Modulation of the Discharge and Corrosion Properties of Aqueous Mg-Air Batteries by Alloying from First-Principles Theory

Mg-air batteries have been rapidly developed with the proposal of several corrosion inhibition strategies for magnesium anodes. However, researchers have been puzzled by the limited improvement in discharge voltage caused by alloying and the theoretical mechanism of alloying on corrosion. Here, a detailed thermodynamic study was carried out combined with the stepwise hydroxide-assisted mechanism for metal dissolution in alkaline media and the Mg7B (B is the alloying elements) alloy model using first-principles theory. The effects of alloying on the discharge voltage and corrosion of magnesium anodes were simulated for alloying elements intensively investigated. The results indicate that within the range of electrochemical polarization, the discharging of Mg-air batteries at high current densities has a large overpotential while the impact of alloying on the voltage of Mg-air batteries is less than 0.15 V at high current densities. Consequently, without considering other polarization reductions, alloying cannot profoundly change the discharge voltage of Mg-air batteries; contrarily, an increase in corrosion resistance will result in a decrease in voltage for elements with an electrode potential higher than magnesium.