Abstract: An ion permeable material particularly useful for electrode separators. The material is a uniform mixture of 30 to 70% by weight colloidal size asbestos fibers and 20 to 40% by weight unsintered fine polytetrafluoroethylene fibers, bonded together with uniformly dispersed particles of a fluorinated ethylene-propylene copolymer comprising about 5 to 15% by weight of the material. Colloidal size particles of an alkaline earth metal oxide are dispersed throughout the material. The material is initially prepared in a modified paper making process and then heated to a temperature high enough to fuse the fluorinated ethylene-propylene copolymer but not high enough to sinter the polytetrafluoroethylene fibers. An improved zinc-air hybrid fuel cell and an improved silver oxide-zinc secondary battery are made possible with electrode separators such as described herein.

Abstract: In accordance with a preferred embodiment of this invention, the polarization or overvoltage of a carbon black-based air cathode is significantly reduced by adding from 1 to 5 percent, by weight based on the total carbon composition, of carbon derived from poly(vinylidene chloride) (hereinafter PVdC) to the carbon black, prior to the formation of the electrode. To accomplish this, the porous and particulate carbon black is initially blended with a solution of PVdC; the resulting blend is dried, and then dehydrochlorinated and baked at a temperature in the range of from 900.degree. C. to 1,100.degree. C. The electrocatalytic layer of the cathode is then prepared from this tailored carbon substrate.FIELD OF THE INVENTIONThis invention relates to a carbon-based substrate for electrodes used in fuel cells which operate at ambient temperatures and wherein the electrode separates a liquid electrolyte from a gaseous reactant.