microporous films may have suitable gurley numbers ranging from about 1 to about 150 preferably from about 5 to about 80 the gurley number refers to the amount of time for 10 cc of air at 12 2 inches of water to pass through one square inch of the film or coating the gurley number is measured according to astm d726 the microporous film may have an average pore size in the range of from about 0 02 to about 2 microns and a porosity in the range of from about 20 to about 80 in most batteries the separator must be sufficiently porous to transmit ions between the anode portion and the cathode portion the functionalized pvoh containing films are included in the battery separator of the invention the battery separator may consist solely of the functionalized pvoh film or it may be present with or adhered to other layers as for example a coating additional suitable layers that may be used in the separator include polyolefin films cellulosic films and the like the separator film is interposed in a battery between the anode and the cathode in the electrolyte medium to substantially eliminate contact between the plates if the film of the invention is present as a coating on another substrate.