High Energy Density Rechargeable Battery. Phase 2. (Lithium-Metal Sulfide Development

This investigation of high energy density rechargeable batteries attempts to advance the development of high temperature electrochemical systems and assess their suitability for military satellite missions in geosynchronous and mid-altitude orbits. A 5-plate, monopolar, lithium alloy, iron monosulfide cell used in EVs was first considered. These cells performed far below the goal of 100 Whkg and were therefore modified to a 7-plate, 100 Ah, Lithium-Aluminum- Silicon alloy negative electrode, iron monosulfide positive electrode, magnesium powder separator, and ternary lithium halide electrolyte. After optimization of level I cells, two approaches were employed for subsequent cell designs. One was a stable iron disulfide positive electrode developed for incorporation into a monopolar cell. The other was the development of a bipolar-cell design. Results of a Lithium Iron Sulfide test showed a 100 Whkg, one-hour discharge cell is not possible. However, cycle life was increased to 1500, and performance did not degrade after the freeze-thaw routine. The Li-AL-Si alloy negative electrode is less prone to capacity loss with cycling when operated at high current densities than a Li-AL electrode. Above 350 C the iron disulfide electrode showed rapid upper-plateau capacity decline rate. Overall performance achieved was inadequate for a main power source in geosynchronous and mid-altitude orbiting military satellites.