Much electricity from carbon flakes

Science and techno world topic: Electronics

Tiny flakes of pure carbon give very powerful current memory. Corresponding results presented American and Egyptian chemist in the magazine "Science". Manufactured with a simple but elegant method, the capacitor reaches its graph storage capacity of conventional rechargeable batteries, can be recharged within seconds, however.

Graphics: Copyright Science 

"Such a remarkable performance is not reached by commercial elements," the researchers write to Richard Kaner of the University of California at Los Angeles. In addition, you can fold its graphs capacitors as desired and turn. Therefore, "they might be ideally suited for use in flexible and portable electronic devices of the next generation."

Kaner and colleagues present their graphs capacitors forth in a most cost-effective manner. The starting material is composed of pure carbon graphite, as is known from the pencil lead. By treatment with sulfuric acid and oxidizing agents thereof formed graphite, wherein the material disintegrates into individual layers. This oxide flakes divorced from the researchers on a surface, place them in a standard DVD burner. The laser burner drives the oxygen atoms out of the oxide from back and remains a very thin, electrically conductive film extremely well graphene flakes.

A stack of two layers of graphene and a gel-like polymer barrier layer results in a less than 0.1 millimeters thick capacitor, say the chemists. Due to the large internal surface of the graphene film of 1,520 square meters per gram can save the thin and pliable component already at an operating voltage of 1 volt abundant electrical energy.

The efficiency increases when the polymer gel instead of an ionic liquid as a separating medium is used. With an operating voltage of 4 volts now reached the laboratory prototype of an energy density of nearly 200 watt-hours per kilogram and is thus closer to commercial lithium-polymer batteries. Due to the high conductivity of the graphene film, he can hold its charge very quickly and also release it and causing it to a power density of about 2,800 kilowatts per kilogram.

Research: F. El-Kady Maher, Veronica Strong, Sergey Dubin and Richard B. Kaner, Department of Chemistry and Biochemistry and California Nanosystems Institute, University of California, Los Angeles, and Department of Chemistry, Cairo University, Giza

Publication Science, Vol 335, 16 March 2012, pp. 1326-30, DOI 10.1126/science.1216744