July 22, 2010

Water-made nanotubes hold more juice

Use water to make carbon nanotubes and you can store more energy in and get more power out of ultracapacitors.

A water-based method of making densely-packed, vertically-aligned arrays of single-walled carbon nanotubes eliminates most of the impurities that result from other nanotube manufacturing processes.

Ultracapacitor electrodes made with the pure nanotubes have exceptionally high energy storage capacity and power. The nanotubes' purity makes the electrodes more stable, which allows the ultracapacitor to operate at 4 volts rather than the usual 3. Higher operating voltage means higher capacity and power.

A prototype ultracapacitor made with the nanotube electrodes stores 94 watt hours per kilogram of energy and delivers 210 kilowatts per kilogram of power. Commercial ultracapacitors made with activated carbon electrodes typically store 5 watt hours per kilogram of energy and deliver 10 kilowatts per kilogram of power.

Research paper:
Extracting the Full Potential of Single-Walled Carbon Nanotubes as Durable Supercapacitor Electrodes Operable at 4 V with High Power and Energy Density
Advanced Materials, published online June 18, 2010

Researchers' contact:
Kenji Hata

Related report:
Ultracapacitors: Emerging Technologies for High-Power Energy Storage

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