LITHIUM MANGANESE OXIDES FROM LI2MN03 FOR RECHARGEABLE LITHIUM BATTERY APPLICATIONS

Electrochemically active lithium-manganese-oxide phases have been synthesized by chemical leaching of Li2O from the rock salt phase Li2MnO3 (Li2O.MnO2) with acid at 25-degrees-C. Preliminary electrochemical tests have shown that capacities of approximately 200 mAh/g based on the mass of the lithium-manganese oxide electrode can be obtained in room-temperature lithium cells, and that capacities in excess of 140 mAh/g can be achieved on cycling. Although a detailed structure analysis of an extensively delithiated sample has not yet been undertaken, it is believed that it may be a novel layered lithium-manganese oxide compound Li(2-x)MnO3-x/2 (0 < x < 2) with a cubic-close-packed oxygen anion array in which some of the Li+ ions are ion-exchanged with H+ ions. Heat-treatment of an extensively delithiated Li2MnO3 sample at 300-degrees-C in air transforms the product to a gamma/beta-MnO2 type phase, whereas delithiated samples that still contain an appreciable amount of lithium transform on heating to a two-phase product of Li2MnO3 and a compound with a spinel-related structure.