Competition of Desolvation and Stabilization of Organic Electrolytes in Extremely Narrow Nanopores

Organic electrolytes are widely used for electric double-layer capacitors. However, the molecular mechanism involved is far from being understood. We demonstrate the structures and stabilities of tetraethylammonium and tetrafluoroborate ions in propylene carbonate solution in carbon nanopores using Monte Carlo simulations. These ions were significantly desolvated at nanopore widths below 1.0 nm. The nanopore potential compensated for the loss of stability of the ions as a result of desolvation for nanopore widths of 0.7-1.2 nm for Et4N+ and 0.6-0.9 nm for BF4-. High-capacitance electrodes can therefore be obtained using such nanoporous carbons.