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Nonclassical interfacial response in ionic liquids at blocking electrodes

Mahdi Yavarian1,* and Roderick Melnik2

  • *Contact author: mahdi.yavarian@uwaterloo.ca
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Phys. Rev. E 114, 015502 – Published 6 July, 2026

DOI: https://doi.org/10.1103/t4q8-tf6w

Abstract

The linear response of a symmetric binary ionic liquid confined between two parallel, blocking electrodes is analyzed under the influence of electrostatic correlations Lc while systematically comparing the effects of two distinct interfacial boundary conditions: the Bazant–Storey–Kornyshev (BSK) boundary condition, corresponding to the vanishing correlation limit, and the de Souza-Bazant (dSB) boundary condition, which incorporates finite electrostatic correlation effects at charged electrode surfaces. In contrast to conventional weakly nonlinear models involving thin-double-layer scalings based on small parameters λD/L≪1 or λDLc/L≪1, where λD denotes the Debye screening length and L is the half-cell thickness, the present formulation accommodates double layers of arbitrary width. Using matched asymptotic expansions at leading order, both the frequency-dependent response and the equilibrium response are derived in the asymptotic limit ɛ=Lc/L≪1. This separation of length scales gives rise to interfacial dynamics and equilibrium characteristics that are not captured by standard Debye-based asymptotic models. In particular, the frequency response exhibits a low-frequency inductive behavior manifested by a negative real impedance, a negative complex capacitance, and a nonmonotonic phase response, with these effects being significantly enhanced under the dSB boundary condition. The origin of the inductive regime is linked to the emergence of a low-frequency chemical-inductor contribution, which introduces an intrinsic slow dynamical process. Together with the fast Debye timescale serving as the reference scale, this leads to a coupled fast–slow dynamical structure that becomes increasingly pronounced with growing electrostatic correlation length Lc. A scaling analysis in the low-frequency regime further identifies a distinguished intermediate relaxation timescale Lc2/D in the strong-correlation regime, where D denotes the diffusion coefficient of the ion species. At equilibrium, the dSB boundary condition likewise predicts a nonclassical negative differential capacitance that is absent under the BSK boundary condition.

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Information

Phys. Rev. E 114, 015502– Published 6 July, 2026
  • Received 14 March 2026
  • Accepted 10 June 2026
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