Development and Testing of An Asymmetric Supercapacitor Based On a Carbon Foam Electrode Impregnated with Nickel Hydroxide

Supercapacitors have attracted significant attention in recent years due to their potential to power hybrid vehicles, portable audio equipment, and memory back-up devices.  The trend in supercapacitors is to combine a double-layer electrode with a pseudo-capacitance electrode in an asymmetric capacitor configuration.[1]  The double-layer electrode is usually an activated carbon (AC) since it has high surface area, good conductivity, and relatively low cost.[2, 3]  The pseudo-capacitance electrode usually consists of RuO₂, MnO₂, Ni(OH)₂, etc., with the most commonly studied material being Ni(OH)₂ .[4-7]

In this work, a graphitic carbon foam was impregnated with nickel hydroxide active mass using electrochemical deposition to make a nickel-carbon foam electrode.  It served as the pseudo-capacitance electrode in an asymmetric supercapacitor. Carbon foam was used as a conductive holder of the active mass because of its electrical conductivity, pore size, and pore connectivity.  The objective was to reduce the cost and weight of the supercapacitor while maintaining or increasing its capacitance and gravimetric energy storage density.  The specific capacitance of the nickel-carbon foam electrode at different current densities was measured in constant-current flooded cell cycling tests. The measured specific capacitance of 2641 F/g at 5 mA/cm² was higher than a reported value of 2080 F/g for an Al-substituted α-Ni(OH)₂ electrode.[6]  The nickel-carbon foam electrode was then combined with an AC at different ratios of the negative and positive electrode masses to study asymmetric cell performance.  The mass ratio for optimum cell discharge capacity was found to be ~3.7.

References

[1]        A.I. Belyakov, 3rd European Symposium on Supercapacitors and Applications (ESSCAP) Roma, Italy, 2008.

[2]        K. Babel, K. Jurewicz, Journal of Physics and Chemistry of Solids  65 (2004) 275-280.

[3]        P.-L. Taberna, Geoffroy Chevallier, P. Simon, D. Plee, T. Aubert, Materials Research Bulletin  41 (2006) 478-484.

[4]        Jong Hyeok Park, Sungwook Kim, O Ok Park, J.M. Ko, Applied Physics A  82 (2006) 593-597.

[5]        D.-D. Zhao, S.-J. Bao, W.-J. Zhou, H.-L. Li, Electrochemistry Communications  9 (2007) 869-874.

[6]        J.-W. Lang, L.-B. Kong, M. Liu, Y.-C. Luo, L. Kang, Journal of Solid State Electrochemistry  14 (2010) 1533-1539.

[7]        Q. Huang, X. Wang, J. Li, C. Dai, S. Gamboa, P.J. Sebastian, Journal of Power Sources  164 (2007).