Molecular interpretability of the bulk electrochemical impedance of concentrated electrolytes
Abstract
Electrochemical impedance spectroscopy (EIS) is a widely used technique to understand time-dependent response and relaxation under applied voltage. While these spectra contain a wealth of information, major gaps in our understanding can hinder our ability to interpret EIS spectra in terms of microscopic chemical mechanisms. We propose an alternative approach to common empirical fitting procedures for describing the contribution of the bulk electrolyte to the EIS spectrum. This new approach is rooted in determining the moments of the frequencydependent conductivity, with molecular interpretability provided by a generalized Langevin equation description of an effective single particle dynamics; the 'itinerant oscillator' (IO) model. In contrast to a Debye-Falkenhagen description, the IO model makes no assumptions regarding the concentration of the electrolyte, a fact we demonstrate by analysing molecular dynamics simulations of a room-temperature ionic liquid. By analysing the memory function from simulation within the framework provided by the IO model, we reveal the importance of capturing the separation of timescales within the memory function for describing the temperature dependent β-relaxation process. We go on to show how our impedance model directly reports on this distribution of timescales while retaining the simplicity of commonly employed workflows.
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BibTeX
@article{fairchild2026molecular,
title = {{Molecular interpretability of the bulk electrochemical impedance of concentrated electrolytes}},
author = {Connie J Fairchild and Stephen J Cox and Benjamin Rotenberg and Thomas Sayer},
journal = {Electrochimica Acta},
year = {2026},
month = jul,
doi = {10.1016/j.electacta.2026.149863},
eprint = {2607.02316},
archivePrefix = {arXiv},
url = {https://hal.sorbonne-universite.fr/hal-05764056v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Molecular interpretability of the bulk electrochemical impedance of concentrated electrolytes
AU - Connie J Fairchild
AU - Stephen J Cox
AU - Benjamin Rotenberg
AU - Thomas Sayer
PY - 2026
DA - 2026/07/02
JO - Electrochimica Acta
DO - 10.1016/j.electacta.2026.149863
UR - https://hal.sorbonne-universite.fr/hal-05764056v1
AB - Electrochemical impedance spectroscopy (EIS) is a widely used technique to understand time-dependent response and relaxation under applied voltage. While these spectra contain a wealth of information, major gaps in our understanding can hinder our ability to interpret EIS spectra in terms of microscopic chemical mechanisms. We propose an alternative approach to common empirical fitting procedures for describing the contribution of the bulk electrolyte to the EIS spectrum. This new approach is rooted in determining the moments of the frequencydependent conductivity, with molecular interpretability provided by a generalized Langevin equation description of an effective single particle dynamics; the 'itinerant oscillator' (IO) model. In contrast to a Debye-Falkenhagen description, the IO model makes no assumptions regarding the concentration of the electrolyte, a fact we demonstrate by analysing molecular dynamics simulations of a room-temperature ionic liquid. By analysing the memory function from simulation within the framework provided by the IO model, we reveal the importance of capturing the separation of timescales within the memory function for describing the temperature dependent β-relaxation process. We go on to show how our impedance model directly reports on this distribution of timescales while retaining the simplicity of commonly employed workflows.
SN - 0013-4686
ER -