Influence of spark plasma sintering temperature on electrochemical performance of La0.80Mg0.20Ni3.75 alloy

Spark plasma sintering was employed to synthesize La0.80Mg0.20Ni3.75 alloy, using LaNi3, Mg and carbonyl Ni powders as starting materials. The effects of sintering temperature on crystal structure and electrochemical performance of the alloy were investigated in detail. The results by XRD show that the alloys have a multiphase structure, mainly including the (La, Mg)2Ni7, LaNi5 and Ni phases. The relative amount of the (La, Mg)2Ni7 and LaNi5 phases correlates to the sintering temperature. The cell volumes of the (La, Mg)2Ni7 and LaNi5 phases first increase and then decrease with increasing sintering temperature. This effect is more pronounced in (La, Mg)2Ni7 than LaNi5. Some electrochemical properties and kinetic parameters of the alloys, involving discharge capacity, medium voltage, high-rate dischargeability (HRD), the loss angle (ψ) and the limiting current density (IL), get enhanced with increasing sintering temperature. The capacity retention rates (S150) of the alloy electrodes first increase and then decrease with the rise of sintering temperature after 150 charging/discharging cycles. For balancing discharge capacity and cycle stability, the most suitable sintering temperature for synthesis of La0.80Mg0.20Ni3.75 by SPS is recommended to be 1173 K in the present work.