J. M. Tarascon

So‐called "rocking‐chair" rechargeable batteries that use lithium intercalation compounds for the positive and negative electrodes should be safer than batteries that contain free‐lithium metal. Such a cell, using the spinel as the positive electrode and carbon as the negative electrode, 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 of their operating conditions. By systematically studying the stability of several electrolyte systems, we were able to minimize electrolyte 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.

We show that the spinel , can also be used as the cathode in rechargeable rocking‐chair batteries based on lithium intercalation anodes (carbon, either graphite or petroleum coke). At room temperature, such cells show promising cycle life, an average open‐circuit voltage of 3.7 V and a specific energy of 250 Wh/kg of electrode materials . In addition, we report a novel easily reproducible solution technique for synthesizing , at low temperatures (<100°C), using as a mild reducing agent. The cycling behavior of rocking‐chair cells using this lithiated phase as the starting cathode is presented. appears to be a promising practical "air stable" Li‐bearing cathode for rocking‐chair‐type rechargeable cells.