Fe7Se8 encapsulated in N-doped carbon nanofibers as a stable anode material for sodium ion batteries

Transition metal chalcogenides especially Fe-based selenides for sodium storage have the advantages of high electric conductivity, low cost, abundant active sites, and high theoretical capacity. Herein, we proposed a facile synthesis of Fe7Se8 embedded in carbon nanofibers (denoted as Fe7Se8-NCFs). The Fe7Se8-NCFs with a 1D electron transfer network can facilitate Na+ transportation to ensure fast reaction kinetics. Moreover, Fe7Se8 encapsulated in carbon nanofibers, Fe7Se8-NCFs, can effectively adapt the volume variation to keep structural integrity during a continuous Na+ insertion and extraction process. As a result, Fe7Se8-NCFs present improved rate performance and remarkable cycling stability for sodium storage. The Fe7Se8-NCFs exhibit practical feasibility with a reasonable specific capacity of 109 mA h g(-1) after 200 cycles and a favorable rate capability of 136 mA h g(-1) at a high rate of 2 A g(-) when coupled with Na3V2(PO4)(3) to assemble full sodium ion batteries.

Automated summary

By embedding Fe7Se8 in carbon nanofibers, the material exhibits improved rate performance and remarkable cycling stability for sodium storage, showing practical feasibility with a reasonable specific capacity even after 200 cycles.