La3-xYxMgNi14(x=0～2)贮氢合金的相结构与电化学性能研究

系统研究了La3-xYxMgNi14(x=0,1.0,1.5,2.0)贮氢合金的相结构和电化学性能.结构分析表明,合金均由Gd2Co7和Ce2Ni7型结构相组成.随Y含量值x的增加,Gd2Co7型相的丰度增加,Ce2Ni7型相的丰度减少.合金各相的晶胞参数(a,c)和晶胞体积(V)均随x的增加而线性减小.电化学研究表明,随着Y含量的增加,合金电极最大放电容量减小,活化性能显著降低.合金随x的增加,HRD值减小与合金电极电催化活性及氢在合金相中的扩散速率的减小有关.

Investigation of structure and electrochemical properties of hydrogen storage alloys La3-xYxMgNi14(x=0-2)

The phase structure and electrochemical properties of hydrogen storage alloys La_(3-x)Y_xMgNi_(14)(x=0,1.0,1.5,2.0) were investigated systematically.The structure analysis of alloys showed that all these alloys consisted mainly of the rhombohedral Gd_2Co_7-type structure and hexagonal Ce_2Ni_7-type structure.The Gd_2Co_7-type phase content increased with the increase in yttrium content while the Ce_2Ni_7-type phase content decreased.The increase in Y substitution in the alloys led to decrease in both the lattice parameters(a,c) and the cell volume(V).The increase of x led to remarkable decrease of the maximum discharge capacity and the high-rate discharge ability(HRD),but a significant improvement of cycling stability. It was found that the decrease of HRD value for the Y contained alloys was mainly due to the decrease of their electro-catalytic activity and the hydrogen diffusion velocity in the bulk of alloy.