PNNL

Abstract

Ability to predict the solubility and stability of lithium polysulfide is vital in realizing longer lasting lithium-sulfur batteries. Herein we report a combined computational and experimental spectroscopic analysis to understand the dissolution mechanism of lithium polysulfide species in an aprotic solvent medium. Multinuclear NMR and sulfur K-edge X-ray absorption (XAS) analysis reveals that the lithium exchange between polysulfide species and solvent molecule constitutes the first step in the dissolution process. Lithium exchange leads to de-lithiated polysulfide ions which subsequently forms highly reactive free radicals through disproportion reaction. The energy required for the disproportion and possible dimer formation reactions of the polysulfide species are analyzed using density functional theory (DFT) calculations. We validate our calculations with variable temperature electron spin resonance (ESR) measurements. Based on these findings, we discuss approaches to optimize the electrolyte in order to control the polysulfide solubility. The energy required for the disproportion and possible dimer formation reactions of the polysulfide species are analyzed using density functional theory (DFT) calculations. We validate our calculations with variable temperature electron spin resonance (ESR) measurements. Based on these findings, we discuss approaches to optimize the electrolyte in order to control the polysulfide solubility.