An in situ gel electrolyte for the facile preparation of high‐safety Li‐S battery

Lithium‐sulfur (Li‐S) battery shows promising development potential in secondary lithium‐ion batteries. However, the shuttle effect of polysulfides, uncontrollable lithium dendrite growth, and safety hazards in conventional liquid electrolytes limit the popularity of Li‐S batteries in the future commercial market. In this work, a high‐performance gel electrolyte (GPE) was prepared in situ by initiating the ring‐opening polymerization of 1,3‐dioxolane (DOL) with aluminum trifluoromethanesulfonate (Al(OTf)3) and using diethylene glycol dimethyl ether (DME) as a plasticizer, which can effectively improve the interfacial compatibility between sulfur cathode and the electrolyte, as well as the stability of lithium anode. The electrochemical performance of the poly‐DOL (PDOL) GPE was optimized by adjusting the concentration ratio of the initiator. When the concentration of Al(OTf)3 is 4 mM, the PDOL GPE has a high ionic conductivity up to 3.81 × 10−4 S cm−1 and a lithium ion migration number of 0.57. The assembled quasi‐solid‐state Li‐S batteries shows an initial discharge specific capacity of 908.1 mAh g−1 at 0.1 C with a capacity retention of 68% after 240 cycles, and its average Coulombic efficiency is maintained at 96.1%. This gel electrolyte design provides a feasible practical idea in quasi‐solid‐state Li‐S batteries. Schematic diagram of the in situ preparation process of gel lithium‐sulfur battery and its stability analysis