Issue 39, 2014

An electrochemical in situ study of freezing and thawing of ionic liquids in carbon nanopores

Abstract

Room temperature ionic liquids (RTILs) are an emerging class of electrolytes enabling high cell voltages and, in return, high energy density of advanced supercapacitors. Yet, the low temperature behavior, including freezing and thawing, is little understood when ions are confined in the narrow space of nanopores. This study shows that RTILs may show a tremendously different thermal behavior when comparing bulk with nanoconfined properties as a result of the increased surface energy of carbon pore walls. In particular, a continuous increase in viscosity is accompanied by slowed-down charge–discharge kinetics as seen with in situ electrochemical characterization. Freezing reversibly collapses the energy storage ability and thawing fully restores the initial energy density of the material. For the first time, a different thermal behavior in positively and negatively polarized electrodes is demonstrated. This leads to different freezing and melting points in the two electrodes. Compared to bulk, RTILs in the confinement of electrically charged nanopores show a high affinity for supercooling; that is, the electrode may freeze during heating.

Graphical abstract: An electrochemical in situ study of freezing and thawing of ionic liquids in carbon nanopores

Supplementary files

Article information

Article type
Communication
Submitted
21 Jun 2014
Accepted
22 Aug 2014
First published
26 Aug 2014
This article is Open Access
Creative Commons BY license

Phys. Chem. Chem. Phys., 2014,16, 21219-21224

An electrochemical in situ study of freezing and thawing of ionic liquids in carbon nanopores

D. Weingarth, R. Drumm, A. Foelske-Schmitz, R. Kötz and V. Presser, Phys. Chem. Chem. Phys., 2014, 16, 21219 DOI: 10.1039/C4CP02727B

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