STABILIZED ALPHA-MNO2 ELECTRODES FOR RECHARGEABLE 3 V LITHIUM BATTERIES

Manganese dioxide electrodes that have x-ray diffraction patterns char acteristic of alpha-MnO2 (hollandite-type structure) and ramsdellite-M nO2 have been evaluated in rechargeable 3 V lithium cells. Electrochem ical data indicate that these electrodes (162 mAh/g, 10th cycle) provi de superior performance to both single-phase pure alpha-MnO2 (136 mAh/ g, 10th cycle) and ramsdellite-MnO2 electrodes (113 mAh/g, 10th cycle) , and comparable performance to lithia-stabilized alpha-MnO2 (0.15Li(2 )O . MnO2) electrodes (153 mAh/g, 10th cycle). Transmission electron m icroscopy images and convergent-beam electron diffraction patterns sho w that the MnO2 samples consist of grains of alpha-MnO2 grains of rams dellite-MnO2, and grains of ''interconnected'' alpha-MnO2 and ramsdell ite-MnO2 which exhibit a mutual crystallographic orientation. A search is underway to find other interconnected MnO2 materials with even bet ter cycling performance.