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Batteries

Published on April 24th, 2015 | by Tina Casey

14

3-D Printed Graphene “Liquid Smoke” Energy Storage Breakthrough

April 24th, 2015 by  


We already know that graphene is the nanomaterial of the new millennium, and that graphene is beginning to play a big role in next-generation energy storage, including electrical vehicle batteries. We also know that graphene is a quirky, funky little devil of a material to manufacture in bulk, which kind of puts a crimp in the dream of super-long-range but affordable EVs for everybody. However, a research team at Lawrence Livermore National Laboratory is on to a solution that involves 3-D printing and a graphene aerogel, aka “liquid smoke.”

Hey, Why Didn’t They Dip Han Solo In Graphene?

For those of you new to the topic, graphene is a single, two-dimensional sheet of carbon atoms arranged in a lattice pattern resembling chicken wire.

Though ultra-thin and light, graphene is ultra-strong, and its unique electronic properties have engendered thousands of research papers since it was first discovered in 2004.

So, that explains why Han Solo was frozen in carbonite instead of something cool and exotic like graphene — George Lucas did not have graphene in 1980.

That’s probably just as well. As much as we love graphene, carbonite sounds way more badass when you say it out loud, as in, “Oh. They’ve encased him in carbonite.”

We got sidetracked by the carbonite angle because the graphene aerogel involves a carbonization step (see video below), and that’s a good excuse as any to ask you all what you think about the new Star Wars teaser, so drop us a note in the comment thread.



The Graphene Energy Storage Problem

Where were we? Oh, right, 3-D printed graphene aerogel. We did mention that graphene is a bear to manufacture in bulk, which the team from Lawrence Livermore National Laboratory is happy to point out in its new paper titled “Highly compressible 3D periodic graphene aerogel microlattices,” available online at nature.com.

The problem involves building precise, durable 3-D structures from a two-dimensional material.

As described by the Livermore team, the current method of choice is chemical vapor deposition, a conventional fabrication technique that uses a template to guide layers of material into position.

However, the template puts a freeze on scalability, and the overall results are relatively brittle when compression is applied.

More recently, researchers have begun to fabricate graphene aerogels, which is a logical extension of previous work on carbon nanotube aerogels.

Also known as “hard smoke” or “frozen smoke,” aerogels are extremely lightweight because they are based on gas instead of liquid, and they stand up well under compression. That approach is far more promising but according to the Livermore team that still leaves a big problem:

…they possess purely stochastic porous networks, which limit their performance compared with the potential of an engineered architecture.

Stochastic is fancyspeak for random, in case you were wondering. The randomness of conventional graphene aerogels limits their application to flow batteries, among other things.

The 3-D Printed Graphene Aerogel Solution

That brings us to the new 3-D printed graphene aerogel method. By using a 3-D printer instead of a template, the Livermore team was able to design a precise pore structure that would enable more efficient mass transport than graphene aerogels fabricated by vapor deposition.

The ink for the printer consists of graphene oxide and silica, and here’s how the team describes its 3-D printed graphene aerogel:

…high surface area, excellent electrical conductivity, are lightweight, have mechanical stiffness and exhibit supercompressibility (up to 90 percent compressive strain). In addition, the 3D printed graphene aerogel microlattices show an order of magnitude improvement over bulk graphene materials and much better mass transport.

You can get a visual representation of the process from this video (there’s no sound so don’t turn your volume up):

 So, What About That Graphene EV Battery?

Apparently the Livermore research team foresees an application for its graphene aerogel in flow batteries, which at first glance doesn’t make sense for EVs because conventional flow batteries are cumbersome affairs to tote around on wheels.

However, flow battery technology has advanced rapidly in recent years and GE for one is already working on a pocket-sized (relatively speaking) EV flow battery.

Lithium-sulfur batteries could also benefit from the aerogel. Lithium-sulfur technology is promising but suffers from a proclivity to degrade quickly, and researchers are beginning to use graphene to work around that obstacle.

As for the current EV battery gold standard, lithium-ion technology, our friends over at Tesla have been tinkering around with a graphene-integrated battery, so it’s possible that the new aerogel could find a home there, too.

For the record, Rice University and the US Air Force have already been working on a “foam” type graphene battery, based on a generally similar concept to aerogels but involving a laser-based application method.

We’re also seeing some EV battery buzz around perovskite, a naturally occurring crystalline material that can be easily synthesized, so it looks like graphene aerogel could face plenty of competition up ahead.

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Image credit (screenshot and video): courtesy of Lawrence Livermore National Laboratory.


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About the Author

specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Tina’s articles are reposted frequently on Reuters, Scientific American, and many other sites. Views expressed are her own. Follow her on Twitter @TinaMCasey and Google+.



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