Improved cycling performance of bismuth-modified amorphous manganese oxides as cathodes for rechargeable lithium batteries

Bismuth-modified amorphous manganese oxides were synthesized via a room temperature aqueous route. They were galvanostatically tested as intercalation cathodes for rechargeable lithium batteries at 1 mA cm−2 between 1.5 and 4.3 V. In sharp contrast to severe capacity fading of unmodified amorphous manganese oxide synthesized by the same route, a stable cycling performance of the bismuth-modified amorphous manganese oxide was observed. After an initial drop from 185 to 145 mAh g−1 in around 10 cycles, the capacity of the bismuth-modified amorphous manganese oxide remains essentially unchanged for another 40 cycles. Based on results from X-ray diffraction and cyclic voltammetry (CV) characterization, it is suggested that an electrochemically active and stable local structure evolves inside the bismuth-modified amorphous manganese oxide upon initial cycling, leading to the stabilized cycling performance for subsequent cycles.