Boosting Electrolytic MnO<sub>2</sub>-Zn Batteries by a Bromine Mediator.

Zheng, Xinhua; Wang, Yongchao; Xu, Yan; Ahmad, Touqeer; Yuan, Yuan; Sun, Jifei; Luo, Ruihao; Wang, Mingming et al. · Nano Lett · 2021

basic_science · Level V

Where this comes from

Abstract

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