Property Improvement of La-Mg-Ni Hydrogen Storage Alloy Electrodes by Doping Al

To improve the property of La-Mg-Ni hydrogen storage alloy electrodes,Al powders were doped into the alloy powders,and then La0.7Mg0.3Ni2.5-xCo0.5Alx(x=0-0.3) alloys were prepared by spark plasma sintering(SPS) technique.Microstructure and electrode performance of the alloys were investigated by means of XRD,SEM and electrochemical measurements.The results show that all the alloys were composed of hexagonal Ce2Ni7-type(La,Mg)2Ni7 main-phase,rhombohedral PuNi3-type(La,Mg)Ni3 main-phase,small amount of Mg2Ni phase or AlCo and AlLa3 phases.The maximal discharge capacity of the alloys reduced with the increase of x,from 359.0 mAh/g(x=0) to 294.8 mAh/g(x=0.3).All the alloys showed good activation behavior(initial activation process by 1-2 cycles).Doping Al had no obvious influence on the cyclic stability of the alloys,but the discharge voltage platform and hydrogen desorption pressure decreased by 2.5%.