Modelling Coupled Ion Motion in Electrolyte Solutions for Lithium-Sulfur Batteries

We model coupled ion transport in representative electrolyte solutions for Li-S batteries by applying molecular dynamic (MD) simulations on systems of increasing complexity, namely going from solutions of the Li2S4 salt in pure tetraethylene glycol dimethyl ether (TEGDME) and 1,3-dioxolane (DOL) solvents, to Li2S4 in solvent mixtures, and finally incorporating lithium bis (trifluoromethanesulfonyl) imide (LiTFSI) as a reservoir of Li-ions. While the motion of Li2S4 salt in DOL is predominantly vehicular, it is governed by a hopping regime in the more viscous TEGDME solvent. Most importantly, when the two salts are mixed, the presence of the TFSI anions does not slow down the diffusion of the polysulfide anion.