MOF-Derived Fe7 S8 Nanoparticles/N-Doped Carbon Nanofibers as an Ultra-Stable Anode for Sodium-Ion Batteries.

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 Fe7 S8 nanoparticles/N-doped carbon nanofibers (Fe7 S8 /N-CNFs) is designed and synthesized via electrospinning. As an anode for SIBs, Fe7 S8 /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) Fe7 S8 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 Fe7 S8 nanoparticles, and offer numerous active sites for Na+ adsorption and paths for electrolyte diffusion. The fascinating structure and superior electrochemical properties of Fe7 S8 /N-CNFs shed light on developing high-performance SIBs anode materials.