Ultrafast microwave-assisted synthesis of atomically dispersed iodine-doped graphene with tailored charge distribution for superior lithium polysulfide immobilization and conversion

Lithium-sulfur (Li-S) batteries offer exceptional theoretical energy density but are hindered by polysulfide shuttling and sluggish sulfur redox kinetics. In this work, an ultrafast microwave-assisted method is developed to synthesize single-atom iodine-doped reduced graphene oxide (SAI-rGO) within 100 s as a functional separator coating. Experimental characterization and theory calculations reveal that isolated iodine atoms are stabilized at rGO defect sites through C-I bonds, generating locally polarized sites with strong affinity for lithium polysulfides (LiPSs). Iodine incorporation redistributes interfacial electron density and regulates charge transfer between the carbon framework and adsorbed LiPSs, thereby strengthening Li-S interactions and accelerating sulfur-species conversion. Consequently, cells with SAI-rGO-modified separators yield 1059 mAh·g −1 on the initial discharge at 1 C, with capacity loss limited to an average of 0.035% per cycle throughout 1000 cycle. Even at 3 C, a discharge capacity of 825.7 mAh·g −1 is preserved, attesting to the favorable high-rate response. This study demonstrates the rapid synthesis of carbon frameworks containing isolated nonmetal atoms and identifies atomic-scale interfacial charge modulation as a means to restrict polysulfide crossover and expedite sulfur redox conversion.