Oxygen Defects in β-MnO2 Enabling High-Performance Rechargeable Aqueous Zinc/Manganese Dioxide Battery

SUMMARY Rechargeable aqueous Zn/manganese dioxide (Zn/MnO2) batteries are attractive energy storage technology owing to their merits of low-cost, high-safety and environmental-friendliness. However, the β-MnO2 cathode is still plagued by the sluggish ion insertion kinetics due to the relatively narrow tunnelled pathway. Furthermore, the energy storage mechanism is under debate as well. Here, β-MnO2 cathode with enhanced ion insertion kinetics is introduced by the efficient oxygen defect engineering strategy. Density functional theory (DFT) computations show that the β-MnO2 host structure is more likely for H+ insertion rather than Zn2+, and the introduction of oxygen defects will facilitate the insertion of H+ into β-MnO2. This theoretical conjecture is confirmed by the capacity of 302 mA h g-1 and capacity retention of 94% after 300 cycles in the assembled aqueous Zn/β-MnO2 cell. These results highlight the potentials of defect engineering as a strategy of improving the electrochemical performance of β-MnO2 in aqueous rechargeable batteries.