(719f) Solvation Structure and Behavior of Lithium Polysulfide Species in Electrolytes of Lithium-Sulfur Batteries

Batteries with large amounts of energy storage are needed to meet the requirements of modern technology and electronics like electric vehicles or cell phones. Current lithium ion batteries are unable to meet these modern energy demands; new battery technology is required. The lithium-sulfur (Li-S) battery is promising technology that has the theoretical energy capacity to meet societal needs. However, several large issues plague Li-S battery performance such as the polysulfide shuttle reaction which results from migration to the anode side of soluble Li polysulfide species formed at the cathode surface. The dissolution of polysulfide species in the electrolyte is the fundamental problem with this parasitic shuttle reaction. However, the solvation structure and fundamentals are not well known due to the complex interactions and chemistry in Li-S batteries. The molecular processes are difficult to study experimentally and therefore are not well understood.

Quantum density functional theory (DFT) and ab-initio molecular dynamics (AIMD) were used to investigate and screen different electrolyte compositions in order to identify the structure and behavior of lithium and polysulfide solvation. Promising and interesting electrolyte interactions can be identified by computational simulations to help with experimental design of batteries. Electrolytes consisting of dimethoxyethane, dioxolane, and fluorinated ethers were investigated. We determined thermodynamically favorable solvation structures, degree of dissociation of lithium polysulfides, and established the basis for a rational design that may improve overall Li-S battery performance by reducing the shuttle redox reaction.