Most people don’t understand the truly diverse value of hemp (Cannabis sativa). Cultures have depended on this hardy plant for centuries for clothing, fabric, and paper. Today, it is also used for food, fuel, medicine, building materials, and plastics. Now the energy storage industry is starting to take notice, thanks to new Canadian research that shows supercapacitors with electrodes made from hemp-based carbon nanosheets outperform standard supercapacitors by nearly 200%.
Graphene, a carbon nanomaterial, is considered to be one of the best materials for supercapicitor electrodes. Graphene is, however, expensive to manufacture, costing as much as $2,000 per gram. Looking for a less-costly solution, researchers at the University of Alberta/National Institute for Nanotechnology (NINT) NRC, and Alberta Innovates-Technology Futures, led by chemical and materials engineering Professor David Mitlin, developed a process for converting fibrous hemp waste into a unique graphene-like nanomaterial that outperforms graphene. What’s more, it can be manufactured for less than $500 per ton.
“Our work actually opens up a very cheap and mass-producible manufacturing method for graphene-quality material—something that has never been achieved before,” says Mitlin.
Activated carbons, templated carbons, carbon nanofibers, carbon nanotubes, and graphene have all been intensively studied as materials for supercapacitor electrodes. High manufacturing costs is one issue—another is that the power characteristics of many of these carbons are limited. This is a result of high microporosity, which increases ion transport limitations.
“It is becoming well understood that the key to achieving high power in porous electrodes is to reduce the ion transport limitations” says Mitlin. “Nanomaterials based on graphene and their hybrids have emerged as a new class of promising high-rate electrode candidates—they are, however, too expensive to manufacture compared to activated carbons derived from pyrolysis of agricultural wastes, or from the coking operations.”