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Graphene and carbon nanotubes combined to create flexible, wearable supercapacitor

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May 15, 2014

The flexible supercapacitor composed of graphene and carbon nanotubes (Photo: Dr.Dingshan ...

The flexible supercapacitor composed of graphene and carbon nanotubes (Photo: Dr.Dingshan Yu, Nanyung Technical University, Singapore)

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An international team of researchers has developed a supercapacitor composed of graphene and carbon nanotubes that is claimed flexible enough to be woven into clothing and potentially powerful enough to offer a real alternative to batteries for use in portable devices. Capable of being charged and discharged in excess of 10,000 cycles, the new supercapacitor also promises to be significantly lighter, faster to charge, and more robust than current battery technology.

Researchers from Nanyang Technological University (NTU) in Singapore, Tsinghua University in Beijing, China, and Case Western Reserve University in Cleveland, Ohio, produced the supercapacitor by heating and bonding micro-scale graphene sheets and carbon nanotubes to form a continuous, interconnected network of filaments. The result is reported to be a complex hybrid fiber so densely packed that its capacitive surface area is a whopping 396 sq m (4,262 sq ft) per gram.

The researchers say that this results in a capacitance of 300 Farads per cubic centimeter, and a volumetric energy density of 6.3 microwatts per cubic millimeter which, in practical parlance, means that the newly-developed supercapacitor is comparable in power to a 4-volt, 500 microamp, thin film Lithium-ion battery. This is more than enough to run many currently available low-power devices, as well as electronic components such as LEDs.

The team has so far produced a 50 meter (164 ft) long set of interwoven fibers in a continuous melding process in the laboratory that yielded approximately 1 m (3 ft) per hour. It is expected that, scaled-up, this process could eventually see large quantities of supercapacitor fibers made on a commercial scale, bringing down the price and increasing its availability.

Supercapacitor electric circuit (Image: Dr.Dingshan Yu Nanyung Technical University, Singa...

"The fiber supercapacitor continues to work without performance loss, even after ending hundreds of times," said researcher Dingshan Yu. So, when this supercapacitor material does become commercially viable, its ability to be bent continuously out of shape while maintaining its charge and structural integrity could lead to it being woven into clothing, backpacks, shoes, and other items to produce a wearable power system.

In turn, these could then power devices such as medical monitors, GPS devices or any of the other myriad accoutrements to our technological life that would allow us even more mobile freedom. It could also be woven into textiles for use by the military to power soldiers’ equipment, incorporated into other materials to form the case of a device that is also its power supply, or even double as the cover and the battery for an eReader.

But more than this, the low mass, high volumetric density of a graphene and carbon nanotube supercapacitor is so great that it may well provide a solution to a more pressing problem for electric vehicles: weight. At a mere fraction of the bulk of storage batteries, and capable of being charged and discharged for more than 10,000 cycles (less than 1,000 is the norm for rechargeable batteries), this type of superlight power storage could prove to be the answer to the electrical motor industry's prayers.

And, by taking advantage of its bendable nature, it could be so densely packed that many thousands of feet of charged supercapacitor material could be shoehorned into any number of spaces on a vehicle, no matter the shape, thereby freeing electric vehicle designers from the tyranny of having to find very large, very flat areas to house the batteries.

There's still more work to be done, but this new material promises to open up whole new avenues for incorporating electric storage devices as intrinsic components, rather than as separate adjuncts to devices.

The research was recently published in Nature.

Source: Case Western Reserve University

About the Author
Colin Jeffrey Colin discovered technology at an early age, pulling apart clocks, radios, and the family TV. Despite his father's remonstrations that he never put anything back together, Colin went on to become an electronics engineer. Later he decided to get a degree in anthropology, and used that to do all manner of interesting things masquerading as work. Even later he took up sculpting, moved to the coast, and never learned to surf.   All articles by Colin Jeffrey
6 Comments

The author needs to fact check this article. The statement "At a mere fraction of the bulk of storage batteries" is highly inaccurate. First the term "6.3 microwatts per cubic millimeter" is a meaningless term. Energy densities are measured in Joules or watt-hours per volume. Without the hours appended the term has no meaning at all.

Now let's assume that the author just abbreviated the term and this device has an energy density of 6.3microwatt-hours per cubic millimeter. A cubic millimeter is roughly one micro liter so this converts to 6.3 watt/hours per liter. Lithium batteries store in excess of 250watt-hours per liter with some as high as 750watt-hours per liter. So these devices would require 40 times the volume of a low end lithium battery or as much as 120 times as much volume as a high end lithium battery. In other words these devices are in no way comparable to modern battery technology. Now to put the final nail in the coffin of this hype let’s compare them to lead acid batteries. Lead Acid has a low end energy density of 60 watt-hours per liter so they would still require 10 times the volume as comparable lead acid batteries.

Finally the statement that they would resolve weight issues is not supported in any way by the article as there is no weight measure given. How much does that one cubic millimeter of this material weigh? We do not know it we never given in the article.

VirtualGathis
15th May, 2014 @ 10:26 am PDT

I would like to see a goodly amount of square feet of these woven into a jacket with "stun gun" circuitry liberally scattered across the surface.

"No, no mugger, please don't punch me in the chest, I already have sore ribs from a fall"

Punch ...

ZAP!!!!

Sucked in!

Or:

"Hello" (meeting the 'ex' or some other miserable entity) "let's forgive and forget with a hug"

The Skud
15th May, 2014 @ 07:36 pm PDT

Making wings from this stuff would be awesome - electric aircraft where the wings *are* the battery!

@VirtualGathis - Reading the source might have been better than throwing criticism?

It was your mistake/misunderstanding that mixed up the units - power and energy are 2 different things. You sound like you know this, and from the mere fact we're talking about capacitors, it *should* have been obvious?

Here's a snip from the references sources to help clear it up:

" most supercapacitors have high power density but low energy density, which means they can charge quickly and give a boost of power, but don’t last long. Conversely, batteries have high energy density and low power density, which means they can last a long time, but don’t deliver a large amount of energy quickly. "

christopher
15th May, 2014 @ 08:58 pm PDT

Virtualgathis - if you go look at the original work at the universities you will see that "6.3 microwatts per cubic millimeter" is exactly what the researchers say, so how can this be wrong?

I like the idea of finding a alternative to batteries and this looks like it has a lot of potential to me (pun intended)

Razzacatz
15th May, 2014 @ 11:00 pm PDT

"A full micro-supercapacitor with PVA/H3PO4 gel electrolyte, free from binder, current collector and separator, has a volumetric energy density of ~6.3 mWh cm−3"

Or: about 6.3 milli-watt-hour per cubic millimeter

Wizodd
17th May, 2014 @ 01:38 pm PDT

Who knew I would need to wear a super capacitor? i hope it goes well with the rest of my wardrobe.

ralph.dratman
17th May, 2014 @ 07:31 pm PDT
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