Physical and electrochemical properties of lithium-doped 1-butyl-3-methylimidazolium salts

摘要

Two well known room temperature ionic liquids (RTILs), l-butyl-3-methylimidazolium tetrafluoroborate ([BMIm][BF_4]) and l-butyl-3-methylimidazolium iodide ([BMIm][I]), were synthesized. Their physical properties such as reflective indices, densities, viscosities, heat capacities, and heats of dilution were measured. The overall properties of [BMIm][BF_4] obtained after two-step reactions were superior to those of the IL with a halide anion. The incorporation of lithium ions using lithium tetrafluoroborate (LiBF_4) in each IL was carried out and ionic conductivities as a function of temperature and Li ion concentration were investigated. The isothermal conductivity graph showed a parabolic curve shape suggesting that the maximum values exist at a specific concentration condition while they continuously increased as the temperature increased. The conductivities reached as high as 10~(-3) S·cm~(-1).