Electrochemical Cycle Stability and Kinetics of the As-Cast and Spun La_0.75−xZr_xMg_0.25Ni_3.2Co_0.2Al_0.1 (x = 0-0.2) Alloys

Abstract:

The poor electrochemical cycle stability of Re-Mg-Ni system A2B7-type electrode alloys has limited their practical application as the negative electrode materials of Ni-MH battery. In order to improve the electrochemical cycle stability of the La-Mg-Ni system A2B7-type electrode alloys, the partial substitution of Zr for La has been performed. The La0.75-xZrxMg0.25Ni3.2Co0.2Al0.1 (x = 0–0.2) electrode alloys were fabricated by casting and melt-spinning. The microstructures and the electrochemical cycle stability and kinetics of the alloys were investigated. The structure characterized by XRD, SEM and HRTEM reveals that the as-cast and spun alloys have a multiphase structure, composing of two main phases (La, Mg)2Ni7 and LaNi5 as well as a residual phase LaNi2. The as-spun Zr-free alloy displays an entire nanocrystalline structure, but a like amorphous structure is detected in the as-spun alloy substituted by Zr, suggesting that the substitution of Zr for La facilitates the formation of an amorphous structure. The electrochemical measurement indicates that both the substitution of Zr for La and the melt spinning remarkably ameliorate electrochemical cycle stability of the alloys. Furthermore, the high rate discharge ability (HRD), the electrochemical impedance spectrum (EIS) and the potential-step measurements all indicate that both of the melt spinning and the Zr substitution bring on a notable decline of the electrochemical kinetics of the alloys.

• Periodical: Advanced Materials Research (Volumes 560-561)
• Pages: 1016-1020
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.560-561.1016
• Online since: August 2012
• Authors: Yang Huan Zhang, Guo Fang Zhang, Xiao Gang Liu, Le Le Chen, Zhong Hui Hou, Dong Liang Zhao
• Keywords: A₂B₇-Type Alloy, Cycle Stability, Melt-Spinning, Substituting La with Zr

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