In a new study, researchers at Texas A&M University have described their novel plant-based energy storage device that could charge even electric cars within a few minutes in the near future. Furthermore, they said their devices are flexible, lightweight and cost-effective.
“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. Also, the process of making biomaterials generally includes chemical treatments that are hazardous,” said Dr. Hong Liang, Oscar S. Wyatt Jr. Professor in the J. Mike Walker ’66 Department of Mechanical Engineering. “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.”
Their research is outlined in the June issue of the journal Energy Storage.
Energy storage devices are generally in the form of either batteries or supercapacitors. Although both types of devices can deliver electrical currents when required, they have some fundamental differences. While batteries can store large amounts of charge per unit volume, supercapacitors are much more efficient at generating a large quantity of electric current within a short duration. This burst of electricity helps supercapacitors to quickly charge up devices, unlike batteries that can take much longer.
Supercapacitors have an internal architecture that is more in line with basic capacitors. Both these devices store charge on metal plates or electrodes. However, unlike basic capacitors, supercapacitors can be made in different sizes, shapes and designs, depending on the intended application. Furthermore, supercapacitor electrodes can also be built with different materials.
For their work, Liang and her team were attracted to manganese dioxide nanoparticles for designing one of the two supercapacitor electrodes.
“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,” said Liang. “But a major drawback of manganese dioxide is that it suffers from lower electrical conductivity.”
Past research has shown that lignin, a natural polymer that glues wood fibers together, used with metal oxides enhances the electrochemical properties of electrodes. However, Liang said there have been few studies looking into combining manganese dioxide and lignin to leverage both of their useful properties.
To create their electrode, Liang and her team treated purified lignin with a commonly available disinfectant, called potassium permanganate. They then applied high heat and pressure to initiate an oxidation reaction that results in the breaking down of potassium permanganate and the deposition of manganese dioxide on lignin.