Boosting Electrolytic MnO2-Zn Batteries by a Bromine Mediator

An aqueous electrolytic MnO2-Zn battery with eye-catching Mn2+/MnO2 cathode chemistry has been attracting immense interest for next-generation energy storage devices due to its irreplaceable advantages. However, the limited MnO2 conductivity restricts its long service life at high areal capacities. Here, we report a high-performance electrolytic MnO2-Zn battery via a bromine redox mediator, to enhance its electrochemical performance. The MnO2/Br-2-Zn battery displays a high discharge voltage of 1.98 V with a capacity of similar to 5.8 mAh cm(-2). It also shows an excellent rate performance of 20 C with a long-term stability of over 600 cycles. Furthermore, the scaled-up MnO2/Br-2-Zn battery with a capacity of similar to 950 mAh exhibits a stable 100 cycles with a practical cell energy density of similar to 32.4 Wh kg(-1) and an attractively low energy cost of below 15 US$ kWh(-1). The design approach can be generalized to other electrodes and battery systems, thus opening up new possibilities for large-scale energy storage.