Researchers have managed to use compounds found in green tea to develop a flexible and compact rechargeable energy storage device that as the potential of powering smartphones and wearable devices.
According to the team of scientists behind the study that led to this discovery, in future wearable devices could be made more comfortable to wear by using softer materials made in part with an unexpected ingredient – green tea.
Wearable devices are small and powering such small devices is a hurdle that scientists haven’t still leapfrogged efficiently. Most supercapacitors are rigid, and the compressible supercapacitors developed so far have run into roadblocks.
Researchers say that their objective is to fabricate wearable electronic devices and for that purpose, compressible energy storage devices are the first step towards achieving that objective. Supercapacitors have been made with carbon-coated polymer sponges, but the coating material tends to bunch up and compromise performance.
Researchers including those from CSIR-National Chemical Laboratory in Pune and Academy of Scientific and Innovative Research (AcSIR) in New Delhi wanted to take a different approach. The researchers prepared polymer gels in green tea extract, which infuses the gel with polyphenols. The polyphenols converted a silver nitrate solution into a uniform coating of silver nanoparticles. Thin layers of conducting gold and poly(3,4-ethylenedioxythiophene) were then applied.
The resulting supercapacitor demonstrated power and energy densities of 2,715 watts per kilogramme and 22 watt-hours per kilogramme – enough to operate a heart rate monitor, LEDs or a Bluetooth module. “If you brew green tea and leave it for a while in a glass, you will see a coating. The coating comprises polyphenols, which are the antioxidants in green tea. They are capable of reducing metal ions such as silver,” said Krishnamoorthy.
“We could use polyphenols in green tea to prepare metal coated sponges that are essential for the fabrication of compressible supercapacitors,” he said. The researchers tested the device’s durability and found that it performed well even after being compressed more than 100 times. The study was published in The Journal of Physical Chemistry C.