RECHARGEABLE COMPACT LI CELLS WITH LIXCR0.9V0.1S2 AND LI1+XV3O8 CATHODES AND ETHER-BASED ELECTROLYTES

The electrochemical parameters of compact disk cells with cathodes of Li1+x.V3O8, LiCr0.9V0.1S2, and electrolytes based on cyclic ethers, are studied. It is shown that the decrease of discharge time from 10 to 1.3h has but a small effect on cathode utilization, which drops from 80% to about 70% for both cathode materials. The polarization resistances of freshly deposited Li, from electrolytes of ethers, and their mixtures with ethylene carbonate, are identical. Continuous cycling tests with maximum cathode utilization in the electrolyte of composition 1.5M LiAsF6/2MeTHF/THF(1:1)/0.2% 2MeF demonstrate a cycling efficiency of 96-97% for Li. A lower efficiency of about 94% is obtained in ethylene carbonate containing electrolytes. It is suggested that an increase in the thickness of the passive film formed on the Li electrode is responsible for the capacity decay at the end of the cycling life. The rate of self-discharge at room temperature for a fully charged cell is about 5-8% per month. This self-discharge is attributed to the Li electrode, which is passivated during storage in the ether-based electrolytes. © 1990, The Electrochemical Society, Inc. All rights reserved.