Manipulating Oxygen Vacancies by K⁺ Doping and Controlling Mn²⁺ Deposition to Boost Energy Storage in β-MnO₂

Aqueous zinc-ion batteries (ZIBs) have gained wide attention for their low cost, high safety, and environmental friendliness in recent years. β-MnO₂, a potential cathode material for ZIBs, has been restricted by its small channels for efficient charge storage. Herein, β-MnO₂ nanorods with oxygen vacancies are fabricated by a K⁺-doping strategy to improve the performance of ZIBs. The assembled batteries exhibit a capacity of 468 mAh g^-1, a power density of 2605 W kg^-1, and an energy density of 179 Wh kg^-1, which outperforms most reported ZIBs. Such a performance is owing to the synergistic combination of the oxygen vacancies in β-MnO₂ and concurrent deposition of ε-MnO₂ from Mn²⁺ in the electrolyte. Furthermore, superior cycling stability with negligible capacity decay in these batteries is demonstrated over 1000 cycles at a high current of 2 A g^-1. This study reveals the importance of oxygen vacancies and Mn²⁺ deposition effect in understanding the mechanism of charge storage in MnO₂-based ZIBs.