Hierarchically porous nanofibers comprising multiple core–shell Co₃O₄@graphitic carbon nanoparticles grafted within N-doped CNTs as functional interlayers for excellent Li–S batteries

Hierarchically porous nanofibers (NFs) comprising multiple core–shell Co₃O₄@graphitic carbon (GC) nanoparticles grafted within N-doped carbon nanotubes (CNTs) (Co₃O₄@GC/N-CNT NF) were rationally designed as functional interlayers for excellent Li–S batteries (LSBs). The well-grafted N-doped CNTs (N-CNTs) and high-conductivity GC layer coated on Co₃O₄ nanoparticles provided conductive channels for fast ionic/electronic transfer during charging–discharging. The Co₃O₄ nanoparticles inside the GC layer served as active polar sites for efficient anchoring of dissolved lithium polysulfides and ensured their reuse during redox reactions via fast charge transfer processes. Consequently, the assembled Li–S cell featuring a Co₃O₄@GC/N-CNT NF-coated separator and a pure sulfur electrode (70 wt% and 2.0 mg cm⁻² loading) presented an excellent electrochemical performance, namely a high-rate capability and stable cycling performance at C-rates of 0.1, 0.5, and 1.0C. In addition, the Li-ion diffusion coefficient of the assembled Li–S cell (10⁻⁸ cm² s⁻¹) was one order of magnitude higher than those of the assembled Li–S cells featuring bare Co₃O₄ NF-coated and pristine separators (10⁻⁹ cm² s⁻¹). The remarkable overall cell performance was attributed to the combination of highly conductive N-CNTs, GC layer, and polar Co₃O₄ nanoparticles, which effectively trapped polysulfides. Therefore, we believe that the proposed unique nanostructure synthesis method can provide new insights into the development of sustainable and highly conductive polar materials as functional interlayers for advanced LSBs.