Oxygen Defects in β-MnO Enabling High-Performance Rechargeable Aqueous Zinc/Manganese Dioxide Battery.

Rechargeable aqueous Zn/manganese dioxide (Zn/MnO) batteries are attractive energy storage technology owing to their merits of low cost, high safety, and environmental friendliness. However, the β-MnO cathode is still plagued by the sluggish ion insertion kinetics due to the relatively narrow tunneled pathway. Furthermore, the energy storage mechanism is under debate as well. Here, β-MnO cathode with enhanced ion insertion kinetics is introduced by the efficient oxygen defect engineering strategy. Density functional theory computations show that the β-MnO host structure is more likely for H insertion rather than Zn, and the introduction of oxygen defects will facilitate the insertion of H into β-MnO. This theoretical conjecture is confirmed by the capacity of 302 mA h g and capacity retention of 94% after 300 cycles in the assembled aqueous Zn/β-MnO cell. These results highlight the potentials of defect engineering as a strategy of improving the electrochemical performance of β-MnO in aqueous rechargeable batteries.