title: Superionic state in double-layer capacitors with nanoporous electrodes.
abstract: In recent experiments (Chmiola et al 2006 Science 313 1760; Largeot et al 2008 J. Am. Chem. Soc. 130 2730) an anomalous increase of the capacitance with a decrease of the pore size of a carbon-based porous electric double-layer capacitor has been observed. We explain this effect by image forces which exponentially screen out the electrostatic interactions of ions in the interior of a pore. Packing of ions of the same sign becomes easier and is mainly limited by steric interactions. We call this state 'superionic' and suggest a simple model to describe it. The model reveals the possibility of a voltage-induced first order transition between a cation(anion)-deficient phase and a cation(anion)-rich phase which manifests itself in a jump of capacitance as a function of voltage.
authors.affiliation: Department of Chemistry, Faculty of Natural Sciences, Imperial College London, SW7 2AZ, UK.
authors.forename: S
authors.initials: S
authors.lastname: Kondrat
authors.forename: A
authors.initials: A
authors.lastname: Kornyshev
mesh_terms: D025802:Electric Capacitance; D004566:Electrodes; D007477:Ions; D049329:Nanostructures / Q000737:chemistry*; D016062:Porosity
chemical_list: D007477:Ions