Construction of FeSe₂ nanoparticles encapsulated in TiN/N-doped carbon nanofibers intertwined with in-situ grown CNTs for pseudocapacitive Na⁺ storage

Metal selenides are recognized as potential anodes for sodium-ion batteries because of their high theoretical capacity. However, they face the hurdles of low electronic conductivity and significant volume change. In this study, a composite material consisting of FeSe₂ nanoparticles enclosed within TiN/N-doped carbon nanofibers intertwined with in-situ grown carbon nanotubes (FeSe₂@TNCF/CNTs) is successfully prepared by electrospinning, carbonization, and selenization approach. The TiN/N-doped carbon nanofibers enhance electronic conductivity, active sites for sodium-ion storage, and structural stability. Moreover, carbon nanotubes (CNTs) that in-situ grown on the carbon nanofibers not only enhance conductivity but also facilitate electrolyte penetration and buffer volume expansion. Benefiting from the synergistic effects of FeSe₂, TiN, N-doped carbon nanofibers and CNTs, the hybrid FeSe₂@TNCF/CNTs anode demonstrates long-term cycling stability and ultrafast pseudocapacitive sodium storage capability, with a specific capacity of 388.5 mAh/g delivered at 0.2 A/g after 1000 cycles. This work could provide inspiration for further research into the design and manufacture of high-performance materials for use in energy storage systems.