A research group led by Prof. LI Xianfeng from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) has developed a Bromine-assisted-MnO2-based hybrid single flow battery, which exhibits advantages of high energy density and reversibility.
This study was published in Angewandte Chemie International Edition on Oct. 26.
Mn2+/Mn3+ redox pair has been considered as a promising cathode for high-energy-density batteries, due to its attractive features of high redox potential, solubility and outstanding kinetics. However, the disproportionation side reaction of Mn3+, which results in accumulation of "dead" MnO2, limits its reversibility and energy density.
In this study, the researchers provided a new concept to solve the issue of "dead" MnO2 by introducing Br-/Br2 into Mn2+/MnO2 catholyte in a highly acidic environment.
Br- was firstly oxidized to Br2 during charge, and then Mn2+ was oxidized to Mn3+, which could be partially disproportionated to form MnO2 simultaneously. During discharge, Mn3+ and part of MnO2 were reduced to Mn2+ firstly and Br2 was reduced to Br-. Then the produced Br- could react with "dead" MnO2 to Br2, participating in discharge, completing the reduction process, and avoiding the accumulation of "dead" MnO2.
Furthermore, the researchers assembled Bromine-Manganese flow battery (BMFB) coupling with Cd/Cd2+ as anode. The battery exhibited high energy density of 360 Wh L-1 and stable running for over 500 cycles at a current density of 80 mA cm-2.
"The battery assembled with silicotungstic acid as anode could continuously run for over 2000 cycles at 80 mA cm-2, which further confirmed the reliability and universality of the catholyte," said Prof. LI. "We believe the BMFB has great potential for large-scale energy storage."
