Skip to main content
U.S. Department of Energy
Office of Scientific and Technical Information

Electric double layer capacitance for ionic liquids in nanoporous electrodes: Effects of pore size and ion composition

Journal Article · · Journal of Molecular Liquids
 [1];  [2];  [3];  [1]
  1. Univ. of California, Riverside, CA (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  3. Brigham Young Univ., Provo, UT (United States)

The energy density of an electric double layer (EDL) capacitor, a type of supercapacitor, depends on the ion distribution within the micropores of electrodes that are typically made of amorphous carbon. By using coarse-grained models and the classical density functional theory, we investigate the distributions of ionic species among different idealized nanopores in contact with an asymmetric ionic liquid mixture and the effects of the bulk electrolyte composition on capacitive energy storage. We find that a charged pore is always small-ion selective, provided all ions have the same valence and similar non-electrostatic interactions. While small ions enhance both the EDL capacitance and the accessibility of micropores, an ionic mixture containing ions of different sizes may yield a capacitance higher than those corresponding to pure ionic liquids. Furthermore, the increased capacitance may be attributed to more efficient ion packing near the charged surface. At certain conditions, the improvement is on a par with the anomalous capacitance rise for pure ionic liquids in electrodes with ultranarrow pores.

Research Organization:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Grant/Contract Number:
AC05-00OR22725
OSTI ID:
1557520
Alternate ID(s):
OSTI ID: 1470616
Journal Information:
Journal of Molecular Liquids, Journal Name: Journal of Molecular Liquids Journal Issue: C Vol. 270; ISSN 0167-7322
Publisher:
ElsevierCopyright Statement
Country of Publication:
United States
Language:
English

References (25)

Formulation of Ionic-Liquid Electrolyte To Expand the Voltage Window of Supercapacitors journal March 2015
Supercapacitors based on high-surface-area graphene journal January 2014
Density functional theory for differential capacitance of planar electric double layers in ionic liquids journal March 2011
High capacitance of coarse-grained carbide derived carbon electrodes journal February 2016
Structure and Nanostructure in Ionic Liquids journal June 2015
Structure and Dynamics of an Electrolyte Confined in Charged Nanopores journal March 2014
Real Ionic Solutions in the Mean Spherical Approximation. 1. Simple Salts in the Primitive Model journal January 1996
Solvent Effect on the Pore-Size Dependence of an Organic Electrolyte Supercapacitor journal June 2012
Theoretical interpretation of adsorption behavior of simple fluids in slit pores journal July 1993
Ion Correlations in Nanofluidic Channels: Effects of Ion Size, Valence, and Concentration on Voltage- and Pressure-Driven Currents journal January 2013
In Situ Monitoring of Diffuse Double Layer Structure Changes of Electrochemically Addressable Self-Assembled Monolayers with an Atomic Force Microscope journal April 1999
Oscillation of Capacitance inside Nanopores journal December 2011
Water in Ionic Liquids at Electrified Interfaces: The Anatomy of Electrosorption journal October 2014
Materials for electrochemical capacitors journal November 2008
Enhanced ordering reduces electric susceptibility of liquids confined to graphene slit pores journal June 2016
A classical density functional theory for interfacial layering of ionic liquids journal January 2011
Some exact results and the application of the mean spherical approximation to charged hard spheres near a charged hard wall journal December 1978
Analytical solution of the mean spherical approximation for an arbitrary mixture of ions in a dipolar solvent journal July 1987
Ion distribution and selectivity of ionic liquids in microporous electrodes journal May 2017
Mean spherical model for asymmetric electrolytes: I. Method of solution journal November 1975
Room-Temperature Ionic Liquids: Excluded Volume and Ion Polarizability Effects in the Electrical Double-Layer Structure and Capacitance journal September 2009
Double Layer in Ionic Liquids: Overscreening versus Crowding journal January 2011
Physics of Size Selectivity journal December 2005
Molecular Layering of Fluorinated Ionic Liquids at a Charged Sapphire (0001) Surface journal October 2008
Selective adsorption of ions in charged slit-systems journal January 2013

Cited By (3)


Similar Records

Oscillation of Capacitance inside Nanopores
Journal Article · Fri Dec 31 23:00:00 EST 2010 · Nano Letters · OSTI ID:1033160

Ion distribution and selectivity of ionic liquids in microporous electrodes [Ionic distribution and selectivity of ionic liquids in microporous electrodes]
Journal Article · Tue May 02 00:00:00 EDT 2017 · Journal of Chemical Physics · OSTI ID:1468250

Electrochemical Behavior of Nanoporous Supercapacitors with Oligomeric Ionic Liquids
Journal Article · Wed May 30 00:00:00 EDT 2018 · Journal of Physical Chemistry. C · OSTI ID:1566350