稀土元素取代对Ti_(0.26)Zr_(0.07)V_(0.24)Mn_(0.1)Ni_(0.33)贮氢合金结构和电化学性能的影响

研究了5种稀土元素部分取代V对Ti0.26Zr0.07V0..24Mn0.1Ni0.33合金的微观结构和电化学性能的影响。结果表明,Ti0.26Zr0.07V0.24Mn0.1Ni0.33和Ti0.26Zr0.07V0.24-xMn0.1Ni0.33REx(x=0.005;RE=La,Ce,Nd,Ho,Y)均由体心立方结构的钒基固溶体相和六方结构的C14 Laves相组成。在合金中加入稀土元素,会使合金中两相的晶胞体积同时增大。稀土元素部分取代V均改善了合金电极的活化性能。La和Nd元素取代后,合金电极的最大放电容量明显增加,而Ce的取代提高了合金电极的循环稳定性。Ce,Nd,Ho,Y均改善了合金电极的倍率放电性能。合金电极在高温状态下表现出了良好的放电性能,其中Nd在333 K时放电容量可达550.4 mAh·g-1。稀土元素对荷电保持率的影响各异。

Effect of Rare Earth Element Substitution for Vandium on Structure and Electrochemical Characteristic of Ti0.26Zr0.07V0.24Mn0.1Ni0.33 Hydrogen Storage Alloys

Microstructure and electrochemical properties of Ti_0.26Zr_0.07V_0.24-xMn_0.1Ni_0.33RE_x(x=0.005, RE=Ce, Nd, Ho, Y) hydrogen storage electrode alloys have been investigated systematically. The results of X-ray diffraction (XRD) show that the matrix phase structure of the alloys are composed of V-based solid solution phase with body centered cubic (bcc) structure and a continuous C14 Laves phase with hexagonal structure. The cell volumes of the two phases are both increase by rare earth elements substitution. The partial substitution of Vby rare earth elements can almost improve the activation characteristics and maximum discharge capacity. Lanthanum and neodymium substitution can enhance the maximum discharge capacity of the alloy electrodes observably, and cerium can improve the cyclic stability. Cerium, neodymium, holmium, yttrium can all improve the high-rate ability (HRD) of the alloy electrodes. The alloy electrodes under the condition of high temperature show a favourable discharge performance, and the maximum value of the discharge capacity for the alloy electrodes with neodymium substitution is 550.4 mAh·g^-1. The effect on charge retention ability is different with the different rare-earth elements substitutions.