# US 6,296,969 B1 · Separator for battery having a function of avoiding dangers caused by overheat, and method for producing the same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 6,296,969 B1 - Document ID: US6296969B1 - Status: Granted - Kind: B1 - Application number: 09/277,742 - Filed: 1999-03-29 - Granted: 2001-10-02 - Earliest claimed: 1998-03-30 - Assignees: Noritake Co., Limited; Sanyo Chemical Industries, Ltd. - Inventors: Kenji Yano; Misao Iwata; Hirokazu Matsunaga; Yukio Shibata; Yoshio Tanimizu - Web page: https://patentgrep.com/patent/US6296969B1 ## CPC - H01M 50/44: Fibrous material - H01M 50/434: Ceramics - H01M 10/05: Accumulators with non-aqueous electrolyte (H01M10/39 takes precedence) - H01M 10/30: Nickel accumulators (H01M10/34 takes precedence) - H01M 10/345: {Gastight metal hydride accumulators} - H01M 50/489: Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties - H01M 50/494: Tensile strength - Y02E 60/10: Energy storage using batteries - H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY - Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION ## Abstract To provide a separator for a battery with high safety and a method for producing the same in which the separator has a shutdown function and capability of preventing meltdown, complete melting and cracks when the battery performs unusually. This separator comprises a porous ceramic sheet having ceramic fibers bonded to each other at their intersection points and polyolefin and comprises micropores for impregnation of an electrolyte. ## Claims ### Claim 1 A separator for a battery comprising a porous ceramic sheet formed of ceramic fibers bonded to one another at their points of intersection and a polyolefin bonded to the ceramic sheet and having micropores capable of being impregnated with an electrolyte. ### Claim 2 (depends on 1) The separator for a battery according to claim 1, wherein the ceramic sheet is constituted of ceramic fibers bonded to one another at their points of intersection through sintering. ### Claim 3 (depends on 1) The separator for a battery according to claim 1, wherein the polyolefin has been bonded directly to the ceramic sheet, or bonded to the ceramic sheet via a silane coupling agent. ### Claim 4 (depends on 1) The separator for a battery according to claim 1, wherein the porous ceramic sheet holds the polyolefin within interstice of the ceramic fibers bonded to one another at their points of intersection. ### Claim 5 (depends on 1) The separator for a battery according to claim 1, wherein the ceramic fibers arc constituted of amorphous silica fibers reinforced with one or more fibers selected from the group consisting of alumina fibers, aluminosilicate fibers and aluminoborosilicate fibers. ### Claim 6 (depends on 1) The separator for a battery according to claim 1, wherein the polyolefin is at least one selected from the group consisting of a polyethylene, a polypropylene, an ethylene-propylene copolymer, an ethylene-butene copolymer, an ethylene-hexene copolymer and an ethylene-octene copolymer. ### Claim 7 (depends on 1) The separator for a battery according to claim 1, wherein the polyolefin has been chemically bonded to the ceramic sheet. ### Claim 8 (depends on 1) The separator for a battery according to claim 1, wherein the ceramic fibers have a diameter of at least 0.65 μm and at most 3.0 μm. ### Claim 9 (depends on 1) The separator for a battery according to claim 1, wherein the polyolefin has micropores of at least 0.05 μm and at most 10 μm. ### Claim 10 (depends on 1) The separator for a battery according to claim 1, wherein the polyolefin is in the form of film. ### Claim 11 (depends on 10) The separator for a battery according to claim 10, wherein the film is formed from a liquid containing a polyolefin dissolved or dispersed therein or a polyolefin thin film containing a plasticizer added thereto. ### Claim 12 (depends on 1) The separator for a battery according to claim 1, wherein the micropores have been formed by elution of a pore forming agent within the polyolefin. ### Claim 13 (depends on 1) The separator for a battery according to claim 1, wherein the polyolefin is a modified polyolefin having an acid value in the range from 0.1 to 20. ### Claim 14 (depends on 1) In a battery having a separator incorporated therein, the improvement which comprises using as a separator the separator according to claim 1. ### Claim 15 (depends on 1) In a lithium battery comprising: a positive electrode, a negative electrode, a separator separating the positive electrode and the negative electrode, a positive electrode can contacted with the positive electrode, a negative electrode can contacted with the negative electrode and an electrical insulating gasket, said lithium battery containing an electrolyte, the improvement which comprises using as a separator the separator according to claim 1. ### Claim 16 (depends on 1) The separator for a battery according to claim 1, obtained by: sintering a boron compound mixed with ceramic fibers to form a porous ceramic sheet comprised of the ceramic fibers bonded to one another at their points of intersection, applying a polyolefin containing a pore forming agent to the ceramic sheet to form a polyolefin layer bonded to the ceramic sheet, and removing the pore forming agent from the polyolefin layer to produce a separator. ### Claim 17 (depends on 16) The separator for a battery according to claim 16, wherein the ceramic fibers are constituted of amorphous silica fibers reinforced with one or more fibers selected from the group consisting of alumina fibers, aluminosilicate fibers and aluminoborosilicate fibers. ### Claim 18 (depends on 16) The separator for a battery according to claim 16, wherein the boron compound is a nonmetal-based boron compound. ### Claim 19 (depends on 16) The separator for a battery according to claim 16, wherein organic fibers have been mixed with the ceramic fibers and the boron compound and have disappeared during the sintering. ### Claim 20 (depends on 19) The separator for a battery according to claim 19, wherein the organic fibers have been mixed with the ceramic fibers and the boron compound in an amount of 5 to 40% by weight based on the total weight of the ceramic filers and the boron compound. ### Claim 21 (depends on 16) The separator for a battery according to claim 16, wherein the boron compound is boron nitride and has been mixed with the ceramic fibers in an amount of 3 to 7.5% by weight based on the total weight of the ceramic fibers. ### Claim 22 (depends on 16) The separator for a battery according to claim 16, wherein said polyolefin is applied to the ceramic sheet through dipping the ceramic sheet into a liquid containing a polyolefin dissolved or dispersed therein. ### Claim 23 (depends on 16) The separator for a battery according to claim 16, wherein said polyolefin is applied to the ceramic sheet through thermally contact-bonding a polyolefin film with the ceramic sheet to obtain a composite sheet of the ceramic sheet and the polyolefin. ### Claim 24 (depends on 16) The separator for a battery according to claim 16, wherein the pore forming agent is selected from the group consisting of silicic acid, calcium silicate, calcium carbonate, talc, dibutyl phthalate, dioctyl phthalate, dinonyl phthalate, dibutyl sebacate, tributyl phosphate and liquid paraffin. ### Claim 25 (depends on 1) The separator for a battery according to claim 1, obtained by sintering a boron compound mixed with ceramic fibers to form a porous ceramic sheet comprised of the ceramic fibers bonded to one another at their points of intersection, dipping the porous ceramic sheet into a liquid containing a polyolefin dissolved or dispersed therein to adhere the polyolefin onto the ceramic fibers, and forming micropores within the interstices of the polyolefin adhered to the ceramic fibers to produce a separator. ### Claim 26 A separator for a battery comprising a porous ceramic sheet formed of ceramic fibers bonded to one another at their points of intersection and a polyolefin bonded to the ceramic sheet and having micropores capable of being impregnated with an electrolyte, wherein the ceramic sheet has been surface-treated with a silane coupling agent. ### Claim 27 A separator for a battery comprising a porous ceramic sheet formed of ceramic fibers bonded to one another at their points of intersection and a polyolefin bonded to the ceramic sheet, and having micropores capable of being impregnated with an electrolyte, wherein the polyolefin comprises a modified polyolefin selected from the group consisting of a carboxyl-modified polyolefin, a dicarboxylic anhydride-modified polyolefin and an epoxy-modified polyolefin, or said polyolefin comprises a mixture of the modified polyolefin with an unmodified polyolefin. ### Claim 28 (depends on 27) The separator for a battery according to claim 27, wherein the polyolefin has an acid value not higher than 20 and comprises a modified polyolefin of at least one polyolefin selected from the group consisting of an ethylene polymer, a propylene polymer, an ethylene-propylene copolymer, a polybutene and a poly-4-methylpentene-1, wherein said polyolefin has been modified with an unsaturated dicarboxylic acid, a derivative of an unsaturated dicarboxylic acid or an epoxy-containing vinylic compound. ### Claim 29 (depends on 27) The separator for a battery according to claim 27, wherein the polyolefin has been chemically bonded to the ceramic sheet, directly or via a silane coupling agent having an amino group, through reaction of the carboxyl group, the dicarboxylic anhydride group or the epoxy group of the modified polyolefin with a hydroxyl group on the ceramic fiber, or with the amino group of the silane coupling agent on the surface of the ceramic fiber.