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 Mg 0.5 Al 12.5 Ni 12.5 Fe 12.5 Cr 12.5 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 °C. These results highlight the potential of Mg 0.5 Al 12.5 Ni 12.5 Fe 12.5 Cr 12.5 HEAs for applications in hydrogen storage and electrochemical energy storage systems. • Lamination method reduced Mg loss to ∼7 %, ensuring uniform alloy. • Alloy contains 90.6 % BCC phase with 5–20 nm nanostructure. • Max H 2 absorption: 2.04 wt% at 300 °C with fast kinetics. • Discharge capacity: 269 .→ 140 mAh/g after 50 cycles. • Rare-earth-free alloy is promising for Ni-MH anodes.