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.