Manganese-based flow battery based on the MnCl2 electrolyte for energy storage

Manganese-based flow batteries are attracting considerable attention due to their low cost and high safe. However, the usage of MnCl2 electrolytes with high solubility is limited by Mn3+ disproportionation and chlorine evolution reaction. Herein, the reversible Mn2+/MnO2 reaction without the generation of Mn3+ and Cl2 in the manganese-based flow batteries with the MnCl2 electrolyte is successfully achieved by adding amino acid additives. The effect and the function mechanism of a series of amino acid additives are discussed in detail via the experiment and theoretical calculation. Benefiting from the hydrogen bond between Cl- and amino acid, the chlorine evolution reaction is effectively avoided. In addition, the interaction of the Mn2+ and amino acid boosts the Mn2+/MnO2 reaction and inhibits the production of unstable Mn3+. As a result, the zinc-manganese flow battery with high-concentration MnCl2 electrolyte exhibits an outstanding performance of 82 % EE with a low capacity decay rate (1.45% per cycle over 1000 cycles) and wide temperature adaptability (from −10 ℃ to 65 ℃). This study opens a new opportunity for the application of flow batteries with high-concentration chloride electrolytes.