Comparison of electrochemical and hydrogen storage performance of Mg-rich alloys as negative electrode materials in Ni-MH batteries

In this study, we aim to develop magnesium containing multicomponent anode materials to potentially replace rare earth elements in Nickel Metal Hydride (NiMH) batteries. Specifically, we investigate Mg0.5Al12.5Ni12.5-Fe12.5Cr12.5 high entropy alloys (HEAs) for application as NiMH anodes. These alloys were produced using Vacuum Arc Melting under an argon atmosphere and subjected to detailed phase, microstructural, and electrochemical characterizations. X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed the formation of predominantly body-centered cubic (BCC) phases, along with minor hexagonal close-packed (HCP) phases. Electrochemical performance, assessed through charge-discharge cycling, yielded a maximum discharge capacity of 269 mAh/g +/- 0.33 with a capacity retention rate of 51.85 % after 50 cycles. Electrochemical impedance spectroscopy (EIS) and hydrogen storage testing revealed rapid hydrogenation/dehydrogenation kinetics, with a maximum hydrogen absorption capacity of 2.04 wt% at 300 degrees C. These results highlight the potential of Mg0.5Al12.5Ni12.5Fe12.5Cr12.5 HEAs for applications in hydrogen storage and electrochemical energy storage systems.