Lithium ion battery separators: Development and performance characterization of a composite membrane

The overall stability of the lithium ion battery separators, under potentially extreme battery operating conditions, will require leading edge design and fabrication techniques to exceed manufacturing and end performance requirements for large scale applications. This paper features the development and performance characterization of an inorganic fiber enhanced composite separator for LIBs. This composite separator can offer a thermally stable alternative for conventional porous polyolefin separators, which shrink significantly at high temperatures. The relative affinities between the electrolyte and the submicron inorganic fibers and the electrolyte and the polyvinylidene fluoride binder ensured a superior wettability of the final separator by the liquid electrolyte. The high porosity and the open porous structure of the composite separator resulted in a good effective ionic conductivity. Coin cells with this composite separator also exhibited stable cycle performance and improved rate capabilities, especially when discharged at rates greater than C/2.