Theory of Cation Solvation and Ionic Association in Non-Aqueous Solvent Mixtures

TL;DR

This paper presents a comprehensive theory for understanding cation solvation and ionic association in non-aqueous solvent mixtures, aiding the design of advanced electrolytes for batteries.

Contribution

It introduces a high-fidelity theoretical framework applicable to super-concentrated electrolytes, explaining experimental and simulation data and guiding electrolyte design.

Findings

Accurately explains cation solvation in non-aqueous electrolytes.

Provides design principles for high entropy electrolytes.

Unifies understanding of solvation structures in concentrated systems.

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 non-aqueous solvent mixtures that can be applied with high fidelity, up to super-concentrated electrolytes. Our theory can naturally explain simulation and experimental values of cation solvation in ''classical'' non-aqueous electrolytes. Moreover, we utilise our theory to understand general design principles of emerging classes of non-aqueous electrolyte mixtures, such as high entropy electrolytes. It is hoped that this theory provides a systematic framework to understand simulations and experiments which engineer the solvation structure and ionic associations of concentrated non-aqueous electrolytes.