A separator membrane for use in silver-
zinc batteries is produced by extruding a blend of two fillers with the same
chemical formula but different particle size. A polyolefine
polymer and a
plasticizer are blended and extruded to form a
thin sheet of 1 to 10 mil thickness. The
plasticizer is then extracted to leave submicron voids in the membrane. Plasticizers are added as
processing aids, and can be either soluble or insoluble in water, and include
petroleum oils, lubricating oils, fuel oils, and
natural oils such as tall oils and linseed oils. The oil are then extracted from the membrane by conventional procedures such as
single stage extraction using a suitable
solvent. Commercially available
wetting agents known to the art such as dodecylphenoxy polyethoxy
ethanol and isooctyl phenyl polyethoxy
ethanol are coated onto the sheet to improve wettability. The sheet is then dried, and boiled in
distilled water for one minute or more, before being finally dried.