Structural supercapacitor could let objects be batteries

Structural supercapacitor could let objects be batteries

Technology News |
Researchers at Vanderbilt University have developed a structural supercapacitor that stores and releases electrical charge while subject to stresses or pressures up to 44 psi and vibrational accelerations more than 80g.
By eeNews Europe

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The development opens the prospect to build the capacity to store electrical energy directly into a wide range of products, such as a laptop whose casing serves as its battery, or an electric car powered by energy stored in its chassis, or a home where the dry wall and clading store the electricity that runs the lights and appliances.

In a paper in the journal Nano Letters, graduate student Andrew Westover and Assistant Professor of Mechanical Engineering Cary Pint in Vanderbilt’s Nanomaterials and Energy Devices Laboratory detail a supercapacitor that stores electricity by assembling electrically charged ions on the surface of a porous material, instead of storing it in chemical reactions the way batteries do. As a result, supercaps can charge and discharge in minutes, instead of hours, and operate for millions of cycles, instead of thousands of cycles like batteries.

“These devices demonstrate – for the first time as far as we can tell – that it is possible to create materials that can store and discharge significant amounts of electricity while they are subject to realistic static loads and dynamic forces, such as vibrations or impacts,” explained Pint.

“When you can integrate energy into the components used to build systems, it opens the door to a whole new world of technological possibilities. All of a sudden, the ability to design technologies at the basis of health, entertainment, travel and social communication will not be limited by plugs and external power sources.”

The mechanical robustness of the device does not compromise its energy storage capability. “In an unpackaged, structurally integrated state our supercapacitor can store more energy and operate at higher voltages than a packaged, off-the-shelf commercial supercapacitor, even under intense dynamic and static forces,” explained Pint.


One area where supercapacitors lag behind batteries is in electrical energy storage capability: Supercaps must be larger and heavier than lithium bateries to store the same amount of energy. However, the difference is not as important when considering multifunctional energy storage systems.

“Battery performance metrics change when you’re putting energy storage into heavy materials that are already needed for structural integrity,” said Pint. “Supercapacitors store ten times less energy than current lithium-ion batteries, but they can last a thousand times longer. That means they are better suited for structural applications. It doesn’t make sense to develop materials to build a home, car chassis, or aerospace vehicle if you have to replace them every few years because they go dead.”

Westover’s wafers consist of electrodes made from silicon that have been chemically treated so they have nanoscale pores on their inner surfaces and then coated with a protective ultrathin graphene-like layer of carbon. Sandwiched between the two electrodes is a polymer film that acts as a reservoir of charged ions, similar to the role of the electrolyte paste in a battery. When the electrodes are pressed together, the polymer oozes into the tiny pores in much the same way that melted cheese soaks into the nooks and crannies of artisan bread in a panini. When the polymer cools and solidifies, it forms a strong mechanical bond.

“The biggest problem with designing load-bearing supercaps is preventing them from delaminating,” said Westover. “Combining nanoporous material with the polymer electrolyte bonds the layers together tighter than superglue.”


The use of silicon in structural supercapacitors is best suited for consumer electronics and solar cells, but Pint and Westover are confident that the rules that govern the load-bearing character of their design will carry over to other materials, such as carbon nanotubes and lightweight porous metals like aluminum.

Amrutur Anilkumar, professor of the practice in mechanical engineering, postdoctoral associate Shahana Chatterjee, graduate student Landon Oakes, undergraduate mechanical engineering majors John Tian, Shivaprem Bernath and Farhan Nur Shabab and high school student Rob Edwards collaborated in the project.

Related articles and links:

www.vanderbilt.edu

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