Long Cycle Life Secondary Lithium Cells Utilizing Tetrahydrofuran.

Cycle lifes of secondary Li cells utilizing THF/LiAsF6 solutions have been significantly improved by the use of small amounts of additives such as 2,methyl-furan, 2,methyl-thiophene or similar unsaturated organic compounds. A most important consequence of the discovery has turned out to be the practical utility of the mixed electrolyte, 50 v/o THF:50 v/o 2Me-THF/LiAsF6(1.5M). This solution combined with approx. 3.5 v/o 2Me-furan has enabled 5 A-hr Li/TiS2 cells to exhibit more than 200 cycles at 60% depth-of-discharge. This cycle life is twice that achieved with 2Me-THF/LiAsF6(1.5M). In addition, the mixed electrolyte cells have shown low temperature discharge capabilities superior to those containing either THF/LiAsF6(1.5M) or 2Me-THF/LiAsF6(1.5M).