Influence of Nanoporous Carbide-Derived Carbon Electrode Morphology on Charge Accumulation in Supercapacitors

Electrochemical devices that utilize ionic liquids and porous carbon electrode materials have garnered significant interest due to their promising characteristics. A thorough understanding of the charging mechanisms at the molecular level is essential to enhancing energy and power densities simultaneously. In this work, we simulated supercapacitors using realistic atomic models of electrodes and a room-temperature ionic liquid (RTIL) to investigate how the local environment within the electrodes affects the charge accumulated on the electrode atoms. Three atomistic models with realistic structural features of experimentally synthesized carbide-derived carbon (CDC) at different temperatures were generated following the annealing simulation methodology with an analytic bond-order potential (ABOP) force field. It was observed that the pore size distribution (PSD) of the CDC electrodes shifted to the right as the synthesis temperature increased. The results obtained from simulating supercapacitors with these electrode models indicated that counter-ions are strongly confined and isolated from co-ions in electrodes with smaller average pore sizes in supercapacitors than those with larger average pore sizes. This finding was supported by changes in the profiles of the coordination number and degree of confinement (DoC). However, electrodes with small pores limited the number of counter-ions that could be accommodated. In contrast, electrodes with larger average pore sizes permitted more counter-ions and facilitated faster diffusion within the electrode. As a result of these opposing trends─confinement and the number of adsorbed counter-ions─there was a peak in the accumulated charge for the electrode with an intermediate average pore size.