| abstract |
A microporous film having at least one of the following properties: unrestrained MD shrinkage, when the film is baked unrestrained at 90°C for 1 hour, of 2% or more; unrestrained MD shrinkage, when the film is baked unrestrained at 105°C for 1 hour, of 2.5% or more; MD restrained growth, when measured using the MD restrained growth test, of less than or equal to 0.2%; rebound or recovery of 5% or greater when measured by the compressibility test; a max compression greater than or equal to 18% when measured by the compressibility test; swelling in DEC when measured according to the swelling in DEC test of 0.95% or less; the film exhibits a round-shaped, not a slit-shaped opening when subjected to the puncture test; the lamellae of the film have a thickness no greater than 250nm; a normalized puncture strength above 350 g/16 micron; and having higher modulus and lower elongation before break of less than 40% in the machine direction. Also disclosed is a battery separator, battery, or device comprising at least one microporous film as described herein. |