Patent ID: 6074692
Filing Date: 2000-06-13
Classification: H01M,Y02E,Y02P

Abstract:
In the process of making a membrane-electrode assembly for a PEM fuel cell said membrane-electrode-assembly having x and y directions perpendicular to each other in a plane of the membrane-electrode-assembly and a z direction through a thickness of the assembly normal to said plane, said process comprising the principal steps of (a) preparing an electrode-forming slurry comprising finely divided catalyst, a polymer binder for said catalyst and a liquid vehicle for the catalyst and binder, (b) coating a proton-conductive, polymeric membrane-electrolyte with said slurry to form a slurry-coated membrane, and (c) heating said slurry-coated membrane to remove said vehicle and cure said polymer binder, the improvement comprising:i. before said coating, contacting said membrane-electrolyte with said vehicle for a time sufficient to swell said membrane-electrolyte in the x, y and z directions, and thereby form a preswollen membrane-electrolyte;ii. constraining said preswollen membrane-electrolyte against shrinking in said x and y directions during drying;iii. coating the preswollen and constrained membrane with said slurry to form a slurry-coated membrane; andiv. heating the slurry-coated membrane to dry said slurry-coated membrane and cure said polymer binder, said heating being conducted while continuing said constraining to prevent the coated membrane from said shrinking.