Encapsulation of VC Nanodots within N-Doped Carbon Nanofibers as a Robust and Capacitive Anode for Advanced Sodium-Ion Capacitors

Sodium ion hybrid capacitors (SIHCs) are garnering substantial interest in the energy storage field due to their unique capability to integrate high energy density and power density with the economic advantages of abundant sodium resources. However, the kinetic mismatch between battery-type anodes and capacitor-type cathodes presents a significant obstacle, severely limiting the performance potential of high-performance SIHCs. Herein, we report the development of a favorable pseudocapacitive Na+ storage nanohybrid, featuring VC nanodots confined within an N-doped carbon nanofiber network (VC@N-CNFs), which has been successfully applied to SIHCs. The integration of VC nanodots with a conductive carbon fiber framework significantly enhances electron transport and provides ample interface between the electrolyte and VC active material, thereby effectively improving the reaction kinetics of the anode. Consequently, the VC@N-CNFs demonstrate exceptional sodium storage capability, achieving a high capacity of 160.2 mA h g–1 at 1 A g–1 after 2000 cycles. Thanks to the favorable kinetic matching between the anode and cathode, the assembled SIHCs exhibit high energy and power densities of 97.8 W h kg–1 and 4118.3 W kg–1, respectively, alongside remarkable cycling performance, retaining 73.5% of their capacity after 6000 cycles.