MOF‐Derived Fe7S8 Nanoparticles/N‐Doped Carbon Nanofibers as an Ultra‐Stable Anode for Sodium‐Ion Batteries

Abstract Sodium‐ion batteries (SIBs) have aroused wide concern due to their potential applications in large‐scale energy‐storage systems. In this work, a hybrid of Fe 7 S 8 nanoparticles/N‐doped carbon nanofibers (Fe 7 S 8 /N‐CNFs) is designed and synthesized via electrospinning. As an anode for SIBs, Fe 7 S 8 /N‐CNFs exhibit a high reversible capacity of 649.9 mAh g −1 at 0.2 A g −1 after 100 cycles, and superior cycling stability for 2000 cycles at 1 A g −1 with only 0.00302% capacity decay per cycle. Such excellent performance originates from: i) Fe 7 S 8 nanoparticles (average diameter of 17 nm), which shorten the Na + diffusion distance; ii) the unique 3D N‐CNFs, which enhance the conductivity, alleviate the self‐agglomeration and large volume change of Fe 7 S 8 nanoparticles, and offer numerous active sites for Na + adsorption and paths for electrolyte diffusion. The fascinating structure and superior electrochemical properties of Fe 7 S 8 /N‐CNFs shed light on developing high‐performance SIBs anode materials.