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Capacitance of Nanoporous Carbon-Based Supercapacitors Is a Trade-Off between the Concentration and the Separability of the Ions

Burt, Ryan and Breitsprecher, Konrad and Daffos, Barbara and Taberna, Pierre-Louis and Simon, Patrice and Birkett, Greg and Zhao, X. S. and Holm, Christian and Salanne, Mathieu Capacitance of Nanoporous Carbon-Based Supercapacitors Is a Trade-Off between the Concentration and the Separability of the Ions. (2016) The Journal of Physical Chemistry Letters, 7 (19). 4015-4021. ISSN 1948-7185

(Document in English)

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Official URL: http://dx.doi.org/10.1021/acs.jpclett.6b01787


Nanoporous carbon-based supercapacitors store electricity through adsorption of ions from the electrolyte at the surface of the electrodes. Room temperature ionic liquids, which show the largest ion concentrations among organic liquid electrolytes, should in principle yield larger capacitances. Here, we show by using electrochemical measurements that the capacitance is not significantly affected when switching from a pure ionic liquid to a conventional organic electrolyte using the same ionic species. By performing additional molecular dynamics simulations, we interpret this result as an increasing difficulty of separating ions of opposite charges when they are more concentrated, that is, in the absence of a solvent that screens the Coulombic interactions. The charging mechanism consistently changes with ion concentration, switching from counterion adsorption in the diluted organic electrolyte to ion exchange in the pure ionic liquid. Contrarily to the capacitance, in-pore diffusion coefficients largely depend on the composition, with a noticeable slowing of the dynamics in the pure ionic liquid.

Item Type:Article
Additional Information:Thanks to ACS editor. The definitive version is available at http://pubs.acs.org/ The original PDF of the article can be found at The Journal of Physical Chemistry Letters website : http://pubs.acs.org/journal/jpclcd
HAL Id:hal-01494252
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Commissariat à l'Energie Atomique et aux énergies alternatives - CEA (FRANCE)
French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)
Other partners > Université Paris 1 Panthéon-Sorbonne (FRANCE)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UT3 (FRANCE)
Other partners > Universität Stuttgart (GERMANY)
Other partners > Université Paris-Sud 11 (FRANCE)
Other partners > University of Queensland - UQ (AUSTRALIA)
Laboratory name:
The Australia Research Council (ARC) - French National Research Agency (Labex STORE-EX - EoCoE
Deposited On:23 Mar 2017 08:19

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