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. Lao.80-xYxMg0.20Ni2.85Mn0.10Coo.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）2Ni7 phases, the introduction of Y promoted the formation of （La,Mg）2Ni7 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 （HRDl800） in- creased from 23.6% to 39.7% at room temperature. In addition, the measured HRD1800 showed a linear dependence on both the ex- change current density and the hydrogen diffusion coefficient at different temperatures, respectively.
