SECONDARY LI CELLS .1. A COMPARISON OF THE BEHAVIOR OF CATHODES BASED ON PURE AND LITHIATED MANGANESE OXIDES

In an attempt to better understand the rechargeability of some MnO2-based cathodes in Li cells, an investigation on some pure MnO2 (CMD and EMD) and Li-Mn-O phases has been carried out. It has been found that all forms of pure MnO2 investigated are inherently reversible, but with different kinetic limitations. Faradiser WS Li (CMD) shows an excellent cycling behaviour provided it is not heat-transformed into a beta-phase. Spinel-like compounds and Li-birnessite (a layered phase) do not perform as well as the best CMD's. The products of the reactions of CMD or EMD with LiNO3 or LiOH have been examined. As a function of the synthesis conditions, phases predominantly containing Li(x)MnO2 or phases with consistent amounts of spinels and Li2MnO3 can be obtained. A product formed from HNO3-treated CMD and LiNO3 (7 : 3 molar ratio) at 370-degrees-C shows an especially satisfactory cycling behaviour.