Stabilized Alpha‐ MnO2 Electrodes for Rechargeable 3 V Lithium Batteries

Manganese dioxide electrodes that have x-ray diffraction patterns characteristic of α-MnO2 (hollandite-type structure) and ramsdellite-MnO2 have been evaluated in rechargeable 3 V lithium cells. Electrochemical data indicate that these electrodes (162 mAh/g, 10th cycle) provide superior performance to both single-phase pure α-MnO2 (136 mAh/g, 10th cycle) and ramsdellite-MnO2 electrodes (113 mAh/g, 10th cycle), and comparable performance to lithia-stabilized α-MnO2 (0.15Li2O · MnO2) electrodes (153 mAh/g, 10th cycle). Transmission electron microscopy images and convergent-beam electron diffraction patterns show that the MnO2 samples consist of grains of α-MnO2 grains of ramsdellite-MnO2, and grains of "interconnected" α-MnO2 and ramsdellite-MnO2 which exhibit a mutual crystallographic orientation. A search is underway to find other interconnected MnO2 materials with even better cycling performance.