A self-healing electrocatalyst for manganese-based flow battery

Abstract

Manganese-based flow battery has attracted wide attention due to its nontoxicity, low cost, and high theoretical capacity. However, the increasing polarization at the end of the charging process greatly limits the battery capacity. Here we found that the introduction of specific transition metal ions could induce the formation of uniform MnO2 layer on the cathode of titanium-manganese flow batteries. Excitingly, the uniform MnO2 layer can catalyze the electrochemical reaction of Mn2+ to Mn3+, and then obviously enhance the charge capacity. Herein, the MnO2 layer formation mechanism and catalysis effect of the MnO2 layer have been analyzed in detail. More interestingly, the MnO2 layer would be consumed at the end of the discharge process and regenerated again after the next charge process. Different from the conventional catalysts, the MnO2 layer could self-heal in every cycle, which could mitigate the fall-off and deactivation risk of the catalyst and prolong the cycle life of the battery. As a result, the TMFB achieves a volume capacity of 45 Ah L−1 and runs over 400 charge–discharge cycles (42 days). Besides, the design route of a self-healing catalyst was summarized in the work, which is expected to be applied widely in the electrochemical systems.