Lithium cation conducting TDI anion-based ionic liquids

Leszek Niedzicki; Ewelina Karpierz; Maciej Zawadzki; Maciej Dranka; Marta Kasprzyk; Aldona Zalewska; Marek Marcinek; Janusz Zachara; Urszula Domańska; Władysław Wieczorek

doi:10.1039/C3CP55354J

Lithium cation conducting TDI anion-based ionic liquids†

Leszek Niedzicki,*^a Ewelina Karpierz,^a Maciej Zawadzki,^b Maciej Dranka,^a Marta Kasprzyk,^a Aldona Zalewska,^a Marek Marcinek,^a Janusz Zachara,^a Urszula Domańska^b and Władysław Wieczorek^a

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^a Warsaw University of Technology, Faculty of Chemistry, Department of Inorganic Chemistry and Solid State Technology, Noakowskiego 3, 00664 Warsaw, Poland
E-mail: lniedzicki@ch.pw.edu.pl
Fax: +48 22 628 2741
Tel: +48 22 234 7421

^b Warsaw University of Technology, Faculty of Chemistry, Department of Physical Chemistry, Noakowskiego 3, 00664 Warsaw, Poland

Abstract

In this paper we present the synthesis route and electrochemical properties of new class of ionic liquids (ILs) obtained from lithium derivate TDI (4,5-dicyano-2-(trifluoromethyl)imidazolium) anion. ILs synthesized by us were EMImTDI, PMImTDI and BMImTDI, i.e. TDI anion with 1-alkyl-3-methylimidazolium cations, where alkyl meant ethyl, propyl and butyl groups. TDI anion contains fewer fluorine atoms than LiPF₆ and thanks to C–F instead of P–F bond, they are less prone to emit fluorine or hydrogen fluoride due to the rise in temperature. Use of IL results in non-flammability, which is making such electrolyte even safer for both application and environment. The thermal stability of synthesized compounds was tested by DSC and TGA and no signal of decomposition was observed up to 250 °C. The LiTDI salt was added to ILs to form complete electrolytes. The structures of tailored ILs with lithium salt were confirmed by X-ray diffraction patterns. The electrolytes showed excellent properties regarding their ionic conductivity (over 3 mS cm⁻¹ at room temperature after lithium salt addition), lithium cation transference number (over 0.1), low viscosity and broad electrochemical stability window. The ionic conductivity and viscosity measurements of pure ILs are reported for reference.

Physical Chemistry Chemical Physics

Lithium cation conducting TDI anion-based ionic liquids†

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Lithium cation conducting TDI anion-based ionic liquids

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