Charge Oscillations in Ionic Liquids: A Microscopic Cluster Model

Abstract

In spite of their enormous applications as alternative energy storage devices and lubricants, room temperature ionic liquids (ILs) still pose many challenges from a pure scientific view point. We develop an IL microscopic theory in terms of ionic clusters, which describes the IL behavior close to charged interfaces. The full structure factor of finite-size clusters is considered and allows us to retain fine and essential details of the system as a whole. Beside the reduction in the screening, it is shown that ionic clusters cause the charge density to oscillate near charged boundaries, with alternating ion-size thick layers, in agreement with experiments. We distinguish between short-range oscillations that persist for a few ionic layers close to the boundary, as opposed to long-range damped oscillations that hold throughout the bulk. The former can be captured by finite-size ion pairs, while the latter is associated with larger clusters with pronounced quadrupole (or higher) moment. The long-wavelength limit of our theory recovers the well-known Bazant-Storey-Kornyshev (BSK) equation in the linear regime, and elucidates the microscopic origin of the BSK phenomenological parameters.

8 pages, 6 figures

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• The Electrostatic Screening Length in Concentrated Electrolytes Increases with Concentration
• Underscreening in concentrated electrolytes
• Are Room Temperature Ionic Liquids Dilute Electrolytes?
• Structural interactions in ionic liquids linked to higher order Poisson-Boltzmann equations
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Cited by in corpus (1)

• Statistical field theory of ion-molecular solutions