Graphite oxide is a yellowish substance that has been the subject of previous research into graphene manufacture, since it can yield a form of graphene under a variety of treatments including pulses of light. The problem is to achieve the precise, uniform structure of natural graphene, in bulk quantities.
The LightScribe laser works around that by reducing and stripping a thin layer of graphite oxide to form graphene on the spot. The result is a flat surface without the performance-inhibiting pores that characterize activated carbon.
Peel-away electrodes for your DIY supercapacitor
The graphite oxide coating is preceded onto the blank DVD by a layer of plastic. When the LightScribe operation is finished, the plastic can simply be peeled off the DVD with its atom-thick layer of graphene intact, and cut into shape literally with a pair of scissors (check out YouTube for a video of the process). Two of the sheets, with an electrolyte in between, form the supercapacitor.
Source: Clean Technica (http://s.tt/17zJE)
youtube wrote:Imagine having an energy storage device that stores as much energy as a conventional battery, yet, can be charged 100 to 1000 times faster. Supercapacitors store charge in electrochemical double layers whereas batteries store charge through electrochemical reactions. Although supercapacitors can charge and discharge much faster than batteries, they are still limited by low energy densities and slow rate capabilities.
Researchers at UCLA have successfully used an inexpensive precursor (graphite oxide) to produce high-performance graphene-based supercapacitors using a computerized LightScribe DVD drive. These devices exhibit ultrahigh energy density values in different electrolytes approaching those of batteries, yet they can be charged in seconds. The devices can be charged and discharged for more than 10,000 cycles without losing much in performance compared with a normal life-time of less than 1000 cycles typical for batteries. Additionally, the devices are completely flexible and maintain excellent performance under high mechanical stress.
Read more at Chemistry World
Chemistry World wrote:DVD player burns graphene to disc
15 March 2012
Producing a highly sought wonder material can be as easy as burning a DVD. That is according to chemists in the US, who have used a standard DVD player to reduce films of graphite oxide to graphene. These graphene films can be made into high-performance, flexible capacitors fit for bendy solar cells or roll-up displays.
A lot of current research is focused on producing high-performance capacitors for energy storage. Electrochemical capacitors, otherwise known as supercapacitors, have some promising attributes - they can undergo frequent charge and discharge cycles, for instance - but in general they are still limited by low energy and power densities. Higher energy densities would enable devices to run longer, while higher power densities would enable them to run faster.
Graphene - the subject of the 2010 physics Nobel prize - is one material that could improve the performance of electrochemical capacitors. A sheet of graphite just one atom thick, it has an extremely high surface area and electrical conductivity, which suggests it would offer high energy and power densities. Unfortunately, graphene has proved difficult to fabricate and samples that are produced often stick together, reducing their surface area.
Maher El-Kady and others at the University of California at Los Angeles have now found a way to fabricate graphene films, and graphene capacitors, without any sticking together. The researchers take a DVD and apply a layer of plastic, followed by a film of graphite oxide. They then insert the DVD into a standard DVD drive, so that the in-built laser chemically reduces the graphite oxide to graphene. Having removed the disc, the researchers peel off the plastic, which is then coated in graphene, and cut it into whatever shapes they desire.
To make the graphene films into capacitors, El-Kady's group fill the space between two parallel sheets of the laser-scribed graphene with an electrolyte, phosphoric acid. Not only are these capacitors flexible, but they have an electrical performance that surpasses other commercial energy-storage devices, according to the researchers' tests. Compared with a carbon electrochemical capacitor, for instance, the graphene capacitors had energy densities that were twice as high and power densities that were 20 times higher.
'We believe that our devices will pave the way to further applications - for example, flexible power supplies for roll-up computer displays, wearable electronics, and energy-storage systems to be combined with flexible photovoltaic cells,' says El-Kady.
Yury Gogotsi, a materials scientist at Drexel University in Philadelphia, US, is impressed by the fabrication technique. '[The] two main points that are most novel ... are not particularly the high gravimetric capacitance and energy density of the devices, but the simple fabrication process and exceptional mechanical stability, which has not been previously reported anywhere else,' he says.
El-Kady says the next step is to demonstrate that the fabrication volume can be improved, while minimising cost. 'Our initial calculations show that the price of the precursor, graphite oxide, and the whole process is viable for commercial applications,' he adds.