Adding transparency to graphene paper improves supercapacitor capacitance

April 27, 2015 by Lisa Zyga feature
(a, b) Photographs and (c) an SEM micrograph of the new material: flexible, freestanding, and transparent graphene paper. In (b), the Sun Yat-Sen University logo is clearly seen behind the transparent graphene sheet. Credit: Na Li, et al. ©2015 American Chemical Society

(Phys.org)—For the first time, scientists have integrated transparency into freestanding, flexible graphene paper (FFT-GP), and demonstrated that the new material can greatly improve the performance of supercapacitors.

"Freestanding flexible and transparent paper was synthesized for the first time, and the capacitance was improved by nearly 1000-fold compared with that of the laminated or wrinkled graphene-film-based ," Chengxin Wang, Professor at Sun Yat-sen (Zhongshan) University in Guangzhou, China, told Phys.org. "The capacitance for the supercapacitors based on FFT-GP is also at least ten times greater than previously reported values for transparent and flexible supercapacitors based on pure carbon materials. However, some carbon-based nontransparent supercapacitors still perform better than the FFT-GP-based transparent supercapacitor."

Wang and his coauthors have published a paper on the new material in a recent issue of Nano Letters.

The improved performance stems in large part from the prism-like graphene building blocks that the FFT-GP is made of. The hollow structures of the prism-like graphene that give the material its transparency also provide additional space for chemical reactions to occur compared to other materials. In addition, the aligned and interconnected prism-like structures provide a wide open freeway for ions and electrons to travel along, and the good charge transport leads to an overall better performance.

To make the new material, the researchers had to overcome the biggest obstacle facing the synthesis of thin, transparent graphene sheets, which is that the sheets fracture easily when being removed from their template. Here, the researchers used NaCl powder—essentially finely ground table salt—as the template for FFT-GP growth. Using a method called microwave plasma-enhanced chemical vapor deposition, the researchers created a "plasma atmosphere" of NaCl, carbon, and hydrogen. At the end of this process, the NaCl is allowed to recrystallize on a silicon substrate. These NaCl crystals serve as templates upon which graphene fragments form and grow into prism-like graphene, which can be peeled off the substrate using a razor blade.

Two supercapacitors placed across a smartphone screen demonstrate optical transparency while powering an LED. Credit: Na Li, et al. ©2015 American Chemical Society

Although the FFT-GP created here is somewhat wrinkly and has a light brown color, the researchers demonstrated that it can still withstand more than 1,000 bending and stretching cycles with little capacity loss, and still clearly transmits light. The researchers also demonstrated a tandem device made of two integrated FFT-GP-based supercapacitors placed over a smartphone screen (to demonstrate transparency) that lights up an LED.

The material's combination of flexibility, transparency, electrical conductivity, and large surface area open the doors to many new potential applications, such as stretchable and transparent solar cells, rolled-up displays, and self-powered and wearable optoelectronics. The hollow structure of the prism-like graphene could also be exploited for other uses, such as storing more light-absorbing dye in dye-sensitized . The researchers plan to explore these possibilities in the future.

"First, we are trying to use FFT-GP in ," Wang said. "Due to its hollow and porous prism-like graphene building blocks with large efficient surface area, larger amounts of light-absorbing dye could be stored than in other graphene materials. Maybe this design is a better solution to improve the dye adsorption and to enhance the light trapping and scattering capability compared to other graphene materials. Second, FFT-GP-based high-theoretical-capacitance composites will be synthesized to improve the energy density of FFT-GP-based transparent supercapacitors. Third, FFT-GP could be applied as lithium-ion battery anodes, and then a transparent all-solid-state lithium-ion battery can be developed."

Explore further: Graphene sheets could make effective transparent electrodes in certain types of photovoltaic cells

More information: Na Li, et al. "Free-Standing and Transparent Graphene Membrane of Polyhedron Box-Shaped Basic Building Units Directly Grown Using a NaCl Template for Flexible Transparent and Stretchable Solid-State Supercapacitors." Nano Letters. DOI: 10.1021/acs.nanolett.5b00364

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gkam
3.7 / 5 (6) Apr 27, 2015
Are we setting ourselves up for a nasty surprise? Having been part of the team which tested graphite fiber materials for NASA, I have to warn you of potential problems with it. They may not be in Wiki. Ask politely for references to the tests.

When burned, this stuff ablates, becomes friable, and produces a smoke of tiny needles of carbon fibers, ablated to fine diameters. Borne by convection currents, this "smoke" is unlike any other: It is opaque to RF and conductive. That means radar and radio and light do not get through it. It coats wires and insulators of power systems and takes them out.

If we get a fire on an airport ramp, they could lose radio, some radar, and perhaps their power system, as well.

We do not know the health effects of these fibers, except that many are tiny enough to lodge in the lungs,and perhaps travel through the body as tiny needles.
Sonhouse
5 / 5 (3) Apr 27, 2015
Sounds like, if that is the case when you burn graphite paper, the military will be interested in it for chaff. Think about how much of the stuff will enter the atmosphere THEN.
gkam
2.3 / 5 (3) Apr 27, 2015
Sonhouse, my first thought was they would militarize this. And I think they did. I saw reports of them taking out the Baghdad electrical system at night with something not specified, just before we bombed it the next day.

We did the tests for NASA in 1978-79. They were only concerned with the development and distribution of the fibers, not their effects.
Eikka
5 / 5 (3) May 03, 2015
Having been part of the team which tested graphite fiber materials for NASA


I very much doubt that.

And I think they did. I saw reports of them taking out the Baghdad electrical system at night with something not specified, just before we bombed it the next day.


They did, but not with "carbon fiber smoke". They made special shells that shot out carbon fiber ribbons when they burst in the air above a substation. The technique was well-reported at the time.

gkam
1 / 5 (3) May 03, 2015
"I very much doubt that. "
-----------------------------

Oh, good. that is one report with my name on it. That means I get an apology?

Let's see, . . .

by Wilton, Kamburoff, . .
19810025595 NASA Technical Memorandum 81308

X80-10OO9"_ Scientific Service, Inc., Redwood City, Calif. NOTICE: Available to U.S. Government Agencies and Their FIRE TESTING OF NASA SAMPLES, PHASE I Contractors. C. Wilton. G. Kamburoff. and J. Boyes Feb. 1979 161 p (Contract NAS2-9945)

"The results of the burning and impact testing of graphite measure the chemical composition of atmospheric aerosols. epoxy test samples to determine the quantity and distribution of graphite fibers that might be released from aircraft crash/fire situations are reported. The design, construction, and calibration of the impact/fire test facility is described along with the tests conducted including sample preparation, test procedure, data collection, and test results."
Eikka
3.7 / 5 (3) May 05, 2015
Oh, good. that is one report with my name on it. That means I get an apology?


Yes. Credit where credit is due.

However, how do you know graphene behaves the same way as graphite fibers? One is a two dimensional sheet of carbon, whereas the other is made of filaments to begin with.

Graphene is essentially the same thing as what's in soft pencil lead. Pencil lead consists of tiny graphene flakes packed together - which is where graphene was discovered from - and burning pencil lead doesn't give off harmful graphite needles as far as I'm aware.


Eikka
4 / 5 (4) May 05, 2015
Borne by convection currents, this "smoke" is unlike any other: It is opaque to RF and conductive. That means radar and radio and light do not get through it. It coats wires and insulators of power systems and takes them out.

If we get a fire on an airport ramp, they could lose radio, some radar, and perhaps their power system, as well.


This part isn't supported by the material you've given so far, and neither by your own statement:

We did the tests for NASA in 1978-79. They were only concerned with the development and distribution of the fibers, not their effects.


Do you have any other supporting material for the claims on the effects, or do you wish to concede to personal conjecture?

gkam
1 / 5 (3) May 05, 2015
Eikka, you are a real coward. I gave you unearned points for character, apparently.

Read the document!
Eikka
5 / 5 (3) May 05, 2015
Eikka, you are a real coward. I gave you unearned points for character, apparently.

Read the document!


The "19810025595 NASA Technical Memorandum 81308" is 270 pages long. I'm not going to trawl through all that to find out that it doesn't say what you claimed it said. You haven't even said what exactly it is I should be looking for.

If there is some proof to what you're saying, surely you can quote or even tell me what page number I should be looking at.

This is what I meant when I criticized you for leading people on to wild goose chases.
gkam
1 / 5 (3) May 05, 2015
All you have to do is use control F and my name, and it will send you to page 41, at the top (I think). But you already read the entry. I do not have the report, and have asked for it through FOIA. They do not respond.

This could be a serious problem, but I cannot get anyone interested in it. We will have to see if it is as bad as I think the possibilities could be.
Eikka
5 / 5 (3) May 05, 2015
This could be a serious problem, but I cannot get anyone interested in it. We will have to see if it is as bad as I think the possibilities could be.


The whole document is just a listing of articles and their abstracts, not the articles themselves. There's absolutely nothing on your claims about the properties and effects of graphite fiber smoke.

And yet, I still think you're comparing apples to oranges. Carbon fiber is not graphene. They're different atomic structures. One wouldn't expect graphene to give off nanofibers when burned, but small flakes not unlike pencil dust.

gkam
1 / 5 (3) May 05, 2015
Never mind. I am not here to play semantic games, or make silly guesses. I tested the materials for NASA and said so. You denied it, and I gave you proof. Now you bring up something else, as a dodge.

You assumed I was lying, and you were wrong. So now I get personal attacks.

We should start over.


Eikka
5 / 5 (3) May 05, 2015
Never mind. I am not here to play semantic games.


There's no semantics here. It's whether you do have the proof for what you're claiming, whether you can show it, or whether you're just making it up while playing yourself an expert of yet another subject.

You assumed I was lying, and you were wrong. So now I get personal attacks.


You still haven't shown that you aren't. Just that you were involved in a paper related to the subject. Of the paper itself, the contents, we have no idea.

Don't call people cowards and then tell them to read papers that have nothing in them.

You get personal attacks for dragging your person into the subject at hand.


We should start over.


Yes. Let's start over from the point where you claim that graphene produces graphite fiber smoke, and I ask you for the proof of it.

gkam
1 / 5 (3) May 05, 2015
You do not know what is in it because you did not read it.

My god, where do they find folk like you and otto who cannot admit error? If you want to be a professional, it is a prime test of character necessary for science or engineering.
Eikka
5 / 5 (3) May 05, 2015
You do not know what is in it because you did not read it.


Because it's not available to be read!

You can say anything about papers that nobody else can check.

If you want to be a professional, it is a prime test of character necessary for science or engineering.


Even a professional would want to double check before taking the word of someone with your track record.
gkam
1 / 5 (3) May 05, 2015
My assertion was that I tested graphite fiber materials for NASA. You denied it. I gave you proof.

Now what?
Eikka
5 / 5 (3) May 05, 2015
My assertion was that I tested graphite fiber materials for NASA. You denied it. I gave you proof.

Now what?


Yes. I admitted that proof.

Then I asked you for further clarification and support for the further claims you made that were not supported by the article abstract or any other information you gave. Namely:

When burned, this stuff ablates, becomes friable, and produces a smoke of tiny needles of carbon fibers, ablated to fine diameters. Borne by convection currents, this "smoke" is unlike any other: It is opaque to RF and conductive. That means radar and radio and light do not get through it. It coats wires and insulators of power systems and takes them out.


So, do you have any or not?
gkam
1 / 5 (3) May 05, 2015
Oh, another hoop to jump through? And when I find the information, what silly challenge will you have then?

You lost.
Eikka
4 / 5 (4) May 05, 2015
Oh, another hoop to jump through? And when I find the information, what silly challenge will you have then?


No. Just what I've been asking for all along. Read up, it's only a dozen or so messages above this one.

The only hoop to jump through is to follow through and provide evidence for your own claims that burning graphene produces the same kind of fibrous smoke that burning carbon fiber, and that it has the properties and effects you claimed it has.

You said so yourself, so you prove it yourself.

You lost.


Shitting on the chessboard and claiming victory now, I see.

The problem here is that for the one time you actually directly showed that you have authority in something, you appear to have abused that authority to slip us some conjecture as fact, and refuse to admit it.

TheGhostofOtto1923
2.3 / 5 (3) May 06, 2015
This is what I meant when I criticized you for leading people on to wild goose chases... You can say anything about papers that nobody else can check.
Well its apparent that to george, the contents of the report and his specific role in it are irrelevant to the authority he thinks it gives him.

These teams are usually composed of a degreed expert or 2 and a tech who does the grunt work. The report lists techs on an equal footing in order to make them feel good.

Which one of these roles did you play george? Lets see back in 1980 you didnt even have your soft science MS yet. Correct?
You assumed I was lying, and you were wrong
You were obviously lying. Citing a reference you cant produce, and claiming you had some role in it greater than the guy who lit the bunsen burner, is in effect a lie until you can prove otherwise.

You referred to the doc you did list as if it were the actual paper, indicating that you werent familiar with it at all. MORE LIES.
gkam
1 / 5 (1) May 06, 2015
otto, please grow up or go away. You are ruining this forum with your adolescent vendettas. You have already admitted you are a sniper, hiding behind several aliases, playing games online with the rest of us.

Well, the rest of us are real, and would like to use this forum for discussion, not your "games".

Do we have a moderator here at all?

Eikka, you contested my construction, operation, and report on testing graphite fiber materials for NASA. You said I did not do the tests, I showed you I did. Now you can apologize, or hide when you look in the mirror.

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