Hierarchical Composite Electrodes of Nickel Oxide Nanoflake 3D Graphene for High-Performance Pseudocapacitors

• Published in: Advanced functional materials Vol. 24; no. 40; pp. 6372 - 6380
• Main Authors: Wang, Chundong, Xu, Junling, Yuen, Muk-Fung, Zhang, Jie, Li, Yangyang, Chen, Xianfeng, Zhang, Wenjun
• Format: Journal Article
• Language: English
• Published: Blackwell Publishing Ltd 29.10.2014
• Subjects: Asymmetry; Capacitance; Capacitors; Density; Electrodes; Graphene; hierarchical composite electrodes; Nanostructure; nickel oxide nanoflakes; pseudocapacitors; Three dimensional
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201401216

NiO nanoflakes are created with a simple hydrothermal method on 3D (three‐dimensional) graphene scaffolds grown on Ni foams by microwave plasma enhanced chemical vapor deposition (MPCVD). Such as‐grown NiO‐3D graphene hierarchical composites are then applied as monolithic electrodes for a pseudo‐supercapacitor application without needing binders or metal‐based current collectors. Electrochemical measurements impart that the hierarchical NiO‐3D graphene composite delivers a high specific capacitance of ≈1829 F g−1 at a current density of 3 A g−1 (the theoretical capacitance of NiO is 2584 F g−1). Furthermore, a full‐cell is realized with an energy density of 138 Wh kg−1 at a power density of 5.25 kW kg−1, which is much superior to commercial ones as well as reported devices in asymmetric capacitors of NiO. More attractively, this asymmetric supercapacitor exhibits capacitance retention of 85% after 5000 cycles relative to the initial value of the 1st cycle. Hierarchical nickel oxide nanoflake 3D graphene electrodes are developed by growing NiO nanoflakes atop 3D architecture of graphene on Ni foam. The optimum structure enables the 3‐electrode pseudocapacitors and 2‐electrode full cells to deliver outstanding electrochemical performance. In a full cell configuration, the achieved power density is much higher than that of commercially available asymmetric capacitors.