La0．67Mg0．33Ni2．5Co0．5贮氢合金的制备和MH电极性能研究

采用高频感应熔炼方法制备了PuNi3型La0.67Mg0.33Ni2.5Co0.5合金；用X射线衍射分析和电化学方法研究了添加不同Mg含量以补偿Mg元素烧损时合金的组织结构和电化学性能。X射线衍射分析(XRD)表明，铸态合金由．PuNi3型主相和少量的CaCu5型第二相组成，铸态合金经1223K和10h退火处理后，CaCu5型第二相可明显减少，其中Mg增加10％时得到纯度较高的PuNi3型组织。电化学测试表明，增加适当Mg含量和进行退火热处理能明显提高和改善合金电极容量、循环稳定性和大电流放电性能。与AB5型和。482型Laves相贮氢合金比较，PuNi3型La0.67Mg0.33Ni2.5Co0.5贮氢合金具有电极容量高及优良的大电流放电性能。

Preparation of Hydrogen Storage Alloy La0.67Mg0.33Ni2.5Co0.5 and Its Electrochemical Properties

The La0.67Mg0.33Ni2.5Co0.5 hydrogen storage alloy with PuNi3-type was prepared using induction melting followed by heating treatment. In order to compensate Mg loss during alloy melting, the different mass percent Mg was supplemented into the melt. The microstructure and electrochemical properties of the alloys were investigated by using XRD and electrochemical method. The results show that the ingot is composed of main phase with PuNi3 type structure and a little second phase with CaCu5 structure. After heat treatment at 1 223 K for 10 h, the amount of the second phase in the annealed alloy is remarkably decreased and a more homogenous and purified PuNi3 type microstructure is obtained in the case of 10% Mg supplement. The electrochemical analyses show that the electrochemical properties of the alloy, such as activation, capacity, cycling stability and discharge ability at different current density, are well improved by supplementing proper Mg and annealing heat treatment. In comparison with AB5 type and AB2 with laves phase hydrogen storage alloys, the La0.67Mg0.33Ni2.5Co0.5 alloy has high capacity and quite good kinetics of electrochemical reaction.