Thin battery separators and methods
In accordance with at least selected aspects, objects or embodiments, optimized, novel or improved membranes, battery separators, batteries, and/or systems and/or related methods of manufacture, use and/or optimization are provided. In accordance with at least selected embodiments, the present invention is related to novel or improved battery separators that prevent dendrite growth, prevent internal shorts due to dendrite growth, or both, batteries incorporating such separators, systems incorporating such batteries, and/or related methods of manufacture, use and/or optimization thereof. In accordance with at least certain embodiments, the present invention is related to novel or improved ultra thin or super thin membranes or battery separators, and/or lithium primary batteries, cells or packs incorporating such separators, and/or systems incorporating such batteries, cells or packs. In accordance with at least particular certain embodiments, the present invention is related to shutdown membranes or battery separators, and/or lithium primary batteries, cells or packs incorporating such separators, and/or systems incorporating such batteries, cells or packs.
1. A method of making a battery separator comprising the steps of:
extruding a parison having one or more polymer layers;
collapsing the parison onto itself to form a multi-ply flat sheet comprising two plies;
trimming or slitting the edges of the multi-ply flat sheet;
annealing the multi-ply flat sheet;
stretching the multi-ply flat sheet; and
forming the battery separator from the multi-ply flat sheet, the battery separator having a thickness in the range of about 2 μm to about 12 μm, a shutdown layer thickness of less than 6 microns, and a puncture strength of at least 112 grams.
2. The method according to claim 1 wherein stretching the multi-ply flat sheet comprises stretching in at least two steps, one a cold stretch step, and the other, a hot stretch step.