July 22, 2010
Water-made nanotubes hold more
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.
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
Emerging Technologies for High-Power Energy Storage
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