Ionic liquids based on S-alkylthiolanium cations and TFSI anion as potential electrolytes

New ionic liquids based on S-alkylthiolanium cations with TFSI anions were synthesized and characterized. The physical and electrochemical properties, including melting point, thermal stability, solubility, viscosity, conductivity and electrochemical window, were reported. Relation between these properties and the structure of the cations was discussed. In this series, T₄TFSI and T₅TFSI have melting points below −60°C, and their conductivities are 2.10 mS/cm and 1.46 mS/cm; their electrochemical windows are 4.1 V and 4.5 V at room temperature. These cyclic alkylthiolanium-based ionic liquids are promising as novel electrolytes in various electrochemical devices, especially under low temperature condition. Supported by National Key Project of China for Basic Research (Grant No. 2006CB202600), the National High Technology Research and Development Program of China (Grant No. 2007AA03Z222), and Technical Innovation Fund for Small and Medium-sized Enterprises of Jiangsu Province (Grant No. BC2007103). And be grateful to the Research Center of Analysis and Measurement of Shanghai Jiao Tong University for NMR Measurement.