Abstract:The influence of annealing temperature on the structure and electrochemical properties of La1.5Mg0.5Ni7.0 hydrogen storage electrode alloys was studied. XRD and SEM analyses show that the as-cast alloy consists of LaNi5 phase, LaMgNi4 phase, (La, Mg)Ni3 phase and Gd2Co7 type phase. After heat treatment, the alloys consist of Gd2Co7 type phase, Ce2Ni7 type phase and (La, Mg)Ni3 phase, and the (La, Mg)Ni3 phase content decreases and the Ce2Ni7 type phase content increases with increasing of annealing temperature. The unit cell volumes and a-axes of PuNi3 type phase increase with increasing of annealing temperature. The electrochemical studies show that the discharge capacity and cyclic stability of the alloy electrodes have been improved markedly after annealing treatment. The discharge capacity of the alloy annealed at 1073 K is the highest (391.2 mAh/g) and then decreases with increasing of annealing temperature. However, with the increase of annealing temperature, the cyclic stability of the alloy electrode increases and the cycle life of the alloy annealed at 1173 K is the longest (C150/Cmax=82%). In addition, both the as-cast and the annealed alloy electrodes have quite good HRD. The high rate dischargeability (HRD) of the alloy electrodes increases with increasing of annealing temperature and the alloy annealed at 1173 K is the best. The exchange current density (I0), the limit current density (IL) and the hydrogen diffusion coefficient (D) of the alloy electrodes are consistent with the variation of the high rate dischargeability (HRD).