B, F Co-Doping Flexible Carbon Nanofibers as a Fast and Stable Anode for Potassium-Ion Hybrid Capacitor

Potassium ion hybrid capacitors (PIHCs) have attracted widespread attention because of combining the advantages of potassium ion batteries (PIBs) with supercapacitors. The research of PIHCs is closely related to K + storage materials that are capable of accommodating large-size K + and possess high conductivity. Herein, we synthesized a boron and fluorine co-dop ing interconnected porous carbon nanofibers (BF-PCNFs) for the freestanding anode of PIHCs. Benefiting from the B, F co-doping and unique nanostructure of BF-PCNFs, the anode shows a reversible capacity of 176 mAh g -1 at 1000 mA g -1 after 6000 cycles and the capacity retention from 100 mA g -1 to 5000 mA g -1 is 62%. Furthermore, the PIHCs based on BF-PCNFs as anode and activated carbon as cathode exhibit an energy density of 87 Wh kg -1 and a power density of 393 W kg -1 . The capacity retention is as high as 78% over 4000 cycles. Considering the exceptional rate performance, long cyclability and high-mass-loading, our work may supply a new strategy for designing novel energy storage devices with outstanding performance