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

The quaternary alloys La0.8-xCexMg0.2Ni3.8 (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 La4MgNi19 alloys contain LaNi5 phase, (La,Mg)2Ni7(3R-Ce2Ni7 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 A5B19 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.