Hierarchical CoSe2/TiN/nitrogen-doped carbon nanofibers wrapped with carbon nanotubes: A binder-free anode for enhanced sodium-ion storage

Transition metal chalcogenide anodes have attracted significant attention for sodium-ion batteries (SIBs) owing to their relatively high theoretical capacity. However, the inherently poor electronic conductivity and rate performance hinder their practical application. In this study, hierarchically structured CoSe 2 /TiN/nitrogen-doped carbon nanofibers wrapped with in-situ grown carbon nanotubes (CNTs) on the surface (denoted as CoSe 2 @N-TCF/CNTs) are designed and fabricated as binder-free anodes for SIBs. The rational design can effectively avoid the agglomeration of CoSe 2 nanoparticles, improve the conductivity of the composite materials, provide enough space for electrolyte penetration and volume expansion during the cycling process and shorten the transmission paths of electrons and Na + . With these structural and compositional advantages, the as-obtained hierarchical CoSe 2 @N-TCF/CNTs deliver a high reversible capacity of 401.2 mAh g −1 after 1000 cycles at 0.2 A g −1 and maintained at 353.7 mAh g −1 even at a high current density of 2 A g −1 when directly used as a binder-free anode for SIBs. The superior sodium-ion storage performance can be attributed to the decreased charge transfer resistance , improved Na + diffusion rate and the pseudocapacitance behavior, as is evidenced by kinetics analysis .