Hydrogen Storage Properties of Co-free La-Mg-Ni-Based Alloys

摘要:

在Ar气保护下采用磁悬浮感应熔炼方法，制备无Co La1.8Ti0.2MgNi9-xAlx (x=0, 0.1, 0.2, 0.3, 0.4)合金，系统研究Al取代Ni对合金的结构及贮氢性能的影响。所有合金均包含LaMg2Ni9相，当Al含量x≥0.1，La(Ni,Al)5相取代LaNi5相、LaNi3相消失、LaNi2相出现。测试合金的焓变值与LaNi5合金（–30.6 kJ/molH2）相近。Al取代Ni不仅提高合金电极的放电容量，而且改善循环稳定性及电化学动力学性能。La1.8Ti0.2MgNi8.7Al0.3合金贮氢性能较好，30 ℃下有效吸氢质量分数为1.32%；最大放电容量达到340 mAh/g；1400 mA/g放电电流密度下高倍率放电性能HRD1400高达79.8%；经100次充放电循环放电容量保持率为60%

Abstract:

A series of Co-free La1.8Ti0.2MgNi9-xAlx (x=0, 0.1, 0.2, 0.3, 0.4) hydrogen storage alloys were prepared by magnetic levitation melting under Ar atmosphere. The effects of partially substituting Al for Ni on the structure and hydrogen storage properties of the alloys were investigated. For the La1.8Ti0.2MgNi9-xAlx (x=0, 0.1, 0.2, 0.3, 0.4) alloys, LaMg2Ni9 phase is contained in all samples. when Al content x≥0.1, La(Ni, Al)5 phase replaces LaNi5 phase, LaNi3 phase disappears and LaNi2 phase appears. The enthalpies of the test alloys are close to –30.6 kJ/molH2 of the LaNi5 compound. Al substitution for Ni favors the improvement of discharge capacity, cycling stability and electrochemical kinetics. The optimum alloy is found to be La1.8Ti0.2MgNi8.7Al0.3 alloy, with the effective hydrogen storage capacity of 1.32 wt% (at 30 °C), the maximum discharge capacity of 340 mAh/g, the HRD1400 of 79.8% and the discharge capacity retention of 60% after 100 charging/discharging cycles