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The physical and electrochemical properties of LixMnO2 and LixTi0.11Mn0.89O2 synthesized from precursors made by glycine-nitrate combustion (GNC) and solid-state synthesis methods (SS) are examined in this paper. The highest specific capacities in lithium cells are obtained for SS-LixMnO2 electrodes at low current densities, but GNC-LixTi0.11Mn0.89O2 electrodes show the best high rate performance. These results can be explained by changes in the voltage characteristics and differences in the particle morphologies induced by the Ti-substitution and synthesis method. Ti-substitution also results in a decrease in the electronic conductivity, but greatly improves the thermal properties and imparts dissolution resistance to the electrode. For these reasons, it is preferable to use LixTi0.11MnO0.89O2 in lithium battery configurations rather than LixMnO2. Suggestions for improving the electrochemical performance of the Ti-substituted variant are given based on the results described herein.

Abstract: Computational and experimental work directed at exploring the electrochemical properties of tetrahedrally coordinated Mn in the +5 oxidation state is presented. Specific capacities of nearly 700mAhg−1 are predicted for the redox processes of Li x MnO4 complexes based on two two-phase reactions. One is topotactic extraction of Li from Li3MnO4 to form LiMnO4 and the second is topotactic insertion of Li into Li3MnO4 to form Li5MnO4. In the experiments, it is found that the redox behavior of Li3MnO4 is complicated by disproportionation of Mn5+ in solution to form Mn4+ and Mn7+ and by other irreversible processes; although an initial capacity of about 275mAhg−1 in lithium cells was achieved. Strategies based on structural considerations to improve the electrochemical properties of MnO4 n− complexes are given. [Copyright &y& Elsevier]