Bead‐Like Coal‐Derived Carbon Anodes for High Performance Potassium‐Ion Hybrid Capacitors

Abstract The pursuit of long life, high rate and low‐cost anode materials is of great significance for potassium‐ion hybrid capacitors (PIHCs). Here, the bead‐like coal‐derived carbon films (BCCFs‐800) for PIHCs were synthesized with low‐cost coal as precursor. Benefiting from the well‐designed composite structure, the wettability on the electrode surface was enhanced and the diffusion of electrolyte ions was also facilitated, thereby improving the electrochemical performance of the electrode. A potassium ion hybrid capacitor was fabricated with BCCFs‐800 as battery‐type anode and active carbon as capacitor‐type cathode, and it delivered promising energy and power densities (119 Wh kg −1 at 186 W kg −1 and 2187 W kg −1 at 52 Wh kg −1 ). The as‐obtained earth‐abundant and high performance electrodes will promote the green and clean utilization of coal and accelerate the development of potassium ion electrochemical storage technology.