掺铝改善镧-镁-镍贮氢合金电极的性能

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

为了提高镧-镁-镍贮氢合金电极的性能,向该合金粉体中掺加少量的铝粉,并用放电等离子烧结技术制备了La0.7Mg0.3Ni2.5-xCo0.5Alx(x=0～0.3)合金,用X射线衍射仪、扫描电镜和电化学测试系统等研究了该合金的组织和相应的性能。结果表明:制备的合金为多相结构,主相均为六方Ce2Ni7型的(La,Mg)2Ni7相和菱方PuNi3型的(La,Mg)Ni3相,另外还有少量的Mg2Ni相或AlCo相和AlLa3相;合金的最大放电容量在x=0时达到最大值359.0 mAh/g,随x值的增大,放电容量逐渐减小,当x=0.3时降低到294.8 mAh/g;合金均具有良好的活化性能(初始活化次数为1～2次);元素铝的加入对合金循环稳定性的作用不明显,但降低了合金的放电平台电压和放氢压力,降低幅度约为2.5%。

To improve the property of La-Mg-Ni hydrogen storage alloy electrodes, Al powders were doped into the alloy powders, and then La0. 7 Mg0. 3 Ni2. 5-x Coo. 5 Alx （x = 0- 0. 3） alloys were prepared by spark plasma sintering（SPS） teehnique. 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 Mg2 Ni 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%.