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article imageHemp batteries could be a reality

By Tim Sandle     Sep 14, 2014 in Science
Researchers have found a way to boost the energy density of supercapacitors through the use of more sophisticated electrodes. These electrodes are composed of hemp fibers, and they have a high energy storage capacity.
The development breakthrough has been made by a Canadian start-up company, led by Dr. David Mitlin. The idea arose from some applied thinking, when Mitlin's group decided to see if they could make graphene-like carbons from hemp bast fibers.
From Mitlin's research, it seems that hemp fibers can hold as much energy and power as graphene, the current favored material for supercapacitors. Supercapacitors are energy storage devices that have huge potential to transform the way future electronics are powered. Unlike batteries, which store energy chemically in the material of their electrodes, a capacitor stores energy physically, on the electrodes’ surfaces.
Mitlin's group discovered that when hemp fibers were heated for 24 hours at a little over 350 degrees Fahrenheit this would exfoliated the material into carbon nanosheets. From the reformed material, the group constructed supercapacitors using the hemp-derived carbons as electrodes and an ionic liquid as the electrolyte. In tests, the devices performed far better than commercial supercapacitors. This was assessed by examining for energy density and across a range of temperatures. The hemp-based devices yielded energy densities as high as 12 Watt-hours per kilogram, which is two to three times higher than currently available commercial systems.
Interviewed by Phys.Org, Mitlin expands on the success so far: "Our device's electrochemical performance is on par with or better than graphene-based devices. The key advantage is that our electrodes are made from biowaste using a simple process, and therefore, are much cheaper than graphene."
The parallels with graphene are a reference to the considerable research that has gone into to new variant of carbon. Graphene is a single-layer mesh of carbon atoms. Graphene is considered the new "wonder material," due its durability and lightness. Graphene can be described as a one-atom thick layer of graphite.
Mitlin's new research could trigger the electronic industry to move in a new direction. The research group are currently preparing the hemp-based prototype supercapacitor for small-scale manufacturing.
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