Boosting Electrolytic MnO-Zn Batteries by a Bromine Mediator.

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