Microstructural, hydrogenation and electrochemical properties of La2Mg1-xYxNi10Mn0.5 (x= 0.1, 0.38) alloys for Ni-MH battery anode

Metal hydride alloys are promising materials for hydrogen storage and Ni-MH battery applications, yet challenges remain in optimizing their composition and performance. In this study, hydrogen absorbent alloys La₂Mg_1-xY_xNi₁₀Mn_0.5 (x = 0.1, 0.38) were produced by vacuum electric arc remelting. Crystal structure investigations revealed the presence of the LaNi₅ phase in both alloys and the formation of the (La, Mg)₂ Ni₇ phase in La₂Mg_0·62Y_0·38Ni₁₀Mn_0.5 alloy. The alloy with x = 0.38 demonstrated superior properties, including increased hydrogen absorption capacity (1.925 wt% vs 1.667 wt%) and improved hydrogenation kinetics which were related to the A₂B₇ superstructure phase. Electrochemical tests conducted at temperatures of 273, 283, 298, 313, and 338 K showed that an increasing temperature improved electrode surface activation. At room temperature, the retention rates of the discharge capacity after 50 charge and discharge cycles for the alloy electrodes (x = 0.1, 0.38) were 93.32 % and 96.56 % respectively, with maximum discharge capacities of 378.01 and 400.77 mAh/g. The high rate dischargeability (HRD) was evaluated, at different temperatures, demonstrating that the presence of a multiphase structure in the alloy with x = 0.38 created interphase boundaries, which reduced distortion, and network strain. These interphase boundaries also provided tunnels for hydrogen diffusion, improving activation and electrochemical stability. These findings suggest that partial substitution of Y for Mg in La–Mg–Ni based alloys offers a promising approach for developing high-performance hydrogen storage materials.