Improved electrochemical kinetic performances of La-Mg-Ni-based hydrogen storage alloys with lanthanum partially substituted by yttrium

Yttrium (Y) has been used as the partial substitution element for lanthanum (La) to improve the electrochemical kinetic performances of La-Mg-Ni-based hydrogen storage alloys. La0.80-xYxMg0.20Ni2.85Mn0.10Co0.55Al0.10 (x=0.00, 0.05 and 0.10) alloys were prepared by the inductive melting technique. The alloys were composed of LaNi5 and (La,Mg)(2)Ni-7 phases, the introduction of Y promoted the formation of (La,Mg)(2)Ni-7 phase, and thus the Y-substituted alloy electrodes exhibited higher discharge capacities. Y substitution was also found to be effective to improve the discharge kinetics of the alloy electrodes. When the Y content x increased from 0.00 to 0.10, the high-rate dischargeability of the alloy electrodes at a discharge current density of 1800 mA/g (HRD1800) increased from 23.6% to 39.7% at room temperature. In addition, the measured HRD1800 showed a linear dependence on both the exchange current density and the hydrogen diffusion coefficient at different temperatures, respectively.