Weed, not graphene, may be a better supercapacitor. What?!?
Cannabis may be better than graphene when it comes to building supercapacitors, according to a new study.
Graphene, a sheet of a single layer of carbon atoms, is considered to be the industry standard when it comes to designing this new generation of electronics. Development of the technology could lead to super-batteries capable of storing large amounts of energy. These devices could be integrated into renewable energy distribution networks, easing transition to green energy.
Hemp has been utilized in manufacturing tens of thousands of products for thousands of years. Cultivation of the plant, related to marijuana, was prohibited by law in the United States for most of the 20th century. Many of those prohibitions are now being lifted, as states start to reform laws regarding cannabis.
Current rechargeable batteries take several hours to take on a charge. Supercapacitors can come to a full load, and release it, in just a few seconds. However, these devices are unable to store as much energy as a typical battery. Physicists refer to this total capacity as energy density.
Hemp can be used for electrodes in the supercapacitor, and test results show their performance is on par with the wonder material believed to be the ultimate choice for the parts.
"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," David Mitlin, developer of the new hemp devices, said.
Bast, the inner bark of hemp plants, was utilized by Mitlin and his team to manufacture a material possessing many of the same qualities as graphene. This bast is often discarded by manufacturers creating more traditional hemp products, such as clothes and soaps.
Sheets of graphene, laid together, can be shaped into supercapacitors, but high-quality samples of the material are expensive. Hemp is inexpensive, growing without pesticides or herbicides, making it both cheap and ecologically-friendly.
Mitlin and his team heated the bast at a little over 350 degrees Fahrenheit, then subjected the test material to more intense waves of heat. Structures within the bast then fell apart, leaving behind a sheet of carbon, resembling graphene.
Electrodes constructed from the hemp bast were placed in an electrolyte, yielding a supercapacitor. Energy densities in the new devices were two to three times higher than current commercial models. Hemp electrodes also operated under a wide range of temperatures, from as high as 200 degrees Fahrenheit down to freezing.
This could revolutionize electronics, as users of laptops, tablets and smartphones will be able to charge their devices in a matter of moments.
Research into the use of hemp in production of supercapacitors was presented at a national meeting of the American Chemical Society (ACS).