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

摘要

The(La0.67Mg0.33)1-xTixNi2.75Co0.25(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)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(C100/Cmax) 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.