Engineers and scientists at The University of Texas at Austin have achieved a nanotechnology breakthrough in the use of a new carbon-based material with the potential to store large quantities of energy from sources such as renewable wind and solar power.
The researchers believe believe a one-atom thick structure called "graphene" could eventually double the capacity of existing ultracapacitors, which are manufactured using an entirely different form of carbon.
"Through such a device, electrical charge can be rapidly stored on the graphene sheets, and released from them as well, for the delivery of electrical current and, thus, electrical power," says Rod Ruoff, a UT Austin professor. "There are reasons to think that the ability to store electrical charge can be about double that of current commercially used materials. We are working to see if that prediction will be borne out in the laboratory."
Two main methods exist to store electrical energy: in re-chargeable batteries and in ultracapacitors, which are becoming increasingly commercialized but are not yet as popularly known.
Ultracapacitors can be used in a wide range of energy storage applications and are used either by themselves as the primary power source or in combination with batteries or fuel cells.
Ruoff says ultracapcitors offer advantages over batteries, including: higher power capability, longer life, a wider thermal operating range, lighter weight, more flexible packaging and lower maintenance.
Ruoff and his team prepared chemically modified graphene material and, using several types of common electrolytes, have constructed and electrically tested graphene-based ultracapacitor cells.
The amount of electrical charge stored per weight (called "specific capacitance") of the graphene material has already rivaled the values available in existing ultracapacitors, and modeling suggests the possibility of doubling the capacity.
"Our interest derives from the exceptional properties of these atom-thick and electrically conductive graphene sheets, because in principle all of the surface of this new carbon material can be in contact with the electrolyte," Ruoff said. "Graphene’s surface area of 2630 square meters per gram (almost the area of a football field in about 1/500th of a pound of material) means that a greater number of positive or negative ions in the electrolyte can form a layer on the graphene sheets resulting in exceptional levels of stored charge."
The U.S. Department of Energy has said that an improved method for storage of electrical energy is one of the main challenges preventing the substantial installation of renewable energies such as wind and solar power.
The findings of Ruoff’s team will be published in the Oct. 8 edition of Nano Letters. The article was posted on the journal’s Web site this week.
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