Potassium-ion hybrid capacitors (PIHCs), as a new type of electrochemical energy storage device, have become one of the candidates for large-scale energy storage technology due to their low cost and abundant resources. Carbon-based materials exhibit excellent conductivity, chemical stability, abundant availability, and low cost, making them become the most promising anode materials used for PIHCs. Notably, introducting local nanographitic domains into heteroatom-doped and defect-rich carbon-based materials is expected to provide sufficient reactive sites and structural stability, together with maintaining good electrical conductivity and ion diffusion rate. However, the larger radius of potassium ions leads to slow migration rates, and the repeated intercalation and deintercalation processes easily cause structural collapse of the active material, which limits the application of the devices. In this regard, developing low-cost carbon materials to achieve rapid ion diffusion and good cyclic stability has become an important challenge for the current development of PIHCs. Herein, the N/P co-doped coal-based carbon materials with local graphitic domain structure were prepared with a high-temperature catalytic confinement strategy by using cheap coal pitch as the carbon precursor, and their potassium storage properties and reaction kinetics were investigated. The study shows that N/P dual doping introduced abundant defects, which provide a large number of edge-active sites for the adsorption/desorption of K⁺. Meanwhile, the catalytically grown nanoscale graphitic domains facilitate rapid electron and ion transport. Thanks to the synergistic effect of the localized graphitic domains, rich active nitrogen, and defect network structure in the coal-based carbon material, the optimized NPC-800 anode exhibits excellent potassium storage capability (a specific capacity of 196.3 mA h g^-1 at 2 A g^-1) and cycling stability (1000 cycles). In addition, the assembled PIHCs (AC//NPC-800) with commercial activated carbon (AC) cathode and the NPC-800 anode achieves a high energy density of 101.4 Wh kg^-1 and long cycling stability (1000 cycles), demonstrating its promising application prospects. Given the abundance and low cost of coal tar pitch and potassium resources, this work provides a feasible strategy for the application of low-cost coal-based carbon materials in secondary batteries and electrochemical capacitors.

Key words: potassium-ion hybrid capacitors, coal pitch, carbon material, rich defect, local graphitic domain