Theory of Cation Solvation and Ionic Association in Nonaqueous Solvent Mixtures

Abstract

Conventional lithium-ion batteries, and many next-generation technologies, rely on organic electrolytes with multiple solvents to achieve the desired physicochemical and interfacial properties. The complex interplay between these properties can often be elucidated via the coordination environment of the cation. We develop a theory for the coordination shell of cations in nonaqueous solvent mixtures that can be applied with high fidelity, up to extremely high salt concentrations. Our theory can naturally explain simulation and experimental values of cation solvation in “classical” nonaqueous electrolytes. Moreover, we utilize our theory to understand general design principles of emerging classes of nonaqueous electrolyte mixtures, such as high entropy electrolytes. It is hoped that this theory provides a systematic framework to understand simulations and experiments that engineer the solvation structure and ionic associations of concentrated nonaqueous electrolytes.