| 摘要 |
PROBLEM TO BE SOLVED: To provide a battery separator which has excellent heat resistance even in an electrolytic solution and in which superior battery stability can be maintained over a long period of time.SOLUTION: A battery separator comprises: a polyolefin resin porous film (A); and a porous layer (B) on at least one face of the polyolefin resin porous film. The porous layer includes: an inorganic filler (b-2); and a resin binder (b-1) having a gel fraction of 90-99 mass% in a toluene liquid solution, showing a glass transition temperature in a region under 30°C, and having a degree of swelling of 105-200% to an ethylene carbonate/diethyl carbonate mixture solution (whose volume proportion is 2/3). In the case of the battery separator subjected to ultrasonication in the ethylene carbonate/diethyl carbonate mixture solution (whose volume proportion is 2/3) of 25°C for ten minutes, the remaining percentage of the porous layer (B) is 60% or larger.SELECTED DRAWING: None |
