Hemp Makes Better Supercapacitor Electrodes


Researchers at the University of Alberta’s National Institute for Nanotechnology (NINT) have discovered that hemp based electrodes for supercapacitors outperform standard supercapacitors by nearly 200%. At present, the preferred material for making electrodes is graphene. Electrodes are what connect an electrical storage medium to the outside world. Some materials can handle high current applications and others allow quick access times. Graphene does both.

Hemp makes better electrodes

There is one drawback, however. Graphene costs about $2,000 per gram. Looking for a less costly solution, researchers at NINT, 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 materia — something that has never been achieved before,” says Mitlin.

Carbon is the primary component of most electrodes. Whether it is activated carbon, templated carbon, carbon nanofibers, carbon nanotubes, or graphene, all have been intensively studied as materials for supercapacitor electrodes. Many are expensive to manufacture. They also have limited power characteristics.

“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.”

Mitlin decided to test hemp bast fiber’s unique cellular structure to see if it could produce graphene-like carbon nanosheets. Hemp fiber waste was heated under pressure at 180 °C for 24 hours. The resulting carbonized material was treated with potassium hydroxide and then heated to temperatures as high as 800 °C, resulting in the formation of uniquely structured nanosheets. Testing of this material revealed that it discharged 49 kW of power per kg of material — nearly triple what standard commercial electrodes supply, 17 kW/kg.

“The resultant graphene-like nanosheets possess fundamentally different properties, such as pore size distribution, physical interconnectedness, and electrical conductivity—as compared to conventional biomass-derived activated carbons,” Mitlin tells the American Society of Mechanical Engineers.

“We were delighted at how well this material performed as supercapacitor electrodes,” says Mitlin. “This novel precursor-synthesis route presents a great potential for facile large scale production of high performance carbons for a variety of diverse applications including energy storage, portable electronics, uninterruptable power sources, medical devices, load leveling, and hybrid electric vehicles.”

This breakthrough, if it an be commercialized successfully, could be a significant factor in reducing the cost of electric vehicles and energy storage systems.


About the Author

I have been a car nut since the days when Rob Walker and Henry N. Manney, III graced the pages of Road & Track. Today, I use my trusty Miata for TSD rallies and occasional track days at Lime Rock and Watkins Glen. If it moves on wheels, I’m interested in it. Please follow me on Google + and Twitter.

  • Marcel

    That’s so cool, add that to the long list of hemp applications.

    • bioburner

      Yes hemp has many applications. Problem is Jonny law does not know the difference between low THC industrial hemp and “Weed”. Its our loss.

  • smartacus

    that 4-letter word is carte blanche for them to break down your front door, shoot your dog, burn your toddler with a flashbang in his crib
    -we are just doing our job keeping you safe, citizen

    • Steve Hanley

      You have a rather dour view of the American criminal justice industry, errr, I mean, criminal justice system!

      • smartacus

        yeah 🙂

  • Rick Danger

    Passes the capacitor back to Steve… 😎


    If this works out, and Elon Musk starts using hemp electrodes at his Gigafactory, it’s GAME OVER for the internal combustion engine and coal/oil fired power plants !

    • Steve Hanley

      It can take years to go from the laboratory to commercial production, unfortunately. But this is the kind of breakthrough that the world has been waiting for. It can’t get here soon enough.

      • AaronD12

        (whispers) “Hemp fiber waste was pressure under pressure at 180 °C for 24 hours.” It probably should be “…was heated under pressure…”

        • Steve Hanley

          Fixed. Thanks for catching that.