Understanding Dynamics of Electrochemical Double Layers via a Modified Concentrated Solution Theory

Abstract

Understanding the dynamics of an electrochemical double layer (EDL) is of fundamental importance to a wide array of electrochemical energy devices. We develop in this study a modified concentrated solution theory to simulate EDL dynamics in the concentrated regime, in which the driving force of ion transport in EDL is derived from a free energy functional that considers ion size effect, short-range correlations, and solvent polarization. The model features a mobility matrix with non-zero off-diagonal elements due to short-range correlations. Model results are compared with molecular dynamic simulations and surface force measurement for an EDL in ionic liquids. The model gives out insights into how the ion size, various short-range correlations, and the solvent polarization affect the charging dynamics. The model is instrumental to design, optimization and control of high-power electrochemical devices.