Elucidate confinement effect of pore defect in activated carbon supercapacitors by first-principles calculation

The performance of activated carbon-based supercapacitors is profoundly influenced by their nanoporous structure, yet the charge storage mechanisms within confined spaces remain incompletely understood. In this study, we construct fully self-passivated graphene pore defect models to simulate the orifice structure of KOH-activated activated carbon. Using first-principles calculations, we elucidate the confinement behavior of organic electrolyte components within the pores and identify three distinct confinement states from a thermodynamic perspective: surface adsorption, in-pore strong confinement, and in-pore weak confinement. Crucially, we discover that strong confinement induces specific adsorption behaviors, leading to molecular distortion and even decomposition of electrolytes (e.g., bond alteration in acetonitrile, decomposition of BF₄⁻). These phenomena may potentially enhance capacitance through induced pseudocapacitive effects, but also risk triggering side reactions that cause pore blockage and accelerated device failure. This work clarifies the dual role of the confinement effect at the atomic level, for both charge storage and device degradation, providing theoretical guidance for the design of high-performance carbon electrodes.