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 as combining the advantages of potassium ion batteries (PIBs) with supercapacitors . However, the sluggish kinetics caused by the large radius of K + hinder the practical application of PIHCs. Herein, we synthesized a boron and fluorine co-doping interlaced network porous carbon nanofibers (BF-PCNFs), which was used as the freestanding anode of PIHCs the freestanding anode of PIHCs to alleviate large volume expansion and increase conductivity. Benefiting from the B, F co-doping and porous interlace nanostructure of BF-PCNFs, the anode shows 185 mA h g −1 under a load of 12.6 mg cm −2 , a reversible capacity of 176 mA h 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.