Single-layer lithium ion battery separators exhibiting high low-shrinkage rates at high temperatures

A battery separator comprising fibers of length less than 2.54 cm (1 inch), such fibers comprising at least 5% of thermally stable fibers that have no melting point, glass transition temperature or thermal degradation below about 300° C., wherein said fibers are polymeric materials selected from the group consisting essentially of polyacrylonitriles, polyolefins, polyolefin copolymers, polyamides, polyvinyl alcohol, polyethylene terephthalate, polybutylene terephthalate, polysulfone, polyvinyl fluoride, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polymethyl pentene, polyphenylene sulfide, polyacetyl, polyurethane, aromatic polyamide, semi-aromatic polyamide, polypropylene terephthalate, polymethyl methacrylate, polystyrene, synthetic cellulosic polymers, polyaramids, and blends, mixtures and copolymers including said polymeric materials, wherein such battery separator exhibits no observable spectral reflectance of after application of a drop of an electrolyte on the surface thereof, wherein such battery separator has a mean flow pore size less than 2000 nm, wherein said separator allows for lithium ion transport with an electrolyte within a lithium ion battery, and wherein said separator exhibits an apparent density of at least 0.564 g/cm3.