Prussian Blue Analogue-Derived Fe-Doped CoS2 Nanoparticles Confined in Bayberry-like N-Doped Carbon Spheres as Anodes for Sodium-Ion Batteries

Obvious volume change and the dissolution of polysulfide as well as sluggish kinetics are serious issues for the development of high performance metal sulfide anodes for sodium-ion batteries (SIBs), which usually result in fast capacity fading during continuous sodiation and desodiation processes. In this work, by utilizing a Prussian blue analogue as functional precursors, small Fe-doped CoS₂ nanoparticles spatially confined in N-doped carbon spheres with rich porosity were synthesized through facile successive precipitation, carbonization, and sulfurization processes, leading to the formation of bayberry-like Fe-doped CoS₂/N-doped carbon spheres (Fe-CoS₂/NC). By introducing a suitable amount of FeCl₃ in the starting materials, the optimal Fe-CoS₂/NC hybrid spheres with the designed composition and pore structure exhibited superior cycling stability (621 mA h g^-1 after 400 cycles at 1 A g^-1) and improved the rate capability (493 mA h g^-1 at 5 A g^-1). This work provides a new avenue for the rational design and synthesis of high performance metal sulfide-based anode materials toward SIBs.