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 (11-20)/(10-10) 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.