High-performance asymmetric supercapacitors of advanced double ion-buffering reservoirs based on battery-type hierarchical flower-like Co3O4-GC microspheres and 3D holey graphene aerogels

Abstract

We have prepared 2D macromolecular brushes of G>N-PEGm nanosheets and CNT>N-PEGm from the Graphene and CNTs with methoxypolyethylene glycol (mPEG) via Nitrene Chemistry, respectively. Owing to a typical solvothermal method, the hierarchical flower-like spheres of Co3O4-G>N-PEGm-CNT>N-PEGm (Co3O4-GC) ternary composites have been synthetized, which present honeycomb-like structures as “ion-buffering reservoir” and substantial ion-diffusion channels in the ultrathin 2–4 nm Co3O4 nanosheets. And as typical battery-type positive electrode materials, a high capacity of Co3O4-GC can be calculated up to 173.3 mAh g−1 at 0.5 A g−1 (the specific capacitance can be achieved to 1783 F g−1). On the other hand, 3D holey reduced graphene oxide and carboxylic CNT aerogels (HRGOCNTc, denoted as HRGC) formed with holey graphene and the acid-modified CNTc are summarized as 282.3 Fg−1 (78.4 mAh g−1) at 0.5 A g−1, demonstrating excellent long cycling performance. The advanced double “ion-buffering reservoirs” of asymmetric supercapacitors Co3O4-GC//3D HRGC energy devices are further fabricated based on advanced battery-type Co3O4-GC as positive electrode and 3D HRGC aerogels as negative electrode, meanwhile the asymmetric devices with excellent electrochemical performance also exhibit 42.6 Wh kg−1 at power densities of 775 W kg−1 and 81.1% capacitance maintained after 10,000 cycles for energy-storage and energy-conversion potential application.