Heterostructural Three-Dimensional Reduced Graphene\nOxide/CoMn₂O₄ Nanosheets toward a Wide-Potential\nWindow for High-Performance Supercapacitors

Abstract

Hybrid nanostructures\nhave been extensively utilized for supercapacitors, because the hybrid\napproach offers opportunities to combine Faradaic and capacitive energy\nstorage mechanisms into one material. However, the fabrication of\nhybrid nanostructures with controllable morphologies and electronic\nstructure and an understanding of the synergetic effects mechanism\nbetween components remain a common and critical challenge for the\nuse of hybrid nanostructures as electrodes for supercapacitors. Here,\nwe develop a simple method for the fabrication of interconnected CoMn₂O₄ mesoporous nanosheets on three-dimensional reduced\ngraphene oxide supported by nickel foam as the electrode for supercapacitors.\nResulting from their different work functions, interface charge separation\nand built-in electric field are induced by the CoMn₂O₄/3DrGO heterostructure, thus modulating the charge transfer\nkinetics and the operation voltage. As a result, the CoMn₂O₄/3DrGO heterostructure exhibits increased operating\nvoltage, specific capacitances, and cycling stability. As a proof-of-concept\napplication, an all-solid-state flexible asymmetric supercapacitor\nwith CoMn₂O₄/3DrGO as the positive electrode\nand 3DrGO electrode as the negative electrode is fabricated. The obtained\nall-solid-state flexible supercapacitor with an extended operating\nvoltage window of 1.8 V achieves an exceptional energy density of\n46.35 W h kg^–1, as well as excellent cyclability\nwith 89.7% capacitance retention after 5000 cycles and good structural\nflexibility. This work provides a novel strategy for enhancing kinetic\naspects and energy densities by controlling electronic properties\nof the hybrid nanostructures.