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

Mg-airbatteries have been rapidly developed with the proposalof several corrosion inhibition strategies for magnesium anodes. However,researchers have been puzzled by the limited improvement in dischargevoltage caused by alloying and the theoretical mechanism of alloyingon corrosion. Here, a detailed thermodynamic study was carried outcombined with the stepwise hydroxide-assisted mechanism for metaldissolution in alkaline media and the Mg7B (B is the alloyingelements) alloy model using first-principles theory. The effects ofalloying on the discharge voltage and corrosion of magnesium anodeswere simulated for alloying elements intensively investigated. Theresults indicate that within the range of electrochemical polarization,the discharging of Mg-air batteries at high current densities hasa large overpotential while the impact of alloying on the voltageof Mg-air batteries is less than 0.15 V at high current densities.Consequently, without considering other polarization reductions, alloyingcannot profoundly change the discharge voltage of Mg-air batteries;contrarily, an increase in corrosion resistance will result in a decreasein voltage for elements with an electrode potential higher than magnesium.