热处理对La0．7Mg0．3Ni2．8Co0．5贮氢合金电化学性能的影响

Effects of Heat Treatment on Electrochemical Properties of La0. 7Mg0. 3Ni2. 8Co0. 5 Hydrogen Storage Alloy

摘要:

La0．7Mg0．3Ni2．8Co0．5贮氢电极合金经过适当热处理后(1123K)，最大放电容量、循环稳定性、高倍率放电性能(HRD)、交换电流密度(I0)以及极限电流密度(IL)都有明显改善，铸态合金电极的最大放电容量为392mAh／g，放电电流密度，Id=2000mA／g时，HRD2000=74．0％，I0=266．7mA／g，IL=3425．5mA／g；经1123K保温8h退火的合金电极的最大放电容量提高到414mAh／g，HRD2000=76．2％，I0=407．9mA／g，IL=3753．6mA／g。X射线衍射(XRD)分析表明，衍射峰宽度随着退火温度的升高而变窄，其原因是合金经退火处理相结构的变化和成分的均匀化。

Abstract:

The effects of heat treatment on the electrochemical properties and structure of La0.7Mg0.3Ni2.8Co0.5 hydrogen storage alloy were studied. It is found, by electrochemical studies, that the discharge capacity, cycle stability, high rate dischargeability (HRD), exchange current density I0 and the limiting current density IL of the alloy electrodes increase after annealing treatment. The discharge capacity of the alloy annealed at 1 123 K and the cycle life of the alloy annealed at 1 223 K are the highest and the best, respectively. In addition, the exchange current density I0 and the limiting current density IL of the alloy electrode increase with annealing at 1 123 K and then decrease with increasing annealing temperature. Meanwhile, the improvement of the high rate dischargeability (HRD) of the annealing samples is consistent with the variation of the exchange current density I0 and the limiting current density IL. Furthermore, it is found, by XRD analysis, that the peak positions and peak intensities change with increasing annealing temperature, which can be ascribed to the structural change and more homogeneous composition after annealing treatment.