期刊
CHEMISTRY OF MATERIALS
卷 28, 期 6, 页码 1794-1805出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.chemmater.5b04880
关键词
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资金
- NorthEast Center for Chemical Energy Storage (NECCES), an Energy Frontier Research Center - U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences [DE-SC0012583]
- DOE Office of Science [DE-AC02-06CH11357]
In this work, we demonstrate the stable cycling of more than one Li in solid-state-synthesized epsilon-LiVOPO4 over more than 20 cycles for the first time. Using a combination of density functional theory (DFT) calculations, X-ray pair distribution function (PDF) analysis and X-ray absorption near edge structure (XANES) measurements, we present a comprehensive analysis of the thermodynamics, kinetics, and structural evolution of epsilon-LixVOPO4 over the entire lithiation range. We identify two intermediate phases at x = 1.5 and 1.75 in the low-voltage regime using DFT calculations, and the computed and electrochemical voltage profiles are in excellent agreement. Operando PDF and EXAFS techniques show a reversible hysteretic change in the short (<2 angstrom) V-O bond lengths coupled with an irreversible extension of the long V-O bond (>2.4 angstrom) during low-voltage cycling. Hydrogen intercalation from electrolyte decomposition is a possible explanation for the similar to 2.4 angstrom V-O bond and its irreversible extension. Finally, we show that e epsilon-LixVOPO4 is likely a pseudo-1D ionic diffuser with low electronic conductivity using DFT calculations, which suggests that nanosizing and carbon coating is necessary to achieve good electrochemical performance in this material.
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