In Situ Fabrication of Carbon-Encapsulated Fe7X8 (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 Fe(7)X(8)pC (X = S, Se) composites were obtained via a one-step pyrolysis strategy applied to SIB anode materials. The formed carbon skeleton could prevent the Fe7X8 nanoparticles from agglomeration and stabilize the interface of Fe/Na2X generated in the redox reactions. Fe7X8@C (X = S, Se) exhibits excellent reversible specific capacity (1005.3 mAh g(-1) under 0.2 A g(-1) for Fe7S8@C and 458.5 mAh g(-1) under 0.5 A g(-1) for Fe7Se8@C), outstanding rate performance (654.7 mAh g(-1) for Fe7S8@C and 392.9 mAh for Fe7Se8@C going through 300 loops even under 2 A g(-1)), and excellent cycling properties (795.8 mAh g(-1) after 50 loops under 0.2 A g(-1) for Fe7S8@C and 399.9 mAh g(-1) going through 150 loops under 0.5 A g(-1) for Fe(7)Se(8)pC). The excellent electrochemical performance of Fe7X8@C composites makes them promising anode materials for SIBs.