Countering the Polysulfide Shuttle Reaction with Next Generation Cathodes and Electrolytes

Batteries with large amount 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. This parasitic reaction can be countered by using next generation carbon composite electrodes and advanced electrolytes that strongly adsorb soluble long chained lithium polysulfides. However, finding these materials can be difficult due to complex interactions and chemistry. The molecular processes are not well understood.

Quantum scale density functional theory (DFT) and ab-initio molecular dynamics (AIMD) were used to investigate and screen different materials and electrolytes in order to identify cathode and electrolyte combinations that improve battery performance. Promising electrolytes and cathode materials can be determined by computational simulations Chalcogenides and materials used for hydrodesulphurization like MoS₂, MnO₂, and Al₂O₃ were investigated due to their strong interactions with sulfur. However, retaining polysulfides at the cathode may also be dependent on the nature of the electrolyte. Electrolytes consisting of Dimethoxyethane, Dioxolane, and fluorinated ethers in the presence of lithium salts were also investigated both independently and in the presence of the cathode. We gained a better fundamental understanding of interfacial phenomena and established the basis for a rational design that may improve overall Li-S battery performance by reducing the shuttle redox reaction.