Maxwell displacement current and nature of Jonsher’s “universal” dynamic response in nanoionics

Abstract

A new notion—Maxwell displacement current on a potential barrier—is introduced in the structure-dynamic approach of nanoionics for the description of a collective phenomenon: coupled ion transport and dielectric-polarization processes occurring during the ionic space charge formation and relaxation in a nonuniform potential landscape. We simulate the processes: (i) in an electronic conductor (EC)/advanced superionic conductor (AdSIC) ideally polarizable coherent heterojunction, (ii) in a few strained monolayers of a solid electrolyte (SE) located between two AdSICs forming coherent interfaces with SE. We prove that the sum of ionic current over any barrier and Maxwell displacement current through the same barrier is equal to the current of the current generator. A “universal” dynamic response, Reσ*(ω) ∝ ω n (n < ≈1), was found for the frequency-dependent complex conductivity σ*(ω) for case (ii) with an exponential distribution of potential barrier heights in SE. The nature of the phenomenon is revealed. The amplitudes of nonequilibrium ion concentrations (and induced voltages) in the space charge region of SE change approximately as ∝ ω −1. These amplitudes made a main linear contribution to Reσ*(ω). The main deviation from linearity is provided by the cosine of phase shift φ between current and voltage in SE-space charge region but the cosφ depends relatively slightly on ω (near constant loss effect) for coupled ion transport and dielectric-polarization processes.