Plant-based supercapacitor keeps costs low and energy storage high

Plant-based supercapacitor kee...
A prototype of the plant-based supercapacitor developed at Texas A&M University
A prototype of the plant-based supercapacitor developed at Texas A&M University
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A prototype of the plant-based supercapacitor developed at Texas A&M University
A prototype of the plant-based supercapacitor developed at Texas A&M University

Supercapacitors have the potential to pave the way for electric vehicles that charge in minutes rather than hours, overcoming one of the barriers to widespread adoption and being good for drivers and the environment. In a step towards such a reality, scientists at Texas A&M University have demonstrated a plant-based supercapacitor with excellent energy storage potential.

With an ability to charge almost in an instant and discharge huge amounts of power as its needed, supercapacitors are an energy storage technology with massive potential. And we have seen a number of interesting advances made in building the devices out of sustainable materials, including upcycled plastic bottles, hemp and and even discarded cigarette butts.

The team at Texas A&M University looked to make use of a natural polymer that gives plants and trees their rigidity called lignin. This is produced in huge amounts as a waste product by the paper manufacturing industry, and we have actually seen some interesting breakthroughs in efforts to recycle the polymer into other products, such as stronger concrete and biopastes for 3D printing.

The authors of the new study, however, hope to use it to supercharge the performance of a material used in supercapacitor electrodes called manganese dioxide. Nanoparticles of this compound offer a number of benefits over other solutions, but the electrochemical performance is where they tend to fall down.

“Manganese dioxide is cheaper, available in abundance and is safer compared to other transition metal oxides, like ruthenium or zinc oxide, that are popularly used for making electrodes,” says study author Hong Liang. “But a major drawback of manganese dioxide is that it suffers from lower electrical conductivity.”

Previous research had indicated that lignin combined with metal oxides could boost the electrical performance of supercapacitor electrodes, but the team wanted to investigate how it could enhance the function of manganese oxide specifically. So they designed a supercapacitor in which these two components formed the key building blocks.

The team started by purifying the lignin in a common disinfectant and then applied heat and pressure, which caused the liquid to break down and for manganese dioxide to be deposited onto the lignin. This mixture was then used to coat an aluminum plate to form the electrode, which was paired with another electrode made of aluminum and activated charcoal to form the supercapacitor, with a gel electrolyte sandwiched in between.

The researchers describe the new device as light, flexible and cost effective, increasing its potential to be used as structural energy storage elements in vehicles. They also report that it stood up extremely well in testing, finding that it had “very stable electrochemical properties,” and that it maintained its ability to store an electrical charge over thousands of cycles.

The performance was compared to other cutting-edge supercapacitor designs through existing literature, including ones with electrodes made wholly from activated carbon, or graphene combined with other materials. It outperformed them all in terms of specific capacitance, a measure of the device's ability to store a charge. When compared to one supercapacitor with an electrode made from tin diselenide, the new device offered a specific capacitance that was 900 times greater.

“Integrating biomaterials into energy storage devices has been tricky because it is difficult to control their resulting electrical properties, which then gravely affects the devices’ life cycle and performance” says Liang. “Also, the process of making biomaterials generally includes chemical treatments that are hazardous. We have designed an environmentally friendly energy storage device that has superior electrical performance and can be manufactured easily, safely and at much lower cost.”

The research was published in the journal Energy Storage.

Source: Texas A&M University

Hi Nick,

Some of us have the technical knowledge to appreciate some numbers in the article, such as the dimensions of the capacitor in the figure accompanying the article and the capacitance of this capacitor. Are we talking 1 farad the size of a dime, or 0.1 farad the size of a coffee filter? Hard to tell. Difficult to assess where this stacks up in comparison to over the counter "super" capacitors...
If it's everything they claim it is why isn't it in production? The answer probably lies in everything they are not telling us, like the technical specs.
I'm not a scientist but would it make sense to us a supercapacitor on board an electric car to charge the car battery? My understanding is that a supercapacitor can't store electricity for very long but if you immediately started transferring electricity from the supercapacitor to the battery, the battery could store electricity over longer periods.
As a follow up to an earlier comment, could a supercapacitor simultaneously provide electricity to an electric engine and charge a car battery? This way you could quickly recharge a supercapacitor in your car and be on your way in minutes. Supercapacitors don't hold a charge for very long but if you immediately started transferring energy from the supercapacitor to the car battery, the battery could hold the charge for a much longer period of time.