Porous Multishelled NiO Hollow Microspheres Encapsulated within Three-Dimensional Graphene as Flexible Free-Standing Electrodes for High-Performance Supercapacitors
Exploring electrode materials with well-defined nanostructures and good flexiblity is an efficient approach for achieving high-performance and flexible energy storage systems. However, it is still challenging to well integrate active materials into flexible electrodes and simultaneously maintain satisfactory electrochemical performance. Herein, we successfully synthesized a novel three-dimensional graphene (3DG) encapsulated porous multishelled NiO hollow microspheres (3DG/pMS-NiO) composite aerogel via a modified self templating method and the dopamine (DA) assistant self-assembly route. The well-designed highly interconnected porous 3DG network and the close contact NiO-graphene structure of the 3DG/pMS-NiO composite aerogel offers multiple advantages of the high porosity and accessiable area, improved conductivity, enhanced electrolyte diffusion and simple electrode preparation process. Thus, the as-prepared flexible 3DG/pMS-NiO electrodes showed significantly improved specific capacitance of 710.4 A g-1 at 0.5 A g-1 and excellent rate capability with the ultrahigh capacitance retention of 92.5% at 10 A g-1. In addition, the fabricated asymmetric supercapacitors (3DG/pMS-NiO//AC) delivered a high specific capacitance of 34.4 F g-1 at 1 A g-1 with the voltage windows of 0-1.6 V, the large energy density of 12.3 Wh kg-1 at the power density of 815.3 W kg-1, as well as decent cycling stability. This work profoundly enlightens the material design and electrode preparation, and even opens up an avenue for the development of high-performance and flexible energy storage systems.