Novel Bilayer-Shelled N, O-Doped Hollow Porous Carbon Microspheres as High Performance Anode for Potassium-Ion Hybrid Capacitors

Highlights Proposing a one-step pyrolysis strategy to fabricate a novel bilayer-shelled N, O-doped hollow porous carbon microspheres (NOHPC) anode. The optimized NOHPC anode displays a high K-storage capacity of 325.9 mAh g−1 at 0.1 A g−1 and excellent rate performance (201.1 mAh g−1 at 5 A g−1 after 6000 cycles). The assembled NOHPC//hollow porous activated carbon microspheres (HPAC) potassium ion hybrid capacitors deliver a high energy density of 90.1 Wh kg−1 at a power density of 939.6 W kg−1 even over 6000 cycles.