A series of titanium-substituted manganese oxides, LixTiyMn1-yO2 (y = 0.11, 0,22, 0.33, 0.44, and 0.55) with the Na0.44MnO2, struclure were prepared from NaxTiyMn1-yO2 (x approximate to 0.44) precursors. The electrochemical characteristics of these compounds, which retain the unique double-tunnel structure during ion exchange, were examined in lithium/polymer electrolyte cells operating at 85 degreesC. All of the substituted cathode materials intercalated lithium reversibly, with LixTi0.22Mn0.78O2 exhibiting the highest capacity in polymer cells, about 10-20% greater than that of unsubstituted LixMnO2 made from Na0.44MnO2. In common with LixMnO2, the Ti-substituted materials exhibited good capacity retention over one hundred or more cycles, with some compositions exhibiting a fade rate of less than 0.03% per cycle. (C) 2004 Elsevier B.V. All rights reserved.