Influences of low-Ti substitution for la and Mg on the electrochemical and kinetic characteristics of AB₃-type hydrogen storage alloy electrodes

(La_0.67Mg_0.33)_1-x Ti _x Ni _2.75Co_0.25 (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)Ni₃, LaNi₅ phases, and the lattice parameters and the cell volumes of the (La, Mg)Ni₃ 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 AB₃-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.