New Insights into the Crystal and Electronic Structures of Li1+xV1鈥?i>xO2 from Solid State NMR, Pair Distribution Function Analyses, and First Principles Ca
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- 作者：Fr茅d茅rique Pourpoint ; Xiao Hua ; Derek S. Middlemiss ; Paul Adamson ; Da Wang ; Peter G. Bruce ; Clare P. Grey
- 刊名：Chemistry of Materials
- 出版年：2012
- 出版时间：August 14, 2012
- 年：2012
- 卷：24
- 期：15
- 页码：2880-2893
- 全文大小：822K
- 年卷期：v.24,no.15(August 14, 2012)
- ISSN：1520-5002
文摘
Pair distribution function (PDF) analyses of synchrotron data obtained for the anode materials Li1+xV1鈥?i>xO2 (0 鈮?x 鈮?0.1) have been performed to characterize the short to medium range structural ordering. The data show clear evidence for the magnetically-induced distortion of the V sublattice to form trimers, the distortion persisting at even the highest excess Li content considered of x = 0.1. At least three distinct local environments were observed for the stoichiometric material LiVO2 in 6Li nuclear magnetic resonance (NMR) spectroscopy, the environments becoming progressively more disordered as the Li content increases. A two-dimensional Li鈥揕i correlation NMR experiment (POST-C7) was used to identify the resonances corresponding to Li within the same layers. NMR spectra were acquired as a function of the state of charge, a distinct environment for Li in Li2VO2 being observed. The results suggest that disorder within the Li layers (in addition to the presence of Li within the V layers as proposed by Armstrong et al. Nat. Mater.2011, 10, 223鈥?29) may aid the insertion of Li into the Li1+xV1鈥?i>xO2 phase. The previously little-studied Li2VO2 phase was also investigated by hybrid density functional theory (DFT) calculations, providing insights into magnetic interactions, spin鈥搇attice coupling, and Li hyperfine parameters.