In‐Built Compatible Electrode‐Electrolyte Interphases for Quasi‐Solid‐State Li‐SPAN Batteries

Lithium‐sulfur batteries have been regarded as a promising candidate for next‐generation energy storage systems owing to their high energy density and low cost. Sulfurized polyacrylonitrile (SPAN) as a cathode material has received wide interest due to the solid‐solid conversion mechanism, while the Li‐SPAN cell performance has been limited by the notorious issue of lithium metal anode. Developing solid‐state electrolytes for lithium‐sulfur batteries with favorable electrode‐electrolyte compatibility is urgently desired. Herein, we demonstrate a dual‐interface optimization strategy through in‐situ polymerization interface construction, which synergistically enhances interfacial compatibility between the solid polymer electrolyte (SPE) and both the lithium metal anode and SPAN cathode. The initiator pre‐buried in the SPE triggers the in‐situ polymerization of 1,3‐dioxolane (DOL) at the interface, thereby greatly reducing the electrode/electrolyte interfacial impedance. Additionally, the released fluoroethylene carbonate (FEC) into the poly‐DOL interface could further reduce the impedance and enhance the interface stability during cycling, simultaneously preventing the dissolution of polysulfides, owing to the inorganic‐rich and dense cathode electrolyte interphase formed on SPAN. As a result, the Li‐SPAN cell could operate more than 200 cycles at 0.5C with a capacity retention of 90%. We believe that this strategy provides prospects for the development of high‐energy solid‐state lithium‐sulfur batteries.