SEPARATOR AND NONAQUEOUS ELECTROLYTE SECONDARY BATTERY

摘要

A separator whose dynamic hardness (DH) at reaching of press member load to 12 kgf/cm² is 1000 or above is used in a nonaqueous electrolyte secondary battery. This separator has at least one porous layer (X) containing a polyolefin and at least one porous layer (Y) containing a heat resistant resin. The void ratio of the porous layer (X) is in the range of 35 to 65%. In the pore diameter distribution of the porous layer (X) as measured by a mercury porosimeter, pores of 0.02 to 0.2 µm diameter occupy 40 vol.% or more of the whole pore volume. The heat resistant resin exhibits a thermal deformation temperature of 160°C or higher.