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.An inherently low cost manufacturing process of coating the composite separator on a reuseable release substrate followed by delamination is shown on full scale production equipment to make the free-standing composite separator at high quality.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, so that the composite separator exceeds the tensile strength requirements while providing a high porosity and electrolyte conductivity over the battery lifetime.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 and 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.