New Ionic Liquids Based On Tertiary Sulfoniums And Perfluoroalkyltrifluoroborates: Synthesis, Characterization And Properties

Ionic liquids (ILs) are fluid media comprised entirely of ions, and usually have amelting point at or below room temperature. In recent years, ILs have received broadinterest, because of their potential use as electrolytes for various electrochemical devices,such as lithium or lithium-ion batteries, dye-sensitized solar cells, and electrochemicalcapacitors. Compared with conventional organic solvents and nonaqueous liquidelectrolytes, ILs have many marked advantages, such as negligible volatility,non-flammability, high thermal stability, and wide liquid ranges, which may improve thesafety of electrochemical devices.In this paper, a new series of ionic liquids based on relatively small tertiarysulfonium cations ([R 1R2R3S]+, wherein R1, R2, R3 = CH3 or C2H5, R3 =CH2CH2OCH3,CH2CH2COOCH3) and perfluoroethyltrifluoroborates anion ([C2F5BF3]?) have beenprepared. Their chemical structures and compositions were characterized by 1H NMR, 19FNMR and elemental analysis. The important physicochemical and electrochemicalproperties of these salts have been measured, in terms of melting point, glass transition,viscosity, ionic conductivity, thermal and electrochemical stability. The influence ofstructure variation in the tertiary sulfonium cations on the above physicochemicalproperties is discussed. Among these new salts, most of them are liquids at roomtemperature and show the desirable properties, including low-melting points, lowviscosities, and high conductivities, while some of the salts are solid and exhibit plasticcrystalline phase in ambient-temperature region. All these desired properies make themuseful for energy devices.