Correlation between phase structure and electrochemical properties of Ce2Ni7-type La-RE-Mg-Ni (RE = Nd, Sm, Y) alloys: A comparative study

The correlation between phase structure and electrochemical properties of La0.83Mg0.17Ni3.1Co0.3Al0.1 was investigated firstly by partial substitution of La with Sm. It was found that the La0.83-xSmxMg0.17Ni3.1Co0.3Al0.1 alloy consists mainly of the Ce2Ni7-type phase, the abundance of which reaches the maximum (92.23 wt.%) at x = 0.2 when x is changed from 0 to 0.4. The alloy containing more Ce2Ni7-type phase exhibited the better the cyclic and high rate discharge ability examined by electrochemical measurements, i.e. the best electrochemical performance was confirmed at x = 0.2. Furthermore, the influence of unit cell volumes of the Ce2Ni7-type main phase on electrochemical properties was investigated systematically based on the comparison of substitution effect of Sm, Nd and Y for La at x = 0.2. Compared to those of Nd- and Y-substitutions, the Sm-substituted alloy containing Ce2Ni7-type main-phase showed better overall electrochemical properties, especially C-max = 393.3 mAh g(-1) and S-100 = 87.2%. Such superior electrochemical performance may result from appropriate cell volumes and anti-pulverization abilities. (C) 2018 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.