Nav: Home

Spinning a lighter, safer electrode

September 20, 2017

A group of Drexel University researchers have created a fabric-like material electrode that could help make energy storage devices -- batteries and supercapacitors -- faster and less susceptible to leaks or disastrous meltdowns. Their design for a new supercapacitor, which looks something like a furry sponge infused with gelatin, offers a unique alternative to the flammable electrolyte solution that is a common component in these devices.

The electrolyte fluid inside both batteries and supercapacitors can be corrosive or toxic and is almost always flammable. To keep up with our advancing mobile technology, energy storage devices have been subject to material shrinking in the design process, which has left them vulnerable to short circuiting -- as in recent cases with Samsung's Galaxy Note devices -- which, when compounded with the presence of a flammable electrolyte liquid, can create an explosive situation.

So instead of a flammable electrolyte solution, the device designed by Vibha Kalra, PhD, a professor in Drexel's College of Engineering, and her team, used a thick ion-rich gel electrolyte absorbed in a freestanding mat of porous carbon nanofibers to produce a liquid-free device. The group, which included Kalra's doctoral assistant Sila Simotwo and Temple researchers Stephanie L.Wunder, PhD, and Parameswara Chinnam, PhD, recently published its new design for a "solvent-free solid-state supercapacitor" in the American Chemical Society journal Applied Materials and Interfaces.

"We have completely eliminated the component that can catch fire in these devices," Kalra said. "And, in doing so, we have also created an electrode that could enable energy storage devices to become lighter and better."

Supercapacitors are another type of energy storage device. They're similar to batteries, in that they electrostatically hold and release energy, but in our technology -- mobile devices, laptops, electric cars -- they tend to serve as a power backup because they can disburse their stored energy in a quick spurt, unlike batteries that do so over long period of use. But, like batteries, supercapacitors use a flammable electrolyte solution, as a result they're vulnerable to leakage and fires.

Not only is the group's supercapacitor solvent-free -- which means it does not contain flammable liquid -- but the compact design is also more durable and its energy storage capacity and charge-discharge lifespan are better than comparable devices currently being used. It is also able to operate at temperatures as high as 300 degrees Celsius, which means it would make mobile devices much more durable and less likely to become a fire hazard due to abuse.

"To allow industrially relevant electrode thickness and loading, we have developed a cloth-like electrode composed of nanofibers that provides a well-defined three-dimensional open pore structure for easy infusion of the solid electrolyte precursor," Kalra said. "The open-pore electrode is also free of binding agents that act as insulators and diminish performance."

The key to producing this durable device is a fiber-like electrode framework that the team created using a process called electrospinning. The process deposits a carbon precursor polymer solution in the form of a fibrous mat by extruding it through a rotating electric field -- a process that, at the microscopic level, looks something like making cotton candy.

The ionogel is then absorbed in the carbon fiber mat to create a complete electrode-electrolyte network. Its excellent performance characteristics are also tied to this unique way of combining electrode and electrolyte solutions. This is because they are making contact over a larger surface area.

If you think of an energy storage device as a bowl of corn flakes, then the place where energy storage happens is roughly where the flakes meet the milk -- scientists call this the "electrical double layer." It's where the conductive electrode that stores electricity meets the electrolyte solution that is carrying the electric charge. Ideally, in your cereal bowl, the milk would make its way through all the flakes to get just the right coating on each -- not too crunchy and not too soggy. But sometimes the cereal gets piled up and the milk -- or the electrolyte solution, in the case of our comparison -- doesn't make it all the way through, so the flakes on top are dry, while the flakes on the bottom are saturated. This isn't a good bowl of cereal, and its electrochemical equivalent -- an electron traffic jam en route to activation sites in the electrode -- is not ideal for energy storage.

Kalra's solid-state supercapacitor is like putting shredded wheat in the bowl, instead of cornflakes. The open architecture lets the milk permeate and coat the cereal, much like the ionogel permeates the carbon fiber mat in Kalra's solid-state supercapacitor. The mat provides a greater surface area for ions from the ionogel to access the electrode, which increases the capacity and improves the performance of the energy storage device. It also eliminates the need for many of the scaffolding materials that are essential parts of forming the physical electrode, but don't play a role in the energy storage process and contribute a good bit to the device's overall weight.

"State of the art electrodes are composed of fine powders that need to be blended with binding agents and made into a slurry, which is then applied into the device. These binders add dead weight to the device, as they are not conductive materials, and they actually hinder its performance," Kalra said. "Our electrodes are freestanding, thus eliminating the need for binders, whose processing can account for as much as 20 percent of the cost of manufacturing an electrode."

The next step for Kalra's group will be applying this technique to the production of solid-state batteries as well as exploring its application for smart fabrics.
-end-


Drexel University

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

Digital Manipulation
Technology has reshaped our lives in amazing ways. But at what cost? This hour, TED speakers reveal how what we see, read, believe — even how we vote — can be manipulated by the technology we use. Guests include journalist Carole Cadwalladr, consumer advocate Finn Myrstad, writer and marketing professor Scott Galloway, behavioral designer Nir Eyal, and computer graphics researcher Doug Roble.
Now Playing: Science for the People

#530 Why Aren't We Dead Yet?
We only notice our immune systems when they aren't working properly, or when they're under attack. How does our immune system understand what bits of us are us, and what bits are invading germs and viruses? How different are human immune systems from the immune systems of other creatures? And is the immune system so often the target of sketchy medical advice? Those questions and more, this week in our conversation with author Idan Ben-Barak about his book "Why Aren't We Dead Yet?: The Survivor’s Guide to the Immune System".