Structural and chemical synergistic effect of CoS nanoparticles and porous carbon nanorods for high-performance sodium storage

Considering inherent large structural deterioration of conversion-type anode materials during repeated sodiation/desodiation process, the ingenious integration of both nanostructure engineering and chemical hybridization is highly desirable and challenging. Here, ultrafine CoS nanoparticles embedded in porous carbon nanorods (denoted as 7-CoS/C) were facilely fabricated via simultaneous in-situ carbonization and sulfidation of Co-metal organic frameworks (Co-MOF) and have been applied as anode materials for sodium-ion batteries (SIBs). Benefiting from the advantageous embedding architecture between the nanoparticles and porous nanorods, the 7-CoS/C delivers long-term cycling stability (542 mAh g⁻¹ after 2000 cycles with a capacity retention of 91.4% at 1 A g⁻¹) and excellent rate performance (discharge capacities of 510 mAh g⁻¹ at 5 A g⁻¹ and 356 mAh g⁻¹ even at 40 A g⁻¹), which is proved to be characterized of partial pseudocapacitive behaviors during the sodiation/desodiation process. In addition, Na₃V₂(PO₄)₃/7-CoS/C full cell with excessive amount of Na₃V₂(PO₄)₃ has been assembled and exhibits a capacity of 352 mAh g⁻¹ at 0.5 A g⁻¹. This meaningful approach can be extended to build embedded porous structure of other hybrid composites for next-generation energy-storage technology.