A self-healing electrocatalyst for manganese-based flow battery

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 MnO 2 layer on the cathode of titanium-manganese flow batteries. Excitingly, the uniform MnO 2 layer can catalyze the electrochemical reaction of Mn 2+ to Mn 3+ , and then obviously enhance the charge capacity. Herein, the MnO 2 layer formation mechanism and catalysis effect of the MnO 2 layer have been analyzed in detail. More interestingly, the MnO 2 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 MnO 2 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.