稀土元素R对储氢合金(LaRMg)(NiCoAlZn)_(3.5)相结构和电化学性能的影响

以(LaRMg)(NiCoAlZn)3.5(R=La、Ce、Pr、Nd、Gd、Y和Sc)合金为研究对象,研究稀土元素R部分替代La后对合金相结构和相组成及电化学性能的影响.XRD和EPMA方法分析结果表明,合金(LaRMg)(NiCoAlZn)3.5退火组织主要由Ce2Ni7型相(或Gd2Co7型)、PuNi3型相和CaCu5型相组成;Ce、Pr和Nd元素的替代对合金相组成没有明显影响,而Gd元素替代使合金中CaCu5型相明显减少,Ce2Ni7型(或Gd2Co7型)相显著增加,其相丰度达到79.03%;Y和Sc元素替代时合金中Gd2Co7型相基本消失.电化学测试和分析表明, 稀土元素R替代La后对合金电极活化性能影响不大,其中Nd、Gd、Y和Sc部分替代La在一定程度上提高合金的最大放电容量,而Gd元素替代时合金电极容量最高达到343.1 mAh/g;Gd和Nd元素部分替代La使合金电极的循环稳定性得到明显提高,S100分别达到95.3%和93.0%.此外,Sc部分替代La能有效改善合金电极的高倍率放电性能.

Influence of rare-earth elements R on phase-structure and electrochemical properties of hydrogen storage alloys(LaRMg)(NiCoAlZn)_(3.5)

Taking alloys(LaRMg)(NiCoAlZn)3.5 as objects of investigation,the influence of rare-earth R(La,Ce,Pr,Nd,Gd,Y and Sc) substituted for partial La on the phase-structure and electrochemical properties was investigated.XRD analysis and EPMA showed that the annealing structure of (LaRMg)(NiCoAlZn)3.5 consisted mainly of CaCu5-type phase,Ce2Ni7(or Gd2Co7-type) and PuNi3-type phase.The substitution of elements Ce,Pr and Nd had no significant influence on the phase-structure of the alloys.However,CaCu5-type phase d...