In the research of modern electrochemical energy storage, ultra-high power capacitors, and electroactive actuators, achieving efficient storage and rapid transmission of charges is a core physical issue. When ionic liquids (Ionic Liquids, ILs) - a type of non-volatile molten salt composed entirely of cations and anions and in a liquid state at room temperature - are introduced into the carbon or graphene aerogels with three-dimensional conductive nanochannel networks, an electroactive aerogel composite system is formed. In this system, the cations and anions in the ionic liquids interact strongly with the high specific surface area nanochannel walls of the conductive aerogels, forming complex double-layer (Electric Double Layer, EDL) capacitance coupling dynamics within the nanometer-sized pores.
Unlike traditional liquid electrolyte solutions, ionic liquids do not contain any conventional organic solvents and are entirely composed of high-density independent ions. When an external potential difference is applied to the electroactive aerogel, the charged carbon aerogel nanoskeleton will rapidly induce an equal amount of opposite charges on its surface. To balance these surface charges, the anions or cations in the ionic liquids will undergo directional migration driven by the electric field and penetrate deeply into the micropores of the aerogel, which are only a few nanometers wide.
Within the nanoscale confined space, the arrangement of ions and the chemical state of the solvent have undergone a qualitative change. Due to the aerogel pore size being at the same order of magnitude as the ion size (nanometer scale), the adsorption of ions on the surface of the pore walls often presents a "highly ordered layered packing" (Layered Ion Packing), and even the superionic state (Superionic State) phenomenon may occur. This double-layer capacitance coupling process within the confined space breaks the traditional Gouy-Chapman double-layer theoretical model of flat electrodes and requires the introduction of microscopic electrochemical statistical mechanics models including ion hard sphere repulsion effects and local density functional theory (DFT) to describe it.
From a kinetic perspective, the three-dimensional interconnected mesoporous network of the aerogel provides a low-resistance "fast ion highway" for the rapid diffusion of ionic liquids, while the micropores provide a vast storage capacity for the double-layer charges. This "mesoporous transport, microporous storage" synergy mechanism enables electroactive aerogel supercapacitors to maintain excellent power density and cycle stability even at extremely high charging and discharging current densities (up to several hundred $text{A/g}$). By precisely controlling the chemical structure of the ionic liquid and the matching degree of the aerogel micropore diameter, materials physicists can push the capacitance performance of the electrochemical double layer to the physical limit.