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

• Published in: Small (Weinheim an der Bergstrasse, Germany) Vol. 14; no. 12
• Main Authors: Liu, Tao, Zhang, Liuyang, You, Wei, Yu, Jiaguo
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 22-03-2018
• Subjects: asymmetric; Co3O4; Cobalt oxides; Electrode materials; Electrodes; Flux density; hollow carbon spheres; Hydrothermal crystal growth; Nanorods; Nanosheets; Nanotechnology; nitrogen (N)‐doped; Silicon dioxide; Structural hierarchy; Supercapacitors
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.201702407

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.
The Co3O4/N‐doped carbon hollow sphere (Co3O4/NHCS) with a core–shell structure, where Co3O4 nanosheets serve as the shell and NHCS as the core, has large surface area and hierarchical porous structure. The asymmetric supercapacitor assembled with Co3O4/NHCS as a positive electrode and activated carbon as a negative electrode exhibits an excellent electrochemical performance.