Impedance resonance in narrow confinement

TL;DR

This paper investigates the AC response of a narrow electrolyte capacitor, revealing a hidden impedance resonance caused by ion condensation and coherent ion motion under large voltage amplitudes.

Contribution

It introduces a detailed dynamic density functional theory model for narrow electrolyte capacitors and uncovers a previously unknown impedance resonance phenomenon.

Findings

Revealed a hidden impedance resonance in narrow electrolyte capacitors.

Identified ion condensation and coherent ion motion as key mechanisms.

Used a single ion analogue to interpret the resonance phenomenon.

Abstract

The article explores the ion flux response of a capacitor configuration to an alternating voltage. The model system comprises a symmetric binary electrolyte confined between plan-parallel capacitor plates. The AC response is investigated for the sparsely studied albeit practically important case of a large amplitude voltage applied across a narrow device, with the distance between the two plates amounting to a few ion diameters. Dynamic density functional theory is employed to solve for the spatiotemporal ion density distribution as well as the transient ion flux and complex impedance of the system. The analysis of these properties reveals a hitherto hidden impedance resonance. A single ion analogue of the capacitor, which is equivalent to neglecting all interactions between the ions, is employed for a physical interpretation of this phenomenon. It explains the resonance as a consequence of field-induced ion condensation at the capacitor plates and coherent motion of condensed ions in response to the field variation.