The effect of substitution Al for Ni on the electrochemical properties of La0.7Mg0.3Ni2.75−xAlxCo0.75 hydrogen storage alloys

La0.7Mg0.3Ni2.75−xAlxCo0.75 (x = 0.0–0.4) hydrogen storage alloys were prepared and the effects of partial substitution Al for Ni on the structure, electrochemical properties of the alloys were investigated systematically. In the alloys, Mg2Ni phase appears in all alloys and La (Ni, Co, Al)5 phase with the hexagonal CaCu5-type structure replaces La(Ni,Co)5 phase with Al substituting for Ni. The plateau pressure declines gradually and the hysteresis between the hydrogen absorption and desorption decreases with the amount of substitution Al for Ni increasing. The substitution Al for Ni can improve thermal stability for La0.7Mg0.3Ni2.75−xAlxCo0.75 (x = 0.0–0.4) alloy hydrides, slow down the capacity degradation and prolong cycle life for La0.7Mg0.3Ni2.75−xAlxCo0.75 (x = 0.0–0.4) alloy electrodes.