Reactive polymer-supported porous film for battery separator, method for producing the porous film and electrode/porous film assembly

A reactive polymer-supported porous film for separator, that has sufficient adhesiveness between electrodes and separator and can suitably be used to produce a battery having low internal resistance and high rate performance, a method for producing the porous film, a method for producing a battery using the porous film, and an electrode/porous film assembly are disclosed. The reactive polymer-supported porous film for battery separator includes a porous film substrate having supported thereon a reactive polymer obtained by reacting a crosslinkable polymer having at least one reactive group selected from the group consisting-of 3-oxetanyl group and epoxy group in the molecule, with an acid anhydride, thereby partially crosslinking the polymer.