In order to meet today’s energy demands, engineers are getting creative—making batteries out of packing peanuts, using the gas from rotting trash to fuel vehicles, and now—turning scrap tires into supercapacitors. As the name implies, a supercapacitor has very high capacitance (ability to store an electrical charge). Researchers from the Department of Energy’s Oak Ridge National Laboratory (ORNL) and Drexel University developed a technology for processing old tires so they could be used in supercapacitors for vehicles or even electrical grid storage.
The new technology follows an earlier ORNL discovery of a method to use scrap tires for batteries. “Each tire can produce carbon with a yield of about 50 percent with the ORNL process,” said researcher Yury Gogotsi. “If we were to recycle all of the scrap tires, that would translate into 1.5 million tons of carbon, which is half of the annual global production of graphite.”
To transform tires into supercapacitors, the researchers first soaked crumbs of tire rubber in sulfuric acid. Then they washed the rubber and heated it, gradually increasing the temperature to as high as 1,100 degrees Celsius. After additional processing, they mixed the refined material with an electrically conductive polymer to make the supercapacitors.
“We anticipate that the same strategy can be applied to deposit other pseudocapacitive materials with low-cost tire-derived activated carbon to achieve even higher electrochemical performance and longer cycle life, a key challenge for electrochemically active polymers,” Gogotsi said. This simultaneously meets two needs: energy storage and getting rid of the 300 million tires that are thrown out each year in the U.S. alone.