Electrochemical Hydrogen Storage Characteristics of the as-Cast and Annealed La0.8-xPrxMg0.2Ni3.35Al0.1Si0.05 (x=0∼0.4) Electrode Alloys

Abstract

Abstract The electrode alloys with the chemical compositions of La 0.8- x Pr x Mg 0.2 Ni 3.35 Al 0.1 Si 0.05 ( x =0, 0.1, 0.2, 0.3, 0.4) were prepared by casting and annealing. The effects of Pr substitution on the structure and electrochemical hydrogen storage characteristics of the alloys were investigated. The results indicate that the as-cast and the annealed alloys consist of Ce 2 Ni 7 -type hexagonal (La, Mg) 2 Ni 7 phase and CaCu 5 -type hexagonal LaNi 5 phase as well as a little residual phase LaNi 3 . The substitution of Pr for La observably affects the electrochemical hydrogen storage characteristics of the alloys. The discharge capacity and the high rate discharge ability (HRD) of the as-cast and the annealed alloys first increase and then decline with the growing of Pr content. The as-cast and the annealed ( x =0.3) alloys yield the largest discharge capacities of 363.1 and 389.7 mAh/g, respectively. The electrochemical cycle stability of the as-cast and the annealed alloys markedly grows with the rising of Pr content. The capacity retaining rate ( S 100 ) at 100th charging and discharging cycle is enhanced from 64.96% to 77.94% for the as-cast alloy, and from 72.82% to 91.81% for the as-annealed alloy by raising Pr content from 0 to 0.4.