, or 5000 mmol / kg or more, from the viewpoint of further improving the adhesion of the insulating layer to the current collector. The urea group concentration of the polyurethane urea resin may be 10000 mmol / kg or less, 8000 mmol / kg or less, or 7000 mmol / kg or less, from the viewpoint of improving the flexibility of the insulating layer and suppressing damage during winding. From the above viewpoint, the urethane group concentration of the polyurethane resin may be 500-10000 mmol / kg, 1000-8000 mmol / kg, 1500-7000 mmol / kg, 2000-7000 mmol / kg, 3000-7000 mmol / kg, 4000-7000 mmol / kg, or 5000-7000 mmol / kg.

[0080] The mass ratio of the content of high molecular weight polyol-based structural units to the content of low molecular weight polyol-based structural units may be 0.001 or higher, 0.01 or higher, or 0.02 or higher, from the viewpoint of improving the insulating properties and flexibility of the insulating layer. The mass ratio of the content of high molecular weight polyol-based structural units to the content of low molecular weight polyol-based structural units may be 50 or less, 20 or less, 10 or less, 5 or less, or 1 or less, from the viewpoint of improving electrolyte resistance. From the above viewpoint, the mass ratio of the content of high molecular weight polyol-based structural units to the content of low molecular weight polyol-based structural units may be 0.001 to 50, 0.001 to 20, 0.001 to 10, 0.01 to 5, or 0.02 to 1.

[0081] Polyurethane urea resin includes, for example, structural units based on polyols, structural units based on polyisocyanates, and structural units based on polyamines. The polyols, polyisocyanates, and polyamines may be the polyols, polyisocyanates, and polyamines exemplified as monomers for polyurethane resins and polyurea resins, respectively. Each of the polyols, polyisocyanates, and polyamines may be used individually or in combination of two or more.

[0082] The content of polyol-based constituent units may be 10-90% by mass, 15-85% by mass, or 20-80% by mass, based on the total mass of the polyurethane urea resin, from the viewpoint of further improving the insulating properties of the insulating layer.

[0083] The content of structural units based on high molecular weight polyols may be 0.5% by mass or more, 5% by mass or more, or 10% by mass or more, based on the total mass of the polyurethane urea resin, and may also be 90% by mass or less, 85% by mass or less, 80% by mass or less, 60% by mass or less, 40% by mass or less, or 20% by mass or less. From the viewpoint of achieving both flexibility and electrolyte resistance of the insulating layer, the content of structural units based on high molecular weight polyols may be 0.5 to 90% by mass, 0.5 to 85% by mass, 0.5 to 80% by mass, 0.5 to 60% by mass, 0.5 to 40% by mass, 0.5 to 20% by mass, 5 to 85% by mass, or 10 to 80% by mass, based on the total mass of the polyurethane urea resin.

[0084] The content of constituent units based on low molecular weight polyols may be 0% by mass or more, 5% by mass or more, 8% by mass or more, 10% by mass or more, or 15% by mass or more, based on the total mass of the polyurethane urea resin, and may also be 30% by mass or less, 25% by mass or less, or 20% by mass or less. From the viewpoint of achieving a higher level of compatibility between adhesion of the insulating layer to the current collector and blocking resistance, the content of constituent units based on low molecular weight polyols may be 0-30% by mass, 5-30% by mass, 8-30% by mass, 10-30% by mass or 15-30% by mass, 5-25% by mass or 10-20% by mass, based on the total mass of the polyurethane urea resin.

[0085] The content of polyisocyanate-based structural units may be 10-90% by mass, 20-85% by mass, or 30-80% by mass, based on the total mass of the polyurethane urea resin, from the viewpoint of achieving both blocking resistance and electrolyte resistance of the insulating layer. If the polyisocyanate includes aromatic polyisocyanate, the content of structural units based on aromatic polyisocyanate may be within the above range. If the polyisocyanate includes non-aromatic polyisocyanate, the content of structural units based on non-aromatic polyisocyanate may be within the above range.

[0086] The content of polyamine-based structural units may be 10-90% by mass, 15-85% by mass, or 20-80% by mass, based on the total mass of the polyurethane urea resin, from the viewpoint of further enhancing the insulating properties of the insulating layer.

[0087] The content of the structural units based on high molecular weight polyamine may be 0.5 to 90% by mass, 5 to 85% by mass, or 10 to 80% by mass, based on the total mass of the polyurethane urea resin, from the viewpoint of achieving both flexibility and electrolyte resistance of the insulating layer.

[0088] The content of the constituent units based on low molecular weight polyamine may be 0-30% by mass, 5-25% by mass, or 10-20% by mass, based on the total mass of the polyurethane urea resin, from the viewpoint of achieving a higher level of both adhesion of the insulating layer to the current collector and resistance to blocking.

[0089] The polyurethane urea resin may be a reaction product of the polyol, polyisocyanate, and polyamine described above.

[0090] The reaction between polyols, polyisocyanates, and polyamines may be carried out in a non-aqueous solvent at a temperature of 0 to 150°C. The same non-aqueous solvents described later can be used. Other reaction conditions may be set according to known methods.

[0091] [Polyamide resin] Polyamide resins are resins that have multiple amide groups. Polyamide resins may also have bonding groups other than amide groups as bonding groups (X). However, resins that have multiple amide and imide groups are classified as polyamide-imide resins. The amount of amide groups relative to the total number of bonding groups (X) in a polyamide resin may be, for example, 60 mol% or more or 80 mol% or more. Polyamide resins do not need to have bonding groups other than amide groups as bonding groups (X).

[0092] Polyamide resins include, for example, structural units based on polycarboxylic acids and structural units based on polyamines. In this specification, "based on polycarboxylic acids" means that the structural unit has a structure obtained by removing functional groups (e.g., carboxyl groups) from a polycarboxylic acid.

[0093] The polycarboxylic acid may be any of the polycarboxylic acids exemplified as polyvalent basic carboxylic acids. One type of polycarboxylic acid may be used alone, or two or more types may be used in combination.

[0094] The content of polycarboxylic acid-based constituent units may be 10-90% by mass, 15-85% by mass, or 20-80% by mass, based on the total mass of the polyamide resin.

[0095] The polyamine may be any of the polyamines exemplified as monomers for polyurea resins. One type of polyamine may be used alone, or two or more types may be used in combination.

[0096] The content of polyamine-based constituent units may be 10-90% by mass, 15-85% by mass, or 20-80% by mass, based on the total mass of the polyamide resin.

[0097] The content of the constituent units based on high molecular weight polyamine may be 0.5 to 90% by mass, 5 to 85% by mass, or 10 to 80% by mass, based on the total mass of the polyamide resin.

[0098] The content of constituent units based on low molecular weight polyamine may be 0-30% by mass, 5-25% by mass, or 10-20% by mass, based on the total mass of the polyamide resin.

[0099] The polyamide resin may be a reaction product of the polycarboxylic acid and polyamine described above.

[0100] The reaction between polycarboxylic acid and polyamine may be carried out in the range of 40 to 150°C. Other reaction conditions may be set according to known methods.

[0101] [Polyamide-imide resin] Polyamide-imide resin is a resin having multiple amide groups and imide groups. Polyamide-imide resin may have bonding groups other than amide groups and imide groups as bonding groups (X). The total amount of amide groups and imide groups relative to the total amount of bonding groups (X) in polyamide-imide resin may be, for example, 60 mol% or more or 80 mol% or more. Polyamide-imide resin may not have bonding groups other than amide groups and imide groups as bonding groups (X). The amount of amide groups relative to the total amount of amide groups and imide groups in polyamide-imide resin may be, for example, 20 mol% or more, 40 mol% or more or 60 mol% or more, 80 mol% or less, 60 mol% or less or 40 mol% or less, 20 to 80 mol%, 40 to 60 mol%, 60 to 80 mol%, or 20 to 40 mol%.

[0102] Polyamide-imide resins include, for example, structural units based on acid anhydrides having carboxyl groups and structural units based on polyisocyanates. In this specification, when a structural unit is described as "based on acid anhydrides having carboxyl groups," it means that the structural unit has a structure obtained by removing functional groups (e.g., carboxyl groups and acid anhydride groups) from an acid anhydride having carboxyl groups.

[0103] Examples of acid anhydrides containing a carboxyl group include cyclohexanetricarboxylic acid anhydride and trimellitic anhydride. A single acid anhydride containing a carboxyl group may be used, or two or more may be used in combination.

[0104] The content of constituent units based on acid anhydrides having carboxyl groups may be 10-90% by mass, 20-80% by mass, or 30-70% by mass, based on the total mass of the polyamide-imide resin.

[0105] The polyisocyanate may be any of the polyisocyanates exemplified as monomers for polyurethane resins. One type of polyisocyanate may be used alone, or two or more types may be used in combination.

[0106] The content of constituent units based on polyisocyanate may be 10-90% by mass, 20-80% by mass, or 30-70% by mass, based on the total mass of the polyamide-imide resin. If the polyisocyanate includes aromatic polyisocyanate, the content of constituent units based on aromatic polyisocyanate may be within the above range. If the polyisocyanate includes non-aromatic polyisocyanate, the content of constituent units based on non-aromatic polyisocyanate may be within the above range.

[0107] The polyamide-imide resin may be a reaction product of an acid anhydride having a carboxyl group as described above and a polyisocyanate.

[0108] The reaction between an acid anhydride containing a carboxyl group and a polyisocyanate may be carried out in a non-aqueous solvent at a temperature of 40 to 200°C. The same non-aqueous solvents described later can be used. A catalyst such as potassium fluoride may be used in the above reaction. Other reaction conditions may be set according to known methods.

[0109] The weight-average molecular weight of resin (A) may be 10,000 or more, 30,000 or more, 60,000 or more, 100,000 or more, or 150,000 or more, from the viewpoint of superior insulation, adhesion to current collectors, and blocking resistance. The weight-average molecular weight of resin (A) may be 1,000,000 or less, 700,000 or less, 500,000 or less, 300,000 or less, or 100,000 or less, from the viewpoint of improving the handling and coating properties of composition (I). From the above viewpoint, the weight-average molecular weight of resin (A) may be 10,000 to 1,000,000, 30,000 to 700,000, 60,000 to 500,000, 100,000 to 300,000, 150,000 to 100,000, or 10,000 to 100,000. The above weight-average molecular weight is measured by gel permeation chromatography (GPC) and is a standard polystyrene equivalent value (unit: g / mol). Details of the measurement conditions for weight-average molecular weight are shown in the examples.

[0110] The content of the resin (A) may be 1 to 99% by mass, 5 to 95% by mass, 10 to 90% by mass, 20 to 80% by mass, or 30 to 50% by mass based on the total mass of the composition (I).

[0111] (Non-aqueous solvent) The non-aqueous solvent is, for example, an organic solvent in which the dispersion term (δd) in the Hansen solubility parameter is 17 MPa 0.5 or more and 19 MPa 0.5 less, the polarity term (δp) is 12 MPa 0.5 or more and 17 MPa 0.5 less, and the hydrogen bonding term (δh) is 7 MPa 0.5 or more and 12 MPa 0.5 less.

[0112] The dispersion term (δd), polarity term (δp), and hydrogen bonding term (δh) in the Hansen solubility parameter are parameters that take into account the polarity of a substance, which are obtained by dividing the solubility parameter (SP value: δ) introduced by Hildebrand into three components: the dispersion term δd, the polarity term δp, and the hydrogen bonding term δh, and represented in three-dimensional space, and the following relationship holds. δ[(cal / cm 3 ) 0.5 =(δd 2 +δp 2 +δh 2 ) 0.5 The above-mentioned dispersion term δd, polarity term δp, and hydrogen bonding term δh have been determined by Hansen and subsequent researchers in large numbers, and are listed, for example, in VII-698 to 711 of Polymer Handbook (4th edition). In addition, Hansen solubility parameters for many solvents and resins have been investigated, and these solubility parameters are described, for example, in Industrial Solvents Handbook (by Wesley L. Archer). They can also be determined using the software of Hansen Solubility Parameters in Practice (HSPiP).

[0113] The non-aqueous solvent may be an aprotic solvent or an aprotic polar solvent. Examples of non-aqueous solvents include acetone, tetrahydrofuran, acetonitrile, propionitrile, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylformamide, dimethyl sulfoxide, sulfolane, 1,3-dimethyl-2-imidazolidinone, and hexamethylphosphoric triamide. The non-aqueous solvent may be used alone or in combination of two or more.

[0114] The non-aqueous solvent may include at least one non-aqueous solvent selected from the group consisting of N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide, from the viewpoint of resin solubility. Among these, the above effect is easily obtained when N-methyl-2-pyrrolidone is used.

[0115] The content of the non-aqueous solvent may be 1 to 90% by mass, 1 to 70% by mass, 5 to 60% by mass, or 10 to 50% by mass, based on the total mass of composition (I).

[0116] (Other ingredients) [Other resins] Composition (I) may contain resins other than resin (A) described above (hereinafter referred to as "other resins"), to the extent that they do not impair the effects of the present disclosure. The content of other resins may be 0 to 10% by mass based on the total mass of composition (I). The content of other resins may be 5% by mass or less or 1% by mass or less based on the total mass of composition (I).

[0117] [Additives] Composition (I) may further contain various additives as needed, such as surfactants, antioxidants, light stabilizers, plasticizers, viscosity modifiers, and organic or inorganic fillers, to the extent that they do not impair the effects of the present disclosure. The total content of additives may be 0 to 50% by mass based on the total mass of composition (I). The total content of additives may be 25% by mass or less, or 10% by mass or less, based on the total mass of composition (I).

[0118] Among the above, in particular, when composition (I) further contains an inorganic filler, the adhesion to the current collector and the blocking resistance tend to be further improved.

[0119] As inorganic fillers, materials with heat resistance and electrochemical stability are preferred. Examples include boehmite (AlO(OH)), alumina (Al2O3), silica (SiO2), silicon carbide (SiC), magnesium oxide (MgO), magnesium hydroxide (Mg(OH)2), calcium oxide (CaO), manganese oxide (MnO2), cobalt oxide (Co3O4), titanium oxide (TiO2), titanium hydroxide (Ti(OH)4), tin oxide (SnO2), zinc oxide (ZnO), cerium oxide (CeO2), barium titanate (BaTiO3), zirconium oxide (ZrO2), zeolite, boron nitride, apatite, insulating carbon black, inorganic dyes, and kaolin. Among these, when boehmite is used, adhesion to the current collector and blocking resistance tend to be improved. Inorganic fillers may be used individually or in combination of two or more types.

[0120] The inorganic filler is, for example, particulate. The average particle size of the inorganic filler may be 0.5-4 μm, 0.5-0.8 μm, 0.8-1.0 μm, or 1.0-1.5 μm, from the viewpoint of ensuring coating thickness and thermal stability. The above average particle size is measured using a laser diffraction particle size analyzer.

[0121] From the viewpoint of further improving adhesion to the current collector and blocking resistance, the inorganic filler content may be 0.1 parts by mass or more, 0.5 parts by mass or more, 1 part by mass or more, 5 parts by mass or more, or 10 parts by mass or more per 100 parts by mass of resin (A). From the viewpoint of easily ensuring sufficient insulation, the inorganic filler content may be 300 parts by mass or less, 200 parts by mass or less, 100 parts by mass or less, 50 parts by mass or less, 10 parts by mass or less, or 5 parts by mass or less per 100 parts by mass of resin (A). From the above viewpoint, the inorganic filler content may be 0.1 to 300 parts by mass, 0.5 to 200 parts by mass, 1 to 100 parts by mass, 5 to 50 parts by mass, 10 to 300 parts by mass, 0.1 to 10 parts by mass, or 0.1 to 5 parts by mass per 100 parts by mass of resin (A).

[0122] The inorganic filler content may be 1-99% by mass, 5-95% by mass, 10-90% by mass, 20-80% by mass, or 30-50% by mass, based on the total mass of composition (I).

[0123] Composition (I) may also contain fluorinated compounds (compounds containing fluorine atoms) as other components, but in order to address legal regulations on fluorinated compounds, the content of fluorinated compounds may be 1% by mass or less or 0.1% by mass or less based on the total mass of composition (I).

[0124] The composition (I) described above can be manufactured, for example, by a method comprising at least one of the following steps (1) to (5). (1) A step of reacting a polyol with a polyisocyanate. (2) A step of reacting a polyamine with a polyisocyanate. (3) A step of reacting a polyol with a polyisocyanate and a polyamine. (4) Step of reacting polycarboxylic acid with polyamine (5) A step of reacting an acid anhydride having a carboxyl group with a polyisocyanate.

[0125] The details of the compounds (reactants) and reaction conditions in (1) to (5) are as described above. Among the above, it is preferable that the method for producing composition (I) includes step (1) and that the polyol includes a low molecular weight polyol.

[0126] In each of the above steps, resin (A) is obtained. When a non-aqueous solvent is used as the reaction solvent, composition (I) can be obtained as a reaction mixture containing resin (A) in each of the above steps.

[0127] The method for producing composition (I) may include a step of performing post-treatment (such as purification) on the reaction product (reaction mixture) obtained in each of the above steps.

[0128] The method for producing composition (I) may include a step of mixing the reaction product (reaction mixture) or processed product thereof obtained in each of the above steps with a non-aqueous solvent and / or the above additive.

[0129] <Current collector with insulating layer> Another embodiment of the present disclosure is a current collector with an insulating layer for a lithium-ion secondary battery, comprising an insulating layer formed from the insulating layer composition of the above embodiment.

[0130] The insulating layer is, for example, a cured product of an insulating layer composition. The insulating layer may contain resin (A) and may further contain the other components mentioned above (such as inorganic fillers). The content of each material in the insulating layer may be the same as the content of each material in composition (I). That is, the content based on the total mass of composition (I) mentioned above may be read as the content based on the total mass of the insulating layer.

[0131] The thickness of the insulating layer may be, for example, 10 to 200 μm or 10 to 50 μm. The width of the insulating layer may be, for example, 2 to 20 mm. Here, the width of the insulating layer refers to the dimension (line width) in the short direction perpendicular to the longitudinal direction of the insulating layer (the direction in which the insulating layer extends) within the main plane of the insulating layer. If the insulating layer is formed along the boundary between the region on the current collector where the electrode active material layer is formed and the region where the electrode active material layer is not formed, the length in the in-plane direction perpendicular to the direction along the boundary may be 2 to 20 mm.

[0132] The material of the current collector may be aluminum, copper, nickel, titanium, stainless steel, etc. The current collector may contain one or more of these materials. The shape of the current collector may be a strip shape such as foil, perforated foil, or mesh. The current collector may be a porous material such as porous metal (foamed metal), or carbon paper. The current collector may be a current collector without current collecting tabs (a so-called tabless current collector).

[0133] The current collector may be either a positive electrode current collector or a negative electrode current collector. From the viewpoint of easily obtaining the effect of the insulating layer (e.g., short-circuit suppression effect), the current collector may be a positive electrode current collector.

[0134] A current collector with an insulating layer can be formed, for example, by applying the insulating layer composition of the above embodiment to a region on the current collector where the electrode active material layer is not formed. The region on which the insulating layer composition is applied (formed) may be, for example, the portion along the boundary between the region on the current collector where the electrode active material layer is formed and the region where the electrode active material layer is not formed. The insulating layer composition may also be applied (formed) beyond the boundary onto the electrode active material layer (for example, on the surface of the portion along the boundary).

[0135] Methods for applying the insulating layer composition to the current collector include, for example, metal mask printing, electrostatic coating, dip coating, spray coating, roll coating, doctor blade coating, gravure coating, and screen printing. After applying the insulating layer composition, rolling treatment using a flat plate press, calender roll, etc., may be performed as needed.

[0136] Since the insulating layer composition contains a non-aqueous solvent, drying may be performed after application of the insulating layer composition as needed. The drying temperature may be, for example, 80 to 200°C. The drying time may be, for example, 30 to 120 minutes.

[0137] <Electrodes for lithium-ion secondary batteries> Another embodiment of the present disclosure is an electrode for a lithium-ion secondary battery, comprising a current collector with an insulating layer for a lithium-ion secondary battery as described in the above embodiment, and an electrode active material layer.

[0138] The electrode may be either a positive or negative electrode. That is, the electrode active material layer may be either a positive electrode active material layer or a negative electrode active material layer. The electrode may be a positive electrode from the viewpoint of easily obtaining the effect of the insulating layer (e.g., short-circuit suppression effect).

[0139] The electrode active material layer is a layer containing an electrode active material. The electrode active material is not particularly limited as long as it is an electrode active material that can be used in lithium-ion secondary batteries, and known electrode active materials can be used. For example, as the positive electrode active material, lithium-cobalt composite oxides (LCO) such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2), and composite oxides thereof (LiNixCoyMnzO2, x+y+z=1, lithium-nickel-manganese-cobalt composite oxide (NMC)) can be used. These may be used individually or in combination of two or more types. In addition to the electrode active material, the electrode active material layer may also contain known binders (adhesives) and additives (conductive materials, etc.) that can be used in electrode active material layers for lithium-ion secondary batteries.

[0140] The electrode for the lithium-ion secondary battery may be obtained by forming an electrode active material layer in the region where the electrode active material layer is formed in the current collector with an insulating layer for the lithium-ion secondary battery according to the above embodiment, or by forming an electrode active material layer in the region where the electrode active material layer is formed in a current collector without an insulating layer, and then forming the insulating layer in the region of the current collector where the electrode active material layer is not formed. The method for forming the electrode active material layer is not particularly limited and may be obtained by conventionally known methods (for example, by applying an electrode slurry and drying it).

[0141] <Lithium-ion rechargeable battery> Another embodiment of the present disclosure is a lithium-ion secondary battery comprising the lithium-ion secondary battery electrodes of the above embodiment.

[0142] From the viewpoint of easily obtaining the effects of an insulating layer (e.g., short-circuit suppression effect), the lithium-ion secondary battery may be equipped with the lithium-ion secondary battery electrode of the above embodiment as the positive electrode.

[0143] The configuration of the lithium-ion secondary battery may be one of those of a conventionally known lithium-ion secondary battery. For example, the lithium-ion secondary battery may be a lithium-ion secondary battery comprising a pair of electrodes (positive electrode and negative electrode) including the lithium-ion secondary battery electrodes of the above embodiment, a separator, and an electrolyte. The separator and electrolyte are not particularly limited as long as they are separators and electrolytes that can be used in lithium-ion secondary batteries, and known separators and electrolytes can be used.

[0144] Lithium-ion secondary batteries may be non-aqueous secondary batteries. Examples of non-aqueous lithium-ion secondary batteries include non-aqueous electrolyte secondary batteries and solid-state electrolyte secondary batteries. [Examples]

[0145] The present disclosure will be specifically described below with reference to examples. However, the present disclosure is not limited to the examples described below.

[0146] <Example 1> In a reaction vessel equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet, 400 parts by mass of N-methyl-2-pyrrolidone (NMP) as a non-aqueous solvent, 0.5 parts by mass of polyester diol (number average molecular weight 2000) obtained by condensation polymerization of adipic acid and ethylene glycol as a high molecular weight polyol, 19.8 parts by mass of ethylene glycol as a low molecular weight polyol, and 79.7 parts by mass of diphenylmethane diisocyanate as a polyisocyanate were charged. The mixture was heated to 80°C while stirring and reacted at 80°C for 10 hours. After the reaction solution temperature was returned to room temperature, the solid content concentration was adjusted to 10% by mass with NMP to obtain an insulating layer composition containing polyurethane resin and NMP. The total concentration of bonding groups (X) (urethane group concentration) and aromatic ring concentration in the polyurethane resin, as well as the weight-average molecular weight, are shown in Table 1. The weight-average molecular weight of the resin in this example was measured using the following apparatus and conditions. [Equipment and Conditions] Equipment: Tosoh Corporation's "HLC-8320 GPC (product name)" Guard column: "HXL-L (product name)" manufactured by Tosoh Corporation. Column: "TSK-GEL G2000HXL", "TSK-GEL G3000HXL", "TSK-GEL G4000HXL", "TSK-GEL G5000HXL", and "TSK-GEL G6000HXL" are connected in series in this order (all manufactured by Tosoh Corporation, product names). Column temperature: 40℃ Developing solvent: N,N-dimethylformamide (containing 0.1% lithium bromide by mass) Streptomy solvent flow rate: 1.0 ml / min Detector: RI (Differential Refractometer) Data processing: Calibration curves were created using Tosoh Corporation's "GPC Workstation EcoSEC-WorkStation" and Tosoh Corporation's monodisperse polystyrenes with known molecular weights, namely "A-500", "A-1000", "A-2500", "A-5000", "F-1", "F-2", "F-4", "F-10", "F-20", "F-40", "F-80", and "F-128" (all product names), as standard polystyrenes.

[0147] <Example 2> An insulating layer composition containing polyurethane resin and NMP was obtained in the same manner as in Example 1, except that polyester diol was changed to 10 parts by mass, ethylene glycol to 17.6 parts by mass, and diphenylmethane diisocyanate to 72.4 parts by mass. The total concentration of binding groups (X) in the polyurethane resin (urethane group concentration), the aromatic ring concentration, and the weight-average molecular weight are shown in Table 1.

[0148] <Example 3> An insulating layer composition containing polyurethane resin and NMP was obtained in the same manner as in Example 1, except that polyester diol was changed to 50 parts by mass, ethylene glycol to 8.7 parts by mass, and diphenylmethane diisocyanate to 41.3 parts by mass. The total concentration of binding groups (X) in the polyurethane resin (urethane group concentration), the aromatic ring concentration, and the weight-average molecular weight are shown in Table 1.

[0149] <Example 4> An insulating layer composition containing polyurethane resin and NMP was obtained in the same manner as in Example 1, except that polyester diol was changed to 70 parts by mass, ethylene glycol to 4.2 parts by mass, and diphenylmethane diisocyanate to 25.8 parts by mass. The total concentration of binding groups (X) in the polyurethane resin (urethane group concentration), the aromatic ring concentration, and the weight-average molecular weight are shown in Table 1.

[0150] <Example 5> An insulating layer composition containing polyurethane resin and NMP was obtained in the same manner as in Example 1, except that polyester diol was changed to 80 parts by mass, ethylene glycol to 2.0 parts by mass, and diphenylmethane diisocyanate to 18.0 parts by mass. The total concentration of binding groups (X) in the polyurethane resin (urethane group concentration), the aromatic ring concentration, and the weight-average molecular weight are shown in Table 1.

[0151] <Example 6> An insulating layer composition containing polyurethane resin and NMP was obtained in the same manner as in Example 1, except that polyester diol was changed to 88.9 parts by mass, ethylene glycol to 0 parts by mass (not included), and diphenylmethane diisocyanate to 11.1 parts by mass. The total concentration of binding groups (X) in the polyurethane resin (urethane group concentration), the aromatic ring concentration, and the weight-average molecular weight are shown in Table 1.

[0152] <Example 7> In a reaction vessel equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet, 400 parts by mass of NMP as a non-aqueous solvent, 0.5 parts by mass of polybutadiene polyol (NISSO-PB G-2000, manufactured by Nippon Soda Co., Ltd., number average molecular weight 1900) as a high molecular weight polyol, 19.0 parts by mass of ethylene glycol as a low molecular weight polyol, and 80.5 parts by mass of dicyclohexylmethane 4,4'-diisocyanate as a polyisocyanate were charged. The mixture was heated to 80°C while stirring and reacted at 80°C for 10 hours. After the reaction solution was allowed to cool to room temperature, the solid content was adjusted to 10% by mass with NMP to obtain an insulating layer composition containing polyurethane resin and NMP. The total concentration of binding groups (X) in the polyurethane resin (urethane group concentration), aromatic ring concentration, polyolefin structure content, and weight-average molecular weight are shown in Table 2.

[0153] <Example 8> An insulating layer composition containing polyurethane resin and NMP was obtained in the same manner as in Example 7, except that polybutadiene polyol was changed to 10 parts by mass, ethylene glycol to 17.0 parts by mass, and dicyclohexylmethane 4,4'-diisocyanate to 73.0 parts by mass. The total concentration of binding groups (X) in the polyurethane resin (urethane group concentration), aromatic ring concentration, polyolefin structure content, and weight-average molecular weight are shown in Table 2.

[0154] <Example 9> An insulating layer composition containing polyurethane resin and NMP was obtained in the same manner as in Example 7, except that polybutadiene polyol was changed to 50 parts by mass, ethylene glycol to 8.2 parts by mass, and dicyclohexylmethane 4,4'-diisocyanate to 41.8 parts by mass. The total concentration of binding groups (X) in the polyurethane resin (urethane group concentration), aromatic ring concentration, polyolefin structure content, and weight-average molecular weight are shown in Table 2.

[0155] <Example 10> An insulating layer composition containing polyurethane resin and NMP was obtained in the same manner as in Example 7, except that polybutadiene polyol was changed to 70 parts by mass, ethylene glycol to 3.9 parts by mass, and dicyclohexylmethane 4,4'-diisocyanate to 26.1 parts by mass. The total concentration of binding groups (X) in the polyurethane resin (urethane group concentration), aromatic ring concentration, polyolefin structure content, and weight-average molecular weight are shown in Table 2.

[0156] <Example 11> An insulating layer composition containing polyurethane resin and NMP was obtained in the same manner as in Example 7, except that polybutadiene polyol was changed to 80 parts by mass, ethylene glycol to 1.7 parts by mass, and dicyclohexylmethane 4,4'-diisocyanate to 18.3 parts by mass. The total concentration of binding groups (X) in the polyurethane resin (urethane group concentration), aromatic ring concentration, polyolefin structure content, and weight-average molecular weight are shown in Table 2.

[0157] <Example 12> An insulating layer composition containing polyurethane resin and NMP was obtained in the same manner as in Example 7, except that polybutadiene polyol was changed to 87.9 parts by mass, ethylene glycol to 0 parts by mass (not included), and dicyclohexylmethane 4,4'-diisocyanate to 12.1 parts by mass. The total concentration of binding groups (X) in the polyurethane resin (urethane group concentration), aromatic ring concentration, polyolefin structure content, and weight-average molecular weight are shown in Table 2.

[0158] <Example 13> In a reaction vessel equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet, 400 parts by mass of NMP as a non-aqueous solvent, 85 parts by mass of hydrogenated polyisoprene polyol (EPOL, manufactured by Idemitsu Kosan Co., Ltd., number average molecular weight 2500) as a high molecular weight polyol, 1.3 parts by mass of ethylene glycol as a low molecular weight polyol, and 13.7 parts by mass of diphenylmethane diisocyanate as a polyisocyanate were charged. The mixture was heated to 80°C while stirring and reacted at 80°C for 10 hours. After the reaction solution was allowed to cool to room temperature, the solid content was adjusted to 10% by mass with NMP to obtain an insulating layer composition containing polyurethane resin and NMP. The total concentration of binding groups (X) in the polyurethane resin (urethane group concentration), aromatic ring concentration, polyolefin structure content, and weight-average molecular weight are shown in Table 3.

[0159] <Example 14> In a reaction vessel equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet, 400 parts by mass of NMP as a non-aqueous solvent, 29.9 parts by mass of polyester diol (number average molecular weight 2000) obtained by condensation polymerization of adipic acid and ethylene glycol as a high molecular weight polyol, 10.2 parts by mass of ethylene glycol as a low molecular weight polyol, 7.0 parts by mass of 4,4'-diaminodiphenylmethane as a low molecular weight polyamine, and 52.9 parts by mass of diphenylmethane diisocyanate as a polyisocyanate were charged. The mixture was heated to 80°C while stirring and reacted at 80°C for 10 hours. After the reaction solution temperature was returned to room temperature, the solid content concentration was adjusted to 10% by mass with NMP to obtain an insulating layer composition containing polyurethane urea resin and NMP. The total concentration of binding groups (X) in the polyurethane urea resin (sum of urethane group concentration and urea group concentration), urethane group concentration, urea group concentration and aromatic ring concentration, and weight-average molecular weight are shown in Table 3.

[0160] <Example 15> In a reaction vessel equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet, 250 parts by mass of polyethylene glycol propylene glycol diamine (Jeffermin ED-2003, Huntsman, number average molecular weight 2000) as a high molecular weight polyamine, 1.5 parts by mass of 4,4'-diaminodiphenylmethane as a low molecular weight polyamine, and 33.2 parts by mass of diphenylmethane diisocyanate were charged. The mixture was heated to 40°C while stirring and reacted at 40°C for 10 hours. After the reaction solution was allowed to cool to room temperature, the solid content concentration was adjusted to 10% by mass with NMP to obtain an insulating layer composition containing polyurea resin and NMP. The total concentration of binding groups (X) in the polyurea resin (urea group concentration), the aromatic ring concentration, and the weight-average molecular weight are shown in Table 3.

[0161] <Comparative Example 1> Polyvinylidene fluoride resin (Kureha KF Polymer W#7200, manufactured by Kureha Corporation) and NMP were mixed to obtain an insulating layer composition containing polyvinylidene fluoride resin and NMP, with a solid content concentration of 10% by mass. The weight-average molecular weight of the polyvinylidene fluoride resin is shown in Table 3.

[0162] <Comparative Example 2> In a reaction vessel equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet, 400 parts by mass of NMP as a non-aqueous solvent, 94.1 parts by mass of polyester diol (number average molecular weight 4000) obtained by condensation polymerization of adipic acid and ethylene glycol as a high molecular weight polyol, and 5.9 parts by mass of diphenylmethane diisocyanate as a polyisocyanate were charged. The mixture was heated to 80°C while stirring and reacted at 80°C for 10 hours. After the reaction solution was allowed to cool to room temperature, the solid content concentration was adjusted to 10% by mass with NMP to obtain an insulating layer composition containing polyurethane resin and NMP. The total concentration of bonding groups (X) in the polyurethane resin (urethane group concentration), the aromatic ring concentration, and the weight-average molecular weight are shown in Table 3.

[0163] <Examples 16-22> The polyurethane resin synthesized in Example 1, boehmite particles (C06, manufactured by Daimyo Chemical Industry Co., Ltd., with an average particle size of 0.7 μm) as an inorganic filler, and NMP as a non-aqueous solvent were mixed in the mass ratios shown in Table 4 and stirred to obtain an insulating layer composition containing polyurethane resin, boehmite particles, and NMP.

[0164] <Manufacturing Example 1> LiNi 0.8 Co 0.1 Mn 0.1 96 parts by mass of O2, 2 parts by mass of polyvinylidene fluoride resin (Kureha KF Polymer W#7200, manufactured by Kureha Corporation) as a binder, and 2 parts by mass of carbon black as a conductive material were weighed out and mixed in NMP solvent to produce a positive electrode slurry. The positive electrode slurry was applied onto a current collector (aluminum foil), dried at 140°C for 2 hours, and then the resulting laminate was rolled to obtain a positive electrode having a positive electrode active material layer (average thickness 130 μm). The obtained positive electrode has a region on the current collector where the positive electrode active material layer is not formed (uncoated region).

[0165] <Evaluation of adhesion and blocking resistance> A positive electrode equipped with an insulating layer (hereinafter referred to as "evaluation positive electrode 1") was fabricated using the insulating layer compositions prepared in Examples 1 to 22 and Comparative Examples 1 to 2, and the positive electrode prepared in Manufacturing Example 1. Specifically, an insulating layer-forming composition was applied to the boundary between the positive electrode active material layer and the uncoated area of ​​the positive electrode, and then dried at 140°C for 2 hours to form an insulating layer with a thickness of 20 μm. This obtained evaluation positive electrodes 1 for Examples 1 to 22 and Comparative Examples 1 to 2, respectively.

[0166] (Adhesion evaluation) The laminated portion of the positive electrode 1 used for evaluation (the portion not including the positive electrode active material layer) between the current collector and the insulating layer was punched out using a punching machine to obtain strip-shaped test pieces. The obtained test pieces were attached to a stainless steel plate with double-sided tape (Nitto Denko Corporation No. 5015) and pressed down by moving a roller weighing approximately 2 kg back and forth 10 times to create a sample for adhesion evaluation. This sample was mounted on a peel test machine (Shimadzu Corporation Autograph AG-XPlus), and the peeling force (peel strength) was measured by pulling one side of the current collector at a peeling angle of 180 degrees and a peeling speed of 100 mm / min. If the measured value was 8 N / m or higher, the insulating layer was evaluated as having excellent adhesion to the current collector. The results are shown in Tables 1 to 4.

[0167] (Blocking resistance evaluation) After attaching aluminum foil to the insulating layer surface of the positive electrode 1 used for evaluation, a 1 kg weight was placed on the aluminum foil and left undisturbed for 48 hours. Next, the laminated portion of positive electrode 1 and aluminum foil was punched out using a punching machine to obtain strip-shaped test pieces. The obtained test pieces were attached to a stainless steel plate with double-sided tape (Nitto Denko Corporation No. 5015) and pressed down by moving a roller with approximately 2 kg back and forth 10 times to create a sample for evaluating blocking resistance. This sample was mounted on a peel test machine (Shimadzu Corporation Autograph AG-XPlus), and the peel force (peel strength) was measured by pulling one side of the attached aluminum foil at a peel angle of 180 degrees and a peel speed of 100 mm / min. If the measured value was 5 N / m or less, the insulating layer was evaluated as having excellent blocking resistance. The results are shown in Tables 1 to 4.

[0168] <Insulation evaluation> Using the insulating layer compositions prepared in Examples 1-22 and Comparative Examples 1-2, and the positive electrode prepared in Manufacturing Example 1, a positive electrode (hereinafter referred to as "evaluation positive electrode 2") having an insulating layer on the positive electrode active material layer was prepared. Specifically, the insulating layer-forming composition was dip-coated over the entire positive electrode active material layer of the positive electrode, and then dried in a vented dryer (140°C) to form an insulating layer with a thickness of 20 μm. This obtained evaluation positive electrodes 2 for Examples 1-22 and Comparative Examples 1-2, respectively.

[0169] A coin-type half-cell was fabricated using the above-mentioned positive electrode 2, a lithium metal foil as the negative electrode, and an electrolyte containing 1M LiPF6 in a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) (EC:DMC:DEC (volume ratio) = 1:2:1). The discharge capacity of this coin-type half-cell was measured under conditions of room temperature (25°C), 0.1C, and a 2.5V cutoff. The insulating layer was evaluated as having excellent insulating properties if the measured value was 5mAh / g or less. The results are shown in Tables 1 to 4.

[0170] [Table 1]

[0171] [Table 2]

[0172] [Table 3]

[0173] [Table 4]

Claims

1. A composition for the insulating layer of a current collector for lithium-ion secondary batteries, A resin (A) having at least one bonding group selected from the group consisting of urethane groups, urea groups, amide groups, and imide groups, and a non-aqueous solvent, An insulating layer composition wherein the total concentration of the bonding groups in the resin (A) is 500 to 10,000 mmol / kg.

2. The insulating layer composition according to claim 1, wherein the total concentration of the bonding groups in the resin (A) is 1,000 to 8,000 mmol / kg.

3. The insulating layer composition according to claim 1, wherein the resin (A) comprises at least one resin selected from the group consisting of polyurethane resin, polyurea resin, and polyurethane urea resin.

4. The insulating layer composition according to claim 1, wherein the resin (A) has an aromatic ring.

5. The insulating layer composition according to claim 4, wherein the aromatic ring concentration in the resin (A) is 1,000 to 8,000 mmol / kg.

6. The insulating layer composition according to claim 1, wherein the resin (A) comprises a polyolefin structure.

7. The insulating layer composition according to claim 6, wherein the polyolefin structure comprises the structure of at least one polyolefin selected from the group consisting of polybutadiene, polyisoprene, and hydrogenated versions thereof.

8. The insulating layer composition according to claim 6, wherein the content of the polyolefin structure is 10 to 80% by mass, based on the total mass of the resin (A).

9. The insulating layer composition according to claim 1, wherein the weight-average molecular weight of the resin (A) is 10,000 to 1,000,000.

10. The insulating layer composition according to claim 1, wherein the non-aqueous solvent comprises at least one solvent selected from the group consisting of N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide.

11. The insulating layer composition according to claim 1, further containing an inorganic filler.

12. The insulating layer composition according to claim 1, wherein the insulating layer is formed along the boundary between a region on the current collector where the electrode active material layer is formed and a region where the electrode active material layer is not formed.

13. A method for producing an insulating layer composition according to any one of claims 1 to 12, A manufacturing method comprising at least one of the following steps (1) to (5). (1) A step of reacting a polyol with a polyisocyanate. (2) Step of reacting polyamine with polyisocyanate (3) A step of reacting a polyol with a polyisocyanate and a polyamine. (4) Step of reacting polycarboxylic acid with polyamine (5) A step of reacting an acid anhydride having a carboxyl group with a polyisocyanate.

14. A current collector with an insulating layer for a lithium-ion secondary battery, comprising an insulating layer formed from the insulating layer composition described in any one of claims 1 to 12.

15. A current collector with an insulating layer for a lithium-ion secondary battery, as described in claim 14, for use as the positive electrode.

16. An electrode for a lithium-ion secondary battery, comprising a current collector according to claim 14 and an electrode active material layer.

17. A lithium-ion secondary battery comprising the electrode described in claim 16.

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