Capillary Ionization and Jumps of Capacitive Energy Stored in Mesopores

We study ionic liquid-solvent mixtures in slit-shaped nanopores wider than a few ion diameters. Using a continuum theory and generic thermodynamic reasoning, we reveal that such systems can undergo a capillary ionization transition. At this transition, the pores spontaneously ionize or deionize upon infinitesimal changes of temperature, slit width, or voltage. Our calculations show that a voltage applied to a pore may induce a capillary ionization, which-counterintuitively-is followed by a re-entrant deionization as the voltage increases. We find that such ionization transitions produce sharp jumps in the accumulated charge and stored energy, which may find useful applications in energy storage and heat-to-energy conversion.

Automated summary

Ionic liquid-solvent mixtures in slit-shaped nanopores wider than a few ion diameters can undergo a capillary ionization transition, where the pores spontaneously ionize or deionize upon infinitesimal changes of temperature, slit width, or voltage. Interestingly, a voltage applied to a pore may induce capillary ionization followed by re-entrant deionization as the voltage increases. These ionization transitions can result in sharp jumps in accumulated charge and stored energy, which may have useful applications in energy storage and heat-to-energy conversion.