磁热处理对La-Mg-Ni-Co合金微结构与电化学性能的影响

Effects of magnetic-heat treatment on microstructure and electrochemical properties of La-Mg-Ni-Co alloys

考察La0.67Mg0.33Ni2.5Co0.5合金分别在铸态、热处理及磁热处理3种状态下的微结构及其电化学性能。通过XRD衍射及SEM分析贮氢合金的物相组成和电极合金循环后的形貌,研究Co部分替代Ni以及有无外加磁场下热处理对合金微结构与电化学性能的作用规律。结果表明:经Co部分取代的La-Mg-Ni铸态合金经过50次循环后,放电容量保持率从64.46%提高到74.80%;经磁热处理后,La0.67Mg0.33Ni2.5Co0.5合金的最大放电容量为324.80 mA·h/g,较常规热处理合金的容量提高了10.59%,放电容量保持率为83.07%,其放电平台更为宽广且平坦;磁热处理的引入进一步降低贮氢合金电极的极化电阻,改善合金电极动力学性能。

The microstructure and electrochemical performances of La0.67Mg0.33Ni2.5C0.05 hydrogen storage alloys treated by casting, heat treatment and magnetic-heat treatment were studied. The influence of the substitution of Co for Ni and heat treatment with and without magnetic field on the structures and electrochemical performances of La-Mg-Ni alloys were investigated by XRD and SEM. The results show that the retention of discharge capacity of as-cast La0.67Mg0.33Ni2.5C0.05 alloy increases from 64.46% to 74.80% for as-cast La0.67Mg0.33Ni2.5C0.05 after 50 cycles. The maximum discharge capacity of Lao.67Mgo.33Ni2.sCo0.5 alloy heat treated under magnetic field is 324.8 mA.h/g, which is larger by 10.59% than that of La0.67Mg0.33Ni2.5C0.05 alloy after conventional heat treatment. The retention of discharge capacity of the former is 83.07%. The discharge voltage platform of La0.67Mg0.33Ni2.5C0.05 alloy after magnetic-heat treatment is more broadened and flatter. The magnetic-heat treatment reduces the polarization resistance and improves the electrochemical kinetic properties of alloy electrode.