As the world’s thirst for energy escalates, so does the need for better ways to store it. Which makes it evermore important for those energy-storing technologies to be sustainable. In a step towards that goal, researchers have made a supercapacitor using materials derived from plants. They presented the work in the journal Energy Storage.
Supercapacitors are energy-storage devices that, like batteries, are made of two electrodes and an electrolyte. But they offer much faster charging and higher power. They are already used in cars, trains, heavy machinery, and power tools to provide short-term energy storage and bursts of power.
Researchers from Texas A&M University decided to make supercapacitor electrodes with plant-based materials. They use lignin, a natural polymer found in plants that makes them strong and rigid. Lignin is a waste product of the paper-processing industry. But researchers have been trying to use it as a sustainable raw material for chemicals and fuels. Past research has shown that combining lignin with metal oxides boosts the storage capacity of electrodes.
So mechanical engineering professor Hong Liang and her colleagues coupled lignin with manganese oxide. Manganese oxide is cheaper and safer than other metal oxides that have been considered ideal for supercapacitor electrodes in the past, such as ruthenium oxide, Liang said in a press release. But it hasn’t been considered a promising electrode material because of its low conductivity.
The team purified lignin and deposited manganese oxide nanoparticles on it. Then they coated the mixture on an aluminum film to make an electrode. They made a supercapacitor by sandwiching a gel electrolyte between this plant-based electrode and another electrode made of aluminum and activated charcoal.
A prototype of the green supercapacitor made by Dr. Hong Liang’s team. | Image: Dr. Hong Liang
The new energy-storing device is lightweight, flexible and low-cost. And its charge-storing capability is comparable with other devices reported before.
“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,” Liang said. The team now wants to build supercapacitors entirely with green, environmentally materials.
Source: Swarn Jha et al. Design and synthesis of high performance flexible and green supercapacitors made of manganese‐dioxide‐decorated alkali lignin. Energy Storage, 2020.
