温度对La-Mg-Ni-Co-Mn贮氢电极合金电化学性能的影响

Effects of temperature on electrochemical properties of La-Mg-Ni-Co-Mn hydrogen storage electrode alloy

系统研究了温度对La0.7Mg0.3Ni2.875Co0.525Mn0.1贮氢合金电化学性能尤其是电化学动力学性能的影响。结果表明:La0.7Mg0.3Ni2.875Co0.525Mn0.1合金由(La,Mg)Ni3相和LaNi5相构成。合金的最大放电容量随着温度升高从-20℃时的277.5mAh/g增加到30℃时的406.2mAh/g。随着温度升高,合金放电平台电位逐渐变负,放电过电位逐渐减小,合金电极的极化减弱。高倍率性能、交换电流密度、氢的扩散系数研究表明合金的电化学动力学性能随着温度升高不断提高。该合金的氢扩散活化能为17.6kJ/mol。

Effects of temperature on the electrochemical properties of the La_(0.7)Mg_(0.3)Ni_(2.875)Co_(0.525)Mn_(0.1) hydrogen storage electrode alloy were systematically investigated, particularly for the electrochemical kinetic properties. The results indicate that the La_(0.7)Mg_(0.3)Ni_(2.875)Co_(0.525)Mn_(0.1) alloy consists of the (La, Mg)Ni_3 phase and the LaNi_5 phase. The maximum discharge capacity of the La_(0.7)Mg_(0.3)Ni_(2.875)Co_(0.525)Mn_(0.1)alloy increases from 277.5 mAh/g to 406.2 mAh/g with increasing temperature from -20 ℃ to 30 ℃. Moreover, with increasing temperature, the discharge plateau potential is more negative, the discharge overpotential declines, and the polarization of the alloy electrode decreases. The high rate dischargeability, exchange current density and hydrogen diffusion coefficient of the alloy electrode all increase with increasing temperature, which indicates that the electrochemical kinetic property of the alloy electrode is improved. The activation energy for hydrogen diffusion in the alloy electrode is calculated to be 17.6 kJ/mol.