Tailoring electrolyte additives for controlled Mg-Ca anode activity in aqueous Mg-air batteries

Abstract

Aqueous primary Mg-air batteries exhibit many merits as potential energy storage and conversion devices. In this work, the discharge performance of water based Mg-air batteries with advanced Mg-Ca anode was boosted by adding Mg2+ complexing agents into the electrolyte. The effect of electrolyte additives on the corrosion behavior and discharge properties of micro-alloyed Mg-Ca anode was investigated via hydrogen evolution test and half-cell discharge test. Electrochemical impedance spectroscopy (EIS) was performed to evaluate the effect of different electrolyte additives on the discharge activity of Mg-Ca anode. Basic characteristics of aqueous Mg-air battery in selected additive solution were tested and compared to pure NaCl solution. The results show that the addition of dedicated Mg2+ complexing agents can efficiently increase the discharge voltage and specific energy of respective Mg-air batteries. At 0.5 mA cm−2, the discharge voltage reaches 1.86 V with regard to the cell containing 0.1 M 5-Sulfosalicylate, which is 270 mV higher than the discharge voltage in bulk 3.5 wt % NaCl. The highest specific energy for the tested system is above 3.0 kWh kg−1 in NaCl solution with 0.1 M citrate at 1 mA cm−2 discharge current density.