快淬对MlNi3.55Co0.75Mn0.4Al0.3/5wt％Mg2Ni复合储氢合金电化学性能的影响

摘要

In order to improve the discharge capacity and the cycling stability of AB5-type hydrogen storage alloy, the effects of rapid quenching rate on the microstructures and electrochemical properties of MlNi3.55Co0.75Mn0.4Al0.3/5wt% Mg2Ni composite alloy were investigated by means of inductively coupled plasma (ICP), X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectrometry (EDS), transmission electron microscope (TEM) and electrochemical measurements. The results show that the as-cast composite alloy is composed of the LaNi5 phase and a small amount of the Mg2Ni phase. However, the quenched composite alloys consist of the (La,Mg)Ni3 new phase and the LaNi5 phase. When the rapid quenching rate is higher than 15 m/s, nan℃rystalline structure are formed and partial amorphous structure appears in the composite alloys. Electrochemical studies show that the maximum discharge capacity and the capacity retention of quenched composite alloys increase firstly and then decrease with increasing rapid quenching rate. The maximum discharge capacity and the capacity retention after 100 cycles of the quenched composite alloy at 20 m/s is up to 344 mAh/g and 93.9%, respectively.%为了改善AB5型储氢合金的放电容量和循环稳定性,研究了快淬速度对MlNi3.55Co0.75Mn0.4Al0.3/5wt％Mg2Ni复合储氢合金结构和电化学性能的影响.电感耦合等离子发射光谱(ICP)、X射线衍射(XRD)、扫描电镜(SEM/EDS)和透射电子显微镜(TEM)分析表明,铸态复合合金由LaNi5相和少量的Mg2Ni相组成,而快淬态复合合金却由(La,Mg)Ni3新相和LaNi5相组成.当快淬速度≥15 m/s时,复合合金中形成明显的纳米晶组织并伴有部分非晶化倾向.电化学性能测试表明,快淬态复合合金的最大放电容量和容量保持率随快淬速度的增大呈现出先增大后减少的变化规律,其中快淬速度为20 m/s时合金电极的最大放电容量达最大值344 mAh/g,经100次充放电循环后该电极的容量保持率为93.9％.