Dynamic Response of Concentrated Electrolytes to Chirp Signals.

Abstract

Electrolytes, chirp signals, Brownian dynamics, conductivity, Maxwell-Wagner relaxation This study investigates the dynamic response of electrolyte/macroion solutions to time-varying electric fields, which is vital for applications from water desalination to neuromorphic computing and sensor technologies. Using large-scale Brownian dynamics simulations coupled with Poisson's equation, we examined the frequency-dependent conductivity of symmetric and binary electrolytes/nanoparticles across various concentrations. We reveal a comprehensive picture of charge transport mechanisms by employing chirp signals that excite multiple frequencies. Our results identify three distinct dynamic regimes: (1) instantaneous response at low frequencies, (2) increased lagging and imaginary conductivity at intermediate frequencies, and (3) diminished conductivity at high frequencies due to short-time ion/macroion dynamics. Significant deviations from ideal behavior at low frequencies and high concentrations are attributed to packing and many-body interactions. We propose a modified Maxwell-Wagner relaxation time that incorporates excluded volume effects, offering a more accurate time scale for the dynamic response of concentrated electrolytes/macroions. This new framework scales the frequency-dependent conductivity, revealing universal responses across different concentrations and interaction strengths.