Hydrogen storage and electrochemical properties of mechanically alloyed La1.5-xGdxMg0.5Ni7 (0 ≤ x ≤ 1.5)

Abstract

RE-Mg-Ni-based alloys with their unique superlattice structures have been considered to be possible candidates for hydrogen storage containers as well as electrodes in Ni-MHx batteries. In this study, mechanical alloying with subsequent annealing in the argon atmosphere at 1123 K for 0.5 h, was applied to produce the La1.5-xGdxMg0.5Ni7 (0 ≤ x ≤ 1.5) alloys. Hydrogen storage and electrochemical properties of the synthesized material have been investigated. For example, at the 50th cycle the La1.5Mg0.5Ni7 material shows a much lower reversible electrochemical capacity than La1.25Gd0.25Mg0.5Ni7 alloy. Additionally, the partial substitution of La by Gd improves the kinetics of hydrogen absorption. On the other hand, the stability of the electrochemical discharge capacity increases with the increasing value Gd up to x = 1.0. However, a significant reduction in the discharge capacity was observed for the Gd content above x = 0.25. From the application point of view, only La1.25Gd0.25Mg0.5Ni7 alloy show great potential in the future application as electrode material in Ni-MHx batteries.