Walnut-Like CoS₂/Carbon Freestanding Cathode: Enabling Dynamic Regulation of Polysulfide Diffusion–Conversion in Lithium–Sulfur Batteries

Lithium-sulfur (Li-S) batteries are considered a promising next-generation energy storage system owing to their exceptionally high theoretical energy density. However, their practical deployment is hindered by the severe polysulfide shuttle effect arising from the dissolution and migration of lithium polysulfides. Herein, we report the rational design of a hierarchical freestanding cathode architecture consisting of carbon nanotube-embedded porous carbon nanofibers (PCNF/T) decorated with in situ grown CoS₂ nanocrystals (PCNF/T@CoS₂). This integrated structure is fabricated via electrospinning, high-temperature carbonization, and a subsequent hydrothermal process. Uniquely, the flexible, binder-free cathode directly replaces traditional aluminum foil current collectors. The 3D conductive framework not only accommodates volume fluctuations during cycling but also enables efficient charge transport. Meanwhile, CoS₂ nanocrystals synergistically suppress polysulfide migration via a combination of strong chemical anchoring and physical confinement, as confirmed by density functional theory (DFT) calculations. Benefiting from this multiscale structural and chemical synergy, the optimized cathode exhibits a high initial capacity of 955.5 mAh g^-1 at 1 C with an ultralow capacity fading rate of 0.07% per cycle over 310 cycles. Even at a high sulfur loading of 6.7 mg cm^-2, the battery can still retain a capacity of 521 mAh g^-1 after 100 cycles. This work offers a viable strategy toward the development of high-loading, long-life Li-S battery cathodes.