Electrochemical cell electrode separator and method of making it and fuel cell containing same

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.