Construction of Fe7Se8@Carbon nanotubes with enhanced sodium/potassium storage

The Fe 7 Se 8 @Carbon (C) nanotubes are successfully synthesized using Fe 3 O 4 @C nanotubes as sacrificial templates. Fe 7 Se 8 @C nanotubes exhibit excellent rate behaviour and maintainable capacity (319 mAh g −1 at 2 A g −1 upon 720 cycles), when utilized as SIBs anode. Moreover, for PIBs anode, Fe 7 Se 8 @C nanotubes also exhibit outstanding rate behaviour and maintainable capacity 222 mAh g −1 at 2 A g −1 upon 500 cycles). The superior electrochemical performance of Fe 7 Se 8 @C nanotubes is ascribed to the unique structure, where the hierarchical hollow tubular characteristic of Fe 7 Se 8 @C composites can mitigate the volume expansion of Fe 7 Se 8 and supply effective transmission paths for both Na + (K + ) and electrons within repeated cycle processes, and additionally, N -doped carbon layer can further protect the integrality of Fe 7 Se 8 @C nanotubes from destruction within the cycle processes, and enhance electronic conductivity.