Physicochemical Properties of Imidazolium-derived Ionic Liquids with Different C-2 Substitutions

Journal Article · Sat Jan 01 00:00:00 EST 2011 · Physical Chemistry Chemical Physics

DOI:https://doi.org/10.1039/c1cp22375e· OSTI ID:1030624

Liao, Chen ^[1]; Shao, Nan ^[1]; Han, Kee Sung ^[1]; Sun, Xiao-Guang ^[1]; Jiang, Deen ^[1]; Dai, Sheng ^[1]

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1. ORNL

Five room temperature ionic liquids based on C-2 substituted imidazolium cations and bis(trifluoromethanesulfonyl)imide (TFSI) anion were synthesized and their physicochemical properties: thermal property, density, viscosity, ionic conductivity, self-diffusion coefficients, and electrochemical stability were systematically investigated. The temperature dependence of both viscosity and ionic conductivities of these ionic liquids can be described by Vogel-Fulcher-Tamman (VFT) equation. Compared with the reference, 1-propyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, the introduction of functional groups at the C-2 position generally increased the viscosity and lowered the ionic conductivity. The introduction of ether group ( CH2OCH2CH2CH2CH3) at the C-2 position not only enhanced the reduction stability of the ionic liquids but also exhibited the lowest solid electrolyte interfacial resistance (RSEI). On the contrary, the introduction of a cyano group ( CN) at the C-2 position not only decreased the reduction stability but also adversely increased the SEI resistance. The effect of the C-2 substitution on the reduction stability was explained by the change of the energy level of the lowest unoccupied molecular orbital. The self-diffusion coefficients (D) of each ion were measured by pulsed field gradient nuclear magnetic resonance (PFG-NMR). The lithium transference number (tLi) of 0.5 M LiTFSI/IL solutions calculated from the self-diffusion coefficients was in the range of 0.04 and 0.09.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: DE-AC05-00OR22725
• OSTI ID: 1030624
• Journal Information: Physical Chemistry Chemical Physics, Vol. 13, Issue 48; ISSN 1463-9076
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ANIONS
CATIONS
ENERGY LEVELS
ETHERS
FUNCTIONALS
IONIC CONDUCTIVITY
LITHIUM
MOLTEN SALTS
NUCLEAR MAGNETIC RESONANCE
SELF-DIFFUSION
SOLID ELECTROLYTES
STABILITY
TEMPERATURE DEPENDENCE
VISCOSITY
Lithium-ion battery
ionic liquids
electrolyte
substitution
imidazolium