Discharge and corrosion behavior of Mg-Al-Sn anodes: An in-depth study of the morphological impact of Mg2Sn phase

Mg-Al-Sn series alloys have emerged as the compelling candidates for the anodes in Mg-air battery systems, attributed to their excellent discharge and corrosion performance. However, the pivotal role of Mg₂Sn phase with various morphologies in these anodes has persisted underexplored. Herein, we meticulously engineer the Mg₂Sn morphology by adopting solution-aging treatment, and systematically examine its effect on the discharge and corrosion behavior of Mg-Al-Sn anodes. The research demonstrates that the large-sized Mg₂Sn phase and Sn-enriched dendrites in as-cast sample compromise corrosion resistance and hinder the detachment of oxidation products during discharge, thus adversely influencing anode performance. Conversely, the dissolution of Mg₂Sn and dendrites, induced by solution treatment, markedly suppresses self-corrosion and improves anodic efficiencies alongside battery capacities. Moreover, the finely dispersed Mg₂Sn phase, generated through aging, significantly accelerates the shedding of oxidation products during discharge, thereby enhancing the voltages of Mg-air battery. The detailed mechanism concerning the morphological impact of Mg₂Sn phase is further revealed from the perspectives of micro-galvanic effect and the analysis of corroded surfaces.