Vanadium Nitride-Induced Phase Evolution and Corrosion−Discharge Behavior of AZ61 Magnesium Anodes

Abstract

Self-corrosion and surface passivation limit the utilization and discharge voltage of Mg−air anodes. In this work, vanadium nitride (VN) particles were introduced into AZ61 to regulate its grain structure and phase distribution. Solution-treated cast AZ61−xVN alloys (x = 0, 0.25, 0.5, and 1 wt %) were prepared, and their microstructure, corrosion behavior, and discharge performance were investigated. AZ61−0.25VN exhibited the smallest average grain size of 73.5 ± 2.8 μm, the lowest corrosion current density of 24.32 μA cm−2, and the highest charge-transfer resistance of 824.75 Ω cm2. At 20 mA cm−2, it delivered an average discharge voltage of 1.143 V, a specific capacity of 1419.7 mAh g−1, and an anodic efficiency of 63.75%. XRD and local SEM/EDS support in situ AlN formation and identify residual VN near Al8Mn5 particles. XPS after 48 h immersion identifies Mg oxide/hydroxide-related products, with the highest fitted O 1s M−O contribution (81.6%) in AZ61−0.25VN. AlN-associated refinement and particle distribution may promote more distributed dissolution and limit localized Mg loss, while residual VN may facilitate discharge activation. Higher VN additions accompany greater particle heterogeneity, connected surface damage, and lower Mg utilization.