Novel hydrophobic cyclic sulfonium-based ionic liquids as potential electrolyte

A novel series of hydrophobic room temperature ionic liquids based on six cyclic sulfonium cations with TFSI− were synthesized and characterized. Their physical parameter (density and viscosity), electrochemical and thermal properties (electrochemical windows, conductivity, phase transition behavior and decomposition temperature) had been measured. Most of them showed low melting point (<−60 °C) and low viscosity and good conductivity (52 mPa s and 4.10 mS cm− 1 at 25 °C, respectively). Three kinds of phase transition behavior were observed from differential scanning calorimeter curves for these room temperature ionic liquids. The decomposition temperature of these hydrophobic room temperature ionic liquids was near to 80 °C higher than those hydrophilic ones. The result shows that these ionic liquids are suitable for electrochemical devices such as dye-sensitized solar cells even under some rigorous condition and it is an efficient method for improving ionic liquids' properties by modifying the structure of cyclic sulfonium.