Lithium Ion Battery Separator with High Temperature Stability

A separator involving composite materials is provided that meets the lithium ion battery requirements for separators with high temperature stability at 220C and above and with mechanical strength and flexibility. The heat stable properties are obtained from using aluminum oxide particles at over 75% by weight that prevent any shrinkage of the composite separator. The mechanical strength without any brittleness is obtained from using a strong and flexible polymer with excellent lithium ion battery compatibility. The resulting composite separator exceeds the tensile strength requirements while providing a high porosity and electrolyte conductivity that is suitable for the high battery cycling rates of lithium ion batteries for vehicles. An inherently low cost manufacturing process of coating the composite separator on a reuseable release substrate followed by delamination is used to make the free-standing composite separator at the desired thickness. This composite separator can be incorporated into lithium ion batteries using existing manufacturing processes as a direct"drop-in"replacement for the current plastic separators that shrink greatly starting at 120C. This heat-resistant composite separator is generic for use with various electrolyte and electrode materials for safer, lower cost, and higher performing lithium ion batteries for vehicles and other applications.