The laser inside a standard DVD drive can be used to produce sheets of carbon a single atom thick, which store nearly as much energy as a battery but charge hundreds of times faster, researchers report in the 16 March issue of Science.
The thin sheets act as supercapacitors, an energy storage alternative to batteries that has undergone intense research in the past two decades. Flexible and tough, the capacitors built by Maher El-Kady of the University of California, Los Angeles, and colleagues someday could power a new generation of roll-up computer displays, or electronic fabrics that harvest and store energy produced by body movements.
Supercapacitors can charge and discharge more rapidly than batteries, but tend to hold less energy than battery designs. To solve this problem, scientists have been experimenting with single-atom-thick sheets of carbon called graphene. Carbon is excellent at conducting electricity, and spreading it thin creates an exceptionally large surface area on which to store more energy.
But graphene is sticky and often clumps together during processing, preventing its use in practical devices. El-Kady and colleagues’ breakthrough was to hone a block of graphite oxide using the laser inside a DVD drive, a technique that produced high-quality, device-ready graphene.
The graphene-based capacitors created by the research team can store nearly as much energy as a battery, “and the devices can be charged and discharged for more than 10,000 cycles without losing much in performance,” said El-Kady, “compared with a normal lifetime of less than 1000 cycles that is typical for batteries.”
The devices also can be bent without losing their high-power performance, which is an encouraging sign for practical applications. In a commentary on the Science report, John E. Miller of Case Western Reserve writes that these high-power, energy-dense, and mechanically tough materials could find a place in military uniforms that change their own camouflage, car interior displays, and even home décor like electronic wallpaper.
Read the abstract, “Laser Scribing of High-Performance and Flexible Graphene-Based Electrochemical Capacitors,” by Maher El-Kady and colleagues.