A new bendable supercapacitor made from graphene has been developed that charges quickly and safely stores a record-high level of energy for use over a long period. The technology overcomes the issue faced by high-powered, fast-charging supercapacitors: they usually cannot hold a large amount of energy in a small space.
The new supercapacitor is extremely promising for next-generation energy storage technology as either a replacement for current battery technology, or for use alongside it, to provide the user with more power. It was designed with materials that give it a high power density and a high energy density. It also can bend to 180 degrees without affecting performance and doesn’t use a liquid electrolyte, which minimizes risk of explosion and makes it suitable for integrating into phones or wearable electronics.
A graphene electrode material with pores can be changed in size to store the charge more efficiently. This tuning maximizes the energy density of the supercapacitor to 88.1 Wh/L (Watt-hour per liter). Similar fast-charging commercial technology has a relatively poor energy density of 5-8 Wh/L and traditional slowcharging; long-running lead-acid batteries used in electric vehicles typically have 50-90 Wh/L. Power density is two orders of magnitude higher at over 10,000 Watt per liter.
The researchers made electrodes from multiple layers of graphene, creating a dense but porous material capable of trapping charged ions of different sizes. They characterized it using a range of techniques and found it performed best when the pore sizes matched the diameter of the ions in the electrolyte. The optimized material, which forms a thin film, was used to build a proof-of-concept device with both high power and high energy density.
The 6 × 6-cm supercapacitor was made from two identical electrodes layered on either side of a gel-like substance that acted as a chemical medium for the transfer of electrical charge. This was used to power dozens of light-emitting diodes (LEDs) and was found to be highly robust, flexible, and stable.