Controllable synthesis of uniform mesoporous H-Nb2O5/rGO nanocomposites for advanced lithium ion hybrid supercapacitors

Abstract

Controllable synthesis of uniform graphene–metal oxide nanocomposites is of great interest in energy storage applications, due to the combination of their merits and the synergistic effects on the enhancement of their electrochemical performance. Herein, we report a controllable synthesis of uniform mesoporous H-Nb₂O₅/rGO nanocomposites, which exhibit higher reversible specific capacity (∼190 mA h g⁻¹), and better rate capability and cycling stability (the capacitance retention is 96.5% over 500 cycles) than pristine H-Nb₂O₅ microflowers, attributed to their large specific surface area (364.17 m² g⁻¹), porous structure, and intimate interface. More remarkably, the H-Nb₂O₅/rGO-based lithium ion hybrid supercapacitor (LIHS) delivered a high energy density of 100.2 W h kg⁻¹ at 50 W kg⁻¹ and still retained 18.3 W h kg⁻¹ at an ultrahigh power density of 20 000 W kg⁻¹, as well as an excellent cycling stability. It is worth noting that some other nanocomposites, including Zn₂Ti₃O₈/rGO, Si/rGO, NaNbO₃/rGO, Nb₄N₅/rGO, and H-Nb₂O₅/2D g-C₃N₄, have also been successfully synthesized by this method, demonstrating that it can be extended to prepare other functional nanocomposites for applications in energy conversion and storage, photocatalytic hydrogen production, sensors, and so on.