' TECHNICAL PAPERS ELECTROCHEMICAL SCIENCE AND TECHNOLOGY

So-called "rocking-chair " rechargeable batteries that use lithium intercalation compounds for the positive and nega-tive electrodes should be safer than batteries that contain free-lithium etal. Such a cell, using the spinel LilVln204 as the positive electrode and carbon as the negative lectrode, was optimized as a function of various operating parameters. These cells reversibly insert 0.32 Li atoms per Mn at an average output voltage of 3.7 V, yielding an effective specific energy of 250 mWh/g of electrode materials (3 times that of Ni-Cd). They can sustain high current rates similar to Ni-Cd batteries, and can be discharged to 0 V without any degradation oftheir operating conditions. By systematically studying the stability ofseveral electrolyte systems, we were able to minimize lectrolyte decomposition (by controlling drastically the charge cut-off voltage) so that these cells show a promising cycle life even at 55°C while maintaining 75 % of their initial capacity. It is now recognized that ambient emperature non-aqueous econdary lithium cells using lithium metal ex-hibit problems which make it difficult for their wide usage in the consumer market. These problems are: the short cycle life for deeply discharged cells, the high cost of th