Promoting the reversibility of electrolytic MnO2-Zn battery with high areal capacity by VOSO4 mediator

Electrolytic MnO2-Zn batteries possess high energy density due to the high reduction potential and capacity of the cathode Mn2+/MnO2. However, the low reversibility of the Mn2+/MnO2 conversion results in a limited lifespan. In this study, we propose the utilization of VOSO4 as a redox mediator in the MnO2-Zn battery to facilitate the dissolution of MnO2. Through various techniques such as electrochemical measurements, ex-situ UV-visible spectroscopy, X-ray diffraction, and scanning electron microscopes, we validate the interaction between VO2+ and MnO2, which effectively mitigates the accumulation of MnO2. The introduction of the redox mediator results in exceptional redox reversibility and outstanding cycling stability of the MnO2/VOSO4-Zn battery at high areal capacities, with 900 cycles at 5 mAh cm-2 and 500 cycles at 10 mAh cm-2. Notably, even in the flow battery device, the battery exhibits a stable cycling performance over 300 cycles at 20 mAh cm-2. These research findings shed light on the potential large-scale application of electrolytic MnO2-Zn batteries.