Structural,hydrogen storage,and electrochemical performance of LaMgNi4 alloy and theoretical investigation of its hydrides

Structural, hydrogen storage, and electrochemical properties of LaMgNi₄ alloy were investigated in this study to determine whether it can be used as an active material of the negative electrode in nickel–metal hydride (Ni/MH) batteries. X-ray diffraction study showed that amorphization occurs at the first dehydrogenation cycle and was recovered crystallization after 873 K annealing.Maximum hydrogen storage capacity reached 1.4 wt% in the first hydrogenation under 373 K. The reannealed alloy showed improved reversible hydrogen storage capacity at ～0.9 wt% due to more LaNi₅ phase composition. Electrodes prepared from the investigated alloy showed maximum discharge capacities of ～340 mAh/g at 10 mA/g. The LaMgNi₄ alloy electrode exhibited satisfactory cycling stability remaining 47% of its initial capacity after 250 cycles. The negative cohesive energy indicated the exothermic process and stable compound structures of the LaMgNi₄ alloy and its hydrides via Density functional theory calculations.