Porous Nb₄N₅/rGO Nanocomposite for Ultrahigh-Energy-Density Lithium-Ion Hybrid Capacitor

To meet the increasing demands for high-performance energy storage devices, an advanced lithium-ion hybrid capacitor (LIHC) has been designed and fabricated, which delivers an ultrahigh energy density of 295.1 Wh kg^-1 and a power density of 41 250 W kg^-1 with superior cycling stability. The high-performance LIHC device is based on the uniform porous Nb₄N₅/rGO nanocomposite, which has an intimate interface between the firmly contacted Nb₄N₅ and rGO through the Nb(Nb₄N₅)-O(rGO)-C(rGO) bonds, significantly improving the electron transport kinetics. Moreover, the introduction of rGO nanosheets can prevent the Nb₄N₅ nanoparticles from agglomeration, not only resulting in a larger specific surface area to provide more active sites but also accommodating the strain during Li ion insertion/deinsertion. Therefore, the Nb₄N₅/rGO nanocomposite exhibits a higher reversible specific capacity and better rate and cycling performance than the Nb₄N₅ nanoparticle. In view of the scalable preparation and superior electrochemical characteristics, the Nb₄N₅/rGO nanocomposite would have great potential practical applications in the future energy storage devices.