This Phase-II research examines sodium-sulfur battery, a leading candiadate for application in electric vehicles. A critical component in sodium-sulfur battery is the electrolyte, Na-B-alumina. In the state-of-the-art sodium-sulfur batteries, electrolyte thickness is approximately 1.5 mm which contributes nearly 40% to cell specific resistance. Two approaches are proposed to favricate thin (20 to 100 um) Na-B-alumina membranes which can reduce electrolyte resistance by a factor of - 30. This should substantially increase power density and energy efficiency. The two techniques proposed are: 1.) electrochemical vapor deposition (EVD), and 2.) fabricate thin membranes of Na-B-alumina by direct conversion of a-aluminia ; 3.) measure conduction properties of thin membranes; 4.) explore the current carrying capacity of Na-B-alumina membranes in electrochemical tests by sodium-sodium tests; 5.)explore the mechanism and the kinetics of the EVD and direct conversion processes, and 6.) supply thin electrolytes to a battery developer for evaluation in sodium-sulfur cells.
