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

With the advantages of high energy/power density, long cycling life and low cost, dual-carbon potassium ion hybrid capacitors (PIHCs) have great potential in the field of energy storage. Here, a novel bilayer-shelled N, O-doped hollow porous carbon microspheres (NOHPC) anode has been prepared by a self-template method, which is consisted of a dense thin shell and a hollow porous spherical core. Excitingly, the NOHPC anode possesses a high K-storage capacity of 325.9 mA h g(−1) at 0.1 A g(−1) and a capacity of 201.1 mAh g(−1) at 5 A g(−1) after 6000 cycles. In combination with ex situ characterizations and density functional theory calculations, the high reversible capacity has been demonstrated to be attributed to the co-doping of N/O heteroatoms and porous structure improved K(+) adsorption and intercalation capabilities, and the stable long-cycling performance originating from the bilayer-shelled hollow porous carbon sphere structure. Meanwhile, the hollow porous activated carbon microspheres (HPAC) cathode with a high specific surface area (1472.65 m(2) g(−1)) deriving from etching NOHPC with KOH, contributing to a high electrochemical adsorption capacity of 71.2 mAh g(−1) at 1 A g(−1). Notably, the NOHPC//HPAC PIHC delivers a high energy density of 90.1 Wh kg(−1) at a power density of 939.6 W kg(−1) after 6000 consecutive charge–discharge cycles. [Image: see text] SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s40820-023-01113-6.