Graphene takes charge

Engineers at The University of Texas at Austin believe that graphene could be used as an effective way to store electrical charge in ultracapacitors.

They claim that graphene (a form of carbon) could eventually be used to double the capacity of existing ultracapacitors, which are presently manufactured using an entirely different form of carbon.

Currently, two main methods exist to store electrical energy: in rechargeable batteries and in ultracapacitors. An ultracapacitor can be used in a range of energy-capture and storage applications where they are used either by themselves as the primary power source or in combination with batteries or fuel cells.

Some advantages of ultracapacitors over more traditional energy storage devices such as batteries include a higher power capability, longer life, a wider thermal operating range, lighter, more flexible packaging and lower maintenance.

To test the effectiveness of graphene in such storage devices, the university’s Prof Rod Ruoff and his team developed a chemically modified graphene material.

Using several types of common electrolytes, they constructed and electrically tested several graphene-based ultracapacitor cells. The amount of electrical charge stored per weight (called the specific capacitance) of the graphene material rivalled the values available in existing ultracapacitors, and modelling suggests that capacity could be doubled.

’Graphene’s surface area of 2630m²/g (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,’ said Ruoff.