Corrosion and discharge behavior of Mg-Zn-Mn-Nd alloys as primary Mg-air batteries anode

The optical microscopy, X-ray diffraction, scanning electron microscopy equipped with energy dispersive spectrometry, electrochemical tests and galvanostatic discharge tests were employed to characterize the microstructure, corrosion resistance and discharge performance of the as-extruded and solution-aged Mg-6Zn-Mn-xNd (ZM61, x=0, 0.2, 0.6, 0.8, 1.0, wt.%) alloys. The results indicate that the micro-alloying with Nd can promote the grain refinement of ZM61 alloys, and the as-extruded and solution-aged ZM61-0.6Nd alloys have the best corrosion resistance and discharge performance. However, the heat treatment deteriorates the comprehensive performance of as-extruded alloys. Among all the investigated alloys, the corrosion current density of the as-extruded ZM61-0.6Nd alloy is 1.611x10-5 A/cm2, and the discharge potentials are -1.517 and -1.336 V vs SCE at current density of 1 and 10 mA/cm2, respectively, during long-time discharge up to 24 h with the anode efficiency of above 36%, which shows the best comprehensive performance. The good discharge performance can be attributed to the improvement of corrosion resistance and cracking effect of the discharge products.

Automated summary

In this study, the microstructure, corrosion resistance, and discharge performance of Mg-6Zn-Mn-xNd (ZM61, x=0, 0.2, 0.6, 0.8, 1.0, wt.%) alloys in as-extruded and solution-aged states were characterized using various techniques. The addition of Nd was found to promote grain refinement in ZM61 alloys, and the ZM61-0.6Nd alloys in both states showed the best corrosion resistance and discharge performance. However, heat treatment had a detrimental effect on the overall performance of as-extruded alloys. Among all the tested alloys, the as-extruded ZM61-0.6Nd alloy exhibited the lowest corrosion current density, discharge potentials of -1.517 and -1.336 V vs SCE at current densities of 1 and 10 mA/cm2, respectively, and an anode efficiency of above 36% after 24 hours of discharge, indicating the best comprehensive performance. The good discharge performance can be attributed to the improved corrosion resistance and cracking effect of the discharge products.