RECHARGEABLE lithium batteries can store more than twice as much energy per unit weight and volume as other rechargeable batteries(1,2). They contain Lithium ions in an electrolyte, which shuttle back and forth between, and are intercalated by, the electrode materials. The first commercially successful rechargeable lithium battery(3), introduced by the Sony Corporation in 1990, consists of a carbon-based negative electrode, layered LiCoO2 as the positive electrode, and a non-aqueous liquid electrolyte. The high cost and toxicity of cobalt compounds, however, has prompted a search for alternative materials that intercalate lithium ions. One such is LiMn2O4, which has been much studied as a positive electrode material(4-7); the cost of manganese is less than 1% of that of cobalt, and it is less toxic. Here we report the synthesis and electrochemical performance of a new material, layered LiMnO2, which is structurally analogous to LiCoO2. The charge capacity of LiMnO2 (similar to 270 mA hg(1)) compares well with that of both LiCoO2 and LiMn2O4 and preliminary results indicate good stability over repeated charge-discharge cycles.