Understanding and Controlling of Solution Chemistry of Lithium Polysulfide to Enable High Energy Li-S Redox Flow Battery

Large-scale energy storage has become an important topic for the modern life. The identification of high energy and low cost energy storage and conversion technologies for stationary applications has gained intensive research interest in recent years. Lithium sulfur (Li-S) redox flow battery is one of the most promising candidates. Fundamental understanding and controlling of polysulfide chemistry were explored to enable high energy Li-S redox flow cells. Different from static Li-S batteries targeting for vehicle electrification, high solubility of all lithium polysulfide generated at different depth of discharge and state of charge is preferred in flow battery in order to take full advantage of multiple electron transitions between S and Li₂S. A new kind of DMSO based electrolyte was first proposed for Li-S redox flow batteries, which not only enable high solubility lithium polysulfide species, especially for the short-chain species, but also stabilize excellent cycling with high Coulombic efficiency. Challenges and opportunities existing in the Li-S redox flow concept have also been discussed in detail.