Propylene resin microporous film and method for producing the same, lithium ion battery separator and lithium ion battery

摘要

PROBLEM TO BE SOLVED: To provide a propylene-based resin micropore film which is excellent in permeability of a lithium ion, can compose a lithium ion battery of high performance, can inhibit short of a positive electrode and a negative electrode by a dendrite, and is excellent in impact resistance.SOLUTION: The propylene-based resin micropore film is a propylene-based resin micropore film which comprises forming a micropore part by carrying out biaxial stretching of a propylene-based resin film, wherein in the propylene-based resin, a weight-average molecular weight is 350,000-500,000, a melting point acquired by a differential scanning calorimetric analysis (DSC) is 160-170°C, and an amount of heat of fusion at at least 155°C is 56-80 mJ/mg, and further, in the propylene-based resin micropore film, air permeability is 40-400 s/100mL, and a value in which a tensile yield strength (MPa) of a width direction at 23°C is divided by an apparent density (g/cm) is at least 40.