Influence of Melt Spinning on the Electrochemical Hydrogen Storage Kinetics of RE-Mg-Ni-Based A2B7-Type Alloys

摘要:

合金的电化学贮氢动力学性能是其应用于动力电池的重要因素。为了提高RE-Mg-Ni系A2B7型贮氢合金的动力学性能，用M (M=Pr, Zr) 部分替代La，并采用快淬处理制备了La0.65M0.1Mg0.25Ni3.2Co0.2Al0.1 (M=Pr, Zr)电极合金。研究了元素替代和快淬处理对合金结构及电化学贮氢动力学性能的影响。XRD及TEM结果显示，铸态及快淬态合金均为多相结构，包含(La, Mg)2Ni7和LaNi5主相以及少量的残余相LaNi2。Pr替代快淬态合金为纳米晶结构，而Zr替代快淬态合金为类非晶结构，说明Zr部分替代La促进了非晶的形成。电化学测试表明合金的高倍率放电性能（HRD）随着快淬速度的增加先增大后减小。此外，电化学阻抗谱（EIS），塔菲尔极化曲线以及电势阶跃测试均表明合金的电化学动力学性能随着快淬速度的增加先增大后减小

Abstract:

In order to improve the electrochemical characteristics of the La-Mg-Ni system A2B7-type electrode alloys, the partial substitution of M (M=Pr, Zr) for La has been performed. The melt spinning technology was used to prepare the La0.65M0.1Mg0.25Ni3.2Co0.2Al0.1 (M=Pr, Zr) electrode alloys. The influences of the melt spinning and substithting La with M (M=Pr, Zr) on the structures and the electrochemical hydrogen storage kinetics of the alloys were investigated. The results obtained by XRD and TEM reveal that the as-cast and spun alloys hold a multiphase structure, containing two main phases (La, Mg)2Ni7 and LaNi5 as well as a residual phase LaNi2. The as-spun (M=Pr) alloy displays an entire nanocrystalline structure, while an amorphous-like structure is detected in the as-spun (M=Zr) alloy, implying that the substitution of Zr for La facilitates the amorphous formation. The electrochemical measurement indicates that the high rate discharge ability (HRD) of the alloys first mounts up and then falls with rising of spinning rate. Furthermore, the electrochemical impedance spectrum (EIS), the Tafel polarization curves and the potential-step measurements all indicate that the electrochemical kinetics first increase and then decreases with growing of spinning rate