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Relation between the Ion Size and Pore Size for an Electric Double-Layer Capacitor

Largeot, Céline and Portet, Christele and Chmiola, John and Taberna, Pierre-Louis and Gogotsi, Yury and Simon, Patrice Relation between the Ion Size and Pore Size for an Electric Double-Layer Capacitor. (2008) Journal of American Chemical Society, vol. 130 (n° 9). pp. 2730-3731. ISSN 0002-7863

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Official URL: http://dx.doi.org/10.1021/ja7106178

Abstract

The research on electrochemical double layer capacitors (EDLC), also known as supercapacitors or ultracapacitors, is quickly expanding because their power delivery performance fills the gap between dielectric capacitors and traditional batteries. However, many fundamental questions, such as the relations between the pore size of carbon electrodes, ion size of the electrolyte, and the capacitance have not yet been fully answered. We show that the pore size leading to the maximum double-layer capacitance of a TiC-derived carbon electrode in a solvent-free ethyl-methylimmidazolium-bis(trifluoro-methane-sulfonyl)imide (EMI-TFSI) ionic liquid is roughly equal to the ion size (0.7 nm). The capacitance values of TiC−CDC produced at 500 °C are more than 160 F/g and 85 F/cm3 at 60 °C, while standard activated carbons with larger pores and a broader pore size distribution present capacitance values lower than 100 F/g and 50 F/cm3 in ionic liquids. A significant drop in capacitance has been observed in pores that were larger or smaller than the ion size by just an angstrom, suggesting that the pore size must be tuned with sub-angstrom accuracy when selecting a carbon/ion couple. This work suggests a general approach to EDLC design leading to the maximum energy density, which has been now proved for both solvated organic salts and solvent-free liquid electrolytes.

Item Type:Article
Additional Information:Thanks to American Chemical Society editor. The definitive version is available at http://pubs.acs.org The original PDF of the article can be found at Journal of the American Chemical Society website : http://pubs.acs.org/journal/jacsat
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution: Université de Toulouse > Institut National Polytechnique de Toulouse - INPT
Université de Toulouse > Université Paul Sabatier-Toulouse III - UPS
French research institutions > Centre National de la Recherche Scientifique - CNRS
Other partners > Drexel University (USA)
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Deposited By: Celine Cabaup
Deposited On:03 Jun 2009 12:27

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