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Title: Uniform second Li ion intercalation in solid state ϵ -LiVOPO 4

Abstract

Full, reversible intercalation of two Li+ has not yet been achieved in promising VOPO4 electrodes. A pronounced Li+ gradient has been reported in the low voltage window (i.e. second lithium reaction) that is thought to originate from disrupted kinetics in the high voltage regime (i.e first lithium reaction). Here we employ a combination of hard and soft x–ray photoelectron and absorption spectroscopy techniques to depth profile solid state synthesized LiVOPO4 cycled within the low voltage window only. Analysis of the vanadium environment revealed no evidence of a Li+ gradient, which combined with almost full theoretical capacity confirms that disrupted kinetics in the high voltage window are responsible for hindering full two lithium insertion. Furthermore, we argue that the uniform Li+ intercalation is a prerequisite for the formation of intermediate phases Li1:50VOPO4 and Li1:75VOPO4. The evolution from LiVOPO4 to Li2VOPO4 via the intermediate phases is confirmed by direct comparison between O K–edge absorption spectroscopy and density functional theory.

Authors:
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Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science - Energy Frontier Research Center - NorthEast Center for Chemical Energy Storage (NECCES)
OSTI Identifier:
1392348
DOE Contract Number:
AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 109; Journal Issue: 5
Country of Publication:
United States
Language:
English

Citation Formats

Wangoh, Linda W., Sallis, Shawn, Wiaderek, Kamila M., Lin, Yuh-Chieh, Wen, Bohua, Quackenbush, Nicholas F., Chernova, Natasha A., Guo, Jinghua, Ma, Lu, Wu, Tianpin, Lee, Tien-Lin, Schlueter, Christoph, Ong, Shyue Ping, Chapman, Karena W., Whittingham, M. Stanley, and Piper, Louis F. J. Uniform second Li ion intercalation in solid state ϵ -LiVOPO 4. United States: N. p., 2016. Web. doi:10.1063/1.4960452.
Wangoh, Linda W., Sallis, Shawn, Wiaderek, Kamila M., Lin, Yuh-Chieh, Wen, Bohua, Quackenbush, Nicholas F., Chernova, Natasha A., Guo, Jinghua, Ma, Lu, Wu, Tianpin, Lee, Tien-Lin, Schlueter, Christoph, Ong, Shyue Ping, Chapman, Karena W., Whittingham, M. Stanley, & Piper, Louis F. J. Uniform second Li ion intercalation in solid state ϵ -LiVOPO 4. United States. doi:10.1063/1.4960452.
Wangoh, Linda W., Sallis, Shawn, Wiaderek, Kamila M., Lin, Yuh-Chieh, Wen, Bohua, Quackenbush, Nicholas F., Chernova, Natasha A., Guo, Jinghua, Ma, Lu, Wu, Tianpin, Lee, Tien-Lin, Schlueter, Christoph, Ong, Shyue Ping, Chapman, Karena W., Whittingham, M. Stanley, and Piper, Louis F. J. 2016. "Uniform second Li ion intercalation in solid state ϵ -LiVOPO 4". United States. doi:10.1063/1.4960452.
@article{osti_1392348,
title = {Uniform second Li ion intercalation in solid state ϵ -LiVOPO 4},
author = {Wangoh, Linda W. and Sallis, Shawn and Wiaderek, Kamila M. and Lin, Yuh-Chieh and Wen, Bohua and Quackenbush, Nicholas F. and Chernova, Natasha A. and Guo, Jinghua and Ma, Lu and Wu, Tianpin and Lee, Tien-Lin and Schlueter, Christoph and Ong, Shyue Ping and Chapman, Karena W. and Whittingham, M. Stanley and Piper, Louis F. J.},
abstractNote = {Full, reversible intercalation of two Li+ has not yet been achieved in promising VOPO4 electrodes. A pronounced Li+ gradient has been reported in the low voltage window (i.e. second lithium reaction) that is thought to originate from disrupted kinetics in the high voltage regime (i.e first lithium reaction). Here we employ a combination of hard and soft x–ray photoelectron and absorption spectroscopy techniques to depth profile solid state synthesized LiVOPO4 cycled within the low voltage window only. Analysis of the vanadium environment revealed no evidence of a Li+ gradient, which combined with almost full theoretical capacity confirms that disrupted kinetics in the high voltage window are responsible for hindering full two lithium insertion. Furthermore, we argue that the uniform Li+ intercalation is a prerequisite for the formation of intermediate phases Li1:50VOPO4 and Li1:75VOPO4. The evolution from LiVOPO4 to Li2VOPO4 via the intermediate phases is confirmed by direct comparison between O K–edge absorption spectroscopy and density functional theory.},
doi = {10.1063/1.4960452},
journal = {Applied Physics Letters},
number = 5,
volume = 109,
place = {United States},
year = 2016,
month = 8
}
  • Cited by 1
  • Full, reversible intercalation of two Li{sup +} has not yet been achieved in promising VOPO{sub 4} electrodes. A pronounced Li{sup +} gradient has been reported in the low voltage window (i.e., second lithium reaction) that is thought to originate from disrupted kinetics in the high voltage regime (i.e., first lithium reaction). Here, we employ a combination of hard and soft x–ray photoelectron and absorption spectroscopy techniques to depth profile solid state synthesized LiVOPO{sub 4} cycled within the low voltage window only. Analysis of the vanadium environment revealed no evidence of a Li{sup +} gradient, which combined with almost full theoreticalmore » capacity confirms that disrupted kinetics in the high voltage window are responsible for hindering full two lithium insertion. Furthermore, we argue that the uniform Li{sup +} intercalation is a prerequisite for the formation of intermediate phases Li{sub 1.50}VOPO{sub 4} and Li{sub 1.75}VOPO{sub 4}. The evolution from LiVOPO{sub 4} to Li{sub 2}VOPO{sub 4} via the intermediate phases is confirmed by direct comparison between O K–edge absorption spectroscopy and density functional theory.« less
  • ε -Li x VOPO 4 is a promising multi-electron cathode for rechargeable lithium-ion bat- teries that has an extremely high theoretical capacity of 318 mAh/g. In this w ork, we demonstrate the stable cycling of more than one Li in solid-state-syn thesized ε - LiVOPO 4 over more than 20 cycles for the first time. Using a combination of densit y functional theory (DFT) calculations, X-ray pair distribution funct ion (PDF) analy- sis and X-ray Absorption Near Edge Structure (XANES) measurements, we pre sent a comprehensive analysis of the thermodynamics, kinetics and stru ctural evolution of ε -Li x VOPOmore » 4 over the entire lithiation range. We identify two intermediate ph ases at x = 1 . 5 and 1.75 in the low-voltage regime using DFT calculations, and the comput ed and electrochemically measured voltage profiles are in excellent agree ment. Operando PDF techniques show a reversible hysteretic change in the short ( < 2° A) V-O bond lengths coupled with an irreversible extension of the long V-O bond ( > 2.4 °A) dur- ing low-voltage cycling. These observations are confirmed with EXAFS spe ctra. We identify hydrogen intercalation from the electrolyte decomposition as a likely explana- tion for the ~ 2 . 4°A V-O bond and its irreversible extension. In terms of electronic conductivity, we find Li x VOPO 4 to be a large band gap insulator across the entire lithiation range, and calculated small polaron migration barriers are similar to those of the olivine LiMPO 4 cathodes. Finally, we demonstrate that ε -LiVOPO 4 is likely to be a one-dimensional diffuser using climbing-image nudged elastic ban d calculations. These results highlight the importance of nano-sizing and carbon coating in achieving good electrochemical performance in this material.« less