A team led by Rice University professor Pulickel Ajayan has been experimenting with the property of graphite oxide to act as an ionic conductor when hydrated. One of the “tricks” they discovered is that they could use this property to make a sheet of GO into a working supercapacitor by writing patterns into it with a laser.
The laser changes GO into reduced graphite oxide. They say the resulting supercapacitors withstand thousands of store–release cycles.
According to a news release from Rice, the investigators didn’t expect to find that hydrated GO can hold ions and serve as a solid electrolyte and an electrically insulating separator. “[W]e’re able to convert a sheet of GO into a supercapacitor without adding anything,” says Ajayan. “All you need are a pattern and the electrodes, and you have a device. Of course, the devices also perform in the presence of external electrolytes, which is even better. I think you’re going to see a lot of tiny devices that need smaller power sources. Intermediate-sized devices might also be powered by this material; it’s very scalable.”
Wei Gao, graduate student and lead author of a paper recent paper published in Nature Nanotechnology (doi:10.1038/nnano.2011.110) (and one of the stars in the above video), says in the release, “This is quite easy, as GO soaks up water like a sponge and can hold up to 16 percent of its weight.”
Gao and her coauthors say the performance of their supercapacitor compares favorably with existing thin-film microsupercapacitors.
Ajayan discourages comparisons to bulk supercapacitors, but says it would be fairly easy to put these thin devices in an array and predicts in the video that with such an assembly, “Ultimately we could get pretty good power.”
Rice says the research opens the way to interesting possibilities, including devices for use in fuel cells and lithium batteries.