Polyolefin-based electrochemical element separator coating composition, electrochemical element separator, and electrochemical element

Abstract

To provide a coating composition that gives a polyolefin-based electrochemical element separator that does not impede ion permeability even when formed in a film form. [Solution] (A) A linear organopolysiloxane containing at least two alkenyl groups bonded to silicon atoms in one molecule. (B)R3SiO 1 / 2 Units and SiO 4 / 2 Resinous organopolysiloxane having units (wherein R in the formula independently represents a monovalent hydrocarbon group having 1 to 6 carbon atoms, but at least two in one molecule are alkenyl groups). (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 the silicon atom in component (C) is 0.5 to 15.0 for each total alkenyl group bonded to the silicon atom in components (A) and (B). (D) Hydrosilylation reaction catalyst A coating composition containing the following:

Description

[Technical Field]

[0001] The present invention relates to a coating composition for polyolefin-based 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] Porous polyolefin separators are widely used in lithium-ion batteries. In recent years, there has been a surge in efforts to improve the energy density of batteries, and separators need to be designed with the lowest possible internal resistance to maximize their ion permeability. To meet this demand for high ion permeability, porous structures and thinning of separators are being explored. Thinning of separators is a crucial technology, especially given the requirements for final batteries. Polyolefin-based separators have been designed with full consideration of the capabilities required of such separators.

[0005] Polyolefin separators are susceptible to heat, and shrinkage and melting can occur at high temperatures. This can cause lithium-ion batteries to ignite, leading to limitations on the operating environment and temperature of lithium-ion batteries. Furthermore, even when used in applicable environments, overheating and ignition due to short circuits can occur, requiring enhanced safety measures when individual battery units are located in close proximity.

[0006] In lithium-ion batteries, to prevent fire damage due to short circuits, overheating, or damage, it is crucial that the anode and cathode remain electrically insulated even in the event of overheating. Therefore, the separator must have the ability to remain in an insulating state without shrinking or melting, even in the event of overheating. Furthermore, possessing this ability allows lithium-ion batteries to be used even at relatively high temperatures.

[0007] On the other hand, lithium-ion battery separators are required to have a high current density. To obtain a high current density, it is necessary to design them with a high porosity. However, such high porosity can cause micro-short circuits due to electrode deposits. It is desirable to minimize micro-short circuits caused by electrode deposits and short circuits in environments where long-term charge-discharge cycles are repeated.

[0008] For these reasons, lithium-ion battery separators are required to have high ion permeability without compromising short-circuit performance, as well as to prevent shrinkage due to heating and prevent the spread of fire due to damage.

[0009] A technology that satisfies both performance requirements requires a separator that maintains porosity while also possessing heat resistance. In this regard, Patent Document 1 proposes a method of coating a separator with a mixture of inorganic particles and a silane salt compound, thereby improving the dispersibility of the inorganic particles and strengthening the adhesion between the inorganic particles and the polyolefin, preventing short circuits during long-term cycle tests and exhibiting heat resistance. However, silane salt compounds containing alkali metals impede the permeation of lithium ions, and the application amount needs to be suppressed within a certain range. That is, in the mass production process, variations in battery characteristics may occur, and it is difficult to control the lithium ion permeability to a constant level.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0011] The present invention has been made in view of the above circumstances, and provides a coating composition for a polyolefin-based electrochemical element separator that does not impede ion permeability even when formed into a film, an electrochemical element separator provided with a film composed of a cured product of the composition, and an electrochemical element provided with the separator.

Means for Solving the Problems

[0012] As a result of intensive studies to achieve the above object, the present inventors have found that by applying and curing a specific curable organopolysiloxane composition (coating composition) to a polyolefin-based separator substrate, a polyolefin-based electrochemical element separator that does not impede ion permeability even when applied and formed into a film can be obtained, and an electrochemical element provided with this separator has characteristics of less deterioration of battery characteristics in long-term charge-discharge cycles and high-temperature states, and thus completed the present invention.

[0013] That is, the present invention is 1. (A) Linear organopolysiloxane containing at least 2 alkenyl groups bonded to silicon atoms in one molecule: 100 parts by mass, (B) R3SiO1 / 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): 0 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 0.5 to 15.0 for each total alkenyl group bonded to a silicon atom in components (A) and (B), (D) Hydrosilylation reaction catalyst A coating composition for polyolefin-based electrochemical element separators containing the following: 2. A polyolefin-based substrate and a coating made of a cured product of one polyolefin-based 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, 0.01 to 1.0 mg per unit. 3. A polyolefin-based substrate and a coating made of a cured product of one polyolefin-based electrochemical element separator coating composition on at least a portion of the substrate, The aforementioned coating thickness is 0.1 to 10 μm for the electrochemical element separator. 4. The substrate is a two or three electrochemical element separator having a plurality of pores, 5. The substrate comprises two or three electrochemical element separators having a layer containing inorganic particles on one side. 6. Electrochemical element comprising two or three electrochemical element separators To provide. [Effects of the Invention]

[0014] The coating composition for polyolefin-based electrochemical element separators of the present invention provides a polyolefin-based electrochemical element separator that does not hinder ion permeability even when coated in a film form, by adhering it to a polyolefin-based separator substrate by means such as coating and curing it. A polyolefin-based electrochemical element separator equipped with a coating made from the coating composition of the present invention can maintain the battery characteristics of the electrochemical element over long-term charge-discharge cycles, as well as in high-temperature environments and during heat generation, thus providing a highly reliable electrochemical element. [Modes for carrying out the invention]

[0015] The present invention will be described in detail below. [1] Polyolefin-based electrochemical element separator coating composition The coating composition for polyolefin-based 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.

[0016] (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.

[0017] 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.

[0018] (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). The content of silicon atom-bonded alkenyl groups can be determined by iodine titration or 29 This can be calculated by Si-NMR measurement.

[0019] 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 have high Li ion permeability, i.e., high air permeability, and more preferably methyl groups and ethyl groups.

[0020] The degree of polymerization of the organopolysiloxane is preferably 100 or higher, more preferably 100 to 10,000, and even more preferably 200 to 7,000. This degree of polymerization can be measured as the weight-average degree of polymerization in polystyrene terms by gel permeation chromatography (GPC) analysis.

[0021] (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).

[0022] (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).

[0023] 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.

[0024] (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. Furthermore, component (B) may have any constituent units other than the M and Q units mentioned above, such as R2SiO 2 / 2 Units (D units) and RSiO 3 / 2 The composition may include units selected from the units (T units) (the R in these units has the same meaning as above). From the viewpoint of improving the hardness of the resulting cured product, the total proportion of the above M units and Q units to the total constituent units is preferably 80 mol% or more, and more preferably 90 mol% or more.

[0025] Specific examples of 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.

[0026] The molecular weight of component (B) is preferably 2,000 to 8,000, more preferably 4,000 to 6,000, based on the weight-average molecular weight of polystyrene calculated by GPC, and is normally solid at room temperature.

[0027] The amount of component (B) is 0 to 50 parts by mass, preferably 10 to 40 parts by mass, per 100 parts by mass of component (A). A flexible coating can be obtained if the amount is within this range, and a stronger coating can be obtained if the amount of component (B) is higher.

[0028] (C) Organohydrogenpolysiloxane 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 cross-linked structure through a hydrosilylation reaction with the alkenyl groups in components (A) and (B) above.

[0029] (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 have high Li ion permeability, i.e., high air permeability, and more preferably methyl groups and ethyl groups.

[0030] Specific examples of the (C) component include 1,1,3,3 - tetramethyldisiloxane, 1,3,5,7 - tetramethylcyclotetrasiloxane, tris(hydrogendimethylsiloxy)methylsilane, tris(hydrogendimethylsiloxy)phenylsilane, methylhydrogencyclopolysiloxane, methylhydrogensiloxane - dimethylsiloxane cyclic copolymer, trimethylsiloxy - terminated methylhydrogenpolysiloxane at both ends of the molecular chain, trimethylsiloxy - terminated dimethylsiloxane - methylhydrogensiloxane copolymer at both ends of the molecular chain, trimethylsiloxy - terminated dimethylsiloxane - methylhydrogensiloxane - methylphenylsiloxane copolymer at both ends of the molecular chain, trimethylsiloxy - terminated dimethylsiloxane - methylhydrogensiloxane - diphenylsiloxane copolymer at both ends of the molecular chain, dimethylhydrogensiloxy - terminated methylhydrogenpolysiloxane at both ends of the molecular chain, dimethylhydrogensiloxy - terminated dimethylpolysiloxane at both ends of the molecular chain, dimethylhydrogensiloxy - terminated dimethylsiloxane - methylhydrogensiloxane copolymer at both ends of the molecular chain, dimethylhydrogensiloxy - terminated dimethylsiloxane - methylphenylsiloxane copolymer at both ends of the molecular chain, dimethylhydrogensiloxy - terminated dimethylsiloxane - diphenylsiloxane copolymer at both ends of the molecular chain, dimethylhydrogensiloxy - terminated methylphenylpolysiloxane at both ends of the molecular chain, dimethylhydrogensiloxy - terminated diphenylpolysiloxane at both ends of the molecular chain, and in each of these exemplified compounds, those in which part or all of the methyl groups are substituted with other alkyl groups such as ethyl groups and propyl groups, and the siloxane unit represented by the formula: R’3SiO 1 / 2 and the siloxane unit represented by the formula: R’2HSiO 1 / 2 and the siloxane unit represented by the formula: SiO 4 / 2 and an organosiloxane copolymer composed of the siloxane unit represented by the formula: R’2HSiO 1 / 2 and the siloxane unit represented by the formula: SiO 4 / 2 and an organosiloxane copolymer composed of the siloxane unit represented by the formula: R’HSiO 2 / 2 and the siloxane unit represented by the formula: 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 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.

[0031] 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 0.5 to 15.0 for each total alkenyl group bonded to silicon atoms in components (A) and (B), and preferably 1.0 to 5.0.

[0032] (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).

[0033] As the catalyst for the hydrosilylation reaction, platinum group metal catalysts are preferred. Specifically, examples 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, or platinum group metal catalysts that exhibit catalytic activity upon ultraviolet irradiation, such as platinum-acetylacetone complexes and platinum-cyclopentadienyl complexes.

[0034] 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 100 ppm, of elemental metal (by mass) per 100 parts by mass of the total of components (A), (B), and (C).

[0035] (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, silicone oils that do not have crosslinkable reactive groups, organic solvents, adhesion modifiers (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 the molecule and do not contain SiH groups, or known siloxanes having epoxy groups, alkoxysilyl groups and SiH groups, etc.), thixotropic agents, etc.

[0036] (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.

[0037] (E2) Non-crosslinked silicone oil The coating composition of the present invention may contain a non-crosslinking silicone oil, which improves workability for forming a 0.1 to 10 μm thick film on a polyolefin-based electrochemical element separator, and also allows for concentration adjustment of components (A) to (D). While this non-crosslinking silicone oil reduces the viscosity of the composition when applied to the separator, it is preferable that it volatilizes during the pre-curing stage or curing process after application. Examples of such silicone oils include hexamethyldisiloxane (KF-96L-0.65cS), octamethyltrisiloxane (KF-96A-1cS), decamethyltetrasiloxane (KF-96L-1.5cS), cyclopentasiloxane (KF-995), and 1,1,1,3,5,5,5-heptamethyl-3-[(trimethylsilyl)oxy]pentanetrisiloxane (TMF-1.5) (all manufactured by Shin-Etsu Chemical Co., Ltd.). Due to the good solubility and volatility of components (A) to (D), hexamethyldisiloxane is particularly preferred.

[0038] (E3) Organic solvents The coating composition of the present invention may contain (E3) organic solvent for the purpose of mixing components (A) to (D) 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; ether solvents such as diisopropyl ether, 1,4-dioxane, and tetrahydrofuran; and halogenated hydrocarbons such as dichloromethane and dichloroethane. These may be used individually or in combination of two or more. Tetrahydrofuran and dichloromethane are particularly preferred from the viewpoint of preventing shrinkage of the polyolefin separator, volatility, and solubility of components (A) to (D).

[0039] 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.

[0040] [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 portion, preferably one or both sides, of a polyolefin-based substrate (hereinafter simply referred to as "substrate") with the above-described coating composition, and then drying and curing it by heating, thereby forming a film made of the cured coating composition on a portion or all of the surface of the substrate, and, if the substrate has pores, on a portion or all of the inside of these pores.

[0041] 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.

[0042] The polyolefin substrate is not particularly limited as long as it is one that is normally used in electrochemical elements such as secondary batteries, but examples of materials include film substrates such as polyethylene and polypropylene. Furthermore, a substrate may be coated with inorganic particles to form a layer containing inorganic particles, and the coating composition of the present invention can also be used as a binder material to adhere the inorganic particles to a separator. Specific examples of inorganic particles include, but are not limited to, Al2O3, SiO2, TiO2, CeO2, CaO, ZnO, ZrO2, MgO, and CaO.

[0043] It is preferable to pre-dehydrate the polyolefin substrate immediately before applying the coating composition of the present invention. Specifically, it is preferable to include a dehydration step in which the substrate is dried at a temperature of 60 to 120°C, particularly 70 to 100°C, under normal or reduced pressure for several hours.

[0044] After applying the coating composition of the present invention onto a dehydrated separator substrate, the coating composition is heated at a temperature of 60 to 120°C, particularly at 70 to 100°C, for at least one hour under normal or reduced pressure to cure the coating composition and form a film.

[0045] Base material 1cm 2 The amount of film consisting of the cured product of the above coating composition per unit is 0.01 to 1.0 mg, preferably 0.05 to 0.5 mg. 0.01 mg / cm 2 If the concentration is less than 1.0 mg / cm³, the resulting electrochemical element separator will have inferior battery characteristics at high temperatures. 2 Beyond this point, ion conduction is hindered, resulting in inferior battery performance during long-term charge-discharge cycles.

[0046] The film thickness of the cured coating of the above coating composition is 0.1 to 10 μm, with 0.5 to 5 μm being preferred. If it is less than 0.1 μm, the resulting electrochemical element separator will have poor battery characteristics at high temperatures. If it exceeds 10 μm, it will hinder ion conduction, resulting in poor battery characteristics in long-term charge-discharge cycles.

[0047] [3] Electrochemical elements The electrochemical element using the separator of the present invention is not particularly limited, but a secondary battery comprising positive and negative electrodes, a separator interposed between these electrodes, and a non-aqueous electrolyte is preferred, and a lithium-ion secondary battery is more preferred.

[0048] The positive electrode includes positive electrode active material, conductive agent, binder, viscosity modifier, etc. The positive electrode active material can be lithium or a lithium-containing compound, and can be used alone or in appropriate combinations of two or more. Specific examples of lithium-containing compounds include lithium-compound oxides, for example. In particular, to increase the energy density, Li pA lithium composite oxide mainly composed of 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-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, etc. Further, as a high-voltage compatible type, LiMet s Mn 1-s O₄ (0 < s < 1) is also used. In this case, Met includes titanium, chromium, iron, cobalt, nickel, copper, zinc, etc.

[0049] 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.

[0050] The negative electrode contains, as a negative electrode material, a negative electrode active material, a conductive agent, a binder, a viscosity modifier, etc. The negative electrode active material can be used alone or in combination of two or more appropriately selected. Specific examples of the negative electrode active material include carbon materials such as non-graphitizable carbon, graphitizable carbon, graphite, pyrolytic carbons, cokes, glassy carbons, fired organic polymer compounds, carbon fibers, activated carbon, etc. Also, materials that can occlude and release lithium and contain one or more selected from metal elements and semi-metal elements as constituent elements are included.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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]

[0059] 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."

[0060] [1] Production of coating compositions for polyolefin-based electrochemical element separators [Example 1-1] (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 / 2The 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 polyolefin-based electrochemical element separators.

[0061] [2] Manufacturing and evaluation of secondary battery separators [Examples 2-1 to 2-5, Comparative Examples 1 to 3] A 15 μm thick polyolefin substrate (Senior Separator SW517G2, manufactured by Shenzhen Senior Technology Material, a porous polyolefin film with 3 μm thick Al2O3 particles bonded to one side) cut to a size of 15 × 20 cm was coated with a coating solution prepared by diluting the electrochemical element separator coating composition prepared in Example 1-1 with hexamethyldisiloxane (KF-96L-0.65 cS) to the concentration shown in Table 1. The substrate was placed on a cellulose sheet beforehand, and the coating solution applied to the substrate was scraped off using a bar coater (No. 3), with the excess absorbed by the cellulose sheet on the back side. The substrate was then dried and cured in an oven at 80°C for 2 hours to obtain a secondary battery separator having a coating film made of the coating composition.

[0062] The coating thickness, coating amount, air permeability, and lithium-ion battery characteristics of the obtained secondary battery separators were measured using the following methods, and the results are shown in Table 1. The results for a secondary battery separator without the coating composition applied to the polyolefin substrate are shown in Comparative Example 1.

[0063] [Coating thickness] The thickness of the separator before and after coating and curing was measured using a thickness gauge, and the coating thickness was calculated. [Coating amount] From the mass of the separator before and after coating and curing, the mass of the polyolefin substrate per 1 cm 2 The amount of coating per unit was calculated. [Air permeability] The air permeability (Gurley value) of the obtained secondary battery separator was measured using a Gurley-type air permeability tester G-B3C (manufactured by Toyo Seiki Seisakusho Co., Ltd.).

[0064] [3] Manufacturing and evaluation of lithium-ion batteries 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.

[0065] Next, the aluminum film with a polyolefin film was placed with the polyolefin film facing upwards. The negative electrode material, secondary battery separator, and positive electrode material prepared above were then 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 negative electrode. Each end of the aluminum film was heated and pressed at 150°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 70°C for 12 hours.

[0066] Next, in a glove box filled with dry N2, the electrolyte was injected into the dried laminate from the uncrimped 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.

[0067] [Battery characteristics] The obtained lithium-ion secondary batteries underwent pre-charge and discharge (chemical treatment), and were then charged to 4.2V with a current of 0.2cA in a 30°C constant temperature bath, and further charged at a constant voltage of 4.2V 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 300 charge-discharge cycles, with the initial capacity set to 100%, was determined, and the retention rate was calculated. A retention rate of 90% or more was marked with ○, 85% or more but less than 90% was marked with △, and less than 85% was marked with ×. [Heat resistance] The obtained lithium-ion secondary batteries underwent a preliminary charge-discharge (chemical treatment), and were then charged in a constant temperature bath at a current of 0.2 cA to 4.2 V. Further charging was performed at a constant voltage of 4.2 V until the current decreased to 0.02 cA. After charging, they were discharged at a current of 0.2 cA to 2.7 V. The battery capacity after performing the above charge / discharge operation at 150°C was calculated, with the battery capacity after performing the above charge / discharge operation at 30°C being set to 100%. A value of 90% or more was marked with ○, 80% or more but less than 90% was marked with △, and less than 80% was marked with ×.

[0068] [Table 1]

[0069] As shown in Table 1, the film thickness of the cured product of the coating composition of the present invention is 0.01 to 1.0 mg / cm². 2 In the range of coating thickness (0.10 to 10.0 μm), both the battery characteristics and heat resistance were good after 300 cycles (Examples 2-1 to 2-5). The coating film has a film thickness of 0.05 to 0.5 mg / cm². 2Even better results were obtained in the range of (coating thickness 0.50 to 5.0 μm) (Examples 2-2 to 2-4). On the other hand, the coating amount is 0.05mg / cm 2 In the following cases (coating thickness of 0.05 μm or less), while battery characteristics for 300 cycles were obtained, heat resistance was not achieved (Comparative Examples 1 and 2). Furthermore, the coating amount is 2.5 mg / cm². 2 In the case of a coating thickness of 25.0 μm (Comparative Example 3), although heat resistance was obtained, degradation of battery characteristics was observed during long-term charge-discharge cycles. This is presumed to be because the separator's air permeability was 1800 sec / 100 ml, resulting in high resistance that significantly hindered ion conduction.

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): 0 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 0.5 to 15.0 for each total alkenyl group bonded to a silicon atom in components (A) and (B), and (D) Hydrosilylation reaction catalyst A coating composition for polyolefin-based electrochemical element separators containing the following:

2. The substrate comprises a polyolefin-based substrate and a coating made of a cured product of the polyolefin-based electrochemical element separator coating composition described in claim 1, The amount of the coating is 1 cm of the substrate. 2 Electrochemical element separator, with a concentration of 0.01 to 1.0 mg per unit.

3. The substrate comprises a polyolefin-based substrate and a coating made of a cured product of the polyolefin-based electrochemical element separator coating composition described in claim 1, An electrochemical element separator having a film thickness of 0.1 to 10 μm.

4. The electrochemical element separator according to claim 2 or 3, wherein the substrate has a plurality of pores.

5. The electrochemical element separator according to claim 2 or 3, wherein the substrate has a layer containing inorganic particles on one side.

6. An electrochemical element comprising the electrochemical element separator according to claim 2 or 3.

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