Clay, an abundant natural material, may hold the answer to developing super high-temperature supercapacitors for powering devices in extreme environments, says new research from Rice University.
According to a report released in Nature’s online journal, Scientific Reports, the supercapacitor created by researchers at Rice University using naturally-occurring clay and room temperature ionic liquids (RTIL) is reliable at temperatures of up to 200°C (392°F), and possibly higher. With such a tolerance, the new supercapacitor design could help raise temperature restrictions on devices used in oil drilling, military and space applications.
“Our intention is to completely move away from conventional liquid or gel-type electrolytes, which have been limited to low-temperature operation of electrochemical devices,” Arava Leela Mohana Reddy, lead author and a former research scientist at Rice University, said.
Though researchers have been trying for years make energy storage devices like batteries and supercapacitors that work reliably in high-temperature environments, traditional materials used to build these devices have limited their success, materials scientist Pulickel Ajayan said. Researchers have been particularly unsuccessful in identifying an electrolyte, which conducts ions between a battery’s electrodes, that won’t break down when exposed to heat. Another problem has been finding a separator that won’t shrink at high temperatures and lead to short circuits.
To solve these problems, the Rice University team created a paste comprised of a room-temperature ionic liquid (RTIL) first developed in 2009 by European and Australian researchers with natural Bentonite clay. The paste was then sandwiched between layers of reduced graphene oxide and two current collectors to form the supercapacitor. According to Reddy, tests and subsequent electron microscope images showed very little change in the paste material after it was heated up to 300°C. Researchers also observed that despite a slight drop in capacity observed in the initial charge/discharge cycles, the supercapacitor remained stable through 10,000 test cycles.
“We found that a clay-based membrane electrolyte is a game-changing breakthrough that overcomes one of the key limitations of high-temperature operation of electrochemical energy devices,” Reddy said. “By allowing safe operation over a wide range of temperatures without compromising on high energy, power and cycle life, we believe we can dramatically enhance or even eliminate the need for expensive thermal management systems.”
