La0.8Mg0.2(Ni2.7Co0.6Al0.1Mn0.1)x贮氢合金的电化学性能分析

采用恒电位法、EIS分析及双电极系统对La0.8Mg0.2(Ni2.7Co0.6Al0.1Mn0.1)x(x=0.9～1.10)系列合金进行电化学性能分析。结果表明,x=1.05的合金具有较好的自放电性能(CR=97.3%),而x=1.10的合金有较高的电化学容量(369 mAh.g-1)。合金电极的电化学阻抗谱(EIS)表明,随着化学计量比x的增大,合金电极的电荷迁移电阻先减小后增大,动力学性能先增强后减弱。线性极化测试表明,随着化学计量比x的增大,合金电极表面的电化学反应速率先增大后减小。通过合金电极阳极电流对时间响应的半对数曲线计算的氢扩散系数D随着化学计量比x的增大先增大后降低,说明合金内部的氢扩散能力先增强后降低。

Electrochemical Performance Study of the La0.8 Mg0.2(Ni2.7 Co0.6 Al0.1Mn0.1)x Hydrogen Storage Alloy

In this paper,the electrochemical performances of La0.8Mg0.2(Ni2.7Co0.6Al0.1Mn0.1)x(x = 0.90-1.10) hydrogen storage alloys were studied by constant potential method,EIS analysis and two-electrode system.The results show that,the alloy electrode for x = 1.05 exhibits good charge retention(CR =97.3%),and the alloy electrode for x = 1.10 shows maximum discharge capacities(369 mAh·g-1).Meanwhile,the results of the electrochemical impedance spectroscopy,linear polarization,anode polarization,and hydrogen diffusion coefficient measurements all indicate that the exchange current density Io,the limiting current density IL and the hydrogen diffusion coefficient D of the alloy electrodes also increase first and then reduce with the increasing of stoichiometric ratio x in alloys,which signifies that appropriate stoichiometric ratio x is favorable to improve the electrochemical kinetic property of the La0.8Mg0.2(Ni2.7Co0.6Al0.1Mn0.1)x(x = 0.90,0.95,1.00,1.05,1.10) hydrogen storage alloys.