Tailoring Interfacial Derivative for Lithium-Sulfur Pouch Cells with Ultra-Long Cycling Performance

The lithium-sulfur (Li-S) battery has been regarded as a promising alternative to lithium-ion battery due to its high theoretical specific capacity. While some efforts have been made in developing high-performance laboratory-scale coin cells, the relevant strategies cannot be readily transferred to a practical pouch cell format because of its poor cycles. Herein a derivative controlled liquid (DCL) electrolyte is demonstrated that contains 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonimide potassium salt and bistrifluoromethanesulfonimide lithium salt to allow the preferential salt decomposition on the surface of Li metal prior to the solvents. Such an electrolyte not only enables the enrichment of inorganic potassium fluoride and lithium fluoride in the solid electrolyte interface (SEI), but also suppresses the solvent consumption via preventing the electron-gaining of solvent molecules from the Li metal. As a result, the Li-S pouch cellsenables a breakthrough from several tens of cycles (<40 cycles) to more than 200 stable cycles at a current of 300 mA per cell, demonstrating great potential for commercialization. This study indicates that inducing preferential decomposition of salts rather than solvents during the formation of the SEI could be a promising method to stabilize the lithium metal anode and enable the production of practical Li-S pouch cells.