POROUS POLYPROPYLENE RESIN FILM, SEPARATOR FOR USE IN A BATTERY, AND BATTERY

摘要

Adjusting the air permeability that the disclosed porous polypropylene resin film exhibits when stretched allows said film to be used as a separator in a battery wherein the holes in said separator, in an wound electrode/separator assembly, are controlled. Said porous polypropylene resin film, which consists primarily of a polypropylene resin, is characterized by a pre-stretching air permeability (Pa) and an air permeability when stretched 5% (Pa') that satisfy the following: (1) Pa' is at most 1000 s/100 ml; and (2) Pa'/Pa is at most 1.5.