First-Principles Investigation of Lithium Polysulfide Structure and Behavior in Solution

The lithium–sulfur battery is a promising next generation energy storage technology that could meet the demands of modern society with a theoretical specific energy near 2500 W h kg –1 . However, this battery chemistry faces unique problems such as the parasitic polysulfide shuttle reaction, which hinders battery performance severely. This shuttle phenomenon is caused by solubilities of intermediate reaction products in the electrolyte during the reduction chemistry of the battery. With molecular simulation and computational chemistry tools, we studied the thermodynamics, solvation structure, and dynamics of the long-chain lithium polysulfide species Li 2 S 6 and Li 2 S 8 in dimethoxyethane and 1,3-dioxolane to gain a deeper fundamental understanding of this process. We determined the structure of the first solvation shell for Li + as well as those of Li 2 S 6, Li 2 S 8 closed, and Li 2 S 8 linear in pure solvents and solvents with extra Li + added. The lithium polysulfide species were found not to favor dissociation and would most likely exist as fully lithiated species in solution.