Ionic Liquid/Non-Ionic Surfactant Mixtures as Versatile, Non-Volatile Electrolytes: Double-Layer Capacitance and Conductivity

Ionic liquids (ILs) are being increasingly used as processing aids to formulate electrode/electrolyte composites where the electrolyte acts as a template, defining the effective electrolyte-filled pore space between 2D materials such as graphene and MXenes. This is often facilitated with non-ionic surfactants. However, little is currently known about how these surfactants impact double-layer formation and ionic conductivity. Herein, we measure these properties for two commonly used non-ionic surfactants, P123 and Triton X-100 (TX-100) mixed with the IL, 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide (EMImTFSI). A significant increase in the minimum capacitance is observed at 40 wt% surfactant by up to 88% and 102% for P123 and TX-100, respectively. On the other hand, the higher viscosity of the mixtures, lowers the ionic conductivity from 8.5 mS cm− 1 (neat IL) to 1 mS cm− 1 (40 wt% surfactant …