# US 2018/0323459 A1 · Catalyst coated membranes and preparation methods for fuel cells > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2018/0323459 A1 - Document ID: US20180323459A1 - Status: Published application - Kind: A1 - Application number: 15/961,916 - Filed: 2018-04-25 - Published: 2018-11-08 - Earliest claimed: 2017-05-06 - Assignees: Daimler AG; Ford Motor Company - Applicants: Daimler AG; Ford Motor Company - Inventors: Yuquan Zou; Scott McDermid; Massimiliano Cimenti; Shun-wen Amy Yang; Liviu Catoiu - Web page: https://patentgrep.com/patent/US20180323459A1 ## CPC - H01M 8/1004: characterised by membrane-electrode assemblies [MEA] (H01M8/12 takes precedence) - H01M 4/881: {Electrolytic membranes} - H01M 4/8814: {Temporary supports, e.g. decal} - H01M 4/8828: {Coating with slurry or ink} - H01M 8/1023: having only carbon, e.g. polyarylenes, polystyrenes or polybutadiene-styrenes - H01M 8/1039: halogenated, e.g. sulfonated polyvinylidene fluorides - H01M 8/1053: consisting of layers of polymers with at least one layer being ionically conductive - H01M 8/1081: starting from solutions, dispersions or slurries exclusively of polymers - H01M 8/109: {thermal other than drying, e.g. sintering} - H01M 8/1067: characterised by their physical properties, e.g. porosity, ionic conductivity or thickness - H01M 2008/1095: {Fuel cells with polymeric electrolytes} - H01M 2300/0082: Organic polymers - H01M 2300/0094: in the form of layered products, e.g. coatings - Y02E 60/50: Fuel cells - Y02P 70/50: Manufacturing or production processes characterised by the final manufactured product - 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 - Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS ## Abstract Simplified methods are disclosed for preparing a catalyst coated membrane that is reinforced with a porous polymer sheet (e.g. an expanded polymer sheet) for use in solid polymer electrolyte fuel cells. The methods involve forming a solid polymer electrolyte membrane by coating membrane ionomer solution onto a first catalyst layer and then applying the porous polymer sheet to the membrane ionomer solution coating, while it is still wet, such that the membrane ionomer solution only partially fills the pores of the porous polymer sheet. A second catalyst ink is then applied which fills the remaining pores of the porous polymer sheet. Not only are such methods simpler than many conventional methods, but surprisingly this can result in a marked improvement in fuel cell performance characteristics. ## Claims ### Claim 1 A method of preparing a catalyst coated membrane assembly for a solid polymer electrolyte fuel cell, the catalyst coated membrane assembly comprising a solid polymer electrolyte membrane comprising a proton-conducting membrane ionomer, first and second catalyst layers comprising first and second catalysts respectively and first and second ionomers respectively and bonded to opposite sides of the solid polymer electrolyte membrane, and a porous polymer sheet at the interface between the second catalyst layer and the solid polymer electrolyte membrane and bonded to both, and wherein the pores of the porous polymer sheet comprise the solid polymer membrane electrolyte and the second catalyst layer; the method comprising: coating a first catalyst ink comprising the first catalyst and the first ionomer onto a supporting substrate; drying the first catalyst ink coating, thereby form ling the first catalyst layer; coating a membrane ionomer solution comprising the membrane ionomer onto the first catalyst layer; applying the porous polymer sheet to the wet membrane ionomer solution coating wherein the membrane ionomer solution partially fills the pores of the porous polymer sheet; drying and annealing the membrane ionomer coating, thereby forming the solid polymer electrolyte membrane; applying a second catalyst ink comprising the second catalyst and the second ionomer to the porous polymer sheet wherein the second catalyst ink fills the remaining pores of the porous polymer sheet; and drying the second catalyst ink coating, thereby forming the second catalyst layer. ### Claim 2 (depends on 1) The method of claim 1 wherein the first catalyst layer is a cathode layer and the second catalyst layer is an anode layer. ### Claim 3 (depends on 1) The method of claim 1 wherein the porous polymer sheet is an expanded polymer sheet. ### Claim 4 (depends on 1) The method of claim 1 wherein the membrane ionomer comprises perfluorosulfonic acid ionomer or hydrocarbon ionomer. ### Claim 5 (depends on 1) The method of claim 1 wherein the membrane ionomer solution comprises greater than about 16% by weight of membrane ionomer solids. ### Claim 6 (depends on 5) The method of claim 5 wherein the membrane ionomer solution comprises about 24% by weight of membrane ionomer solids. ### Claim 7 (depends on 1) The method of claim 1 wherein the membrane ionomer solution has a viscosity greater than about 90 centipoise. ### Claim 8 (depends on 1) The method of claim 1 wherein the membrane ionomer solution comprises a solvent mixture of an alcohol and water in a ratio greater than about 60:40 by weight of alcohol to water. ### Claim 9 (depends on 8) The method of claim 8 wherein the alcohol is n-propanol. ### Claim 10 (depends on 1) A catalyst coated membrane assembly made according to the method of claim 1. ### Claim 11 (depends on 10) The catalyst coated membrane assembly of claim 10 wherein the first catalyst layer is a cathode layer and the second catalyst layer is an anode layer. ### Claim 12 (depends on 11) The catalyst coated membrane assembly of claim 11 wherein the membrane ionomer comprises a perfluorosulfonic acid ionomer. ### Claim 13 (depends on 12) The catalyst coated membrane assembly of claim 12 wherein the first and second ionomers comprise a perfluorosulfonic acid ionomer with a different equivalent weight than that of the membrane ionomer. ### Claim 14 (depends on 11) The catalyst coated membrane assembly of claim 11 wherein the porous polymer sheet is an expanded polymer sheet. ### Claim 15 (depends on 14) The catalyst coated membrane assembly of claim 14 wherein the expanded polymer sheet is an expanded polytetrafluoroethylene sheet. ### Claim 16 (depends on 14) The catalyst coated membrane assembly of claim 14 wherein the porosity of the expanded polymer sheet is between 60 and 90%. ### Claim 17 (depends on 16) The catalyst coated membrane assembly of claim 16 wherein the porosity of the expanded polymer sheet is about 70%. ### Claim 18 (depends on 14) The catalyst coated membrane assembly of claim 14 wherein the expanded polymer sheet is from about 4 to 8 micrometers thick. ### Claim 19 (depends on 18) The catalyst coated membrane assembly of claim 18 wherein the expanded polymer sheet is about 4 micrometers thick. ### Claim 20 (depends on 14) The catalyst coated membrane assembly of claim 14 wherein the pores in about 0.2 micrometers of the thickness of the expanded polymer sheet are filled with the anode catalyst layer. ### Claim 21 (depends on 14) The catalyst coated membrane assembly of claim 14 wherein the pores in greater than about 1% of the thickness of the expanded polymer sheet are filled with the anode catalyst layer ### Claim 22 (depends on 21) The catalyst coated membrane assembly of claim 21 wherein the pores in about 5% of the thickness of the expanded polymer sheet are filled with the anode catalyst layer. ### Claim 23 (depends on 1) A solid polymer electrolyte fuel cell comprising a catalyst coated membrane assembly made according to the method of claim 1. ### Claim 24 (depends on 2) A method of improving voltage reversal tolerance in a solid polymer electrolyte fuel cell comprising a catalyst coated membrane assembly, the method comprising making the catalyst coated membrane assembly according to the method of claim 2.