Unravelling the Secret of Sulfur Confinement and High Sulfur Utilization in Hybrid Sulfur‐Carbons

ABSTRACT Understanding sulfur confinement and chemical transformation in hybrid sulfur‐carbon materials is critical for advancing metal‐sulfur batteries. Here, we investigate the structural evolution of a sulfur‐rich polymer into a hybrid sulfur‐carbon via inverse vulcanization and thermal condensation. Multiscale analyses reveal a stepwise transformation, beginning with the emergence of sulfur radicals at ∼175°C, followed by the progressive development of a carbon matrix above 300°C that stabilizes the radical species. Around 450°C, a transitional phase forms, consisting of conjugated carbon clusters covalently bonded to sulfur chains. This hybrid structure confines sulfur within pseudo‐graphitic nanodomains, effectively suppressing polysulfide dissolution and enhancing redox stability. DFT simulations show how sulfur confinement modulates Na‐S reaction energetics, while electrochemical testing confirms high sulfur utilization, delivering ∼1000 mAh and 1200 Wh , setting a new performance benchmark for room‐temperature Na─S batteries. These findings provide critical insights into the correlation between structural evolution and electrochemical performance, offering design principles for next‐generation sulfur‐based electrodes.