Multifunctional NiCo2O4-NC Heterostructure Nanocage Modified Separator for Mitigating the Shuttle Effect and Kinetic Challenges in Lithium–Sulfur Batteries

Lithium-sulfur batteries have garnered significant attention from the scientific community due to their intrinsic advantages, including low cost, abundant resources, and high specific energy. However, the shuttle effect of soluble polysulfides and the sluggish redox kinetics of sulfur species have greatly hindered their commercialization and practical application. Herein, we propose a straightforward strategy to construct NiCo 2 O 4 -NC heterostructure nanocages, which serve as multifunctional separator modifiers to improve the electrochemical performance of lithium-sulfur batteries. Specifically, nitrogen doping enhances the polarity of the carbon matrix, enabling both physical confinement and chemical anchoring of polysulfide species. Meanwhile, the embedded NiCo 2 O 4 provides abundant catalytic sites that accelerate the redox kinetics of lithium polysulfides. Consequently, the battery assembled with the optimal NiCo 2 O 4 -NC-1 modified separator demonstrates an excellent initial capacity of 1017.8 mAh g −1 at 0.5 C and a remarkable cycling stability with only 0.04% capacity decay per cycle at 2 C. Moreover, NiCo 2 O 4 -NC-1 exhibits stable electrochemical behavior under high sulfur loading, highlighting its multifunctional structural advantages. This work provides a viable strategy for designing advanced separators in high-performance lithium–sulfur batteries.