Microporous membranes, separators, lithium batteries, and related methods

In accordance with at least selected embodiments, novel or improved separator membranes, separators, batteries including such separators, methods of making such membranes and/or separators, and/or methods of using such membranes and/or separators are disclosed or provided. In accordance with at least certain embodiments, an ionized radiation treated microporous polyolefin, polyethylene (PE), copolymer, and/or polymer blend (e.g., a copolymer or blend comprising PE and another polymer, such as polypropylene (PP)) battery separator for a secondary or rechargeable lithium battery and/or a method of making an ionized radiation treated microporous battery separator is disclosed. The ionized radiation treatment may provide a microporous membrane or battery separator having a lower onset temperature of thermal shutdown, an extended thermal shutdown window, physical, dimensional, and/or mechanical integrity maintained at higher temperatures, improved battery safety performance in a rechargeable lithium battery, a treated polyethylene separator membrane with the high temperature performance of a polypropylene membrane or separator membrane, or polypropylene-based trilayer product (by way of example only, a trilayer membrane made of two polypropylene layers with a polyethylene layer in between), reduced thermal shrinkage resulting in both improved thermal stability and high temperature physical integrity, which maintains the separation of cathode and anode in a battery system and avoids thermal runaway in a rechargeable or secondary lithium battery, and/or combinations thereof.