La2Mg0.9Al0.1Ni7.5-xCo1.5Mnx贮氢合金的相结构和电化学性能

Phase Constitution and Electrochemical Characteristics of La2Mg0.9Al0.1Ni7.5-xCo1.5Mnx Hydrogen Storage Alloys

摘要:

研究了Mn替代Ni对La2Mg0.9Al0.1Ni7.5-xCo1.5Mnx (x=0, 0.3, 0.6, 0.9)贮氢合金相结构和电化学性能的影响。XRD Rietveld全谱拟合分析表明：Mn替代改变了合金的物相组成和物相的丰度。LaNi3相消失，αLa2Ni7相丰度的变化表现为先增加(x=0，0.3)后减少(x=0.6，0.9)，LaMgNi4相和La5Ni19相的丰度则随合金中Mn含量x的增加而增加。Mn替代Ni降低了合金的贮氢容量、最大电化学放电容量和活化性能，La2Mg0.9Al0.1Ni7.2Co1.5Mn0.3 合金电极表现出最好的电化学循环稳定性，合金的高倍率放电性能随Mn含量的增加降低，这归因于交换电流密度(I0)和氢扩散系数(D)的降低。

Abstract:

Effect of Mn substitution for Ni on phase constitution and electrochemical characteristics of La2Mg0.9Al0.1Ni7.5-xCo1.5Mnx (x=0, 0.3, 0.6, 0.9) hydrogen storage alloys was studied. It is found that Mn substitution will change phase composition and phase constitution of the alloys. LaNi3 phase disappears; the components of αLa2Ni7 first increases with Mn content from x=0 to x=0.3 and then decreases from x=0.6 to 0.9. Both component of LaMgNi4 phase and La5Ni19 phase increase as x increases in the alloys. Replacement of Ni by Mn will lower hydrogen storage capacity, maximum electrochemical discharge capacity and activation property of the alloy electrodes. La2Mg0.9Al0.1Ni7.2Co1.5Mn0.3 hydride electrode shows the best cycle stability. The high rate dischargeability of the alloys decreases with the increase of Mn content, which would be attributed to the decrease of exchange current density (I0) and diffusion coefficient of the hydrogen atom (D).