Low Temperature Alkali Metal-Sulfur Batteries. Final Report, December 1, 1974-November 30, 1978

摘要

Work on the development of rechargeable, ambient-temperature Li/sulfur and Li/metal sulfide batteries is reported. The Li/S system has the cathode material dissolved in the electrolyte, as Li sub 2 S/sub n/. Tetrahydrofuran, 1M LiAsF sub 6 , is one of the more attractive electrolytes discovered for this cell, since it can dissolve up to approx. 10M S as Li sub 2 Sn. Despite the oxidative nature of the electrolyte, Li is stable in it and can be electrodeposited from it on battery charge. Cells of the configuration Li 5M S (as Li sub 2 S/sub n/), THF, 1M LiAsF sub 6 /carbon can be discharged at 50 exp 0 C with a utilization of nearly 1.5e exp - /S at the C/3 rate. This corresponds to the rate-capacity goal for this battery in its proposed vehicular or load-leveling applications. Further improvements in rate are possible. Rechargeability of 135 cycles of 0.1 e exp - /S and approx. 45 cycles of 0.5 e exp - /S was demonstrated. The self-discharge reaction keeps the Li electrode free of electrically isolated dendrites. Ultimate failure on cycling is due to cathode depletion via precipitation of Li sub 2 S on the anode in a form insoluble in the electrolyte. Attempts to solubilize the Li sub 2 S by the internal generation of an oxidizing scavenger (e.g., Br sub 2 ) or by addition of Lewis acids have met only with limited success. Cells of configuration Li/THF, 1M LiAsF sub 6 /insoluble metal sulfide were investigated, using the following cathodes: CuS, NiS, SiS sub 2 , MnS sub 2 , FeS, and Bi sub 2 S sub 3 . Of these, the most promising new material in terms of energy density and rechargeability is CuS. Well over 100 cycles for Li/CuS cells with moderate cathode loadings were demonstrated. CuS compares favorably with TiS sub 2 in terms of energy density and rechargeability and is superior in terms of economics. 39 figures, 19 tables. (ERA citation 06:010979)