Synthesis, Characterization and Electrochemistry of Lithium Battery Electrodes: xLi2MnO3•(1-x)LiMn0.333Ni0.333Co0.333O2 (0 ≤ x ≤ 0.7)

Lithium- and manganese-rich layered electrode materials, represented by the general formula xLi(2)MnO(3)center dot(1-x)LiMO2 in which M is Mn, Ni, and Co, are of interest for both high-power and high-capacity lithium ion cells. In this paper, the synthesis, structural and electrochemical characterization of xLi(2)MnO(3)center dot(1-x)LiMn0.333Ni0.333Co0.333O2 electrodes over a wide compositional range (0 <= x <= 0.7) is explored. Changes that occur to the compositional, structural, and electrochemical properties of the electrodes as a function of x and the importance of using a relatively high manganese content and a high charging potential (> 4.4 V) to generate high capacity (> 200 mAh/g) electrodes are highlighted. Particular attention is given to the electrode composition 0.3Li(2)MnO(3)center dot 0.7LiMn(0.333)Ni(0.333)Co(0.333)O(2) (x = 0.3) which, if completely delithiated during charge, yields Mn0.533Ni0.233Co0.233O2, in which the manganese ions are tetravalent and, when fully discharges, LiMn0.533Ni0.233Co0.233O2 composite electrode structures with 0.1 M HNO3 chemically activates the Li2MnO3 component and essentially eliminates the first cycle capacity loss but damages electrochemical behavior, consistent with earlier reports for Li2MnO3 component are discussed. Electrochemical charge/discharge profiles and cyclic voltammogram data suggest that small spinel-like regions, generated in cycled manganese-rich electrodes, serve to stabilize the electrodes, particularly at low lithium loadings (high potentials). The study emphasizes that, for high values of x, a relatively small LiMO2 concentration stabilizes a layered Li2MnO3 electrode to reversible lithium insertion and extraction when charged to a high potential.