On activation in solid ionic electrolytes

Ionic conductivity in solid electrolytes is commonly expected to exhibit Arrhenius dependence on temperature, determined by a well-defined activation energy. Consequently, a standard approach involves calculating this energy using quasi-static methods and using the Arrhenius form to extrapolate the numerical results from one temperature range to another. Despite the ubiquity of this Arrhenius-based modeling, disagreements frequently arise between theory and experiment, and even between different theoretical studies. By considering a tractable minimal model, we elucidate the reason behind the breakdown of the Arrhenius conductivity form. This breakdown is driven by non-trivial phase-space boundaries between conducting and non-conducting regimes, and depends on the kinetic properties of the system.