Structural and electrochemical studies of α-manganese dioxide (α-MnO2)

The structural and electrochemical properties of α-MnO2, prepared by acid digestion of Mn2O3, and its lithiated derivatives xLi2O · MnO2 (0 ≤ x ≤ 0.25) have been investigated as insertion compounds in the search for new and viable cathode materials for rechargeable 3 V batteries. The α-MnO2 product fabricated by this technique contains water within the large (2 × 2) channels of the structure; the water can be removed from the α-MnO2 framework without degradation of the structure, and then at least partially replaced by Li2O (lithium oxide). The Li2O-doped α-MnO2 electrodes, described generically as xLi2O · MnO2, stabilize the structure and provide higher capacities on cycling than the parent material. The structures of these α-MnO2-type electrode materials are described, and electrochemical data are presented for both liquid electrolyte and polymer electrolyte Li/α-MnO2 and Li/xLi2O · MnO2 cells.