Photo: Tour Group/Rice University
Almost exactly a year ago, we first got word that researchers at Rice University had developed a method for producing graphene that features a computer-controlled laser. They dubbed the result laser-induced graphene (LIG).
Since then, LIG has been proposed for flexible supercapacitors that could power wearable electronics.
The researchers at Rice have continued to pursue supercapacitors for this new form of graphene and have continued to refine the LIG process to the point where they now believe it may be capable of moving energy storage away from batteries and towards supercapacitors.
The key attribute of LIG is how comparatively easy it is to produce as opposed to graphene made via chemical vapor deposition. For LIG, all that is needed is a commercial polyimide plastic sheet and a computer-controlled laser. The Rice researchers discovered that the laser would burn everything on the polyimide except the carbon from the top layer. What remains is a form of graphene.
You can see a description and demonstration of the process in the video below.
The researchers think that this process will ultimately lend itself to roll-to-roll production. That will eliminate complex manufacturing conditions that have thus far limited the widespread application of microsupercapacitors.
“It’s a pain in the neck to build microsupercapacitors now,” said James Tour, who has been leading this line of research at Rice since the beginning, in a press release. “They require a lot of lithographic steps. But these we can make in minutes: We burn the patterns, add electrolyte and cover them.”
The researchers claim that the microsupercapacitors they have fabricated using LIG have demonstrated an energy density that is on par with thin-film lithium-ion batteries. The microsupercapitors’ capacitance was measured at 934 microfarads per square centimeter; they boast an energy density of 3.2 milliwatt-hours per cubic centimeter. As these are supercapacitors, their power density far exceeds that of batteries. Perhaps most importantly, the devices did not exhibit any degradation over time, maintaining mechanical stability even after being bent 10,000 times.
Encouraging as these numbers are, there yet remains some work to be done before supercapacitors displace batteries.
We’re not quite there yet, but we’re getting closer all the time,” said Tour in the press release. “In the interim, they’re able to supplement batteries with high power. What we have now is as good as some commercial supercapacitors. And they’re just plastic.”