Layered Li(Co0.33Mn0.33Ni0.33)O2 and composite 0.3Li2MnO3·0.7LiMn0.5Ni0.5O2 electrode powders have been treated with NH3 and HNO3 prior to cell assembly. These pre-conditioning reactions improve the electrochemical properties of the electrodes when charged to high electrochemical potentials (≥4.45V versus Li0) in lithium cells. NH3-treatment of Li(Co0.33Mn0.33Ni0.33)O2 increases electrode capacity and improves the coulombic efficiency of the electrochemical reaction after the first charge/discharge cycle, whereas acid-treatment of 0.3Li2MnO3·0.7LiMn0.5Ni0.5O2 electrodes significantly improves the coulombic efficiency of the initial charge/discharge reaction.