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中南大学学报(英文版)

Journal of Central South University

Vol. 21    No. 6    June 2014

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An investigation on electrochemical performances of as-cast and annealed La0.8Mg0.2Ni3.3Co0.2Six (x = 0-0.2) alloy electrodes for Ni/MH battery application
ZHANG Yang-huan(张羊换)1, 2, CHEN Li-cui(陈莉翠)1, 2, ZHAO Chen(赵宸)1, 2, YANG Tai(杨泰)1, 2, XU Chao(徐超)1, 2, ZHAO Dong-liang(赵栋梁)2

1. Key Laboratory of Integrated Exploitation of Baiyun Obo Multi-Metal Resources,
Inner Mongolia University of Science and Technology, Baotou 014010, China;
2. Department of Functional Material Research, Central Iron and Steel Research Institute, Beijing 100081, China

Abstract:The La–Mg–Ni-based A2B7-type La0.8Mg0.2Ni3.3Co0.2Six (x=0-0.2) electrode alloys were prepared by casting and annealing. The influences of the additional silicon and the annealing treatment on the structure and electrochemical performances of the alloys were investigated systemically. Both of the analyses of XRD and SEM reveal that the as-cast and annealed alloys are of a multiphase structure, involving two main phases (La, Mg)2Ni7 and LaNi5 as well as one minor phase LaNi3. The addition of Si and annealing treatment bring on an evident change in the phase abundances and cell parameters of (La, Mg)2Ni7 and LaNi5 phase for the alloy without altering its phase structure. The phase abundances decrease from 74.3% (x=0) to 57.8% (x=0.2) for the (La, Mg)2Ni7 phase, and those of LaNi5 phase increase from 20.2% (x=0) to 37.3% (x=0.2). As for the electrochemical measurements, adding Si and performing annealing treatment have engendered obvious impacts. The cycle stability of the alloys is improved dramatically, being enhanced from 80.3% to 93.7% for the as-annealed (950 °C) alloys with Si content increasing from 0 to 0.2. However, the discharge capacity is reduced by adding Si, from 399.4 to 345.3 mA·h/g as the Si content increases from 0 to 0.2. Furthermore, such addition makes the electrochemical kinetic properties of the alloy electrodes first increase and then decrease. Also, it is found that the overall electrochemical properties of the alloys first augment and then fall with the annealing temperature rising.

 

Key words: A2B7-type electrode alloy; adding Si; annealing treatment; structure; electrochemical performances

中南大学学报(自然科学版)
  ISSN 1672-7207
CN 43-1426/N
ZDXZAC
中南大学学报(英文版)
  ISSN 2095-2899
CN 43-1516/TB
JCSTFT
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