S/N-doped carbon nanofibers affording Fe7S8 particles with superior sodium storage

Iron sulfides draw much attention as electrode candidates for sodium-ion batteries (SIBs) due to the rich chemical stoichiometries and high capacity. However, they usually exhibit poor cycling performance due to the large volume change during sodiation/desodiation process. In this work, we embed Fe7S8 nanopartides into sulfur, nitrogen-doped carbon (S/N-C) nanofibers through electrospinning/sulfurization processes. The heteroatom doped carbon matrixes could effectively protect the Fe7S8 from structural collapse, obtaining a stable cycling performance. Moreover, the conductive matrixes with 1D structure can facilitate the diffusion of electrons, leading to good rate capability. As results, the as-designed Fe7S8@S/N-C nanofibers present a discharge capacity of 347 m Ah g(-1) after 150 cycles at 1 A g(-1) and a high rate capacity of 220 m Ah g(-1) at 5 A g(-1) in virtue of unique structural characteristics.