Compatible Dynamically Wetting Electrolyte–Electrode Interface Design for Solid‐State Lithium–Sulfur Batteries

Solid‐state lithium–sulfur batteries feature high energy density and stability, but their practical application is constrained by limited ion transport at the electrode/solid‐state electrolyte interfaces and safety concerns arising from Li dendrites. This study presents a solid polymer electrolyte (SPSLL) constructed from an ultrathin flame‐retardant sulfonated copolymer (phthalazinone biphenylether sulfone) skeleton, into which a mixed phase of poly(vinylidene fluoride‐co‐hexafluoropropylene), succinonitrile, and lithium bis(trifluoromethanesulfonyl)imide is incorporated, together with a liquid metal interfacial wetting phase. This design enables a dynamic wetting mechanism that facilitates the formation of compatible electrolyte‐electrode interfaces. Through its sulfonated polymer skeleton, SPSLL promotes lithium salt dissociation and enhances thermal stability. Simultaneously, the LM serves as dynamic active sites, both strengthening interfacial physical contact and facilitating the formation of alloyed solid electrolyte interphases. As a result, the SPSLL‐based solid‐state Li‐sulfurized polyacrylonitrile (Li||SPAN) battery exhibits excellent cycling stability, maintaining a capacity retention of 92.2% and a Coulombic efficiency of 99.9% after 500 cycles. Furthermore, the SPSLL single‐layer pouch cell has an initial specific capacity of 948 mAh g −1 . The dynamic wetting strategy presented in this work offers a promising research direction for interface design in solid‐state batteries.