A plant-based supercapacitor with excellent energy storage potential could pave the way for electric vehicles to be recharged in a few minutes, overcoming one of the barriers to widespread adoption and benefiting drivers and the environment.
Supercapacitor can be charged almost instantaneously and release huge energy when needed. It is a kind of energy storage technology with great potential. We've seen some interesting developments in making equipment from sustainable materials, including recycled plastic bottles and even discarded cigarette butts.
The team at Texas A & M University wants to take advantage of a natural polymer, called lignin, that gives plants and trees rigidity, which is produced in large quantities by the paper industry as waste. In fact, we have seen some interesting breakthroughs in trying to recycle this polymer into other products, such as stronger concrete and 3D printed bio pulp.
However, the authors of the new study hope to use it as a material for supercapacitor electrodes, manganese dioxide. The nanoparticles of this compound offer many benefits over other solutions, but the electrochemical performance is where they tend to decline.
"Compared with other transition metal oxides, such as ruthenium or zinc oxide, manganese dioxide is cheaper, more available and safer, and these transition metal oxides are commonly used to make electrodes," said study author Liang Hong. "But one of the main disadvantages of manganese dioxide is its low conductivity."
Previous studies have shown that the combination of lignin and metal oxides can improve the electrical properties of supercapacitor electrodes, but the team hopes to study how to specifically enhance the function of manganese dioxide. So they designed a supercapacitor, and these two components make up the key components.
The team first purified the lignin in a common disinfectant, then applied heat and pressure to decompose the liquid, causing manganese dioxide to deposit on the lignin. The mixture was then coated with aluminum plates to form electrodes, then paired with electrodes made of aluminum and activated carbon to form supercapacitors, sandwiched with gel electrolytes.
The new device is lightweight, flexible and cost-effective, which increases its potential as an energy storage component for automotive structures, the researchers said. They also report that it has stood an excellent test in tests and found that it has "very stable electrochemical properties" and maintains the ability to store charges over thousands of cycles.
In terms of capacitance, supercapacitors perform better than those whose electrodes are made entirely of activated carbon or graphene combined with other materials, which is usually used to measure the storage charge of the device. When compared with a supercapacitor with electrodes made of tin selenide, the new device offers 900 times more capacitance.