Multifunctional SiO₂-anchored catechol-derived coated separators with enhanced thermal safety and polysulfide...

Lithium‑sulfur batteries (LSBs) have attracted significant attention as promising energy storage and power sources due to their exceptionally high energy density (2600 Wh kg^-1) and the low cost of active sulfur materials. However, their practical deployment is hindered by the severe polysulfide shuttle effect and the poor thermal stability of commercial polypropylene (PP) separators, which tend to shrink at elevated temperatures and cause internal short circuits. In this study, a flame-retardant and lithium polysulfides (LiPSs)-anchoring material (SiO₂@PD) is synthesized and coated onto PP separators (SiO₂@PD/PP) via a simple slurry-coating method. The synergistic LiPSs adsorption arises from strong interactions between the phosphorus‑oxygen double bonds (P=O) and hydroxyl groups (-OH) of PD and the Si-O-Si bonds of SiO₂, effectively suppressing the LiPSs shuttle effect and facilitating Li⁺ transport. Moreover, the release of phosphorus species from PD at elevated temperatures, together with the thermal barrier provided by SiO₂, significantly enhances flame retardancy and ensures structural integrity under high-temperature operation. Benefiting from these combined effects, LSBs employing SiO₂@PD/PP separators deliver exceptionally low capacity decay rate of 0.027 % per cycle over 1000 cycles at 2.5 C, and exhibit excellent thermal resilience, retaining 730.32 mAh·g^-1 after 100 cycles at 60 °C. This work provides a practical and scalable strategy for designing multifunctional separators toward high-performance and intrinsically safe LSBs.