Researchers at University of Texas - Austin have created a novel form of three-dimensional carbon that can be used as a greatly enhanced supercapacitor, holding promise for energy storage in everything from energy grids and electric cars to consumer electronics.
The new porous material has the potential to give supercapacitors a boost by delivering significantly more charge, opening the doors to many potential unprecedented uses for this type of electrical energy storage device, say the researchers.
"We synthesized a new sponge-like carbon that has a surface area of up to 3,100 square meters per gram (two grams has a surface area roughly equivalent to that of a football field). It also has much higher electrical conductivity and, when further optimized, will be superb for thermal management as well," said University of Texas team leader Rodney Ruoff. "The processes used to make this porous carbon are readily scalable to industrial levels."
Supercapacitors are similar to batteries in that both store electric charge, but batteries do so through chemical reactions that take time to react, which means energy is stored and released relatively slowly. Supercapacitors, on the other hand, store a charge in a way that is similar to static electricity and are able to deliver energy much faster and more efficiently than batteries, but usually hold much less electrical charge.
The new carbon material developed by the UT-Austin researchers may change that. Supercapacitors made from it have an energy-storage capacity that is approaching that of lead-acid batteries, while retaining the high power density characteristic of supercapacitors.
"This new material combines the attributes of both electrical storage systems," said Ruoff. "After we realized that we had a new carbon with a highly novel structure that showed superb performance as an electrode, we knew that this direction of research — to create carbon materials that consist of a continuous three-dimensional porous network with single-atom-thick walls — was likely to yield the optimum electrode material for supercapacitors." The widths of the pores range from 1 to 5 nanometers, or billionths of a meter.
To synthesize the carbon material, the team used microwaves to first exfoliate graphite oxide and then they treated it with potassium hydroxide, which created a carbon full of tiny holes — essentially a sponge that, when combined with an electrolyte, can store a giant electrical charge.
The next step was to confirm the precise shape of the material. Ruoff turned to scientists at the U.S. Department of Energy’s Brookhaven National Laboratory for a look at its nanoscale structure using the highest resolution microscopes in the world. Their observations confirmed Ruoff's hypothesis that the carbon was a new three-dimensional material having highly curved, single-atom-thick walls of of crystalline carbon that form tiny pores (as seen in the above image).