Theory of The Double Layer in Water-in-Salt Electrolytes

TL;DR

This paper introduces a modified Poisson-Fermi theory to accurately model the electrical double layer in Water-in-Salt Electrolytes, aiding the development of safer, environmentally friendly lithium-ion batteries.

Contribution

It develops a new theoretical framework for WiSEs, integrating molecular simulation data to accurately describe their double layer structure.

Findings

The theory matches molecular simulations with high accuracy.

It reveals the interplay between electrosorption, solvation, and ion correlations.

Provides insights for designing safer electrolytes.

Abstract

One challenge in developing the next generation of lithium-ion batteries is the replacement of organic electrolytes, which are flammable and most often contain toxic and thermally unstable lithium salts, with safer, environmentally friendly alternatives. Recently developed Water-in-Salt Electrolytes (WiSEs) were found to be a promising alternative, having also enhanced electrochemical stability. In this work, we develop a simple modified Poisson-Fermi theory, which demonstrates the fine interplay between electrosorption, solvation, and ion correlations. The phenomenological parameters are extracted from molecular simulations, also performed here. The theory reproduces the electrical double layer structure of WiSEs with remarkable accuracy.