Comparison of Vanadium- and Niobium-Containing MgAlCrNi-Based Alloys for Ni-MH Batteries

This study presents a comparative analysis of two magnesium-based high-entropy alloys (HEAs), MgAlCrNiV and MgAlCrNiNb, synthesized via vacuum arc melting for potential use as negative electrode materials in Ni-MH batteries. Structural characterization using X-ray diffraction (XRD) and scanning electron microscopy (SEM) revealed that MgAlCrNiV exhibits a dual-phase (BCC + HCP) structure, whereas MgAlCrNiNb forms FCC + HCP structure. Electrochemical evaluation, including charge-discharge cycling and cyclic voltammetry, showed that MgAlCrNiNb delivered higher discharge capacity and comparatively better cycling stability, attributed to its homogeneous microstructure and the stabilizing effect of niobium. Although both alloys demonstrated moderate capacities, their performance was in line with previously reported Mg-based systems. This study highlights the influence of elemental selection on phase formation and electrochemical behavior, offering insights into the rational design of HEAs for hydrogen storage applications in rechargeable batteries.