Novel Plant-Based Supercapacitor That Could Charge Devices In A Wink

Researchers from Texas A&M University have created a novel plant-based energy storage device that in the near future could even charge electric cars in a few minutes. Researchers claim that this novel device is flexible, lightweight, cost-effective, and can store a charge up to 900 times greater than state-of-the-art supercapacitors.

The research was led by Dr. Hong Liang, an Oscar S. Wyatt Jr. Professor in the J. Mike Walker ’66 Department of Mechanical Engineering at Texas A&M. Their paper recently appeared in the journal Energy Storage.

“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 include chemical treatments that are hazardous,” said Dr. Hong Liang. “We have designed an environmentally friendly energy storage device that has superior electrical performance and can be manufactured easily, safely, and at a much lower cost.”

As we know, there are two types of energy storage devices, namely
1. Batteries:
2. Capacitors

The advantage of batteries is that they can store more energy whereas capacitors can charge devices quickly.

What is Supercapacitor?
Unlike basic capacitors, supercapacitors can be made in different sizes, shapes, and designs, depending on the intended application, and supercapacitor electrodes can also be built with different materials.

The current research team selected 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.”

It was previously known that a natural polymer named lignin that glues wood fibers together, can be used with metal oxides to enhance 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.

Building Electrode
To create their electrode, the 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. Next, they coated the lignin and manganese dioxide mixture on an aluminum plate to form the green electrode. Finally, the researchers assembled the supercapacitor by sandwiching a gel electrolyte between the lignin-manganese dioxide-aluminum electrode and another electrode made of aluminum and activated charcoal.

On testing the new electrode, the team found that their supercapacitor had very stable electrochemical properties. The ability of the device to store an electrical charge, changed little, even after thousands of cycles of charging and discharging. Also, for an optimal lignin-manganese dioxide ratio, the specific capacitance was observed to be up to 900 times more than what has been reported for other supercapacitors.

“In this study, we have been able to make a plant-based supercapacitor with excellent electrochemical performance using a low-cost, sustainable method,” said Liang. “In the near future, we’d like to make our supercapacitors 100% environmentally friendly by incorporating only green, sustainable ingredients.”

Journal Reference:
Swarn Jha, Siddhi Mehta, Yan Chen, Raj Likhari, Weston Stewart, Dilworth Parkinson, Hong Liang. Design and synthesis of high performance flexible and green supercapacitors made of manganese‐dioxide‐decorated alkali lignin. Energy Storage, 2020; DOI: 10.1002/est2.184

Press Release: Texas A&M University