Effects of stoichiometric ratio La/Mg on structures and electrochemical performances of as-cast and annealed La-Mg-Ni-based A_2B_7-type electrode alloys  

化学计量比La/Mg对铸态及退火态La–Mg–Ni系A_2B_7型电极合金结构及电化学性能的影响（英文）

作　　者：张羊换[1,2] 杨泰[2] 翟亭亭[2] 袁泽明[2] 张国芳[1] 郭世海[2] 

机构地区：[1]内蒙古科技大学内蒙古自治区白云鄂博矿多金属资源综合利用重点实验室,包头014010 [2]钢铁研究总院功能材料研究所,北京100081

出　　处：《Transactions of Nonferrous Metals Society of China》2015年第6期1968-1977,共10页中国有色金属学报（英文版）

基　　金：Projects(51161015,51371094) supported by the National Natural Science Foundation of China

摘　　要：In order to investigate the influences of the stoichiometric ratio of La/Mg （increasing La and decreasing Mg on the same mole ratio） on the structure and electrochemical performances of the La-Mg-Ni-based A2B7-type electrode alloy, the as-cast and the annealed ternary Lao.8＋xMgo.2_xNi3.5 （x=0-0.05） electrode alloys were prepared. The characterization of electrode alloys by X-ray diffraction （XRD） and scanning electron microscopy （SEM） shows that all the as-cast and the annealed alloys hold two major phases of （La,Mg）2Ni7 and LaNi5 as well as a residual phase of LaNi3. Moreover, the increase of La/Mg ratio brings on a decline of （La,Mg）2Ni7 phase and a rise of LaNi5 and LaNi3 phases. The variation of La/Mg ratio gives rise to an evident change of the electrochemical performances of the alloys. The discharge capacities of the as-cast and the annealed alloys evidently decrease with growing the La/Mg ratio, while the cycle stabilities of the alloys visibly augment under the same condition. Furthermore, the high rate discharge ability （HRD）, the electrochemical impedance spectrum （EIS）, the Tafel polarization curves, and the potential step measurements all indicate that the electrochemical kinetic properties of the alloy electrodes increase with the La/Mg ratio rising.采用合金熔炼及退火处理的方法制备La-Mg-Ni系A2B7型La0.8+xMg0.2–xNi3.5(x=0-0.05)电极合金,并研究不同的化学计量比La/Mg对该合金的相结构和电化学性能的影响。通过X射线衍射(XRD)和扫描电子显微镜(SEM)对合金进行表征。结果表明:合金包含(La,Mg)2Ni7和La Ni5两个主相以及一些残余相La Ni3。随着La/Mg比率的增大,合金中的(La,Mg)2Ni7相含量降低,而La Ni5和La Ni3相的含量升高。La/Mg比的变化也使得合金电极的电化学性能发生显著变化。随着La/Mg比率的增加,铸态及退火态合金的放电容量降低,而循环稳定性明显改善。此外,合金电极的高倍率放电性能(HRD)、电化学阻抗谱(EIS)、Tafel极化曲线以及电势阶跃的测量均表明La/Mg比率的增加提高了合金的电化学动力学性能。

关 键 词：hydrogen storage alloy annealing treatment structure electrochemical performance KINETICS 

分 类 号：TG146.45[一般工业技术—材料科学与工程]