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

Abstract

In this contribution, we report on a novel composite solid electrolyte material, SiO2/[BMIM]BF4/LiTf ([BMIM]BF4 = 1-butyl-3-methylimidazolium tetrafluoroborate, LiTf = lithium trifluoromethanesulfonate), prepared via a one-pot sol−gel synthesis route, in which the amorphous SiO2 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 SiO2 network is found to increase with the [BMIM]BF4/LiTf ratio, exhibiting an almost liquidlike mobility, as evidenced by multinuclear solid-state NMR, pulsed-field-gradient solid-state NMR, and impedance spectroscopy.