Disclosed herein is an improved membrane, separator and/or method for forming a multilayer microporous membrane for use in an improved battery separator, particularly a battery separator for a lithium ion secondary battery. Also disclosed herein is the multilayer microporous membrane formed by this method, which has properties that compete with or exceed those of wet process, coated or uncoated, membranes that are also useable in battery separators. Also disclosed are battery separators comprising the multilayer microporous membrane and batteries, vehicles, or devices comprising the separators. The method may comprise at least the following steps: (1) forming a stretched first non-porous precursor film that has pores due to the stretching of a first non-porous precursor film; (2) separately forming a second stretched non-porous precursor film that has pores due to the stretching of a second non-porous precursor film; and then (3) laminating the stretched first non-porous precursor and the stretched second non-porous precursor.