Phase structure and electrochemical performance for super lattice La-Mg-Ni based <i>A</i>₅<i>B</i>₁₉ type negative materials

• Main Authors: XU Jian-yi, ZHANG Guo-fang, HU Feng, WANG Rui-fen, KOU Yong, ZHANG Yin
• Format: Article
• Language: zho
• Published: Journal of Materials Engineering 2020-02-01
• Series: Journal of Materials Engineering
• Subjects: la-mg-ni based; super lattice <i>a</i>₅<i>b</i>₁₉ negative material; rare earth ce substitution; electrochemical performance
• Online Access: http://jme.biam.ac.cn/CN/Y2020/V48/I2/46

The quaternary alloys La_0.8-<i>x</i>Ce_<i>x</i>Mg_0.2Ni_3.8 (<i>x</i>=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 <i>A</i>₅<i>B</i>₁₉ phase and decrease of <i>AB</i>₅ phase accordingly. Ce contributes to the formation of <i>A</i>₅<i>B</i>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 <i>x</i>=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.