La0．7Mg0．3Ni3．4-xCo0．6Mnx（x=0．0～0．5）贮氢电极合金的结构、储氢特性及电化学性能

摘要:

La0．7Mg0．3Ni3．4-xCo0．6Mnx(x=0．0～0．5)合金主要由(La，Mg)Ni3相和LaNi5相构成，各相的晶胞参数和晶胞体积均随Mn含量的增加而增大。随Mn含量的增加，合金的放氢平衡压力从0．128MPa(x=0．0)下降到0．067MPa(x=0．5)，导致最大吸氢量从x=0．0时的1．19％(质量分数，下同)逐渐增加到x=0．4时的1．38％。合金的最大放电容量随Mn含量的增加首先从330．4mAh／g（x=0．0)增加到360．6mAh／g(x=0．4)，然后减小到346．9mAh／g(x=0．5)。随Mn替代量的增加，合金电极的高倍率放电能力先改善后降低，合金电极的表面反应阻抗先降低后升高，而氢的扩散系数先增加后减小，说明合金的电化学动力学性能首先提高然后降低。

Abstract:

La0.7Mg0.3Ni3.4-xCo0.6Mnx (x=0.0-0.5) hydrogen storage alloys are mainly consisted of the (La, Mg)Ni3 phase and the LaNi5 phase. The lattice parameters and cell volumes of the component phases increase with increasing Mn content. P-C-T curves show that the equilibrium pressure for hydrogen desorption decreases from 1.28 atm (x=0.0) to 0.67 atm (x=0.5) with increasing x, and the hydrogen storage capacity increases from 1.19 wt% (x=0.0) to 1.38 wt% (x=0.4). The electrochemical studies show that the maximum discharge capacity increases first from 330.4 mAh/g to 360.0 mAh/g with increasing x from 0.0 to 0.4, and then decreases to 346.9 mAh/g when for x of 0.5. The HRD and the hydrogen diffusion coefficient D of the alloy electrodes increases firstly, then decrease with increasing Mn content, but the charge-transfer reaction resistant Rct decreases firstly, then increases. They imply that the electrochemical kinetics property of the La0.7Mg0.3Ni3.4-xCo0.6Mnx hydrogen storage alloys increases firstly and then decreases with increasing x from 0.0 to 0.5.