APPLICATIONS OF TECHNOLOGY:
- Electric power grid management
- Hybrid automobiles
- Mobile electronic equipment
- Pulsed lasers
- Uninterrupted power supplies
- High power-to-size ratio
- Single step, low temperature fabrication process
- Lower cost than carbon nanotube supercapacitors
Berkeley Lab scientist Yuegang Zhang and colleagues have invented an efficient method of fabricating carbon nanofiber supercapacitors using a nickel foam substrate. This technology eases the way for scaled-up production of versatile charge storage devices with a small form factor and high power-to-size ratio.
Sponge-like nickel foam is highly porous, providing a large surface area for growth of carbon fibers. However, the standard technique for growing carbon nanofibers requires annealing to “rough-up” the nickel surface to prevent the carbon from growing in sheets. The Berkeley Lab technology deposits a thin layer of aluminum oxide on the nickel foam surface. This insulating layer promotes the growth of dense concentrations of carbon nanofibers, but not sheets.
The aluminum oxide layer also inhibits formation of Ni3C, which degrades capacitor performance and makes the nickel brittle. Carbon nanofibers cover the internal and external surfaces of the porous nickel foam. The large surface area of the nanofibers and the metallic foam on which it grows produce a very high capacitance (measured as 1.2 farads/cm2), an energy density that current capacitors cannot approach. Carbon nanotubes are capable of even higher energy densities, but are much more difficult to produce.
Supercapacitors are electrochemical devices capable of storing much higher charges than conventional electrolytic capacitors. The high surface-to-volume ratio of carbon nanotubes and nanofibers make them highly suitable as supercapacitor materials. Yet production of these devices remains a significant scientific and engineering challenge.
DEVELOPMENT STAGE: Proven principle.
STATUS: Patent pending. Available for licensing or collaborative research.
FOR MORE INFORMATION:
Futaba, D.N., Hata, K., Yamada, T., Hiraoka, T., Hayamizu, Y., Kakudate, Y., Tanaike, O., Hatori, H., Yumura, M., Iijima, S., “Shape-engineerable and highly densely packed single-walled carbon nanotubes and their application as super-capacitor electrodes.” Nature Materials. Vol. 5. 987-994 (2006).
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REFERENCE NUMBER: JIB-2821