Temperature Dependence of the Inverse Haven Ratio in Ionic Liquids and “Solvent-in-Salt” Systems

This article proposes a model of the temperature behavior of the inverse Haven ratio (ionicity) in concentrated electrolytes, based on the mechanism of capture of mobile ions into deep localized states (traps). Within the framework of the model, an analytical expression for the temperature dependence of the ionicity is obtained, which is in good agreement with experimental data for some room-temperature ionic liquids. A generalization of the model to systems with spatial heterogeneity is also proposed, which allows one to describe the nonmonotonic temperature behavior of the inverse Haven ratio in highly concentrated salt solutions ("solvent-in-salt" systems).