Realizing Solid‐Phase Reaction in Li–S Batteries via Localized High‐Concentration Carbonate Electrolyte

Abstract Lithium–sulfur (Li–S) batteries have attracted significant attention because of their high theoretical energy density and low cost. However, their poor cyclability caused by the shuttle effect in ether‐based electrolytes remains a great challenge for their practical application. Herein, a novel electrolyte is proposed by combining widely used carbonate solvents diethyl carbonate/fluoroethylene carbonate and inert diluent 1,1,2,2‐tetrafluoroethyl 2,2,3,3‐tetrafluoropropyl ether for Li–S batteries based on typical mesoporous carbon/sulfur (KB/S) materials. Differing from the conventional dissolution‐precipitation mechanism, the sulfur cathodes demonstrate a solid‐phase reaction route in the developed electrolyte, which is realized with the assistance of an in situ formed compact cathode electrolyte interface (CEI) film on the cathode caused by the nucleophilic reaction between lithium polysulfides (LiPSs) and carbonate solvents. The formed CEI film can effectively block the infiltration of carbonate solvents and can completely suppress the generation of LiPSs, thus eliminating the shuttle effect. As a result, the KB/S electrode demonstrates a stable cycling performance at 2 C by maintaining a discharge capacity of 570 mAh g^–1 after 600 cycles, corresponding to an average capacity decay of 0.057% per cycle. More significantly, this strategy provides a new pathway toward future development of Li–S batteries based on solid‐phase conversion.