期刊
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
卷 43, 期 37, 页码 17809-17820出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.ijhydene.2018.07.183
关键词
Hydrogen storage alloy; RE-Mg-Ni compound; Electrochemical properties; Structure stability
资金
- National Natural Science Foundation of China [51571173, 51701175, 51771164]
- National Postdoctoral for Innovative Talents [BX201700204]
- Innovation Fund for the Graduate Students of Hebei Province [CXZZBS2017057]
In order to investigate the formation mechanism of Ce5Co19- type super-stacking structure phase, La0.60M0.20Mg0.20Ni3.80 (M = La, Pr, Nd, Gd) compounds are synthesized by powder sintering method. Rietveld refinements of X-ray diffraction patterns find that La0.80Mg0.20Ni3.80 compound has a single Pr5Co19-type structure. The Ce5Co19-type phase appears and increases with the decrease of atomic radius of M, until the La0.60Gd0.20Mg0.20Ni3.80 compound shows a Ce5Co19-type single phase structure. The cycling stability and high rate dischargeability (HRD) of the alloy electrodes both improve with the increase of Ce5Co19-type phase. The capacity retention of La0.60Gd0.20Mg0.20Ni3.80 compound at the 100th cycle is high to 93.6% and the HRD reaches 66.9% at a discharge current density of 1500 mA g(-1). Moreover after 50 charge/discharge cycles, the Ce5Co19-type particle retains an intact crystal structure while severe amorphization occurs to Pr5Co19-type particle as shown in graphical abstract. The cohesive energy obtained from the First-principle calculations is analyzed combined with the experimental results. It is found that the La0.60Gd0.20Mg0.20Ni3.80 compound with Ce5Co19-type single phase structure has the highest cohesive energy indicating a more stable structure. This work provides new insights into the superior composition-structure design of La-Mg-Ni system hydrogen storage alloys that may improve the cycling stability. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
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