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Title: Partial breaking of the Coulombic ordering of ionic liquids confined in carbon nanopores

Abstract

Ionic liquids are composed of equal quantities of positive and negative ions. In the bulk, electrical neutrality occurs in these liquids due to Coulombic ordering, in which ion shells of alternating charge form around a central ion. Their structure under confinement is far less well understood. This hinders the widespread application of ionic liquids in technological applications. Here we use scattering experiments to resolve the structure of a widely used ionic liquid (EMI–TFSI) when it is confined inside nanoporous carbons. We show that Coulombic ordering reduces when the pores can accommodate only a single layer of ions. Instead, equally charged ion pairs are formed due to the induction of an electric potential of opposite sign in the carbon pore walls. This non-Coulombic ordering is further enhanced in the presence of an applied external electric potential. Furthermore, this finding opens the door for the design of better materials for electrochemical applications.

Authors:
 [1];  [2];  [3];  [4];  [5]; ORCiD logo [6];  [7];  [8];  [1]
  1. Shinshu Univ., Nagano-City (Japan)
  2. Shinshu Univ., Nagano-City (Japan); Shinshu Univ., Matsumoto-City (Japan)
  3. Shinshu Univ., Matsumoto-City (Japan)
  4. Shinshu Univ., Nagano-City (Japan); Drexel Univ., Philadelphia, PA (United States)
  5. Loughborough Univ., Leicestershire (United Kingdom); The Univ. of Adelaide, South Australia (Australia)
  6. Sorbonne Univ., Paris (France); Reseau sur le Stockage Electrochimique de l'Energie (France)
  7. Univ. Paul Sabatier, Toulouse Cedex (France); Marion Technologies, Verniolle (France)
  8. Shinshu Univ., Nagano-City (Japan); Reseau sur le Stockage Electrochimique de l'Energie (France); Univ. Paul Sabatier, Toulouse Cedex (France)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1480605
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Accepted Manuscript
Journal Name:
Nature Materials
Additional Journal Information:
Journal Volume: 16; Journal Issue: 12; Journal ID: ISSN 1476-1122
Publisher:
Springer Nature - Nature Publishing Group
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Futamura, Ryusuke, Iiyama, Taku, Takasaki, Yuma, Gogotsi, Yury, Biggs, Mark J., Salanne, Mathieu, Ségalini, Julie, Simon, Patrice, and Kaneko, Katsumi. Partial breaking of the Coulombic ordering of ionic liquids confined in carbon nanopores. United States: N. p., 2017. Web. doi:10.1038/NMAT4974.
Futamura, Ryusuke, Iiyama, Taku, Takasaki, Yuma, Gogotsi, Yury, Biggs, Mark J., Salanne, Mathieu, Ségalini, Julie, Simon, Patrice, & Kaneko, Katsumi. Partial breaking of the Coulombic ordering of ionic liquids confined in carbon nanopores. United States. doi:10.1038/NMAT4974.
Futamura, Ryusuke, Iiyama, Taku, Takasaki, Yuma, Gogotsi, Yury, Biggs, Mark J., Salanne, Mathieu, Ségalini, Julie, Simon, Patrice, and Kaneko, Katsumi. Mon . "Partial breaking of the Coulombic ordering of ionic liquids confined in carbon nanopores". United States. doi:10.1038/NMAT4974. https://www.osti.gov/servlets/purl/1480605.
@article{osti_1480605,
title = {Partial breaking of the Coulombic ordering of ionic liquids confined in carbon nanopores},
author = {Futamura, Ryusuke and Iiyama, Taku and Takasaki, Yuma and Gogotsi, Yury and Biggs, Mark J. and Salanne, Mathieu and Ségalini, Julie and Simon, Patrice and Kaneko, Katsumi},
abstractNote = {Ionic liquids are composed of equal quantities of positive and negative ions. In the bulk, electrical neutrality occurs in these liquids due to Coulombic ordering, in which ion shells of alternating charge form around a central ion. Their structure under confinement is far less well understood. This hinders the widespread application of ionic liquids in technological applications. Here we use scattering experiments to resolve the structure of a widely used ionic liquid (EMI–TFSI) when it is confined inside nanoporous carbons. We show that Coulombic ordering reduces when the pores can accommodate only a single layer of ions. Instead, equally charged ion pairs are formed due to the induction of an electric potential of opposite sign in the carbon pore walls. This non-Coulombic ordering is further enhanced in the presence of an applied external electric potential. Furthermore, this finding opens the door for the design of better materials for electrochemical applications.},
doi = {10.1038/NMAT4974},
journal = {Nature Materials},
number = 12,
volume = 16,
place = {United States},
year = {2017},
month = {9}
}

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Works referenced in this record:

Ionic-liquid materials for the electrochemical challenges of the future
journal, July 2009

  • Armand, Michel; Endres, Frank; MacFarlane, Douglas R.
  • Nature Materials, Vol. 8, Issue 8, p. 621-629
  • DOI: 10.1038/nmat2448