Effect of La/Mg on the structure and electrochemical performance of La–Mg–Ni system hydrogen storage electrode alloy

In order to improve the electrochemical performances of La–Mg–Ni system (A2B7-type) alloy electrodes, the effects of La/Mg ratio on structures and electrochemical performances of the alloys were investigated in detail. From the XRD analyses, each alloy is composed of the LaNi5, (La, Mg)2Ni7 and a few LaNi2 phases. However, when La/Mg ratio is more than 3, the LaMg phase appears, and the amount of the LaMg phase increases with the increase of La/Mg ratio. With increasing of La/Mg ratio, the discharge capacities of the alloys decrease, the HRD900 of the alloy electrodes decrease from 77.96% (La/Mg = 3) to 61.01% (La/Mg = 17/3) at the discharge rate of 900 mA g−1, charge-transfer resistance and polarization resistance of the alloy electrodes increase, the limiting current densities IL of the alloy electrodes decrease. The cycling stabilities of the alloys enhance from 55.83% (La/Mg = 3) to 67.36% (La/Mg = 17/3) with the increase of La/Mg ratio after 100 charge/discharge cycles.