A new asymmetric sulfonium-based ionic liquid, 1-butyldimethylsulfonium bis(trifluoromethylsulfonyl) imide (S114TFSI), was developed as electrolyte material for lithium secondary battery. Its cathodic po- tential was a little more positive against the Li/Li+, so vinylene carbonate (VC) was added into the LiTFSI/S114TFSI ionic liquid electrolyte to ensure the formation of a solid electrolyte interface (SEI), which effectively prevented the decomposition of the electrolyte. The properties of the Li/LiMn2O4 cell containing S114TFSI-based electrolyte were studied and the cycle performances were compared to those with a conventional organic electrolyte (1 mol/L LiPF6/DMC:EC=1:1(w/w)) at room temperature. Electrochemical impedance spectroscopy (EIS) and X-ray diffraction (XRD) were conducted to analyze the mechanisms affecting the cell performances at different temperatures. The lithium secondary bat- tery system, using the above ionic liquid electrolyte material, shows good cycle performances and good safety at room temperature, and is worthwhile to further investigate so as to find out the potential application.
New ionic liquids based on S-alkylthiolanium cations with TFSI anions were synthesized and charac-terized.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℃,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.
