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Charging dynamics of electric double layer capacitors including beyond-mean-field electrostatic correlations
David Fertig1, Mathijs Janssen1
1Norwegian University of Life Sciences, Institute of Physics, Ås, Norway.
Physical Review. E
|September 16, 2025
Summary
Beyond-mean-field Coulombic interactions significantly impact electric double layer (EDL) formation in supercapacitors. These interactions slow down ion movement in confined electrolytes, affecting charging times.
Area of Science:
- Electrochemistry
- Physical Chemistry
- Condensed Matter Physics
Background:
- Electric double layer (EDL) formation is crucial for supercapacitors and electrochemical devices.
- Beyond-mean-field Coulombic interactions become significant in concentrated or multivalent ion electrolytes.
Purpose of the Study:
- To investigate the effect of beyond-mean-field Coulombic interactions on EDL formation between two parallel electrodes.
- To model the charging dynamics of electrolytes considering correlation length.
Main Methods:
- Combined Nernst-Planck and Bazant-Storey-Kornyshev (BSK) equations.
- Analyzed the characteristic charging timescale (τ) dependence on correlation length (ℓc).
Main Results:
- The charging timescale (τ) exhibits non-monotonic dependence on correlation length (ℓc).
- For small ℓc, τ decreases with increasing ℓc, consistent with dilute electrolyte models.
- Beyond a critical ℓc, τ increases and eventually plateaus, indicating slower ion movement in strongly correlated, confined electrolytes.
Conclusions:
- Beyond-mean-field interactions significantly alter EDL charging dynamics.
- The study provides a more accurate model for ion behavior in confined electrolytes, like ionic liquids.
- Results suggest slower ion mobility than previously predicted in such systems.
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