Balancing interfacial properties and porosity in multiscale porous carbon composite coatings for advanced Li–S battery separators

Advancing lithium–sulfur batteries (LSBs) toward practical commercialization necessitates separator designs that effectively balance pore structure with interfacial chemical functionality. In this study, a unique separator architecture featuring hierarchical carbon microspheres, comprising multiscale porous carbon (MPC) cores encapsulated within functionalized reduced graphene oxide (rGO) shells, is proposed. This structure systematically optimizes pore distribution and surface chemistry to improve lithium polysulfide (LiPS) retention, electrolyte penetration, and electrochemical stability under high sulfur loading and lean electrolyte conditions. Compared to traditional porous separators, the rGO/MPC-coated separator demonstrates significantly enhanced LiPS trapping capability and superior cycling stability, achieving a high initial discharge capacity of 1532 mAh g⁻¹ at 0.1C, sustained capacity retention (decay of only 0.13% per cycle over 300 cycles), and excellent rate capability (944 mAh g⁻¹ at 4C). These results point out the critical role of synergistically tuning porosity and chemical functionalities, establishing a new benchmark for separator engineering in high-performance LSBs.