Influences of low-Ti substitution for La and Mg on the electrochemical and kinetic characteristics of AB(3)-type hydrogen storage alloy electrodes

The (La0.67Mg0.33)(1-x)TixNi2.75Co0.25 (x = 0, 0.05, 0.10, 0.15 and 0.20, at%) alloys were synthesized by arc melting and subsequent heat solid-liquid diffusing method. The structure, electrochemical properties and kinetic characteristics of the alloys were investigated systematically. The results showed that all the alloys mainly consisted of the (La, Mg)Ni-3, LaNi5 phases, and the lattice parameters and the cell volumes of the (La, Mg)Ni-3 and LaNi5 phases decreased with increasing Ti content. The alloy electrodes could be activated to reach their maximum discharge capacity within five cycles. The cycle life after 100 charge/discharge cycles (C-100/C-max) and the high-rate dischargeability at a discharge current density of 1200 mA/g first increased and then decreased. All the results showed that low-Ti content in AB(3)-type hydrogen storage alloys was beneficial to improvements of the overall electrochemical properties, and the optimum overall electrochemical performance of the alloy electrodes was obtained when x = 0.05.