NOVELTY - Producing a microporous membrane (M1) involves extruding a mixture of diluent and polymer to form an extrudate, the polymer comprising first polyethylene having an weight average molecular weight (Mw) less than 1x 106, a second polyethylene having an Mw is greater than or equal to 1x 106, and a polypropylene having an Mw greater than or equal to 5x 105 and Delta Hm is greater than or equal to 80 J/g, and processing the extrudate into a microporous membrane having a thickness of less than or equal to 12 mu m by stretching the extrudate in one planar direction at 108-116 degrees C after removing the solvent to a magnification factor of less than or equal to 1.1.    USE - For producing a microporous membrane for battery used in electric vehicle or hybrid electrical vehicle (claimed).    ADVANTAGE - The membrane has a meltdown temperature greater than or equal to 145 degrees C and a normalized pin puncture strength greater than or equal to 3.20x 102 mN/ mu m, and transverse direction (TD) Tensile strength greater than or equal to 1.4x 105 kPa.    DETAILED DESCRIPTION - Producing a microporous membrane involves (1) extruding a mixture of diluent and polymer to form an extrudate, the polymer comprising first polyethylene having an weight average molecular weight (Mw) less than 1x 106, a second polyethylene having an Mw is greater than or equal to 1x 106, and a polypropylene having an Mw greater than or equal to 5x 105 and Delta Hm is greater than or equal to 80 J/g, where the sum of the amounts of the polypropylene having an Mw is greater than or equal to 5x 105 and Delta Hm is greater than or equal to 80 J/g and the second polyethylene is greater than or equal to 15 wt. %, and (2) processing the extrudate into a microporous membrane having a thickness of less than or equal to 12 mu m by stretching the extrudate in at least one planar direction at 108-116 degrees C after removing the solvent to a magnification factor of less than or equal to 1.1 and excludes any stretching of the extrudate after the step of removing the solvent at a magnification factor of greater than 1.1 and removing at least a portion of the diluent from the extrudate. An INDEPENDENT CLAIM is included for producing battery involving an anode, cathode, an electrolyte, and battery separator located between the anode and the cathode, where the battery separator being a membrane (M1); (b) the membrane has a thickness of less than or equal to 12 mu m; and (c) the membrane is microporous.