Abstract: A ceramic microporous polyolefin battery separator membrane, high in air permeability, low in shrinkage and improved temperature resistance addresses the safety requirements of lithium ion batteries. The separators made by the current invention consists of one or more polyolefin polymers and kaolin fillers comprised of aluminum oxide and silicon oxide. The membranes of current invention have a thickness of 5-200 microns, air permeability of 1-200 sec/10 cc (Gurley seconds), and average pore diameter of less than 1 micron.

Abstract: A method for manufacturing battery separators for use in a lithium-ion battery containing non-aqueous electrolytes, producing batteries being resistant to thermal runaway and explosion, includes the steps of preparing a dryblend comprising two UHMW Polyethylenes and Calcined Kaolin, feeding said dry-blend into an extruder, melt-kneading said dry blend in the extruder while feeding mineral oil, making a solution from a die into the form of a sheet, using casting rolls, thereby cooling the solution down, producing a thick gel sheet, stretching the gel sheet in both machine and transverse directions, producing a 20 micron thick gel sheet containing oil thereby, extracting the oil by use of a solvent and drying the film, heat-setting the film and producing a microporous membrane.

Abstract: A ceramic microporous polyolefin battery separator membrane, high in air permeability, low in shrinkage and improved temperature resistance addresses the safety requirements of lithium ion batteries. The separators made by the current invention consists of one or more polyolefin polymers and kaolin fillers comprised of aluminum oxide and silicon oxide. The membranes of current invention have a thickness of 5-200 microns, air permeability of 1-200 sec/10 cc (Gurley seconds), and average pore diameter of less than 1 micron.