Designing g‐C₃N₄/N‐Rich Carbon Fiber Composites for High‐Performance Potassium‐Ion Hybrid Capacitors

Abstract

Potassium‐based energy storage devices (PEDS) are considered as hopeful candidates for energy storage applications because of the abundant potassium resources in nature and high mobility in the electrolyte. although carbon materials show great potential for potassium‐ion storage, poor rate performance, and unsatisfactory cycle lifespan in existing carbon‐based PIBs anode, it also cannot match the dynamics and stability of the capacitor cathode. Nitrogen doping has been proven to be a effective modification strategy to improve the electrochemical performance of carbon materials. Hence, we prepare carbon nanofibers and g‐C 3 N 4 composites with high nitrogen contents (19.78 at%); moreover, the sum of pyrrolic N and pyridinic N is up to 59.51%. It achieves high discharge capacity (391 mAh g −1 at 0.05 A g −1 ), rate capacity (141 mAh g −1 at 2 A g −1 ), and long cycling performance (201 mAh g −1 at 1 A g −1 over 3000 cycles) when as an anode for PIBs. Furthermore, it can deliver promising discharge capacity of 132 mAh g −1 at 0 °C. Moreover, as battery anode for potassium‐ion hybrid capacitors (PIHC) device with an active carbon cathode, it delivers energy/power density (62 and 2102 W kg −1 ) as well as high reversible capacity (106 mAh g −1 at 1 A g −1 ).