The influence of heat treatment on discharge and electrochemical properties of Mg-Gd-Zn magnesium anode with long period stacking ordered structure for Mg-air battery

This work investigates the influence of heat treatment on the discharge and electrochemical properties of Mg_95.28Gd_3.72Zn_1.00 alloy as an anode for the Mg-air battery. The heat treatment removes the (Mg, Zn)₃Gd eutectic phase and produces the long period stacking ordered (LPSO) structure. The T6 heat treated Mg_95.28Gd_3.72Zn_1.00 alloy shows good discharge performance, including the high and stable cell voltage, high discharge capacity and anodic efficiency, and good specific energy output. The T6 treated Mg_95.28Gd_3.72Zn_1.00 anode has (i) the best discharge capacity and anodic efficiency of 1329 mAh g⁻¹ and 59.9%, respectively, at 40 mA cm⁻², which is 21.4% and 23.3% higher than the as-cast anode, and (ii) the highest specific energy of 1504 mW h g⁻¹, which is 46.4% higher than the as-cast anode. These improved discharge properties are attributed to the LPSO structure, which provides moderate and even stimulation for the dissolution of the α-Mg and helps to exfoliate the discharge products. In contrast, the (Mg, Zn)₃Gd phase produces a passive film, leading to the voltage drop.