Organic redox-active molecules have been identified as promising cathodes for practical usage of potassium-ion batteries (PIBs) but still struggle with serious dissolution problems and sluggish kinetic properties. Herein, we propose a pseudocapacitance-dominated novel insoluble carbonyl-based cathode, [2,6-di[1-(perylene-3,4,9,10-tetracarboxydiimide)]anthraquinone, AQ–diPTCDI], which possesses high reversible capacities of 150 mAh g^–1, excellent cycle stability with capacity retention of 88% over 2000 cycles, and fast kinetic properties. The strong intermolecular interactions of AQ–diPTCDI and in situ formed cathode electrolyte interphase films support it against the dissolution problem. The high capacitive-like contribution in capacities and fast potassium-ion diffusion enhance its reaction kinetics. Moreover, a symmetric organic potassium-ion battery (OPIB) based on AQ–diPTCDI electrodes also exhibits outstanding K-storage capability. These results suggest that AQ–diPTCDI is a promising organic cathode for OPIBs and provide a practicable route to realize high-performance K storage.