Doubling the power output of a Mg-air battery with an acid-salt dual-electrolyte configuration

In this work, a dual-electrolyte acid-salt configuration is demonstrated to significantly improve the voltage and power performances of a Mg-air battery. Using an acidic catholyte and a saline anolyte, the battery benefits from a broadened electrochemical window and reduced passivation, delivering double the peak power density and 46% higher open circuit voltage compared to a conventional single-electrolyte Mg-air battery. To optimize the acid-salt Mg-air battery, the species and concentrations of the salt and acid electrolytes are investigated, while the effect of electrode distance is explored. To understand the practical use of different ion exchange membranes in the dual-electrolyte configuration, we compare the performances of the cation, anion, and bipolar membranes, discussing their merits and limitations. The resulting acid-salt battery exhibits one of the highest performances of Mg-air batteries reported to date, displaying an energy density of 2043 mWh g^-1 at 20 mA cm^-2, and a discharge capacity of 1851 mAh g^-1 with a Coulombic efficiency of 84% at 50 mA cm^-2. This work brings the Mg-air battery closer to its theoretical capability and draws attention to the promising potential of dual-electrolyte systems.