Kinetic
Charging Inversion in Ionic Liquid Electric
Double Layers
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Abstract
The
charging kinetics of electric double layers (EDLs) has a pivotal
role in the performance of a wide variety of nanostructured devices.
Despite the prevalent use of ionic liquids as the electrolyte, relatively
little is known on the charging behavior from a microscopic perspective.
Here, we study the charging kinetics of ionic liquid EDLs using a
classical time-dependent density functional theory that captures the
molecular excluded volume effects and electrostatic correlations.
By examining variations of the ionic density profiles and the charging
density in response to an electrode voltage, we find that at certain
conditions, the electrode charge shows a rapid surge in its initial
response, rises quickly to the maximum, and then slowly decays toward
equilibrium. The electrode charge and voltage may have opposite signs
when the cell width is commensurate with the layer-by-layer ionic
distributions. This unusual charging behavior can be explained in
terms of the oscillatory structure of ionic liquids near the electrodes