Imagine using a mobile phone powered entirely by its casing, or an electric car that runs off power stored in its chassis. Researchers at Vanderbilt University have created a structural supercapacitor that could, they believe, bring this closer to reality, making batteries and power cords obsolete. The structural supercapacitor could make it possible to store energy directly in structural materials, allowing them to deliver power long-term while surviving the real-life mechanical stresses they're bound to experience.

The team's new supercapacitor looks like a thin grey wafer, and is made of silicon electrodes that have been chemically treated to have inner surfaces containing nanoscale pores. Instead of storing energy in chemical reactions, like batteries, the supercapictor stores power by assembling electrically-charged ions on the surface of the porous material. In a recent test, the supercapacitor was able to store and release power without a hitch, the team reported, even when it was subjected to vibrational accelerations exceeding 80 g and stresses of up to 44 psi.

“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,” said Cary Pint, Assistant Professor of Mechanical Engineering at Vanderbilt University.

Being able to create hardy structural materials that can efficiently store and deliver energy opens up many exciting possibilities. For instance, instead of being inert, the walls of a home or a building could store and deliver power to all the home's lights and appliances.

"The majority of building materials that we use in these systems have absolutely no function than to just maintain mechanical integrity," Pint tells Gizmag. "What if we could take the tons of materials used in homes and convert them to energy storage systems that were not more expensive, could perform the same mechanical function as building materials, but could have decades worth of energy storage capability built in?".

"For a home or stationary powered system, this technology is the seed to putting solar panels on the roof and enabling power delivery around the clock without the need for a grid, even when the sun isn't shining," he adds.

The engineers suspended a heavy laptop from the supercapacitor to demonstrate its strength (Photo: Vanderbilt Nanomaterials and Energy Devices Laboratory)

While we've seen a lot of high-energy storage and powerful supercapacitors before, including a silicon supercapacitor from Pint's lab, the present research is reportedly the first to test how structural supercapacitors function under realistic mechanical loads. Making the device more mechanically robust to withstand stresses, Pint says, didn't compromise its energy storing capabilities.

"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,” says Pint.

Compared to batteries that charge for hours and operate for thousands of cycles, the way the structural supercapictor stores energy, the researchers say, will allow it to charge and discharge in minutes and operate for millions of cycles. That's a clear advantage, especially when you consider how supercapacitors typically lag behind batteries when it comes to energy storage.

“Battery performance metrics change when you’re putting energy storage into heavy materials that are already needed for structural integrity,” says 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.”

A mobile phone powered by supercapacitors and charged wirelessly would only need upgrades to its processor or other components over time. While the researchers' current silicon-based structural supercapacitors are more suited for solar cells and consumer electronics, they're confident that they'll be able to carry over the core technology into other materials like aluminum and carbon nanotubes. It may even be possible, they say, to eventually incorporate integrated energy storage into airborne systems.

"I feel that the bridge to a world where flying robots deliver our mail, or police our streets – something that may seem like science fiction now, but the technology has already been developed for – is to develop ways to efficiently power these systems," Pint tells us. "What makes me most excited about load-bearing energy storage is not necessarily the advances that we can achieve to the technology that is 'known,' but rather the advances that will come in technology when we start to put some imagination to what these materials can do."

A paper describing the research recently appeared in the journal Nano Letters

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