Binary Ionic Liquid System Research Articles

A binary ionic liquid system composed of N-methoxyethyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)-imide and lithium bis(trifluoromethanesulfonyl)imide: A new promising electrolyte for lithium batteries

Abstract Room temperature ionic liquids are nowadays the most appealing research target in the field of liquid electrolytes for lithium batteries, due to their high thermal stability, ionic conductivity and wide electrochemical windows. The cation structure of such solvents strictly influences their physical and chemical properties, in particular the viscosity and conductivity. In this paper we report on the preparation and characterization of a complete series of solutions between lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and the promising N-methoxyethyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)-imide (PY1,2O1) ionic liquid. A wide molality range has been explored in order to identify the optimal compositions in terms of conductivity and electrochemical stability. Our thermal results show that the solutions are amorphous independently on the LiTFSI content. Up to salt concentration of 0.4 mol kg−1 the solutions have a very low viscosity (η ∼ 36 cP), a high ionic conductivity, even at temperatures below 0 °C, and a good electrochemical stability. Cations transport numbers ranging between 0.05 and 0.39 have been determined as a function of LiTFSI content. The combination of these properties makes the PY1,2O1-based solutions potentially attractive liquid electrolytes for lithium batteries.

Excess properties for binary systems ionic liquid + ethanol: Experimental results and theoretical description using the ERAS model

Density, isobaric molar heat capacity and excess molar enthalpy were experimentally determined at atmospheric pressure for a set of binary systems of ionic liquids and ethanol. Density and heat capacity were obtained within the temperature range (293.15–318.15 K) whereas excess molar enthalpy was measured at 303.15 K; excess molar volume and excess molar isobaric heat capacity were calculated from experimental data. The Extended Real Associated Solution (ERAS) model is applied to extract information about the association capability of each ionic liquid with ethanol molecules through hydrogen bonds. The chemical nature of the anion is revealed as the main factor that determines the thermodynamic behavior of the studied systems.

Thermodynamic Modeling of the Phase Behavior of Binary Systems of Ionic Liquids and Carbon Dioxide with the Group Contribution Equation of State

The group contribution equation of state (GC-EOS) was applied to predict the phase behavior of binary systems of ionic liquids of the homologous families 1-alkyl-3-methylimidazolium hexafluorophosphate and tetrafluoroborate with CO2. Pure group parameters for the new ionic liquid functional groups [-mim][PF6] and [-mim][BF4] and interaction parameters between these groups and the paraffin (CH3, CH2) and CO2 groups were estimated. The GC-EOS extended with the new parameters was applied to predict high-pressure phase equilibria in binary mixtures of the ionic liquids [emim][PF6], [bmim][PF6], [hmim][PF6], [bmim][BF4], [hmim][BF4], and [omim][BF4] with CO2. The agreement between experimental and predicted bubble point data for the ionic liquids was excellent for pressures up to 20 MPa, and even for pressures up to about 100 MPa, the agreement was good. The results show the capability of the GC-EOS to describe phase equilibria of systems consisting of ionic liquids.

High-pressure phase behavior of the binary ionic liquid system 1-octyl-3-methylimidazolium tetrafluoroborate + carbon dioxide

This paper presents the high-pressure phase behavior of the binary system 1-octyl-3-methylimidazolium tetrafluoroborate ([omim][BF 4]) + carbon dioxide (CO 2) in the mole fraction range 0.1 < x C O 2 < 0.75 , and in the pressure and temperature range of 0.1–100 MPa and 303–363 K, respectively. High solubilities of CO 2 for x C O 2 < 0.6 were established at relatively low-pressure, while for x C O 2 > 0.6 a drastic increase of the equilibrium pressure was observed. From the experimental work, it could be concluded that, according to the Scott and Van Konynenburg classification of fluid phase equilibria, the system [omim][BF 4] + CO 2 most likely shows type-III fluid phase behavior.