Coating composition for electrochemical element separators, electrochemical element separators and electrochemical elements

Abstract

To provide a coating composition for electrochemical element separator that provides an electrochemical element separator which has superior tensile strength and can maintain insulation even in a case of burning.SOLUTION: There is provided a coating composition for electrochemical element separator that contains: (A) linear organopolysiloxane containing at least two alkenyl groups bonded to a silicon atom in one molecule; (B) resin-like organopolysiloxane having an R3SiO1 / 2 unit and an SiO4 / 2 unit (in the formula, R each independently represents a C1-6 univalent hydrocarbon group, but at least two in one molecule are an alkenyl group); (C) organohydrogenpolysiloxane containing at least two hydrogen atoms bonded to silicon atoms in one molecule: and (D) a hydrosilylation reaction catalyst.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a coating composition for electrochemical element separators, an electrochemical element separator, and an electrochemical element. [Background technology]

[0002] In recent years, with the increasing trend towards cordless electronic devices, the development of high-performance electrochemical elements such as capacitors, lithium-ion batteries, and nickel-metal hydride batteries has been actively pursued. Rechargeable batteries, in particular, which can be used repeatedly after recharging, are being used in a wide variety of devices.

[0003] A secondary battery has a structure consisting of two electrodes, an anode and a cathode, which are always immersed in an electrolyte solution, and a separator that separates them. The type of secondary battery is optimized by the electrode material, electrolyte, and separator used, but the separator, in particular, must not only structurally separate the anode and cathode but also have the ability to electrically insulate both electrodes to prevent internal short circuits. Furthermore, the separator must have the ability to permeate ions in order for the electrochemical reaction between the anode and cathode to occur.

[0004] In recent years, there has been a surge in efforts to improve the energy density of batteries, and separators need to have the lowest possible internal resistance in order to increase their ion permeability. At the same time, separators are required to be thin, depending on the devices they are applied to. In light of the capabilities required of such separators, nonwoven fabric-based separators have been developed.

[0005] Nonwoven fabric separators, compared to commonly used polyolefin-based separators, are more heat-resistant and have higher porosity, resulting in higher current densities. This advantage is extremely beneficial for secondary batteries. However, such high porosity can cause micro-short circuits due to electrode deposits. Furthermore, because the distribution of voids between fibers is non-uniform, micro-short circuits due to electrode deposits and full short circuits can occur in areas with large voids, especially in environments with repeated long-term charge-discharge cycles. Since controlling the density of voids is difficult, resolving the above-mentioned short-circuit problem is challenging.

[0006] For these reasons, nonwoven fabric separators are required to have the ability to prevent short circuits without compromising high ion permeability. One technology that can satisfy both performance requirements is to appropriately control the porosity, but it is difficult to appropriately control the porosity of nonwoven fabrics, which have pores of various sizes, according to the size of the pores. Patent Document 1 presents a technology by the inventors in which particles are coated onto the nonwoven fabric to reduce the porosity while not compromising ion permeability. This technology made it possible to prevent short circuits in environments where long-term charge-discharge cycles are repeated. However, in the particle coating process, particle aggregation and variations in particle density during coating can occur, making it difficult to uniformly reduce the porosity.

[0007] Furthermore, preventing combustion is also crucial for lithium-ion batteries. In particular, with thin, laminated lithium-ion batteries, individual battery units are adjacent to each other, raising concerns that short circuits or overheating could cause ignition and widespread combustion. To prevent battery fires caused by overheating or damage, the anode and cathode must remain electrically insulated even if ignition occurs. Therefore, separators are required to have the ability to remain in an insulating state without burning out, even in the event of ignition, i.e., fire spread prevention capability.

[0008] Furthermore, non-woven fabrics have low tensile strength and may break under stress. To solve this problem, Patent Document 2 proposes a technique of overlapping two fibers with different fiber orientation angles. It is presented that this technique can obtain a tensile strength that can withstand the stress in the battery formation process, but increasing the film thickness is inevitable by overlapping two layers of fibers. In particular, in secondary batteries, the thickness of the separator is important, and there is a strong requirement for thinness.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0010] The present invention has been made in view of the above circumstances, and provides a coating composition for an electrochemical element separator that gives an electrochemical element separator having excellent tensile strength and capable of maintaining insulation even when combustion occurs, an electrochemical element separator provided with a film made of a cured product of the composition, and an electrochemical element provided with the separator and having little deterioration in battery characteristics during long-term charge-discharge cycles.

Means for Solving the Problems

[0011] As a result of diligent research to achieve the above objective, the present inventors have found that by applying a specific curable organopolysiloxane composition (coating composition) to a substrate for a separator and curing it, an electrochemical element separator can be obtained that has excellent tensile strength even when the substrate film thickness is thin and can maintain insulation even when combustion occurs, and that an electrochemical element equipped with this separator has the characteristic of less degradation of battery characteristics in long-term charge-discharge cycles, thus completing the present invention.

[0012] In other words, the present invention is 1. (A) A linear organopolysiloxane containing at least two alkenyl groups bonded to silicon atoms in one molecule: 100 parts by mass, (B)R3SiO 1 / 2 Units and SiO 4 / 2 Resinous organopolysiloxane having units (wherein R in the formula each independently represents a monovalent hydrocarbon group having 1 to 6 carbon atoms, but at least two in one molecule are alkenyl groups): 10 to 50 parts by mass, (C)Organohydrogenpolysiloxane containing at least two hydrogen atoms bonded to a silicon atom in one molecule: The amount such that the number of hydrogen atoms bonded to a silicon atom in component (C) is 0.8 to 3.0 for each alkenyl group bonded to a silicon atom in components (A) and (B), and (D) Hydrosilylation reaction catalyst A coating composition for electrochemical element separators containing the following: 2. The substrate has a coating made of a cured product of one electrochemical element separator coating composition on at least a portion of the substrate. The amount of the coating is 1 cm of the substrate. 2 Electrochemical element separator, 0.05 to 1.50 mg per unit. 3. The coating is formed on at least the surface of the substrate, and the amount of the coating is such that the coating is 1 cm² of the substrate. 2 Two electrochemical element separators, each containing 0.05 to 1.20 mg. 4. The electrochemical element separator 3 wherein the substrate has a plurality of pores, and the coating is formed inside at least a portion of these plurality of pores. 5. The electrochemical element separator 4, whose base material is a nonwoven fabric, 6. An electrochemical element comprising one of the electrochemical element separators described in 2 to 5. To provide. [Effects of the Invention]

[0013] By applying the electrochemical element separator coating composition of the present invention to a substrate for a separator by means of coating or other means, and then curing it, the tensile strength of the separator can be improved even when the film thickness is small. An electrochemical element separator equipped with a coating made of the coating composition of the present invention improves the battery characteristics of the electrochemical element during long-term charge-discharge cycles, prevents the spread of fire in the event of ignition, and maintains electrical isolation and insulation between the anode and cathode even after combustion, thereby providing a highly reliable electrochemical element. [Modes for carrying out the invention]

[0014] The present invention will be described in detail below. [1] Coating composition for electrochemical element separator The coating composition for electrochemical element separators according to the present invention (hereinafter simply referred to as "coating composition") is characterized by containing (A) an alkenyl group-containing linear organopolysiloxane, (B) an alkenyl group-containing resin-like organopolysiloxane, (C) an organohydrogenpolysiloxane, and (D) a hydrosilylation reaction catalyst.

[0015] (A) Alkenyl group-containing linear organopolysiloxane Component (A) is the main component (base polymer) of the composition of the present invention, and is a linear organopolysiloxane containing at least two alkenyl groups bonded to silicon atoms (hereinafter referred to as "silicon atom-bonded alkenyl groups") in one molecule.

[0016] The alkenyl group bonded to the silicon atom may be located at the end of the molecular chain, at the non-terminus of the molecular chain (i.e., on the side chain of the molecular chain), or both. However, component (A) is preferably a linear organopolysiloxane having a linear or partially branched structure with alkenyl groups bonded to silicon atoms at least at the end of one molecular chain or at both ends of the molecular chain. Furthermore, component (A) may be a single polymer having these molecular structures, a copolymer consisting of these molecular structures, or a mixture of these polymers or copolymers.

[0017] (A) The silicon atom-bonded alkenyl group in component (A) preferably has 2 to 10 carbon atoms, more preferably 2 to 6 carbon atoms, and specifically includes vinyl, allyl, 1-propenyl, isopropenyl, butenyl, isobutenyl, pentenyl, hexenyl, and cyclohexenyl groups, with vinyl groups being particularly preferred. The content of silicon atom-bonded alkenyl groups is preferably 0.001 to 10 moles, more preferably 0.001 to 1 mole, per 100 g of component (A). 29 This can be calculated by Si-NMR measurement.

[0018] In the organopolysiloxane of component (A), the monovalent organic group bonded to a silicon atom other than the silicon atom bonded alkenyl group (hereinafter also referred to as the "silicon atom bonded organic group") is not particularly limited as long as it does not have an aliphatic unsaturated bond. Examples include unsubstituted or substituted monovalent hydrocarbon groups that do not contain an aliphatic unsaturated bond, preferably having 1 to 12 carbon atoms, more preferably 1 to 10 carbon atoms. Examples of these unsubstituted or substituted monovalent hydrocarbon groups include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, 2-ethylhexyl, nonyl, and decyl groups; cycloalkyl groups such as cyclohexyl groups; aryl groups such as phenyl, tolyl, xylyl, and naphthyl groups; aralkyl groups such as benzyl and phenethyl groups; and halogenated alkyl groups such as chloromethyl, 3-chloropropyl, and 3,3,3-trifluoropropyl groups, in which some or all of the hydrogen atoms of these groups are substituted with halogen atoms such as chlorine, fluorine, or bromine atoms. Among these, alkyl groups and aryl groups are preferred, and methyl groups and phenyl groups are more preferred.

[0019] The viscosity of component (A) at 25°C is not particularly limited, but considering the improvement of the workability of the composition and the mechanical properties of the cured product, it is preferably 100 to 500,000 mPa·s, more preferably 300 to 100,000 mPa·s. In this invention, viscosity can be measured by a rotational viscometer (e.g., BL type, BH type, BS type, cone plate type, rheometer, etc.) (the same applies hereinafter). For similar reasons, the number of silicon atoms (or degree of polymerization) in component (A) is preferably 50 to 1,500, more preferably 100 to 1,000, and even more preferably 120 to 800. In this invention, the degree of polymerization (or molecular weight) can be determined, for example, by the number-average degree of polymerization (or number-average molecular weight) in polystyrene terms in gel permeation chromatography (hereinafter referred to as GPC) analysis using toluene or the like as the developing solvent (the same applies hereinafter).

[0020] (A) Specific examples of component include dimethylpolysiloxane with dimethylvinylsiloxy groups sealed at both ends, dimethylsiloxane-methylvinylsiloxane copolymer with dimethylvinylsiloxy groups sealed at both ends, dimethylsiloxane-diphenylsiloxane copolymer with dimethylvinylsiloxy groups sealed at both ends, dimethylsiloxane-methylvinylsiloxane copolymer with dimethylvinylsiloxy groups sealed at both ends, dimethylsiloxane-methylvinylsiloxane-diphenylsiloxane copolymer with dimethylvinylsiloxy groups sealed at both ends Tylsiloxane / methylvinylsiloxane / methylphenylsiloxane copolymer, methyltrifluoropropylpolysiloxane with dimethylvinylsiloxy groups sealed at both ends, dimethylsiloxane / methyltrifluoropropylsiloxane copolymer with dimethylvinylsiloxy groups sealed at both ends, dimethylsiloxane / methyltrifluoropropylsiloxane / methylvinylsiloxane copolymer with dimethylvinylsiloxy groups sealed at both ends, dimethylsiloxane / vinylmethylsiloxane copolymer with trimethylsiloxy groups sealed at both ends Tylsiloxane / vinylmethylsiloxane / diphenylsiloxane copolymer, dimethylsiloxane / vinylmethylsiloxane / methylphenylsiloxane copolymer with trimethylsiloxy groups sealed at both ends, vinylmethylsiloxane / methyltrifluoropropylsiloxane copolymer with trimethylsiloxy groups sealed at both ends, dimethylpolysiloxane with one end trimethylsiloxy group and one end dimethylvinylsiloxy group sealed, dimethylsiloxane / methylvinylsiloxane copolymer with one end trimethylsiloxy group and one end dimethylvinylsiloxy group sealed at both ends, one end trimethylsiloxy group Dimethylsiloxane / diphenylsiloxane copolymer with methylsiloxy group / one-terminated dimethylvinylsiloxy group, dimethylsiloxane / methylphenylsiloxane copolymer with one-terminated trimethylsiloxy group / one-terminated dimethylvinylsiloxy group, dimethylsiloxane / diphenylsiloxane / methylvinylsiloxane copolymer with one-terminated trimethylsiloxy group / one-terminated dimethylvinylsiloxy group, dimethylsiloxane / methylphenylsiloxane / methylvinylsiloxane copolymer with one-terminated trimethylsiloxy group / one-terminated dimethylvinylsiloxy group,Methyltrifluoropropylpolysiloxane with one end trimethylsiloxy group and one end dimethylvinylsiloxy group sealed, dimethylsiloxane / methyltrifluoropropylsiloxane copolymer with one end trimethylsiloxy group and one end dimethylvinylsiloxy group sealed, dimethylsiloxane / methyltrifluoropropylsiloxane / methylvinylsiloxane copolymer with one end trimethylsiloxy group and one end dimethylvinylsiloxy group sealed, dimethylpolysiloxane with both ends methyldivinylsiloxy group sealed Chain dimethylsiloxane / methylvinylsiloxane copolymer, dimethylsiloxane / diphenylsiloxane copolymer with methyldivinylsiloxy groups sealed at both ends, dimethylsiloxane / methylphenylsiloxane copolymer with methyldivinylsiloxy groups sealed at both ends, dimethylsiloxane / methylvinylsiloxane / diphenylsiloxane copolymer with methyldivinylsiloxy groups sealed at both ends, dimethylsiloxane / methylvinylsiloxane / methylphenylsiloxane copolymer with methyldivinylsiloxy groups sealed at both ends, methyldivinylsiloxy groups Sealed methyltrifluoropropylpolysiloxane, methyldivinylsiloxy group-sealed dimethylsiloxane / methyltrifluoropropylsiloxane copolymer, methyldivinylsiloxy group-sealed dimethylsiloxane / methyltrifluoropropylsiloxane / methylvinylsiloxane copolymer, trivinylsiloxy group-sealed dimethylpolysiloxane, trivinylsiloxy group-sealed dimethylsiloxane / methylvinylsiloxane copolymer, trivinylsiloxy group-sealed dimethylsiloxane / diphenylsiloxane copolymer methylsiloxane copolymer, trivinylsiloxy group-separated dimethylsiloxane / methylphenylsiloxane copolymer, trivinylsiloxy group-separated dimethylsiloxane / methylvinylsiloxane / diphenylsiloxane copolymer, trivinylsiloxy group-separated dimethylsiloxane / methylvinylsiloxane / methylphenylsiloxane copolymer, trivinylsiloxy group-separated methyltrifluoropropylpolysiloxane, trivinylsiloxy group-separated dimethylsiloxane / methyltrifluoropropylsiloxane copolymer,Examples include triorganosiloxy group-sealed diorganopolysiloxanes, such as dimethylsiloxane-methyltrifluoropropylsiloxane-methylvinylsiloxane copolymers, and branched (partially branched linear) organopolysiloxanes in which one or two of the bifunctional diorganosiloxane units constituting the main chain of these linear diorganopolysiloxanes are replaced with branched structures (trifunctional organosylsesquioxane units).

[0021] (B) Alkenyl group-containing resinous organopolysiloxane (B) Component is R3SiO 1 / 2 Units (M units) and SiO 4 / 2 It is an alkenyl group-containing resin-like organopolysiloxane whose essential constituent unit is the unit (Q unit). Here, R is independently a monovalent hydrocarbon group having 1 to 6 carbon atoms, but at least 2, preferably 3 to 8, alkenyl groups are present in one molecule (total constituent units).

[0022] Specific examples of monovalent hydrocarbon groups having 1 to 6 carbon atoms include alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, and hexyl groups; alkenyl groups such as vinyl, allyl, butenyl, pentenyl, and hexenyl groups; cycloalkyl groups such as cyclohexyl groups; cycloalkenyl groups such as cyclohexenyl groups; aryl groups such as phenyl groups; and halogenated alkyl groups such as chloromethyl, 3-chloropropyl, and 3,3,3-trifluoropropyl groups, in which some or all of the hydrogen atoms of these groups are substituted with halogen atoms such as chlorine, fluorine, or bromine atoms. The multiple R groups in component (B) may be the same or different, but from the viewpoint of compatibility with other components, it is preferable that 80 mol% or more of the total number of R groups be methyl groups, and for the same reason, vinyl groups are preferred as alkenyl groups.

[0023] (B) The ratio of M units to Q units in component (M units / Q units) is preferably 0.6 to 1.2, more preferably 0.8 to 1.0, from the viewpoint of preventing gelation and hardness. In addition, as an optional structural unit other than the above M unit and Q unit, the component (B) is R2SiO 2 / 2 unit (D unit) and RSiO 3 / 2 unit (T unit) (these Rs represent the same meaning as above). From the viewpoint of improving the hardness of the obtained cured product, the total proportion of the above M unit and Q unit in all the structural units is preferably 80 mol% or more, more preferably 90 mol% or more.

[0024] Specific examples of the component (B) include copolymers of vinyldimethylsiloxy groups and Q units, copolymers of vinyldimethylsiloxy groups, trimethylsiloxy groups and Q units, copolymers of vinyldimethylsiloxy groups, dimethylsiloxane and Q units, copolymers of vinyldimethylsiloxy groups, phenylsilsesquioxane and Q units, copolymers of vinyldimethylsiloxy groups, dimethylsiloxane, phenylsilsesquioxane and Q units, and copolymers of trimethylsiloxy groups, vinylmethylsiloxane and Q units, etc.

[0025] The molecular weight of the component (B) is such that the weight average molecular weight in terms of polystyrene by GPC is preferably 2,000 to 8,000, more preferably 4,000 to 6,000, and this is usually solid at room temperature.

[0026] The blending amount of the component (B) is 10 to 50 parts by mass, preferably 10 to 40 parts by mass, based on 100 parts by mass of the component (A). If the blending amount is within this range, molding processing becomes easy.

[0027] (C) Organohydrogenpolysiloxane The component (C) is an organohydrogenpolysiloxane containing at least two hydrogen atoms (Si-H groups) bonded to silicon atoms in one molecule, and is a component that forms a crosslinked structure by a hydrosilylation reaction with the alkenyl groups in the above components (A) and (B).

[0028] (C) The silicon atom-bonded organic groups other than the hydrogen atoms bonded to the silicon atoms in component (C) are not particularly limited as long as they do not have aliphatic unsaturated bonds. Examples include unsubstituted or substituted monovalent hydrocarbon groups that do not contain aliphatic unsaturated bonds, preferably having 1 to 12 carbon atoms, more preferably 1 to 10 carbon atoms. Examples of these unsubstituted or substituted monovalent hydrocarbon groups include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, 2-ethylhexyl, nonyl, and decyl groups; cycloalkyl groups such as cyclohexyl groups; aryl groups such as phenyl, tolyl, xylyl, and naphthyl groups; aralkyl groups such as benzyl and phenethyl groups; and halogenated alkyl groups such as chloromethyl, 3-chloropropyl, and 3,3,3-trifluoropropyl groups, in which some or all of the hydrogen atoms of these groups are substituted with halogen atoms such as chlorine, fluorine, or bromine atoms. Among these, alkyl groups and aryl groups are preferred, and methyl groups and phenyl groups are more preferred.

[0029] (C)Specific examples of component include 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, tris(hydrogendimethylsiloxy)methylsilane, tris(hydrogendimethylsiloxy)phenylsilane, methylhydrogencyclopolysiloxane, methylhydrogensiloxane-dimethylsiloxane cyclic copolymer, methylhydrogenpolysiloxane with trimethylsiloxy groups sealed at both ends of the molecular chain, dimethylsiloxane-methylhydrogensiloxane copolymer with trimethylsiloxy groups sealed at both ends of the molecular chain, dimethylsiloxane-methylhydrogensiloxane-methylphenylsiloxane copolymer with trimethylsiloxy groups sealed at both ends of the molecular chain, dimethylsiloxane-methylhydrogensiloxane-diphenylsiloxane copolymer with trimethylsiloxy groups sealed at both ends of the molecular chain , methylhydrogenpolysiloxane with dimethylhydrogensiloxy groups sealed at both ends of the molecular chain, dimethylpolysiloxane with dimethylhydrogensiloxy groups sealed at both ends of the molecular chain, dimethylsiloxane-methylhydrogensiloxane copolymer with dimethylhydrogensiloxy groups sealed at both ends of the molecular chain, dimethylsiloxane-methylphenylsiloxane copolymer with dimethylhydrogensiloxy groups sealed at both ends of the molecular chain, dimethylsiloxane-diphenylsiloxane copolymer with dimethylhydrogensiloxy groups sealed at both ends of the molecular chain, methylphenylpolysiloxane with dimethylhydrogensiloxy groups sealed at both ends of the molecular chain, diphenylpolysiloxane with dimethylhydrogensiloxy groups sealed at both ends of the molecular chain, and in each of these exemplary compounds, some or all of the methyl groups are substituted with other alkyl groups such as ethyl groups and propyl groups, formula: R'3SiO 1 / 2 The siloxane units and formula shown are: R'2HSiO 1 / 2 Siloxane units and formula shown: SiO 4 / 2 An organosiloxane copolymer consisting of siloxane units represented by the formula: R'2HSiO 1 / 2 Siloxane units and formula shown: SiO 4 / 2 An organosiloxane copolymer consisting of siloxane units represented by the formula: R'HSiO 2 / 2 The siloxane units and formula shown are: R'SiO 3 / 2The siloxane units or formula shown are:HSiO 3 / 2 Examples include organosiloxane copolymers consisting of siloxane units represented by , and mixtures consisting of two or more of these organopolysiloxanes. Here, R' is a monovalent hydrocarbon group having 1 to 12 carbon atoms and not containing aliphatic unsaturated bonds.

[0030] The amount of component (C) added is such that, from the viewpoint of the mechanical properties of the resulting cured product, the number of hydrogen atoms bonded to silicon atoms in component (C) is 0.8 to 3.0 for each total alkenyl group bonded to silicon atoms in components (A) and (B), and preferably 1.0 to 2.5.

[0031] (D) Hydrosilylation reaction catalyst The hydrosilylation catalyst of component (D) is a catalyst that promotes crosslinking by hydrosilylation reaction between the alkenyl groups in components (A) and (B) and the Si-H groups in component (C).

[0032] Platinum group metal catalysts are preferred as catalysts for hydrosilylation reactions. Specifically, examples of platinum group metal catalysts include platinum black, platinum-dicin chloride, chloroplatinic acid, reaction products of chloroplatinic acid and monohydric alcohols, complexes of chloroplatinic acid and olefins, complexes of chloroplatinic acid and vinyl group-containing (poly)siloxanes, platinum-acetylacetone complexes, and platinum-cyclopentadienyl complexes.

[0033] The amount of component (D) should be sufficient to cure the composition, but from the viewpoint of curability and cost, it is preferable that the amount is 0.5 to 1,000 ppm, and more preferably 1 to 500 ppm, of elemental metal (by mass) per 100 parts by mass of the total of components (A), (B), and (C).

[0034] (E) Other ingredients In addition to the components (A) to (D) above, the coating composition of the present invention may also contain other components, to the extent that they do not impair the effects of the present invention. Specifically, these include reaction control agents for hydrosilylation reactions, reinforcing agents, organic solvents, adhesion-imparting agents (especially organosilicon compounds such as functional alkoxysilanes that contain at least one functional group selected from alkenyl groups, epoxy groups, amino groups, (meth)acryloxy groups, mercapto groups, etc., in their molecules, and do not contain SiH groups in their molecules), thixotropic agents, and the like.

[0035] (E1) Reaction control agent The coating composition of the present invention may also contain a known reaction control agent that has a reaction control effect on the hydrosilylation reaction catalyst of component (D). Specific examples of reaction control agents include 3-methyl-1-butyne-3-ol, 3-methyl-1-pentin-3-ol, 3,5-dimethyl-1-hexyn-3-ol, 1-ethynylcyclohexanol, 3-methyl-3-trimethylsiloxy-1-butyne, 3-methyl-3-trimethylsiloxy-1-pentine, 3,5-dimethyl-3-trimethylsiloxy-1-hexyn, and 1-ethynyl-1-trimethylsiloxycyclo Examples include hexane, bis(2,2-dimethyl-3-butinoxy)dimethylsilane, 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane, 1,1,3,3-tetramethyl-1,3-divinyldisiloxane, and 1,1,dimethyl-1-trimethylsiloxyethine, with 1-ethynyl-1-cyclohexanol and 1,1,dimethyl-1-trimethylsiloxyethine being preferred.

[0036] (E2) Reinforcement The coating composition of the present invention may contain fine silica powder as a reinforcing material to improve the tensile strength, elongation, tear strength, etc., of the resulting cured product.

[0037] This fine silica powder has a specific surface area (BET method) of preferably 50 m². 2 / g or more, more preferably 50-400m 2 / g, more preferably 100-300m 2 It is / g. The specific surface area is 50m². 2 If the amount is 1 / g or more, sufficient reinforcement can be imparted to the cured product.

[0038] Such fine silica powder has a specific surface area within the above range (50 m²). 2 The amount (1 / g or more) may be a known material that has been conventionally used as a reinforcing filler for silicone rubber, such as aerosol silica (dry silica) or precipitated silica (wet silica). Fine silica powder may be used as is, but it is preferable to use silica treated with organosilicon compounds such as methylchlorosilanes (trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, etc.) or hexaorganodisilazanes (dimethylpolysiloxane, hexamethyldisilazane, divinyltetramethyldisilazane, dimethyltetravinyldisilazane, etc.) to impart good fluidity to the composition. Reinforcing silica may be used alone or in combination of two or more types.

[0039] When reinforcing silica is used, the amount added is preferably 10 to 150 parts by mass, more preferably 30 to 90 parts by mass, and even more preferably 50 to 90 parts by mass, per 100 parts by mass of component (A). If the amount of reinforcing silica is 10 parts by mass or more, the reinforcing effect before and after curing is easily obtained, and if it is 150 parts by mass or less, the dispersion of silica in the composition is good, resulting in excellent processability during curing and molding.

[0040] (E3) Organic solvents The coating composition of the present invention may contain an organic solvent for the purpose of mixing the above components (A) to (D) and any additional components (E) as needed, and / or adjusting their concentrations. Specific examples of organic solvents include aromatic solvents such as toluene and xylene; aliphatic solvents such as n-heptane, n-hexane, n-octane, and isoparaffin; ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone; ester solvents such as ethyl acetate and isobutyl acetate; and ether solvents such as diisopropyl ether and 1,4-dioxane. These may be used individually or in combination of two or more.

[0041] The coating composition of the present invention can be prepared by mixing the above components (A) to (D) and optionally (E) other components using a commonly used mixing and stirring device such as a kneader or planetary mixer, or a kneader or the like.

[0042] [2] Electrochemical element separator The electrochemical element separator of the present invention (hereinafter simply referred to as "separator") is formed by applying or impregnating at least a part, preferably one or both sides, of the above-described coating composition to a substrate, and then drying and curing it by heating, thereby forming a film made of the cured coating composition on a part or all of the surface of the substrate, and, if the substrate has pores, on a part or all of the inside of these pores.

[0043] The method for applying the coating composition of the present invention to a substrate is not particularly limited, but examples include bar coating, spin coating, dip coating, offset printing, and screen printing. Furthermore, the substrate can be immersed in the coating composition of the present invention to impregnate the substrate with the coating composition.

[0044] The substrate for the separator is not particularly limited as long as it is the same as that which is normally used in electrochemical elements such as secondary batteries, but nonwoven fabric can be used particularly well. Examples of nonwoven fabrics include those with a fiber diameter of 0.1 to 5 μm (for example, 0.1 μm, 1 μm, 5 μm, etc.), and vary depending on the manufacturing method, but are not particularly limited in this invention. Furthermore, examples of fibers include cellulose fibers, pulp fibers, carbon fibers, glass fibers, ceramic fibers, aramid fibers, vinylon fibers, and polyamide fibers. From the viewpoint of flame resistance, aramid fibers are preferred, and using them will provide a higher fire spread prevention effect. The thickness of the substrate is preferably 30 μm or less, more preferably 20 μm or less. The lower limit is not particularly limited, but is preferably 1 μm or more.

[0045] It is preferable to dehydrate the nonwoven fabric before applying the coating composition of the present invention. Specifically, it is preferable to include a dehydration step in which the fabric is dried at a temperature of 130 to 260°C, particularly 140 to 200°C, under normal or reduced pressure for 12 hours or more.

[0046] After applying the coating composition of the present invention, the nonwoven fabric is heated at a temperature of 100 to 150°C under normal or reduced pressure for at least one hour to cure the coating composition, thereby completing the bonding between the resin and the fibers.

[0047] Base material 1cm 2 The amount of film consisting of the cured product of the above coating composition per unit is 0.05 to 1.50 mg, preferably 0.05 to 1.20 mg, and more preferably 0.08 to 1.00 mg. 0.05 mg / cm 2 If the concentration is less than 1.50 mg / cm³, sufficient tensile strength cannot be obtained, and the resulting electrochemical element separator will have inferior battery characteristics and flame retardancy during long-term charge-discharge cycles. 2 If this value is exceeded, the separator film thickness increases, leading to a problem of increased internal electrical resistance. The thickness of the resulting separator is preferably 30 μm or less, more preferably 25 μm or less, and even more preferably 24 μm or less. The lower limit is not particularly limited, but is preferably 1 μm or more.

[0048] [3] Electrochemical elements The electrochemical device in which the separator of the present invention is used is not particularly limited, but a secondary battery including a positive electrode and a negative electrode, a separator interposed between these electrodes, and a non-aqueous electrolyte is preferable, and a lithium ion secondary battery is more preferable.

[0049] The positive electrode includes, as a positive electrode material, a positive electrode active material, a conductive agent, a binder, a viscosity modifier, and the like. The positive electrode active material may be lithium or a compound containing lithium, and can be used alone or in appropriate combination of two or more kinds. Specific examples of the compound containing lithium include, for example, lithium composite oxides and the like. Among them, in order to increase the energy density, a lithium composite oxide mainly composed of Li p MetO2 is preferable. Here, Met is preferably at least one of cobalt, nickel, iron, and manganese, and p is usually a value within the range of 0.05 ≦ p ≦ 1.10. Specific examples of such lithium composite oxides include LiCoO2, LiNiO2, LiFeO2, Li q Ni r Co 1-r O2 (where the values of q and r vary depending on the charge and discharge state of the battery, and are usually 0 < q < 1, 0.7 < r ≦ 1), LiNi 0.8 Co 0.1 Mn 0.1 O2, spinel-structured LiMn2O4, orthorhombic LiMnO2, and the like. Further, as a high voltage compatible type, LiMet s Mn 1-s O4 (0 < s < 1) is also used, and in this case, Met includes titanium, chromium, iron, cobalt, nickel, copper, zinc, and the like.

[0050] The lithium composite oxide can be prepared, for example, by pulverizing and mixing a carbonate, nitrate, oxide, or hydroxide of lithium and a carbonate, nitrate, oxide, or hydroxide of a transition metal according to a desired composition, and firing at a temperature within the range of 600 to 1,000 °C in an oxygen atmosphere.

[0051] The negative electrode includes negative electrode active material, conductive agent, binder, viscosity modifier, etc. The negative electrode active material can be used alone or by selecting two or more types as appropriate. Specific examples of negative electrode active materials include carbon materials such as poorly graphitizable carbon, easily graphitizable carbon, graphite, pyrolytic carbons, cokes, glassy carbons, calcined organic polymer compounds, carbon fibers, and activated carbon. Materials capable of intercalating and releasing lithium, and containing one or more elements selected from metallic and metalloid elements, are also acceptable.

[0052] As conductive agents, metal powders and metal fibers such as Al, Ti, Fe, Ni, Cu, Zn, Ag, Sn, and Si, or graphite such as natural graphite, artificial graphite, various coke powders, mesophase carbon, vapor-grown carbon fibers, pitch-based carbon fibers, PAN-based carbon fibers, and various resin-fired bodies can be used. These can be used individually or in combination of two or more as appropriate.

[0053] Examples of binders used in positive and negative electrode materials include polyimide resins, polyamide resins, polyamide-imide resins, and more specifically, polyvinylidene fluoride (PVDF) and styrene-butadiene rubber (SBR). These can be used individually or in combination of two or more as appropriate.

[0054] Viscosity modifiers used in positive and negative electrode materials include carboxymethylcellulose, sodium polyacrylate, other acrylic polymers, or fatty acid esters. These can be used individually or in combination of two or more as appropriate.

[0055] The preferred content (solids mass%) of each component in the positive electrode material is 90-98% by mass for the positive electrode active material, 0.5-5.0% by mass for the conductive agent, 0.5-5.0% by mass for the binder, and 0-3.0% by mass for the viscosity modifier. The preferred content (solids mass%) of each component in the negative electrode material is 75-98% by mass for the negative electrode active material, 1-20% by mass for the conductive agent, 1-20% by mass for the binder, and 0-3.0% by mass for the viscosity modifier.

[0056] Examples of non-aqueous electrolytes include non-aqueous electrolytes obtained by dissolving an electrolyte salt in a non-aqueous solvent. Examples of electrolyte salts include light metal salts, which include alkali metal salts such as lithium salts, sodium salts, and potassium salts; alkaline earth metal salts such as magnesium salts and calcium salts; and aluminum salts. One or more types are selected depending on the purpose. Specific examples of lithium salts include LiBF4, LiClO4, LiPF6, LiAsF6, CF3SO3Li, (CF3SO2)2NLi, C4F9SO3Li, CF3CO2Li, (CF3CO2)2NLi, C6F5SO3Li, and C8F 17 Examples include SO3Li, (C2F5SO2)2NLi, (C4F9SO2)(CF3SO2)NLi, (FSO2C6F4)(CF3SO2)NLi, ((CF3)2CHOSO2)2NLi, (CF3SO2)3CLi, (3,5-(CF3)2C6F3)4BLi, LiCF3, LiAlCl4, C4BO8Li, etc., and one of these can be used alone or in mixtures of two or more.

[0057] There are no particular restrictions on the non-aqueous solvent as long as it can be used as a non-aqueous electrolyte. Generally, aprotic high dielectric constant solvents such as ethylene carbonate, propylene carbonate, butylene carbonate, and γ-butyrolactone are used; aprotic low viscosity solvents such as dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl propyl carbonate, dipropyl carbonate, diethyl ether, tetrahydrofuran, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1,3-dioxolane, sulfolane, methylsulfolane, acetonitrile, propionitrile, anisole, methyl acetate and other acetate esters, and propionic acid esters are used. It is desirable to use these aprotic high dielectric constant solvents and aprotic low viscosity solvents in an appropriate mixing ratio. Furthermore, ionic liquids using imidazolium, ammonium, and pyridinium-type cations can be used. The counter anion is not particularly limited, but BF4- PF6 - , (CF3SO2)2N - These are some examples. Ionic liquids can be used in combination with the aforementioned non-aqueous solvents.

[0058] Furthermore, it can be used as a solid electrolyte or gel electrolyte. In this case, it can contain polymer materials such as glass-based inorganic solid electrolytes, polyether gels, silicone gels, silicone polyether gels, acrylic gels, silicone acrylic gels, acrylonitrile gels, and poly(vinylidene fluoride). These materials may be polymerized beforehand or polymerized after injection. These can be used individually or as a mixture of two or more.

[0059] Furthermore, various additives may be added to the non-aqueous electrolyte as needed. Examples include vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, 4-vinylethylene carbonate, etc., for improving cycle life; biphenyl, alkyl biphenyl, cyclohexylbenzene, t-butylbenzene, diphenyl ether, benzofuran, etc., for preventing overcharging; and various carbonate compounds such as carbon dioxide gas, various carboxylic acid anhydrides, and various nitrogen-containing and sulfur-containing compounds for deoxidation and dehydration. Furthermore, compounds in which some of these compounds are fluorine-substituted are also suitably used.

[0060] Non-aqueous electrolyte secondary batteries are equipped with a battery case that seals the above-mentioned battery configuration, and their shape is arbitrary and not particularly limited. Generally, examples include coin-type batteries in which coin-shaped electrodes and separators are stacked, and rectangular or cylindrical batteries in which electrode sheets and separators are wound in a spiral shape. [Examples]

[0061] The present invention will be specifically described below with reference to examples and comparative examples. The following examples are not intended to limit the present invention in any way. In the following, "Me" means "methyl group," "Vi" means "vinyl group," and "parts" means "parts by mass."

[0062] [1] Production of coating compositions for electrochemical element separators [Example 1] (A) Component consists of 18 parts of dimethylpolysiloxane with dimethylvinylsiloxy groups sealed at both ends of the molecular chain having a viscosity of 1,000 mPa·s at 25°C, and 62 parts of dimethylpolysiloxane with dimethylvinylsiloxy groups sealed at both ends of the molecular chain having a viscosity of 5,000 mPa·s at 25°C, and (B) Component consists of Me2ViSiO 1 / 2 The unit is 6.8 mol%, Me3SiO 1 / 2 The unit is 39.8 mol%, and SiO 4 / 2 25 parts of a resinous organopolysiloxane (weight-average molecular weight 6,000) having 53.4 mol% of units, and (C) component Me2HSiO 1 / 2 The unit is 61.1 mol%, Me3SiO 1 / 2 The unit is 0.8 mol%, and SiO 4 / 2 Five parts of a resinous organohydrogenpolysiloxane having 38.1 mol% units [an amount such that 2.0 moles of silicon-bonded hydrogen atoms of component (C) are present for every 1 mole of silicon-bonded vinyl groups of components (A) and (B)], 0.1 parts of a 1,1-divinyltetramethyldisiloxane complex solution of chloroplatinic acid (platinum concentration 1% by mass) as component (D), and 0.03 parts of 1-ethynyl-1-cyclohexanol as a hydrosilylation reaction control agent were used. These components were kneaded for 10 minutes in a planetary mixer (PLMG-350, manufactured by Inoue Seisakusho Co., Ltd.) to obtain a coating composition for electrochemical element separators.

[0063] [2] Manufacturing and evaluation of secondary battery separators [Examples 2-1 to 2-5, Comparative Examples 2-1 to 2-4] 10 x 10 cm 2A coating solution, obtained by diluting the coating composition obtained in Example 1 with n-hexane to the solid content concentration shown in Table 1, was applied to one side of a nonwoven fabric (20 μm thick aramid fiber nonwoven fabric that had been preheated at 150°C for 12 hours to dehydrate it) cut to size. The nonwoven fabric was pre-placed on a cellulose sheet, and the coating solution that penetrated the nonwoven fabric was absorbed by the cellulose sheet on the back side. The excess coating solution remaining on the surface of the nonwoven fabric was scraped off with a squeegee, and then dried and cured in an oven at 120°C for 2 hours to obtain a secondary battery separator having a coating film made of the coating composition. 2 The amount of coating per unit was calculated from the mass of the separator before and after coating and curing.

[0064] The thickness, combustion test, and lithium-ion battery characteristics of the obtained secondary battery separators were measured using the methods described below, and the results are shown in Table 1. The results for a secondary battery separator without a coating composition applied to the nonwoven fabric are shown in Comparative Example 2-1.

[0065] [Thickness of the separator] The thickness of the obtained secondary battery separator was measured using a thickness gauge. The original separator without coating had a thickness of 20 μm. After coating and drying, the thickness of the separator was marked as ○ if it was 22 μm or less, △ if it was between 22 μm and 25 μm, and × if it was greater than 25 μm.

[0066] [Combustion test] The obtained secondary battery separators were cut to a size of 3.5 cm x 6.5 cm, and both ends in the longitudinal direction (6.5 cm direction) were fixed with two stands in a way that kept them parallel and secure. The separators were ignited from the lower center and left until the fire was extinguished. After that, the separators were visually inspected, and those that maintained their shape were marked with ○, while those that did not maintain their shape and separated were marked with ×.

[0067] [Measuring cutting strength] The obtained secondary battery separator was cut to a size of 2.0 cm x 10.0 cm, and its cutting strength was measured by pulling it in a 180° direction vertically using a Shimadzu Autograph measuring device. The separator to be measured was clamped at the upper and lower fixing parts of the device, with the lower and upper parts being 2.0 cm wide, and pulled in the longitudinal direction of 10.0 cm. The pulling speed was set to 5 mm / min, and the torque at the time of cutting (N / 2 cm) was defined as the cutting strength. The cutting strength of the uncoated separator was 3.0 (N / 2 cm). For the coated separator, a cutting strength value of less than 4.0 was marked with ×, a value between 4.0 and 6.0 was marked with ○, and a value greater than 6.0 was marked with ◎.

[0068] [Battery characteristics test] The battery characteristics of lithium-ion secondary batteries manufactured according to the following procedure were evaluated. LiNi 0.8 Co 0.1 Mn 0.1 O2 was laminated and bonded to a metal plate, and the cathode material was formed by electrowelding the extraction electrode (tab) to the upper metal portion which lacked the positive electrode active material. On the back side, which was not in close contact with the separator, polyimide tape was applied to the entire surface to provide electrical insulation. On the other hand, graphite was laminated and bonded to a metal plate as the negative electrode active material, and electrodes (tabs) were taken from the upper metal part, which lacked the negative electrode active material, and electrically welded to form the negative electrode material. Polyimide tape was applied to the entire back side, which was not in close contact with the separator, to provide electrical insulation.

[0069] Next, the aluminum film with a polyolefin film was placed with the polyolefin film facing upwards, and the negative electrode material, secondary battery separator, and positive electrode material prepared above were stacked in that order. The aluminum film in the areas where the stacked material was not stacked was folded to create an outer seal. The separator was positioned so that the coated surface of the coating composition faced the positive electrode. Each end of the aluminum film was heated and pressed at 180°C to seal it. At this time, only the end where the removal electrode was not exposed was left open without being pressed. The resulting laminate was dried under reduced pressure at 130°C for 12 hours.

[0070] In a glove box filled with dry N2, the electrolyte was injected into the dried laminate from the unsealed end face. The electrolyte used was a LiPF 61 mol / L [ethylene carbonate:ethylene carbonate (1:1 volume%)] solution. Subsequently, the open section was sealed using a vacuum heating laminator inside the glove box to obtain a lithium-ion secondary battery.

[0071] The lithium-ion secondary batteries obtained above underwent pre-charge and discharge (chemical treatment), and were then charged to 4.1V with a current of 0.2cA in a 30°C constant temperature bath. Subsequently, they were charged at a constant voltage of 4.1V until the current dropped to 0.02cA. After charging, the batteries were repeatedly discharged to 2.7V with a current of 0.2cA. The battery capacity after 200 charge-discharge cycles, with the initial capacity set to 100%, was determined, and the retention rate was calculated. A retention rate of 90% or higher was marked with ○, 85% or higher with △, and less than 85% with ×.

[0072] [Table 1]

[0073] As shown in Table 1, the coating amount ranges from 0.05 to 1.20 mg / cm². 2 Within this range, the separator thickness, cutting strength, combustion test, and battery characteristics all showed good results (Examples 2-1 to 2-5). On the other hand, the coating amount is 0.02 mg / cm². 2 In the following comparative examples 2-1 and 2-2, the cutting strength was 3.1 N / 2cm or less, and furthermore, both the combustion test and battery characteristics were insufficient. Furthermore, the amount of coating is excessive (2.00 mg / cm²). 2 In comparative examples 2-3 and 2-4 (exceeding the specified limits), the cutting strength, combustion test, and battery characteristics were good, but the separator thicknesses were 34 μm and 41 μm, respectively, which were unsuitable from the viewpoint of internal electrical resistance and size.

Claims

1. (A) A linear organopolysiloxane containing at least two alkenyl groups bonded to silicon atoms in one molecule: 100 parts by mass, (B)R 3 SiO 1 / 2 Units and SiO 4 / 2 Resinous organopolysiloxane having units (wherein R in the formula each independently represents a monovalent hydrocarbon group having 1 to 6 carbon atoms, but at least two in one molecule are alkenyl groups): 10 to 50 parts by mass, (C) Organohydrogenpolysiloxane containing at least two hydrogen atoms bonded to a silicon atom in one molecule: an amount such that the number of hydrogen atoms bonded to a silicon atom in component (C) is 0.8 to 3.0 for each alkenyl group bonded to a silicon atom in the total of components (A) and (B), and (D) Hydrosilylation reaction catalyst A coating composition for electrochemical element separators containing the following:

2. The substrate has a coating made of a cured product of the electrochemical element separator coating composition described in claim 1 on at least a portion of the substrate. The amount of the coating is 1 cm of the substrate. 2 An electrochemical element separator containing 0.05 to 1.50 mg per unit.

3. The coating is formed on at least the surface of the substrate, and the amount of the coating is such that 1 cm of the substrate 2 The electrochemical element separator according to claim 2, wherein the amount is 0.05 to 1.20 mg per unit.

4. The electrochemical element separator according to claim 3, wherein the substrate has a plurality of pores, and the coating is formed inside at least a portion of these plurality of pores.

5. The electrochemical element separator according to claim 4, wherein the substrate is a nonwoven fabric.

6. An electrochemical element comprising an electrochemical element separator according to any one of claims 2 to 5.

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