Electrochemical capacitors store electrical charge for later discharge when needed. Most capacitors store charge in a sandwich-like double layer too big to fit in the modern-day electronic circuit, limiting their practical applications.
Now, researchers from the University of California, Los Angeles, and Cairo University has designed a tiny, flexible supercapacitor made of graphene that can be fabricated on a single electronic chip, which will help realize the next generation of flexible electronic devices such as electronic paper, displays and health-monitoring kits1.
The team first etched circuits on a DVD disc coated in a film of graphite oxide and exposed it to a laser from a consumer LightScribe DVD burner. They then coated these supercapacitors with an ionogel electrolyte and were left with graphene micro-supercapacitors (MSC).
The MSCs exhibited high power density, meaning such capacitors can charge and discharge energy very quickly, and more than 100 can be produced on a single disc in 30 minutes. The presence of the ionogel electrolyte allowed the MSCs to operate at a voltage window of 2.5 V – higher than most traditional supercapacitors that operate at 1V – giving it a wider set of potential applications. In addition, the MSCs still worked well after 30,000 cycles of charge and discharge and remained electrochemically stable after being bent or twisted.
"These MSCs could be integrated on chips on a large scale at low cost," says Richard Kaner, a co-author of the study.
El-Kady, M. F. et al. Scalable fabrication of high-power graphene micro-supercapacitors for flexible and on-chip energy storage. Nat. Comm. (2013) doi:10.1038/ncomms2446