Microporous polyurethane based battery separator

摘要

A battery separator composed of a microporous sheet product having first and second major surfaces and a thickness of less than about 50 mils, formed from a uniform mixture of a thermoplastic polyurethane polymer having a high degree of hard segments with a filler or said polyurethane with a structure enhancing agent, said sheet product having a sheet embedded within said mixture and between the first and second major surfaces. The sheet product has porosity of at least about 50 volume percent composed of pores such that the nominal pore diameter increases from each major surface towards the interior, center of the sheet product's thickness.