Research engineers at the Illinois Sustainable Technology Center at the University of Illinois (UI) find wood biochar supercapacitors can produce as much power as today’s activated-carbon supercapacitors at a fraction of the cost. The report noted that the wood bio-char would be sourced from forest products waste, an environmentally friendly source to make power storage.
Study leader Junhua Jiang, a senior research engineer at UI noted while batteries rely on chemical reactions to produce sustained electrical energy, supercapacitors collect charged ions on their electrodes (in this case, the biochar), and quickly release those ions during discharge. This allows them to supply energy in short, powerful bursts – for example during a camera flash, or in response to peak demand on the energy grid.
“Supercapacitors are ideal for applications needing instant power and can even provide constant power – like batteries, but at lower cost,” he said. They are useful in transportation, electronics and solar- and wind-power energy storage and distribution.
Many of today’s supercapacitors use activated carbon – usually from a fossil-fuel source, Jiang said.
In the wood biochar supercapacitors, the wood’s natural pore structure serves as the electrode surface, eliminating the need for advanced techniques to fabricate an elaborate pore structure. The wood biochar is produced by heating the wood in a low oxygen environment.
The pore sizes and configurations in some woods are ideal for fast ion transport, Jiang said. The new study used red cedar, but several other woods such as maple and cherry also work well.
The UI research compares to expensive and corrosive chemicals that are often used to prepare the activated carbon used in supercapacitors so giving the electrodes the physical and chemical properties they need to function well, Jiang said.
“The use of those chemicals will probably impose some environmental impacts,” he said. “This should be avoided or at least substantially reduced.”
In an unexpected plus the UI team reported Jiang and his team activated their biochar with mild nitric acid, which washed away the ash (calcium carbonate, potassium carbonate and other impurities) in the biochar. The byproduct of this process has a beneficial use, Jiang said: The resulting solution of nitrate compounds can be used as fertilizer.
That would be great, taking essentially just the carbon in the desired form and returning the metabolic fertilizer components to the soil.
The simple approaches dramatically cut the material and environmental costs of assembling supercapacitors.
“The material costs of producing wood biochar supercapacitors are five to 10 times lower than those associated with activated carbon,” Jiang said. And when a biochar supercapacitor has reached the end of its useful life, the electrodes can be crushed and used as an organic soil amendment that increases fertility.
“The performance of our biochar materials is comparable to the performance of today’s advanced carbon materials, including carbon nanotubes and graphenes,” Jiang said. “We can achieve comparable performance with much less cost and probably much lower environmental costs.”
If this is all repeated, scalable and market worthy the supercapacitor products so needed for and electric transition would come much sooner and at lower consumer cost.
We’ll be watching this. And even at this early point congratulations are in order to the UI team.