NOVELTY - A multi-layer microporous membrane comprises polyethylene and polypropylene, and has a pin puncture strength of less than or equal to 3500 mN, an air permeability after heat compression of less than or equal to 700 seconds/cm3, and a maximum shrinkage in the molten state of less than or equal to 20%.    USE - Multi-layer microporous membrane used as a separator for a battery (claimed) including lithium ion battery, lithium polymer secondary battery, nickel-hydrogen secondary battery, nickel-cadmium secondary battery, nickel-zinc secondary battery, or silver-zinc secondary battery used as a power source for electric vehicles or hybrid electric vehicles.    ADVANTAGE - The membrane has a good balance of important properties including excellent electrochemical stability and low heat shrinkage, and good mechanical strength, compression resistance and electrolytic solution absorption, while maintaining high permeability and heat resistance. Further, the membrane has uniform thickness which reduces the likelihood of short-circuiting.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for:    (1) a battery comprising anode(s), cathode(s), electrolyte, and battery separator located between the anode and the cathode and comprising a multi-layer microporous membrane; and    (2) a method for producing a multi-layer microporous membrane, comprising combining a first polyolefin composition and diluent(s) to form a first mixture, combining a second polyolefin composition and diluent(s) to form a second mixture, extruding the first and second mixtures through dies to produce a layered extrudate having a first layer comprising the first mixture and a second layer comprising the second mixture that is in planar contact with the first layer, cooling the extrudate to form a cooled extrudate, stretching the cooled extrudate in at least one direction at a high stretching temperature to form a stretched sheet, removing a portion of the diluent from the stretched sheet to form a membrane, stretching the membrane in at least one direction to form a stretched membrane, and heat-setting the stretched membrane product to form the multilayer microporous membrane.