Embedding CoS2 nanoparticles within hierarchically porous carbon matrix for enhanced sodium-ion storage and cyclic stability

Cubic phase cobalt disulfide (CoS 2 ) is recognized as a potential negative material for sodium-ion batteries (SIBs) because of its low band gap, simple synthesis process, and high capacity. Nonetheless, the challenges of slow ion diffusion and substantial volume change during cycling, resulting in inadequate rate and cycling performances, remain unresolved. Here, a porous structure is fabricated by etching electrospun carbon nanofibers, subsequently facilitating the growth of CoS 2 nanoparticles at the pore locations. A nitrogen-doped carbon layer is then applied to the surface to buffer the volumetric expansion effect of CoS 2 . The findings indicate that the carbon nanofibers establish a stable conductive network, while the porous architecture of the carbon fibers, in conjunction with the carbon coating, efficiently mitigates volumetric expansion. Furthermore, density functional theory (DFT) studies show the presence of an interlayer van der Waals force between the sulfur atoms in CoS 2 and the carbon atoms, which reduces the band gap, enhances the conductivity of the structure, and lowers the energy barrier of Na + migration. The as-prepared anode achieves a reversible capacity of 302.6 mAh g −1 at 3.2 A g −1 and maintains a capacity of 384.6 mAh g −1 at 1.0 A g −1 over 800 cycles, demonstrating exceptional rate performance and improved cycling stability. This work shows that the combination of hierarchical porous architecture and a unique electronic structure offers valuable insights for designing high-performance negative materials for SIBs. Graphical abstract