Cathode materials that have been synthesized by reduction of lithium-manganese-oxide and manganese-oxide precursors with hydrogen at 300 to 350-degrees-C, and with carbon at 600-degrees-C have been evaluated in rechargeable lithium cells. The cathodes which initially have a composition close to LiMnO2 contain structures related to the lithiated-spinel phase Li2[Mn2]O4 and/or orthorhombic LiMnO2. The orthorhombic LiMnO2 component transforms gradually to a spinel structure on cycling. These cathodes are significantly more tolerant to repeated lithium insertion and extraction, when cycled over both the 4 and 3 V regions, than a standard Lix[Mn2]O4 spinel electrode (0 < x < 2).