Rational Construction of Sulfur-Deficient NiCo2S4–x Hollow Microspheres as an Effective Polysulfide Immobilizer toward High-Performance Lithium/Sulfur Batteries

The synergistic strategy combining architectural design with defect engineering in transition-metal sulfides offers a promising opportunity to realize high-efficiency polysulfide adsorption/conversion surface catalysis in lithium/sulfur (Li/S) batteries. Here, defect-rich yolk–shell hollow spheres composed of ultrafine NiCo2S4–x nanoparticles as sulfur hosts prepared by an anion-exchange method are reported. The elaborate design of sulfur defects endows the NiCo2S4–x hollow spheres with significantly enhanced electronic conductivity and superior affinity for polysulfides as well as expedited sulfur conversion. Meanwhile, the unique yolk–shell NiCo2S4–x hollow sphere structure provides large cavities that not only increase sulfur storage but also relieve the electrode volume expansion during cycling. Combining these favorable features, the NiCo2S4–x-hosted sulfur cathode revealed enhanced cycling stability, corresponding to a negligible capacity fading rate of 0.0754% per cycle after 500 cycles at 1 C, and achieved an outstanding rate capability (628.9 mAh g–1 up to 5 C).