Corrosion behavior and discharge properties of Al-doped Mg–Sn alloys for high performance Mg-air batteries

Abstract

In this study, we report a novel, non-rare earth Mg alloy-based anode for Mg air battery applications. The Mg-xAl-1Sn (x = 0, 3, 6, 9) alloy series were synthesized and subjected to extruding. The microstructural analyses indicated that the as-extruded Mg–0Al–1Sn(AT01) alloy showed coarse dynamically recrystallized (DRXed) grains. The Al-doped alloys showed uniform DRXed grain distribution, and their grain size decreased with increasing Al content. Meanwhile, the solid solubility of Sn changed with the addition of Al; as a result, the amount of Sn dissolved in the matrix was reduced. This promoted the precipitation of the Mg2Sn phase, and the precipitate content increased significantly in the Al-doped alloys. Furthermore, different corrosion behaviors were observed in the Al-doped alloys. Numerous discontinuous Mg17Al12 phases and strong cathode Mg2Sn phases induced rapid galvanic corrosion with the Mg matrix, which caused the latter one to be rapidly dissolved. However, the refined grains and discontinuous precipitates that existed in as-extruded Al-doped alloys were beneficial to the initiation of cracks within the alloy surface, making the self-peeling of discharge products easier. The AT91 alloy-based anode exhibited good discharge stability during long-term cycling at all applied current densities.