Fern Design Boosts Energy-Storing Capacity of Supercapacitors

A research group at RMIT University in Australia have made a breakthrough in energy storage that could help make supercapacitors more efficient energy storage systems. The research team has designed a new electrode, taking inspiration from the pattern of veins that fill the leaf of the Swordfern, a species of fern native to North America. The design uses self-repeating fractals to increase the energy storing capacity of supercapacitors, and could be used in future solar film applications.

Supercapacitors are systems that store energy in an electrostatic field on the surface of the material — unlike battery storage systems, which rely on chemical reactions to store energy. Supercapacitors are great at charging and discharging energy quickly, and can do so millions of times without loss of performance, but the drawback to supercapacitors is that they doesn’t hold very much energy. Supercapacitors have high power density but low energy density.

Batteries, on the other hand, are able to store much more energy by weight, but because battery systems use chemical reactions to store energy, charging and discharging energy takes longer, and the battery’s performance degrades over time. That means batteries have low power density but high energy density.

RMIT research team has boosted the performance of their flexible graphene electrode prototype by mimicking the Swordfern’s vein design to improve energy storage at the nano-level. “The leaves of the western swordfern are densely crammed with veins, making them extremely efficient for storing energy and transporting water around the plant,” said professor Min Gu, leader of the Laboratory of Artificial Intelligence Nanophotonics and associate deputy vice-chancellor for research innovation and entrepreneurship at RMIT. “Our electrode is based on these fractal shapes – which are self-replicating, like the mini structures within snowflakes.”

The self-repeating fractal pattern of veins found on the Western Swordfern, here magnified 400 times. Image source: RMIT

The new and efficient electrodes can be used to beef up supercapacitor energy storage by holding energy for longer periods of time — in other words, increasing the energy density of the supercapacitor. “Our experiments have shown our prototype can radically increase their storage capacity – 30 times more than current capacity limits,” Gu said.

The electrodes could also be added to thin and flexible solar film, to create an all-in-one solar energy capture and storage system. “The most exciting possibility is using this electrode with a solar cell, to provide a total on-chip energy harvesting and storage solution,” said Litty Thekkekara, lead author of the research, which was published last week in Scientific Reports. “We can do that now with existing solar cells but these are bulky and rigid. The real future lies in integrating the prototype with flexible thin film solar – technology that is still in its infancy.”

 

Feature image: CC BY-NC-ND 2.0 by Roy Ostling

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