Heterostructural Three-Dimensional Reduced Graphene Oxide/CoMn₂O₄ Nanosheets toward a Wide-Potential Window for High-Performance Supercapacitors

Hybrid nanostructures have been extensively utilized for supercapacitors, because the hybrid approach offers opportunities to combine Faradaic and capacitive energy storage mechanisms into one material. However, the fabrication of hybrid nanostructures with controllable morphologies and electronic structure and an understanding of the synergetic effects mechanism between components remain a common and critical challenge for the use of hybrid nanostructures as electrodes for supercapacitors. Here, we develop a simple method for the fabrication of interconnected CoMn2O4 mesoporous nanosheets on three-dimensional reduced graphene oxide supported by nickel foam as the electrode for supercapacitors. Resulting from their different work functions, interface charge separation and built-in electric field are induced by the CoMn2O4/3DrGO heterostructure, thus modulating the charge transfer kinetics and the operation voltage. As a result, the CoMn2O4/3DrGO heterostructure exhibits increased operating voltage, specific capacitances, and cycling stability. As a proof-of-concept application, an all-solid-state flexible asymmetric supercapacitor with CoMn2O4/3DrGO as the positive electrode and 3DrGO electrode as the negative electrode is fabricated. The obtained all-solid-state flexible supercapacitor with an extended operating voltage window of 1.8 V achieves an exceptional energy density of 46.35 W h kg–1, as well as excellent cyclability with 89.7% capacitance retention after 5000 cycles and good structural flexibility. This work provides a novel strategy for enhancing kinetic aspects and energy densities by controlling electronic properties of the hybrid nanostructures.