Highly crystalline ramsdellite as a cathode material for near-neutral aqueous MnO2/Zn batteries

Chemically-prepared MnO2 containing a highly crystalline ramsdellite phase was tested as a cathode material in aqueous Zn-salt (ZnSO4 and Zn(CF3SO3)2) based electrolytes for the first time. This aqueous MnO2/Zn cell has shown excellent performance and reversibility, retaining ≈65% of its initial capacity for more than 1000 cycles. The charge storage mechanism is complex and includes a ramsdellite/tetragonal spinel two-phase reaction.