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In Situ NMR Spectroscopy of Supercapacitors: Insight into the Charge Storage Mechanism

Wang, Hao and Forse, Alexander C. and Griffin, John M. and Trease, Nicole M. and Trognko, Lorie and Taberna, Pierre-Louis and Simon, Patrice and Grey, Clare P. In Situ NMR Spectroscopy of Supercapacitors: Insight into the Charge Storage Mechanism. (2013) Journal of the American Chemical Society, 135 (50). 18968-18980. ISSN 0002-7863

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Official URL: http://dx.doi.org/10.1021/ja410287s

Abstract

Electrochemical capacitors, commonly known as supercapacitors, are important energy storage devices with high power capabilities and long cycle lives. Here we report the development and application of in situ nuclear magnetic resonance(NMR) methodologies to study changes at the electrode−electrolyte interface in working devices as they charge and discharge. For a supercapacitor comprising activated carbon electrodes and an organic electrolyte, NMR experiments carried out at different charge states allow quantification of the number of charge storing species and show that there are at least two distinct charge storage regimes. At cell voltages below 0.75 V, electrolyte anions are increasingly desorbed from the carbon micropores at the negative electrode, while at the positive electrode there is little change in the number of anions that are adsorbed as the voltage is increased. However, above a cell voltage of 0.75 V, dramatic increases in the amount of adsorbed anions in the positive electrode are observed while anions continue to be desorbed at the negative electrode. NMR experiments with simultaneous cyclic voltammetry show that supercapacitor charging causes marked changes to the local environments of charge storing species, with periodic changes of their chemical shift observed. NMR calculations on a model carbon fragment show that the addition and removal of electrons from a delocalized system should lead to considerable increases in the nucleus-independent chemical shift of nearby species, in agreement with our experimental observations.

Item Type:Article
Additional Information:Thanks to ACS editor. The original publication is available at http://pubs.acs.org
HAL Id:hal-01116492
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - INPT (FRANCE)
Other partners > University of Cambridge (UNITED KINGDOM)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UPS (FRANCE)
Other partners > Stony Brook University (USA)
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Deposited By: cirimat webmestre
Deposited On:10 Apr 2014 12:54

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