Enhanced Electrical Conductivity of Imidazolium-Based Ionic Liquids Mixed with Carbon Nanotubes: A Spectroscopic Study

We studied imidazolium-based ionic liquids mixed with multiwall carbon nanotubes using impedance spectroscopy and nuclear magnetic resonance.The results show a percolation threshold below 1 wt% of carbon nanotubes, which, due to their high dispersibility in imidazolium-based ionic liquids, is 3-to 8-fold lower than the percolation threshold for carbon nanotubes in typical organic solvents.The addition of carbon nanotubes appears to polarize their interface with imidazolium-based ionic liquids and increases the diffusion coefficient of the anions up to 35%, which is likely due to weak van der Waals interactions between the carbon nanotube walls and the cations.These effects produce a 3-to 5-fold increase in electrical conductivity of the electrolyte mixture, at carbon nanotube concentrations that are under the threshold for percolation.