NOVELTY - A microporous polyolefin membrane comprises polyethylene and polypropylene, where the membrane has an electrolytic solution absorption speed greater than or equal to 4.5.    USE - As battery separator for battery such as lithium ion battery as power source for electric vehicle or hybrid electric vehicle (claimed), and for primary and secondary batteries such as lithium ion secondary batteries, lithium-polymer secondary batteries, nickel-hydrogen secondary batteries, nickel-cadmium secondary batteries, nickel-zinc secondary batteries, silver-zinc secondary batteries.    ADVANTAGE - The microporous membrane has good air permeability, mechanical strength, pin puncture strength, tensile strength, tensile elongation properties, excellent electrolytic solution absorption, heat shrinkage resistance, shut down properties and compression properties, with little variation of thickness and air permeability after heat compression; and provides separators and batteries which are safe, and having excellent heat resistance, storage properties and productivity.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following: A) manufacturing a microporous membrane, involving: 1) combining a polyolefin composition and a diluent, where polyolefin composition comprising (wt.%): polyethylene (75-99) having weight-average molecular weight (Mw) of less than or equal to 7x 105, and polypropylene (1-25) having a heat of fusion greater than or equal to 80 J/g and Mw of 3x 105 to 1.5x 106; 2) extruding the combined polyolefin composition and diluent through a die to form an extrudate; 3)cooling the extrudate to form a cooled extrudate; 4) stretching the cooled extrudate to magnification of 9-400 fold in at least one direction at stretching temperature of crystal dispersion temperature (Ted) to Ted + 30 degrees C to form a stretched cooled extrudate; 5) removing at least a portion of the diluent from the stretched extrudate; 6) stretching the diluent-removed extrudate to a magnification of 1.1-1.8 fold in at least one direction to form stretched film; and 7) heat-setting the stretched film to form the microporous membrane; and B) a battery comprising an anode, cathode, electrolyte, and at least one battery separator located between the anode and the cathode, where the separator including the membrane.