Manganese oxides as positive electrode materials for rechargeable aluminum batteries

Three composites of carbon and amorphous MnO2, crystalline α-MnO2, or Mn2O3 were synthesized and investigated as the positive electrode materials for rechargeable Al batteries. For amorphous MnO2 and crystalline Mn2O3, the maximum discharge capacity was about 300 mAh g-1, which is the highest capacity among nonaqueous rechargeable Al batteries using manganese oxide positive electrodes. The amorphous MnO2 electrode showed a discharge capacity of more than 150 mAh g-1 even after 10 charge-discharge cycles. Crystal structure analysis and electronic state analysis suggested that crystalline Mn2O3 changed to amorphous MnO2 during the first charge process. These results suggest that the amorphous MnO2/carbon composite can be an excellent positive electrode material for rechargeable Al batteries.