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On the molecular origin of supercapacitance in nanoporous carbon electrodes


Lightweight, low-cost supercapacitors with the capability of rapidly storing a large amount of electrical energy can contribute to meeting continuous energy demands and effectively levelling the cyclic nature of renewable energy sources1. The excellent electrochemical performance of supercapacitors is due to a reversible ion adsorption in porous carbon electrodes. Recently, it was demonstrated that ions from the electrolyte could enter sub nanometre pores, greatly increasing the capacitance2,3,4. However, the molecular mechanism of this enhancement remains poorly understood. Here we provide the first quantitative picture of the structure of an ionic liquid adsorbed inside realistically modelled microporous carbon electrodes. We show how the separation of the positive and negative ions occurs inside the porous disordered carbons, yielding much higher capacitance values (125 F g−1) than with simpler electrode geometries5. The proposed mechanism opens the door for the design of materials with improved energy storage capabilities. It also sheds new light on situations where ion adsorption in porous structures or membranes plays a role.

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Figure 1: The EDLC simulation cell.
Figure 2: Typical structure of the ionic liquid inside electrified pores of the CDC-1200 material.
Figure 3: Density profiles normal to the electrode surface for graphite and CDC materials.
Figure 4: Influence of the material local structure on the charging of the carbon atoms.


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We acknowledge the support of the French Agence Nationale de la Recherche (ANR) under Grant ANR-2010-BLAN-0933-02 (‘Modelling the Ion Adsorption in Carbon Micropores’). We are grateful for the computing resources on Hector (UK National HPC) provided by EPSRC through the UKCP consortium. Y.G. is supported by the US National Science Foundation under International Collaborations in Chemistry Grant No. 0924570. P.S. and Y.G. thank the Partner University Fund (PUF) for funding their collaborative efforts. We thank J. C. Palmer and K. Gubbins for providing us the raw data from ref. 21.

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C.M., B.R., P.A.M. and M.S. designed the research. C.M. carried out simulations. All authors contributed to the analysis and discussion of the data and writing the manuscript.

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Correspondence to Mathieu Salanne.

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The authors declare no competing financial interests.

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Merlet, C., Rotenberg, B., Madden, P. et al. On the molecular origin of supercapacitance in nanoporous carbon electrodes. Nature Mater 11, 306–310 (2012).

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