Unlocking MnO₂ electrolysis kinetics via dynamic chromium doping for efficient and stable zinc-manganese flow...

Zinc‑manganese redox flow batteries are attractive for energy storage due to their high energy density and low cost. However, the formation of poor conductivity and inactive MnO₂ limits its reversibility at high areal capacity, leading to sluggish reaction kinetics and poor stability. In this study, the introduction of Cr³⁺ into the electrolyte for the dynamic doping process increases the oxygen vacancies in MnO₂, generates more active electronic states and promotes the charge transfer kinetics, further optimizing the deposition and dissolution of MnO₂. Therefore, the designed zinc‑manganese redox flow battery exhibits a discharge voltage of 1.98 V at 20 mA cm^-2, along with a cycle life over 1800 cycles. Furthermore, the battery demonstrates a high areal capacity of 60 mAh cm^-2, corresponding to an areal energy density of 105 mWh cm^-2. This work effectively alleviates the issue of sluggish MnO₂ electrolysis reaction kinetics, highlighting its potential in grid-scale energy storage applications.