Discharge Performance of Mg-6 wt%Al Alloy Anodes Containing Ca and Zn for Magnesium-Air Batteries

In this study, the discharge performance of Mg-6 wt% Al alloy anodes with varying Ca and Zn contents was evaluated by electrochemical studies and surface analyses. The results indicated that the cell voltage and anode efficiencies changed according to the alloy compositions and discharge currents. The 6 wt%Al-1wt%Zn-1wt%Ca (AZX611) alloy was discovered to exhibit the highest cell voltage of 0.678 V and anode efficiency of 64% at the discharge current of 10 mA cm −2 . Although the calculated charge corresponding to the mass loss of AZX611 was equal to the sum of the calculated charge stemming from the captured H 2 and the discharge current, the other alloys yielded smaller values. The discharge products of these alloys were analyzed by X-ray diffraction to locate the peaks related to metallic Mg species. The electrochemical impedance spectroscopy analysis of the AZX611 alloy, conducted under the discharged state using a proposed equivalent circuit, revealed a close relationship between the resistance in the high frequency loop and the anode efficiency.