Effect of Nitrile-Functionalization of Imidazolium-Based Ionic Liquids on Their Transport Properties, Both Pure and Mixed with Lithium Salts

Abstract

The influence of the presence of a nitrile group in the cation of imidazolium-based ionic liquids on their transport properties was investigated. As these liquids can be used as electrolytes in lithium ion batteries, their mixtures with lithium salts were also considered. 1-Butyl-3-methylimidazolium bis(trifluoromethylsulphonyl)imide, [C1C4Im][NTf2], 1-butylnitril-3-methylimidazolium bis(trifluoromethylsulphonyl)imide, [C1C3CNIm][NTf2], and their mixtures with bis(trifluoromethylsulphonyl)imide lithium, Li[NTf2], were studied. Their mass transport properties (viscosity, ionic conductivity, self-diffusion) were experimentally determined. NMR spectroscopy was also used to explore molecular organization and interactions in these systems. The addition of a cyano group increases the viscosity and the ionicity of the liquid. The effect of lithium ion is more pronounced on [C1C3CNIm][NTf2], with interactions between Li+ and the nitrile group.