2D pores offer an optimal balance of charge storage and charging kinetics

Electrolyte-filled conducting nanopores are central to applications ranging from energy storage to neuromorphic computing, yet the influence of pore geometry and structure on ion confinement remains insufficiently understood. Here, we combine theoretical calculations and molecular simulations to investigate how nanopore charging depends on pore dimensionality and morphology, considering nanostructured electrodes comprising cylindrical (1D) and slit-shaped (2D) pores, as well as 3D disordered porous electrodes exemplified by a carbide-derived carbon (CDC) structure. We show that in 1D confinement, the equilibrium stored charge exhibits a non-monotonic dependence on pore size, whereas 2D pores generally provide higher charge and energy densities per unit surface area. Somewhat counterintuitively, charging dynamics in 2D pores can slow down with increasing pore size but remain substantially faster than in disordered 3D electrodes. Although counterion saturation at high cell voltages reduces the energy stored by subnanometer 2D pores relative to CDC electrodes, this limitation can be overcome by matching the pore width to the operating voltage. Overall, our results indicate that 2D pores offer an optimal balance between charge storage and charging kinetics, highlighting their potential for high-performance capacitive energy storage.