期刊
ADVANCED FUNCTIONAL MATERIALS
卷 31, 期 23, 页码 -出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/adfm.202008708
关键词
1‐ ethyl‐ 3‐ methylimidazolium bis(fluorosulfonyl)imide; ionic liquids; lithium bis(fluorosulfonyl)imide; neutron scattering; operando characterization; solid electrolyte interphase
类别
资金
- United States Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division
- Scientific User Facilities Division, Office of Basic Energy Sciences, United States Department of Energy
- United States Department of Energy [DEAC05-00OR22725]
The formation of the solid electrolyte interphase (SEI) in an ionic liquid electrolyte of 0.5 M lithium bis(fluorosulfonyl)imide (LiFSI) in 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide at high cell voltages (1.7-1.9 V) was investigated in ordered mesoporous carbon (OMC) based Li metal cells using an operando small-angle neutron scattering (SANS) technique coupled with electrochemical impedance spectroscopy and ex situ X-ray photoelectron spectroscopy (XPS). It was demonstrated that discharging the OMC Li metal cells to approximately 2 V and holding the cell voltage constant induces a rapid current increase with time, confirming extensive reduction and SEI formation. XPS analysis revealed that LiF is formed at open cell voltage (OCV), attributed to the carbenes generated at the lithium negative electrode reacting with EMIm cation diffusing to and initiating the reaction with FSI- anions at the carbon positive electrode. It was confirmed that the chemical reaction at OCV and electrochemical reduction at high cell voltage of the FSI- anion plays a protective role against EMIm cation co-intercalation into the carbon positive electrode during the initial discharge. Operando SANS studies also suggest that slight differences occur in the surface composition and reaction mechanism as a function of cell voltage.
The formation of the solid electrolyte interphase (SEI) in an ionic liquid electrolyte of 0.5 m lithium bis(fluorosulfonyl)imide (LiFSI) in 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide at high cell voltages (1.7-1.9 V) is investigated in ordered mesoporous carbon (OMC) based Li metal cells using an operando small-angle neutron scattering (SANS) technique coupled with electrochemical impedance spectroscopy and ex situ X-ray photoelectron spectroscopy (XPS). It is demonstrated that discharging the OMC Li metal cells to approximate to 2 V and holding the cell voltage constant induces a rapid current increase with time, confirming extensive reduction and SEI formation. XPS analysis reveals that LiF is formed at open cell voltage (OCV), which is attributed to the carbenes generated at the lithium negative electrode because of its reaction with EMIm cation diffusing to and initiating the reaction with FSI- anions at the carbon positive electrode. It is confirmed that the chemical reaction at OCV and electrochemical reduction at high cell voltage of the FSI- anion plays a protective role against EMIm cation co-intercalation into the carbon positive electrode during the initial discharge. Operando SANS studies also suggest that slight differences occur in the surface composition and reaction mechanism as a function of cell voltage.
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