Abstract: An activated electrode for a non-aqueous electrochemical cell is disclosed with a precursor thereof a lithium metal oxide with the formula xLi2MnO3.(1?x)LiMn2?yMyO4 for 0.5<x<1.0 such that the spinel component constitutes less than 50 mole % of the precursor electrode and 0?y<1 in which the Li2MnO3 and LiMn2-yMyO4 components have layered and spinel-type structures, respectively, and in which M is one or more metal cations. The electrode is activated by removing lithia, or lithium and lithia, from the precursor. A cell and battery are also disclosed incorporating the disclosed positive electrode.