Constructing N-Doped porous carbon confined FeSb alloy nanocomposite with Fe-N-C coordination as a universal anode for advanced Na/K-ion batteries

Sb-based anodes have shown great potential in sodium-ion batteries (SIBS) and potassium-ion batteries (PIBs) owing to their high theoretical capacities and applicable voltage platforms, but they usually suffer from severe volume change and sluggish ion diffusion kinetic. Herein, a novel N-doped three-dimension porous carbon network confined nanosized FeSb alloy composite (3D FeSb@NC) with a strong Fe-N-C bond is elaborately designed and fabricated, this unique structure sufficiently relieves the volume change of Sb during cycling, reduces the diffusion length for both ion/electrons, enhances the electronic conductivity, and provides abundant active sites for Na+/K+ storage. Moreover, the strong Fe-N-C bond can strengthen the interface adhesion between carbon matrix and alloy particle for sustaining structure integrity. The 3D FeSb@NC anodes delivers outstanding electrochemical performances in both SIBS and PIBs, in terms of ultralong cycling life (capacity retention of 85% after 750 cycles for SIBS and 80% after 1000 cycles for PIBs) and excellent rate capability (231 mAh g at 5 A g(-1) for SIBS and 119.7 mAh g at 2 A g(-1) for PIBs). The kinetic analysis of Na+/K+ storage reveal that the extrinsic pseudo-capacitive contribution accounts for the high rate performance. This work provides an effective strategy to develop nanocomposite anode with superior structural stability and durability for SIBS/PIBs.