Vertical carbon skeleton introduced three-dimensional MnO2 nanostructured composite electrodes for high-performance asymmetric supercapacitors

Abstract

We successfully fabricate a hierarchical three-dimensional (3D) nanocomposite rGO/C/MnO2 composed of 2D/1D rGO/C and MnO2 nanosheets. The vertical porous carbon decorated rGO is obtained by growing covalent organic frameworks (COFs) arrays on the surface of GO with further calcination. After the introduction of the special rGO/C porous substrate, the rGO/C/MnO2 nanocomposite shows the more stable nanostructure, the larger specific surface area (~129.79 m2 g−1), and the better electrical conductivity. Benefiting from these, the rGO/C/MnO2 electrode possesses high specific capacitance (215.2 F g−1 at 0.5 mA cm−2 (~0.15 A g−1)), good rate capability and long cycling stability (72% capacitance retention after 2500 cycles). Solid-state asymmetric supercapacitors are assembled with rGO/C/MnO2 as the positive electrode material, activated carbon (AC) as the negative electrode material, and polyvinyl alcohol (PVA)/LiCl as the gel electrolyte. The device can provide a high power density of 3.6 kW kg−1 at a current density of 20 mA cm−2 (~3.2 A g−1) and a high energy density of 21.2 W h kg−1 at a current density of 1.0 mA cm−2 (~0.16 A g−1). Furthermore, two rGO/C/MnO2//AC asymmetric supercapacitors in series power a commercial LED more than 40 s.