| abstract |
A battery separator comprising a microporous polyolefin membrane having a thickness of 16 µm or less, and a modifying porous layer comprising a fluorine resin and an inorganic particle or cross-linked polymer particle, the modifying porous layer being laminated on one side of the microporous polyolefin membrane, wherein the microporous polyolefin membrane has (a) a shutdown temperature of 135°C or lower, and (b) a rate of air resistance change of 1 × 10 4 sec/100 cc/°C or more, and Expression 1 and Expression 2 are satisfied, and a process for producing the battery separator. 0.01 ¤ absT 1200 ¤ 0.30 absT(1200): Absorbance of an absorption having a peak at or near 1,200 cm -1 per 10 µm thickness of a microporous polyolefin membrane, as measured by infrared spectroscopy (transmission method) after peeling a modifying porous layer off the microporous polyolefin membrane 0.001 ¤ absR 1200 ¤ 0.030 absR(1200): Absorbance of a maximum peak at or near 1,200 cm -1 , as measured by infrared spectroscopy (reflection method) on the surface of a microporous polyolefin membrane that is opposite to a modifying porous layer Provided are a battery separator suitable for high-capacity batteries, which has adhesion to electrodes and is excellent in shutdown properties and electrolyte permeability, and a process for producing the battery separator. |