A group of researchers at the University of California, Riverside have developed a graphene foam which will improve the performance level of supercapacitors. This development could see electric vehicles accelerate faster and the battery life in portable electronics will be extended.
Supercapacitor performance levels improved
The researchers have discovered that supercapacitors, an energy storage device like batteries and fuel cells, based on transition metal oxide modified nanocarbon graphene foam electrode could work safely in aqueous electrolyte and deliver two times more energy and power compared to supercapacitors that are available on the shelves today.
The foam electrode was successfully cycled over 8,000 times and performance levels showed no sign of fading. The research has been documented in a recently published paper, “Hydrous Ruthenium Oxide Nanoparticles Anchored to Graphene and Carbon Nanotube Hybrid Foam for Supercapacitors,” in the journal Nature Scientific Reports.
The paper was written by graduate student Wei Wang; Cengiz S. Ozkan, a mechanical engineering professor at UC Riverside’s Bourns College of Engineering; Mihrimah Ozkan, an electrical engineering professor; Francisco Zaera, a chemistry professor; Ilkeun Lee, a researcher in Zaera’s lab; and other graduate students Shirui Guo, Kazi Ahmed and Zachary Favors.
Enhancing the supercapacitor
Supercapacitors, also known as ultracapacitors, operate in the space between batteries and traditional capacitors when it comes to the metrics of energy density (the amount of energy stored per unit mass) and power density (the maximum amount of power that can be supplied per unit mass.)
Supercapacitors have attracted substantial attention recently due to their extremely high charge and discharge rate, impressive stability, long cycle life and extremely high power density. These characteristics are exactly what electric vehicle and portable electronics manufacturers are after. However, supercapacitors may only serve as standalone power sources in systems that require power delivery for less than 10 seconds because of their relatively low specific energy.
Batteries can actually store more energy than supercapacitors and capacitors can deliver power a lot faster than supercapacitors. However, since supercapacitors can deliver power fast and charge up quickly in comparison to batteries, they are attractive for many applications, like electric vehicles, where they could be charged up in minutes rather than hours. But compared to batteries, supercapacitors have low energy density. Therefore, researchers are aiming to increase energy density. If this can be done, supercapacitors may replace chemical-based batteries.
Ideal for future energy storage
A team led by Cengiz S. Ozkan and Mihri Ozkan at UC Riverside are working to develop and commercialize nano-structured materials for high energy density supercapacitors.
High capacitance, or the ability to store an electrical charge, is critical to achieve higher energy density. Meanwhile, to achieve a higher power density it is important to have a large electrochemically accessible surface area, high electrical conductivity, short ion diffusion pathways and excellent interfacial integrity. Nanostructured active materials provide a mean to these ends.
According to Mr Wang, other than high energy and power density, the designed graphene foam electrode system also demonstrates a facile and scalable binder-free technique for preparing high energy supercapacitor electrodes. He adds, “These promising properties mean that this design could be ideal for future energy storage applications.”