Hemp nanosheets may replace graphene when making supercapacitors

Graphene, a substance long lauded as the premier foundation for supercapacitors, may soon make way for an organic compound whose abundance will have far reaching implication on the side of expense. That material is hemp, and its bast fibers can pack as much energy and power as graphene, but at a fraction of the cost, explains a Canadian startup set to present its research at the 248^th National Meeting & Exposition of the American Chemical Society (ACS).

According to Dr. David Mitlin, Professor and GE Chair in Oil and Gas Systems at Clarkson University, supercapacitors hold the potential for revolutionizing electronics as we know them today, leading into the next generation of technology. Supercapacitors are a form of battery that can charge and discharge within seconds. They’re very efficient at recharging, but unlike batteries, exhibit a very low energy density that results in very low battery life — unless graphene is involved in the fabrication.

The problem is graphene is very costly; by designing the electrodes from the organic fiber, the researchers are able to produce a supercapacitor capable of holding as much energy as graphene, but at a fraction of the cost.

“Our device’s electrochemical performance is on par with or better than graphene-based devices,” Mitlin says. “The key advantage is that our electrodes are made from bio-waste using a simple process, and therefore, are much cheaper than graphene.”

Graphene, with its atom-thick layers of carbon, which when stacked, can be made into electrodes. And thus, it has been at the center of the race to achieve an efficient supercapacitor. These unique properties allow the creation of more powerful and efficient solar cells, water filtration systems, touch-screen technology, and batteries, but technology has yet reached a point where graphene can be fabricated at a reasonable enough price to justify its proliferation.

Mitlin and his team are attempting to recreate the same attributes that make graphene a top contender, but with the hemp bast fibers that line the inside of the inner bark of the plant — fibers that are often discarded from Canadian clothing and construction material manufacturers. At the present, hemp sources limited in the Americas, but the increasingly legality of the substance will eventually see the US as another top supplier.

The research to be presented at the ACS conference describes a supercapacitor constructed using hemp-derived carbons as electrodes and an ionic liquid as the electrolyte. Once fully assembled, its performance surpassed commercial-grade supercapacitors in the range of temperatures over which it can operate under, as well as having achieved an energy density up to 12 watt-hours per kilogram — a figure two to three times higher than the commercial equivalent.

“We’ve pretty much figured out the secret sauce of it,” says Mitlin, who’s now with Clarkson University in New York. “The trick is to really understand the structure of a starter material and to tune how it’s processed to give you what would rightfully be called amazing properties.”

Source: ACS.org