HIGH-TEMPERATURE LITHIUM SULFIDE BATTERIES

Bipolar Li-Al/FeS and Li-Al/FeS2 batteries are being developed for electric vehicle (EV) applications by Argonne National Laboratory. Current technology employs a two-phase Li alloy negative electrode, low melting point LiCl-rich LiCl-LiBr-KBr molten salt electrolyte, and either an FeS or an upper-plateau (UP) FeS2 positive electrode. These components are assembled in an ''electrolyte-starved'' bipolar cell configuration. Use of the two-phase Li alloy (alpha + beta Li-Al and Li5Al5Fe2) negative electrode provides in situ overcharge tolerance that renders the bipolar design viable. Employing LiCl rich LiCl-LiBr-KBr electrolyte in ''electrolyte-starved'' cells achieves low-burdened cells that possess low area-specific impedance; comparable to that of flooded cells using LiCl-LiBr-KBr eutectic electrolyte. The combination of dense U.P. FeS2 electrodes and low-melting electrolyte produces a stable and reversible couple, achieving over 1000 cycles in flooded cells, with high power capabilities. In addition, a family of stable chalcogenide ceramic/sealant materials was developed that produce high-strength bonds between a variety of metals and ceramics, which renders lithium/iron sulfide bipolar stacks practical. Bipolar Li-Al/FeS and Li-Al/FeS2 cells and four-cell stacks using these seals are being built and tested in the 13 cm diameter size for EV applications. To date, Li-Al/FeS cells have achieved 240 W kg-1 power at 80% depth of discharge (DOD) and 130 Wh kg-1 energy at the 25 W kg-1 rate. Li-Al/FeS2 cells have attained 400 W kg-1 power at 80% DOD and 180 Wh kg-1 energy at the 30 W kg-1 rate. When cell performance characteristics are used to model full-scale EV and hybrid vehicle (HV) batteries, they are projected to meet or exceed the performance requirements for a large variety of EV and HV applications.