Discharge properties of Mg-Sn-Y alloys as anodes for Mg-air batteries

Mg-Sn-Y alloys with different Sn contents (wt%) were assessed as anode candidates for Mg-air batteries. The relationship between microstructure (including the second phase, grain size, and texture) and discharge properties of the Mg-Sn-Y alloys was examined using microstructure observation, electrochemical measurements, and galvanostatic discharge tests. The Mg-0.7Sn-1.4Y alloy had a high steady discharge voltage of 1.5225 V and a high anodic efficiency of 46.6% at 2.5 mA·cm−2. These good properties were related to its microstructure: small grain size of 3.8 µm, uniform distribution of small second phase particles of 0.6 µm, and a high content (vol%) of (112¯0\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$11\bar 20$$\end{document})/(101¯0\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$10\bar 10$$\end{document}) orientated grains. The scanning Kelvin probe force microscopy (SKPFM) indicated that the Sn3Y5 and MgSnY phases were effective cathodes causing micro-galvanic corrosion which promoted the dissolution of Mg matrix during the discharge process.