By employing proprietary pretreatment and processing, researchers at Oak Ridge National Laboratory and Drexel University have produced flexible polymer carbon composite films from scrap tires for use as electrodes for supercapacitors.
The first synthesized highly porous carbon (1625 m2 g−1) using waste tires as the precursor. The narrow pore-size distribution and high surface area led to good charge storage capacity, especially when used as a three-dimensional nanoscaffold to polymerize polyaniline (PANI). The resulting composite paper was highly flexible, conductive, and exhibited a capacitance of 480 F g−1 at 1 mV s−1 with excellent capacitance retention of up to 98% after 10,000 charge/discharge cycles.
The team attributed the high capacitance and long cycle life to the short diffusional paths, uniform PANI coating, and tight confinement of the PANI in the inner pores of the tire-derived carbon, which minimized the degradation of the PANI upon cycling.
The technology, described in a paper published in ChemSusChem, follows an ORNL discovery of a method to use scrap tires for batteries. (Earlier post.) Together, these approaches could provide some relief to the problems associated with the 1.5 billion tires manufacturers expect to produce annually by 2035.
Those tires will eventually need to be discarded, and our supercapacitor applications can consume several tons of this waste. Combined with the technology we’ve licensed to two companies to convert scrap tires into carbon powders for batteries, we estimate consuming about 50 tons per day.—Dr. M. Parans Paranthaman, Chemical Sciences Division, ORNL, co-corresponding author
While that amount represents just a fraction of the 8,000 tons that need to be recycled every day, co-corresponding author Dr. Yury Gogotsi of Drexel noted that other recycling companies could contribute to that goal.
Each tire can produce carbon with a yield of about 50 percent with the ORNL process. 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.—Dr. Yury Gogotsi
To produce the carbon composite papers, the researchers soaked crumbs of irregularly shaped tire rubber in concentrated sulfuric acid. They then washed the rubber and put it into a tubular furnace under a flowing nitrogen gas atmosphere. They gradually increased the temperature from 400 degrees Celsius to 1,100 degrees.
After several additional steps, including mixing the material with potassium hydroxide and additional baking and washing with deionized water and oven drying, researchers have a material they could mix with polyaniline, an electrically conductive polymer, until they have a finished product.
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.—Dr. Gogotsi
Funding for this research was provided by DOE’s Office of Science and the Laboratory Directed Research and Development and Technology Innovation programs at ORNL.
Boota, M., Paranthaman, M. P., Naskar, A. K., Li, Y., Akato, K. and Gogotsi, Y. (2015) “Waste Tire Derived Carbon–Polymer Composite Paper as Pseudocapacitive Electrode with Long Cycle Life.” ChemSusChem doi: 10.1002/cssc.201500866