Physicochemical and Electrochemical Properties of 1-Ethyl-3-Methylimidazolium Tris(pentafluoroethyl)trifluorophosphate and 1-Ethyl-3-Methylimidazolium Tetracyanoborate

Abstract

The physicochemical (e.g., density, viscosity, ionic conductivity, and self-diffusion coefficient) and electrochemical (e.g., electrochemical window and electric double-layer capacitor performance) properties of two new types of room-temperature ionic liquids, 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate (EMIm-FAP) and 1-ethyl-3-methylimidazolium tetracyanoborate (EMIm-TCB), were investigated and compared. EMIm-FAP showed a wider electrochemical window with a carbon working electrode compared with EMIm-TCB, in spite of lower viscosity, larger self-diffusion coefficients and higher ionic conductivity. Also, the electric double-layer capacitor using EMIm-FAP shows better cycle reversibility and higher charge/discharge voltage operation (over 3 V) than that using EMIm-TCB.

Densities, Viscosities, and Conductivities of the Imidazolium Ionic Liquids [Emim][Ac], [Emim][FAP], [Bmim][BETI], [Bmim][FSI], [Hmim][TFSI], and [Omim][TFSI]

“…For this IL only limited information is available so far. They are in excellent agreement with the η(T) values published 58 for η(T) in the temperature range of (283.15 to 353.15) K exhibits relative deviations of only −0.034 ≤ δ ≤ 0.01 from the present fit but the dependence of η on temperature is somewhat smaller. They are in excellent agreement with the η(T) values published 58 for η(T) in the temperature range of (283.15 to 353.15) K exhibits relative deviations of only −0.034 ≤ δ ≤ 0.01 from the present fit but the dependence of η on temperature is somewhat smaller.…”

“…Ignatev et al 66 reported a single κ value, determined at 293.15 K with a commercial conductometer of 0.5% relative standard uncertainty, which is 0.9 % below the present fit ( Figure S12). Note that a similar discrepancy also exists for η, where the experimental point (43 mPa·s) of ref 58. Only a single numerical value at 303.15 K was published, together with the parameters of a VFT fit to their data.…”

“…With |δ| ≤ 0.0072 the present conductivity data collected between (278.15 and 468.15) K for this IL in Regensburg showed somewhat larger deviations from their fit with eq 3 than [Emim][Ac] (see above). Using an unspecified sample, Seki et al 58 investigated the temperature range of 243.15 ≤ (T/K) ≤ 353.15 with an impedance analyzer and a commercial conductivity cell, claiming a relative uncertainty of 0.35 % for κ. Ignatev et al 66 reported a single κ value, determined at 293.15 K with a commercial conductometer of 0.5% relative standard uncertainty, which is 0.9 % below the present fit ( Figure S12).…”

Self-Diffusion Coefficients and Related Transport Properties for a Number of Fragile Ionic Liquids

“…Our value for D S+ is 0.87 7 . However, the cation−cation VCC, f ++ , calculated from the self-diffusion data of Seki et al 34 and the conductivities of Nazet et al 44 are positive, which is an unphysical result, and another reason for believing these selfdiffusion data are too low.…”

New hydrophobic ionic liquids with perfluoroalkyl phosphate and cyanofluoroborate anions

“…Ionic liquids based on the FAP anion reveal an excellent electrochemical (Fig.3) [5,[7][8][9][10] and thermal stability [5,11,12]. They are less viscous than corresponding ionic liquids with the [PF 6 ] -anion [5,13,14].…”