Sub-Nanometer Pore Ion Sieving in Supercapacitors

Nanoporous carbon supercapacitor electrodes store charge by packing electrolyte ions into a vast internal network of pores. This simulator zooms into a single slit-shaped nanopore and models the ion-sieving effect that governs how much charge that pore can actually hold: an ion's real size in the electrolyte includes a shell of solvent molecules, and when the pore is narrower than that solvated diameter, the ion must shed some or all of that shell to squeeze through. Because the areal capacitance of the pore wall scales inversely with the distance from ion to wall, this forced desolvation moves the ion's charge closer to the surface and produces a real, counter-intuitive jump in capacitance as pores shrink below roughly one nanometer — the anomalous capacitance increase first reported for carbide-derived carbons. Switch electrolyte ions, dial the pore width down past the solvated and bare diameters, and watch both the 3D ion traffic and the live capacitance readout respond.