A Phosphazene‐Polyphenol Network Binder Enables Catalytic Polysulfide Conversion and Intrinsic Flame Retardancy for Practical Lithium‐Sulfur Batteries

Abstract

ABSTRACT Practical deployment of lithium‐sulfur (Li‐S) batteries is severely hindered by polysulfide shuttling, structural degradation from severe cathode swelling, and flammability risks. Herein, we construct a cross‐linked macromolecular binder (HTP) by integrating bio‐derived tannic acid, branched polyethyleneimine, and a phosphorus/nitrogen‐rich phosphazene framework. This advanced spatial architecture yields abundant heteroatom‐rich active sites that function synergistically to optimize both sulfur electrochemistry and thermal safety. Consequently, the S@HTP cathode demonstrates exceptional cyclic stability, exhibiting an ultralow capacity fading rate of 0.025% per cycle over 2000 cycles at 4 C. Under a sulfur loading of 5.4 mg cm −2 and an E/S ratio of 9 µL mg −1 , the S@HTP cathode still maintains a high areal capacity of 7.5 mAh cm −2 after 100 cycles at 0.1 C. Furthermore, the phosphazene framework facilitates the formation of a protective char layer and suppresses combustion propagation, imparting intrinsic self‐extinguishing characteristics. This structural chemistry approach provides a multifunctional interface‐regulation paradigm for secure, high‐energy energy storage systems.