期刊
JOURNAL OF SOLID STATE CHEMISTRY
卷 181, 期 12, 页码 3303-3307出版社
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.jssc.2008.09.002
关键词
Lithium-ion battery; Positive electrode material; Layered oxide; Li(Ni,Mn,Co)O-2; Fluorine substitution; Coating; X-ray diffraction; NMR spectroscopy
资金
- Region Aquitaine and Saft
A series of Li1+z/2(Ni0.425Mn0.425Co0.15)(1-z/2)O2-zFz materials was prepared by a coprecipitation route and their structure was characterized using X-ray diffraction (XRD), as well as Li-7 and F-19 Magic Angle Spinning (MAS) NMR spectroscopy. Two hypotheses were considered: (i) formation of layered oxyfluoride materials and (ii) formation of a mixture between the layered material and LiF. Structural parameters were refined by the Rietveld method, using XRD diffraction data. The refinement results did not allow us to choose between these two hypotheses: no significant change in crystallinity and structural parameters was observed irrespective of the fluorine ratio. Li-7 and F-19 MAS NMR analyses showed signals with isotropic positions characteristic of LiF, but envelopes characteristic of very strong dipolar interactions with the electron spins of the material, demonstrating that LiF was not incorporated into the layered oxide structure but was instead present as a coating. (C) 2008 Elsevier Inc. All rights reserved.
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