Effects of annealing treatment and partial substitution of Cu for Co on phase composition and hydrogen storage performance of La0.7Mg0.3Ni3.2Co0.35 alloy

In this paper, the phase composition, hydrogen absorption/desorption as well as electrochemical characteristics of as-cast and annealed La0.7Mg0.3Ni3.2Co0.35−XCuX alloys were investigated by X-ray diffraction (XRD), pressure composition isotherm (PCT) and electrochemical measurements. The results showed that La2Ni7 phase and LaNi phase coexisted in the as-cast alloys, but only La0.98Ni5.10 phase was detected in the annealed alloys. The maximum and reversible hydrogen storage capacities of the annealed alloys were higher than that of as-cast alloys, with greatly improved plateau performance. The substitution of Cu for Co made the electrochemical discharge capacity of the annealed alloys lower than that of as-cast alloys.