Physicochemical and Electrochemical Properties of Novel Ionic Liquids Containing Aprotic Heterocyclic Anions Doped with Lithium Salts

Abstract

A series of novel ionic liquids (ILs) based on N, N'- dialkylimidazolium, tetra-alkylphosphonium and dialkylpyrrolidinium cations paired with two aprotic heterocyclic anions (AHAs) were synthesized in the present study. In addition, lithium salts of the corresponding anions were prepared. Physicochemical and electrochemical properties of the neat ILs and their mixtures with the lithium salts at various concentrations were systematically measured from 283.15K to 343.15K at atmospheric pressure, including density (ρ), viscosity (η) and electrical conductivity (σ). The empirical Vogel-Fulcher-Tammann (VFT) was used to analyze the experimental viscosities and electrochemical conductivities. Furthermore, the Walden plot behavior of the pure ILs and ILs doped with lithium salts were investigated. The results provide some insight into the strength of the association between Li+ and the different anions. Consequently, the ILs with low viscosity and good conductivities are promising electrolytes candidates to be used in electrochemical applications.

Viscosity of Ionic Liquids: Theories and Models

“…Arrhenius equation, ,− VFT equation, ,,,, Litovitz equation, , and Orric Erbar equation can be used to describe the temperature dependence of viscosity of ILs with a good accuracy. However, their parameters are IL-specific and must be determined by fitting experimental viscosity data.…”

Recent advances in the synthesis and applications of metal organic frameworks doped with ionic liquids for CO 2 adsorption

“…In a similar approach, the combination of phosphonium cations with aprotic heterocyclic anions (AHAs) produced ILs that primarily react with CO 2 through the anion in a 1:1 stoichiometry [94,[96][97][98][99][100] (Fig. 8).…”

Ionic Liquid–Glycol Mixtures for Direct Air Capture of CO2: Decreased Viscosity and Mitigation of Evaporation Via Encapsulation

“…Conventional ILs, such as 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM]­[PF 6 ], primarily rely on physisorption of CO 2 into free molar volume. , By tailoring the functional moieties, task specific ILs (TSILs) can absorb CO 2 via chemisorption, as well as physisorption, offering a promise as DAC solvents. For example, the Brennecke group developed the TSIL 1-ethyl-3-methylimidazolium 2-cyanopyrrolide ([EMIM]­[2-CNpyr]), and the Gurkan group demonstrated DAC abilities. , The Gurkan group determined two reaction routes are possible for [EMIM]­[2-CNpyr] DAC: the anion reversibly reacts with CO 2 to form carbamate and the cation reacts to form imidazolium-carboxylate . Notably, many TSILs are currently not economically viable for broad implementation in DAC operations compared to current solvents (e.g., aqueous amines, KOH, etc.)…”

“… 8 , 9 By tailoring the functional moieties, task specific ILs (TSILs) can absorb CO 2 via chemisorption, as well as physisorption, 10 offering a promise as DAC solvents. For example, the Brennecke group developed the TSIL 1-ethyl-3-methylimidazolium 2-cyanopyrrolide ([EMIM][2-CNpyr]), 11 and the Gurkan group demonstrated DAC abilities. 12 , 13 The Gurkan group determined two reaction routes are possible for [EMIM][2-CNpyr] DAC: the anion reversibly reacts with CO 2 to form carbamate and the cation reacts to form imidazolium-carboxylate.…”