The integration of electrical double-layer capacitive and pseudocapacitive materials into novel hybrid materials is crucial to realize supercapacitors with high energy and power densities. Here, high levels of energy and power densities are demonstrated in supercapacitors based on a new type of nano-hybrid electrode consisting of polyoxometalate (POM)-coupled graphene in which a polymeric ionic liquid (henceforth simply PIL) serves as an interfacial linker. The adoption of PIL in the construction of nanohybrids enables a uniform distribution of discrete POM molecules along with a large surface area of graphene sheets. When testing electrochemical characteristics under a two-electrode system, as-prepared supercapacitors exhibit a high specific capacitance (408 F g(-1) at 0.5 A g(-1)), rapid rate capability (92% retention at 10 A g(-1)), a long cycling life (98% retention during 2000 cycles), and high energy (56 Wh kg(-1)) and power (52 kW kg(-1)) densities. First-principles calculations and impedance spectroscopy analysis reveal that the PILs enhance the redox reactions of POMs by providing efficient ion transfer channels and facilitating the charge transfer in the nanohybrids.