A micro-alloyed Mg-Zn-Ge alloy as promising anode for primary Mg-air batteries

Alloying is one of the effective approaches to boost the discharge property of magnesium (Mg) anodes for primary Mg-air batteries and recently micro-alloying is highly recommended at the aim of developing advanced primary Mg system. In this study, micro-alloyed extruded Mg0.5Zn0.2Ge (in wt.%) alloy is evaluated as an anode candidate for primary Mg-air batteries in both half-cell and Mg-air full cell configurations, in comparison with commercially accepted Mg anodes, typified by as-cast HP Mg and extruded AZ31 alloy. The corrosion behavior at open circuit potential (OCP) condition of the three materials is also compared through electrochemical tests. Mg0.5Zn0.2Ge alloy displays the most negative OCP value and the highest corrosion resistance at OCP. During discharge, Mg0.5Zn0.2Ge anode exhibits low wasteful-discharge rate and homogeneous dissolution that gives rise to the absence of “chunk effect”. Consequently, the anodic efficiency and specific capacity of Mg0.5Zn0.2Ge anode are superior to those of HP Mg and AZ31 anodes, e.g. 57.3% and 1257 mAh g⁻¹ at 1 mA cm⁻². Additionally, Mg-air battery based on Mg0.5Zn0.2Ge anode offers higher cell voltage and specific energy than those assembled with HP Mg and AZ31 anodes, which can be further optimized by addition of electrolyte additives. Therefore, micro-alloyed Mg0.5Zn0.2Ge alloy can serve as a promising candidate for anode material of primary Mg-air batteries.