Conjugated polyimide-coated carbon nanofiber aerogels in a redox electrolyte for binder-free supercapacitors

Boosting the energy density of supercapacitors without sacrificing power density and lifespan, requires ingenious electrode materials outfitting both sufficient assessable surface area and fast electrochemical reaction kinetics. Herein, hierarchically porous core-sheath nanoarchitecture was elaborately designed, via a robust support-coating strategy using a cellulose-derived porous carbon aerogel as the conductive 3D skeleton to support a uniform coating of conjugated polyimide. The inner carbon aerogel skeleton ensures a fast electron transfer and the outer conjugated polyimide layer affords abundant micropores and sufficient active sites, hence enriching the charge storage in such a porous core-sheath nanoarchitecture. The as-designed electrode was then applied to a redox electrolyte-assisted supercapacitor (RESC) with the KI-doped H2SO4 redox electrolyte. Due to the redox electrolyte further expediting the electrochemical reaction kinetics, the as-fabricated RESC delivers an ultrahigh electrode specific capacitance of 1139 F g−1 at 5 A g−1, high energy density of 94 Wh kg−1 at a well-maintained power density, and long-term capability with 90% capacitance retention after 10,000 cycles at 100 A g−1. The successful construction of high-performance electrode materials and RESC in this work opens a new insight into the development of the state-of-the-art energy storage systems.