DISCHARGE AND AC IMPEDANCE STUDIES OF LITHIUM, CALCIUM, AND MAGNESIUM ANODES IN BROMINE TRIFLUORIDE

The use of bromine trifluoride with lithium and other active metal anodes offers the possibility of new battery systems that have exceptionally high cell voltages and energy densities. Constant current discharge and ac impedance studies are reported for lithium, calcium, and magnesium anodes in bromine trifluoride. Lithium in BrF3 yields one of the highest cell potentials reported (5.1V) and shows good discharge behavior up to 20 mA/cm2. Higher current densities, however, lead to a rapid decline of the potential that is attributed to the rate-limiting transport of lithium ions across the passivating film. The addition of NaF to BrF3 lowers the discharge capacity of the lithium anode. Auger electron spectroscopy studies show that the initial oxide film present on lithium is converted to a passivating LiF film in BrF3. Calcium and magnesium were found to be very poor anodes in BrF3 and severe passivation occurs even at low current densities. The striking difference in behavior between the lithium anode and the calcium or magnesium anode in BrF3 is likely due to the extremely low mobility of the divalent cation in the passivating CaF2 or MgF2 film. © 1990, The Electrochemical Society, Inc. All rights reserved.