Preparation and electrochemical performance of (La, Mg)₂Ni₇ hydrogen storage alloy as a function of sintering time

The (La, Mg)₂Ni₇ hydrogen storage alloy was prepared by vacuum powder sintering with using LaNi₂.₃ and MgNi₁.₅₅ as intermediate alloys. This study shows the effects of sintering time at 800℃ on the phase structure and chemical properties of the (La, Mg) 2 Ni 7 hydrogen storage alloy. The results show that the alloy consisted of the La 1.5 Mg 0.5 Ni 7 -type, La 2 MgNi 9 -type, and LaNi 5 -type phases, and increasing sintering time promote the formation of the LaNi 5 -type phase. Research findings have indicated that appropriately extending the sintering time can increase the alloy's maximum electrochemical capacity (C max ), improves its cycle stability(S 100 ), and enhance its high-rate discharge ability (HRD). For example, the alloy sintered for 4 hours exhibited optimal performance, with C max = 360.23 mAh/g, S 100 = 72.39%, and HRD 900 = 91.35%. It is concluded that as sintering time increases, there is excessive volatilisation of magnesium, which leads to the decomposition of the La 1.5 Mg 0.5 Ni 7 phase, resulting in an increase in the LaNi 5 phase. Electrochemical analysis of the alloy revealed that the alloy's high-rate performance is depended on the combined influence of I₀ and D₀, and exhibited a trend of initial improvement followed by deterioration. • Phase evolution is governed by Mg volatilization during sintering • Optimal performance is achieved at a sintering time of 4 h • Maximum discharge capacity reaches 360.23 mAh g⁻¹ • High-rate performance is controlled by both I₀ and hydrogen diffusion • Sintering time effectively tunes phase structure and electrochemistry