Lithium–sulfur batteries are of great interest due to their high theoretical capacity and low cost. Their discharge mechanism is complicated due to the rich electrochemical and chemical reactions that could occur in both the solution phase and solid state. The exact reaction paths in a battery cell depend on many factors, including the electrolyte and its ability to solvate lithium polysulfide (LiPS) species. Recently, there has been a great interest in using electrolytes with high salt concentrations, also known as solvates, for various battery applications, including Li/S. In a recent study, we discovered a quasi-solid-state reaction mechanism in acetonitrile-hydrofluorinated ether based solvate system that is sparingly solvating to LiPS. In this presentation, we report solubilities of various key LiPS species in different solvents calculated using Density Functional Theory in combination with the Polarizable Continuum Model. We compare the relative stabilities of these species in both solution and solid state and show the thermodynamic drive for these alternate reaction paths in a class of sparingly solvating electrolytes. We also present the local solvation structures of LiPS species in different solvents from Molecular Dynamics simulation studies.

Computational studies of solubilities of lithium polysulfides and reaction mechanisms in Li/S batteries

256th National Meeting (2018)

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