R-Y-Ni系A5B19型(R=Y,La,Pr,Nd,Sm)储氢合金的微观结构和电化学性能

Microstructure and electrochemical properties of R-Y-Ni based AB-type (R=Y,La,Pr,Nd,Sm) hydrogen storage alloys

用真空电弧熔炼和退火处理制备了A5B19型R0.45Y0.55Ni3.5Mn0.2Al0.1(R=Y,La, Pr, Nd, Sm)储氢合金,采用XRD、SEM-EDS与电化学方法系统分析了镧系稀土元素对R-Y-Ni系A5B19型储氢合金微观结构和电化学性能的影响规律。结果表明,退火合金微观组织由Ce5Co19型相、Ce2Ni7型相和CaCu5型多相结构组成,其中R=La和Y时的Ce5Co19型主相丰度较高,Ce5Co19型相的晶胞体积V及晶格常数a、c均随添加稀土R原子半径的减小而减小。电化学测试结果表明,当R=La时,合金电极拥有最大放电容量为389 mAh/g;R=Nd和Sm时合金电极具有最佳的循环寿命(S100=90.0%);当R=Pr时,合金的高倍率放电性能HRD900性能最佳(86.7%),Nd0.45Y0.55Ni3.5Mn0.2Al0.1退火合金具有较好的综合电化学性能。

The R-Y-Ni based A5B19-type R0.45Y0.55Ni3.5Mn0.2Al0.1(R=Y,La, Pr, Nd, Sm) alloys were prepared by vacuum arc melting and followed by annealing treatment. The effects of rare earth element R on the microstructure, hydrogen storage and electrochemical properties of the alloys were investigated systematically by XRD, SEM-EDS and electrochemical method. Results showed that the annealed alloys mainly composed of Ce5Co7-type, Ce2Ni7-type and CaCu5-type phases and the phase abundance of Ce5Co19 type phase is higher When R=La and Y. The lattice constants a, c and cell volume V of the Ce5Co19-type phases decreased in sequence with the decreasing radius of R atoms. The electrochemical results showed that the La-containing alloy electrode had the highest discharge capacity of 389 mAh/g and the alloys of R=La and Sm element exhibited the best cyclic stability(S100=90.0%). The best high rate dischargeability(HRD900=86.7%) was obtained for the R=Nd alloy. Finally, Nd0.45Y0.55Ni3.5Mn0.2Al0.1 annealed alloy had best overall electrochemical performance.