Capacitive Performance of Graphene-based Asymmetric Supercapacitor

• Published in: Electrochimica acta 2017-03, Vol.229, p.173-182
• Main Authors: Ng, C.H., Lim, H.N., Hayase, S., Zainal, Z., Shafie, S., Huang, N.M.
• Format: Article
• Language: English
• Subjects: Asymmetric supercapacitor; Asymmetry; Capacitance; cobalt oxide; Density; Electric potential; Electrode materials; Electrodes; Flux density; Graphene; Nanostructured materials; polypyrrole; Studies; Supercapacitors; Synergistic effect; Zinc oxide
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2017.01.139

[Display omitted] •A highly crystalline flower-like reduced graphene oxide/zinc oxide/cobalt oxide nanostructure positive electrode was fabricated.•The asymmetric supercapacitor exhibited a high energy density of 41.8Wh/kg.•The device exhibited a high specific capacitance and excellent cycling stability.•The asymmetric supercapacitor outperformed the KEMET commercial supercapacitor. A two-electrode asymmetric supercapacitor with positive and negative electrodes was developed. The positive electrode was composed of reduced graphene oxide/zinc oxide/cobalt oxide nanostructures (RZCo) that were prepared using a one-pot hydrothermal process. Meanwhile, polypyrrole/reduced graphene oxide (PyR) was electrodeposited on a graphite sheet as the negative electrode. These electrodes were separated by a 1.0M Na2SO4 filter membrane. The synergistic effect between the positive and negative electrode materials widened the potential window to 1.6V, thus contributing a high energy density of 41.8 Wh/kg at 2mV/s, which was better than that of the KEMET commercial supercapacitor (17.7 Wh/kg). At room temperature (30°C), the RZCo//PyR asymmetric supercapacitor exhibited a retention of 87% after 800 cycles compared to a retention of only 49% at 0°C. Although the asymmetric supercapacitor retained 86% of its original capacitance at 60°C, it possessed a lower specific capacitance than the asymmetric supercapacitor measured at room temperature. The RZCo//PyR asymmetric supercapacitor had a larger specific capacitance and smaller IR drop (0.09V) than the KEMET commercial supercapacitor, which has a huge IR drop (0.22V), providing a specific capacitance of 77.7F/g.