Preparation and hydrogen storage properties of single-phase Ce2Ni7-type La–Sm–Y–Ni based hydrogen storage alloy

Abstract

LaSm0.4Y1.6Ni10.5Mn0.4Al0.2 hydrogen storage alloy with a Ce2Ni7-type single-phase has been prepared and its electrochemical properties and hydrogen storage properties are systematically investigated. The crystal structure of the alloy transformed completely into the Ce2Ni7-type single-phase via annealing at 1323 K for 16 h. The Ce2Ni7-type single-phase alloy has promising electrochemical properties, including 0.2Cmax = 385.8 mAh/g, 1Cmax = 356.8 mAh/g, and S100 = 86.72%. The HRD of the Ce2Ni7-type single-phase alloy is primarily determined by the charge transfer rate, which is HRD1500 = 75.75% and the corresponding electrochemical capacity at 1500 mA/g is 272.7 mAh/g. The PCT curves of the alloy present double pressure platforms owing to the hydrogen atoms occupying the [A2B4] subunit preferentially and entering the [AB5] subunit subsequently. Similarly, because the lattice expansion rates of the [A2B4] and [AB5] subunits vary discordantly throughout hydrogen absorption/desorption, the hydrogen storage capacity of the alloy experiences irreversible losses.