Nav: Home

Inspired by nature: Design for new electrode could boost supercapacitors' performance

February 23, 2018

Mechanical engineers from the UCLA Henry Samueli School of Engineering and Applied Science and four other institutions have designed a super-efficient and long-lasting electrode for supercapacitors. The device's design was inspired by the structure and function of leaves on tree branches, and it is more than 10 times more efficient than other designs.

The electrode design provides the same amount of energy storage, and delivers as much power, as similar electrodes, despite being much smaller and lighter. In experiments it produced 30 percent better capacitance -- a device's ability to store an electric charge -- for its mass compared to the best available electrode made from similar carbon materials, and 30 times better capacitance per area. It also produced 10 times more power than other designs and retained 95 percent of its initial capacitance after more than 10,000 charging cycles.

Their work is described in the journal Nature Communications.

Supercapacitors are rechargeable energy storage devices that deliver more power for their size than similar-sized batteries. They also recharge quickly, and they last for hundreds to thousands of recharging cycles. Today, they're used in hybrid cars' regenerative braking systems and for other applications. Advances in supercapacitor technology could make their use widespread as a complement to, or even replacement for, the more familiar batteries consumers buy every day for household electronics.

Engineers have known that supercapacitors could be made more powerful than today's models, but one challenge has been producing more efficient and durable electrodes. Electrodes attract ions, which store energy, to the surface of the supercapacitor, where that energy becomes available to use. Ions in supercapacitors are stored in an electrolyte solution. An electrode's ability to deliver stored power quickly is determined in large part by how many ions it can exchange with that solution: The more ions it can exchange, the faster it can deliver power.

Knowing that, the researchers designed their electrode to maximize its surface area, creating the most possible space for it to attract electrons. They drew inspiration from the structure of trees, which are able to absorb ample amounts of carbon dioxide for photosynthesis because of the surface area of their leaves.

"We often find inspiration in nature, and plants have discovered the best way to absorb chemicals such as carbon dioxide from their environment," said Tim Fisher, the study's principal investigator and a UCLA professor of mechanical and aerospace engineering. "In this case, we used that idea but at a much, much smaller scale -- about one-millionth the size, in fact."

To create the branch-and-leaves design, the researchers used two nanoscale structures composed of carbon atoms. The "branches" are arrays of hollow, cylindrical carbon nanotubes, about 20 to 30 nanometers in diameter; and the "leaves" are sharp-edged petal-like structures, about 100 nanometers wide, that are made of graphene -- ultra thin sheets of carbon. The leaves are then arranged on the perimeter of the nanotube stems. The leaf-like graphene petals also give the electrode stability.

The engineers then formed the structures into tunnel-shaped arrays, which the ions that transport the stored energy flow through with much less resistance between the electrolyte and the surface to deliver energy than they would if the electrode surfaces were flat.

The electrode also performs well in acidic conditions and high temperatures, both environments in which supercapacitors could be used.
-end-
Fisher directs UCLA's Nanoscale Transport Research Group and is a member of the California NanoSystems Institute at UCLA. Lei Chen, a professor at Mississippi State, was the project's other principal investigator. The first authors are Guoping Xiong of the University of Nevada, Reno, and Pingge He of Central South University. The research was supported by the Air Force Office of Scientific Research.

UCLA Henry Samueli School of Engineering of Applied Science

Related Energy Storage Articles:

Magnetoelectric memory cell increases energy efficiency for data storage
A team of researchers has now developed a magnetoelectric random access memory (MELRAM) cell that has the potential to increase power efficiency, and thereby decrease heat waste, by orders of magnitude for read operations at room temperature.
Thin layers of water hold promise for the energy storage of the future
Researchers have found that a material which incorporates atomically thin layers of water is able to store and deliver energy much more quickly than the same material that doesn't include the water layers.
Current Graphene Science tours its journey of high-performance energy storage devices
Graphene has made its fathomable pathway over wide range of user-friendly energy storage devices.
Bio-inspired energy storage: A new light for solar power
Inspired by the western Swordfern, a groundbreaking prototype could be the answer to the storage challenge still holding solar back as a total energy solution.
Stabilizing energy storage
University of Utah and University of Michigan chemists, participating in a US Department of Energy consortium, predict a better future for these types of batteries, called redox flow batteries.
New hydronium-ion battery presents opportunity for more sustainable energy storage
A new type of battery shows promise for sustainable, high-power energy storage.It's the world's first battery to use only hydronium ions as the charge carrier.
Nanoscale view of energy storage
Through long shifts at the helm of a highly sophisticated microscope, researchers at Stanford recorded reactions at near-atomic-scale resolution.
Sandia Labs, Singapore join forces to develop energy storage
Sandia National Laboratories has signed a Cooperative Research and Development Agreement (CRADA) with the government of Singapore's Energy Market Authority (EMA) that will tap into the labs' expertise in energy storage.
New biofuel cell with energy storage
Researchers have developed a hybrid of a fuel cell and capacitor on a biocatalytic basis.
Energy storage system of tomorrow tested for the first time in Lake Constance
How can the enormous amounts of electricity generated through offshore wind power be temporarily stored on site?

Related Energy Storage Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Jumpstarting Creativity
Our greatest breakthroughs and triumphs have one thing in common: creativity. But how do you ignite it? And how do you rekindle it? This hour, TED speakers explore ideas on jumpstarting creativity. Guests include economist Tim Harford, producer Helen Marriage, artificial intelligence researcher Steve Engels, and behavioral scientist Marily Oppezzo.
Now Playing: Science for the People

#524 The Human Network
What does a network of humans look like and how does it work? How does information spread? How do decisions and opinions spread? What gets distorted as it moves through the network and why? This week we dig into the ins and outs of human networks with Matthew Jackson, Professor of Economics at Stanford University and author of the book "The Human Network: How Your Social Position Determines Your Power, Beliefs, and Behaviours".