Novel Ternary Composite Electrolytes: Li Ion Conducting Ionic Liquids in Silica Glass

In this contribution, we report on a novel composite solid electrolyte material, SiO 2 /[BMIM]BF 4 /LiTf ([BMIM]BF 4 = 1-butyl-3-methylimidazolium tetrafluoroborate, LiTf = lithium trifluoromethanesulfonate), prepared via a one-pot sol−gel synthesis route, in which the amorphous SiO 2 glass network provides the mechanical stability and the ionic liquid/Li salt part the high ionic conductivity (0.5 × 10 −2 S cm −1 at 298 K). The mobility of the ionic liquid and Li salt confined within the pores of the fully condensed SiO 2 network is found to increase with the [BMIM]BF 4 /LiTf ratio, exhibiting an almost liquidlike mobility, as evidenced by multinuclear solid-state NMR, pulsed-field-gradient solid-state NMR, and impedance spectroscopy.