La-Mg-Ni系A5B19超晶格负极材料相结构及电化学性能EI北大核心CSCD

感应熔炼制备La0.8-xCexMg0.2 Ni 3.8(x=0,0.1,0.3,0.5),研究Ce替代部分La对La4MgNi19超晶格负极材料相结构及电化学性能的影响。研究表明,La4MgNi19合金相由LaNi5,(La,Mg)2Ni7,(La,Mg)5Ni19(3R-Ce5Co19)相组成。加入Ce后,(La,Mg)2Ni7相消失,出现2H-Pr 5Co 19结构的(La,Mg)5Ni19相,同时随着Ce替代量的增多,(La,Mg)5Ni19相含量增多,LaNi5相随之减少,Ce加入有利于形成A5B19相,特别是形成2H-Pr5Co19结构。电化学放电容量随着x值的增加呈现先增后减趋势,x=0.1时样品的电化学放电容量380.36 mAh/g最佳。合金电极活化次数、容量保持率和倍率放电性能随着Ce含量增加而增大。H在合金中的扩散速率是影响其倍率放电性能主要因素。

Phase structure and electrochemical performance for super lattice La-Mg-Ni based A5B19 type negative materials

The quaternary alloys La 0.8-xCexMg0.2 Ni3.8(x=0,0.1,0.3,0.5)were prepared by induction melting,and the effects of partial substitution of Ce for La on the phase structure and electrochemical performances of super lattice La4MgNi19 negative materials were investigated.Results show that La 4MgNi 19 alloys contain LaNi 5 phase,(La,Mg)2Ni7(3R-Ce 2Ni7 and 2H-Gd2Co7)phase,(La,Mg)5Ni19(3R-Ce5Co19)phase.The 2H-Pr5Co19 type phase appears while(La,Mg)2Ni7 phase disappears,after partial substitution of Ce for La.The increase of Ce element substitution has led to an obvious increase of the abundance of A5B19 phase and decrease of AB5 phase accordingly.Ce contributes to the formation of A5B 19 phase,especially 2H-Pr5Co19 type phase.With the increase of Ce content from 0 to 0.5,the maximum discharge capacity of alloy electroded increases firstly and then decreased.The x=0.1 alloy exhibits a maximum discharge capacity of 380.36 mAh/g.It is also found that this substitution has caused a significant increase in the activation number,the cyclic stability,high-rate discharge ability.The well performance demonstrates that it is the hydrogen diffusion in the alloy that controls the high rate discharge.