Composite Polymer-Ceramic Electrolyte for High-Energy Lithium Secondary Batteries

Abstract

The demand for high-energy batteries is driving development of high voltage lithium batteries, where the electrolyte must be electrochemically stable and resistant to formation of metallic Li dendrites. Replacing the current liquid electrolytes with a robust solid electrolyte that has high ionic conductivity and good mechanical stability is one path to improve the performance and safety. Polymer electrolyte formed with a dissolved Li ion salt are preferred for their low cost, mechanical flexibility and easy processability, however the low room-temperature conductivity restricts the use of most polymer electrolytes. Composite polymer electrolytes, consisting of a polymer electrolyte containing a dispersed inorganic powder, such as alumina, tend to have high conductivity because the filler impedes crystallization of the polymer.1 Another approach is to disperse powders of a highly conductive ceramic electrolyte, rather than insulating filler, such that both phases in the composite conduct the lithium ions. This permit a high ceramic loading such that the mechanical, transport, and chemical stability can be optimized.2 In the present study, we chose a traditional polymer electrolyte composed of polyethylene oxide (PEO) as the polymer host and Lithium triflate is the mobile ion conducting salt. The solid electrolyte powder from Ohara® Corporation LIC–GC® was selected for the ceramic component because of its inherent high ionic conductivity and stability against water and heat. With these materials, thin composite membranes were fabricated with reasonable conductivity and stability. A solid-state battery consisting of a thin film cathode, the composite electrolyte membrane and vapor deposited metallic Lithium was evaluated. The results to be presented include ionic conductivity of the membrane, stability against Lithium and preliminary cyclic voltammetry of the battery. Acknowledgement: This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U. S. Department of Energy under Contract No. DE-AC02-05CH11231, under the Advanced Battery Materials Research (BMR) Program.