In Situ Fabrication of Carbon-Encapsulated FeX (X = S, Se) for Enhanced Sodium Storage.

Sodium-ion batteries (SIBs) have been regarded as a promising alternative to lithium-ion batteries due to the natural abundance of sodium in the earth's crust. In our work, fusiform FeX@C (X = S, Se) composites were obtained via a one-step pyrolysis strategy applied to SIB anode materials. The formed carbon skeleton could prevent the FeX nanoparticles from agglomeration and stabilize the interface of Fe/NaX generated in the redox reactions. FeX@C (X = S, Se) exhibits excellent reversible specific capacity (1005.3 mAh g under 0.2 A g for FeS@C and 458.5 mAh g under 0.5 A g for FeSe@C), outstanding rate performance (654.7 mAh g for FeS@C and 392.9 mAh g for FeSe@C going through 300 loops even under 2 A g), and excellent cycling properties (795.8 mAh g after 50 loops under 0.2 A g for Fe7S@C and 399.9 mAh g going through 150 loops under 0.5 A g for FeSe@C). The excellent electrochemical performance of FeX@C composites makes them promising anode materials for SIBs.