Capillary Condensation of Ionic Liquid Solutions in Porous Electrodes

We use classical density functional theory to investigate room temperature ionic liquid + solvent mixtures in porous electrodes. We consider those mixtures that display a miscibility gap in the bulk fluid and hence have the capacity to undergo capillary condensation in pores which preferentially attract the ionic liquid component. A novel aspect of this transition is that, when the system is at or near the critical point for this transition, we find an extraordinary increase in the capacitance, which derives from the fact that the capacitance is a thermodynamic response function, diverging at spinodal points.