Core-Shell Nitrogen-Doped Carbon Hollow Spheres/Co3O4 Nanosheets as Advanced Electrode for High-Performance Supercapacitor

Co3O4/nitrogen-doped carbon hollow spheres (Co3O4/NHCSs) with hierarchical structures are synthesized by virtue of a hydrothermal method and subsequent calcination treatment. NHCSs, as a hard template, can aid the generation of Co3O4 nanosheets on its surface; while SiO2 spheres, as a sacrificed-template, can be dissolved in the process. The prepared Co3O4/NHCS composites are investigated as the electrode active material. This composite exhibits an enhanced performance than Co3O4 itself. A higher specific capacitance of 581 F g(-1) at 1 A g(-1) and a higher rate performance of 91.6% retention at 20 A g(-1) are achieved, better than Co3O4 nanorods (318 F g(-1) at 1 A g(-1) and 67.1% retention at 20 A g(-1)). In addition, the composite is employed as a positive electrode to fabricate an asymmetric supercapacitor. The device can deliver a high energy density of 34.5 Wh kg(-1) at the power density of 753 W kg(-1) and display a desirable cycling stability. All of these attractive results make the unique hierarchical Co3O4/NHCS core-shell structure a promising electrode material for high-performance supercapacitors.