Thermophysical Properties of Ionic Liquid–LiX Mixtures

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Date

2009-07-16

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Abstract

Ionic liquids (ILs) have attracted strong interest due to their high chemical, thermal and electrochemical stability; wide liquid range; high ionic conductivity and low volatility. The research objective of this project has been to explore the thermophysical properties of ILs and their mixtures with lithium salts (LiX). These mixtures may become the electrolyte materials essential for the success of safer, high-voltage next-generation lithium batteries targeted for plug-in hybrid electric vehicles (PHEVs) and/or electric vehicles (EVs). At present, there is only a limited amount of data available in the literature regarding the thermal stability and phase behavior of IL-LiX electrolytes. Such information, however, is crucial for determining the electrolyte safety characteristics and useful operating temperature range, as well as for clarifying the composition-temperature relationship for other properties such as ionic conductivity. The thermal phase behavior, thermal stability and other properties (viscosity and density) are reported here for the neat ILs containing 1-alkyl-3-methylimidazolium (IM10R+, R = 1, 2 and 4 for methyl, ethyl and butyl, respectively) or N-alkyl-N-methylpyrrolidinium (PY1R+, R = 3-5) cations with TFSI- or FSI- anions, as well as their mixtures with LiTFSI or LiFSI salts. Three components electrolytes (1-x) PY14TFSI-(x) PY13FSI-LiX mixtures (X = TFSI- and PF6-) have also been examined. Such electrolytes show great promise for meeting the strick demands in properties necessary to achieve the superb Li battery performance and longevity required for the successful widespread use of PHEVs and/or EVs.

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Keywords

Ionic Liquid; Li salt; thermophysical properties

Citation

Degree

MS

Discipline

Chemical Engineering

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