Synergistic Interface Engineering of Heterojunction and Oxygen Vacancies in Multiphase Cobalt Oxide/Graphene Composite Host for High‐Performance Lithium–Sulfur Batteries

ABSTRACT Lithium–sulfur batteries represent an attractive next‐generation energy storage technology, yet face challenges including the insulating nature of sulfur, lithium polysulfide shuttle effect, and sluggish redox kinetics. Herein, we developed a Co ₃ O _{4‐ y} ‐CoO@rG composite catalyst through a triple synergistic design. This designed architecture combines ultrathin mesoporous Co ₃ O ₄ nanosheets with abundant active sites, in situ formed CoO creating p–n heterojunctions, oxygen vacancies, and 3D graphene conductive network with Co─O─C covalent bridges. When deployed as a sulfur host, the Co ₃ O _{4‐ y} ‐CoO@rG cathode delivers high capacities of 1358.0 mAh g ⁻¹ at 0.2 C and 573.2 mAh g ⁻¹ at 5 C, and maintains 701.4 mAh g ⁻¹ after 1000 cycles at 1 C. Under the assembling conditions of high sulfur loading of 6.7 mg cm ⁻² and lean electrolyte of 5.0 µL mg ⁻¹ , it achieves a high areal capacity of 6.92 mAh cm ⁻² with 94.1% initial capacity retention. Moreover, a prototype pouch cell with 45.5 mg sulfur loading exhibits a high initial energy density of 401.0 Wh kg ⁻¹ with 95.3% retention after 120 cycles, confirming its practical viability.