Improved supercapacitors for super batteries, electric vehicles

May 19, 2014 by Sean Nealon
(a) This is a schematic illustration of the preparation process of RGM nanostructure foam. SEM images of (b–c) as-grown GM foam (d) Lightly loaded RGM, and (e) heavily loaded RGM. Credit: UC Riverside

Researchers at the University of California, Riverside have developed a novel nanometer scale ruthenium oxide anchored nanocarbon graphene foam architecture that improves the performance of supercapacitors, a development that could mean faster acceleration in electric vehicles and longer battery life in portable electronics.

The researchers found that , an like batteries and fuel cells, based on transition metal oxide modified nanocarbon graphene foam electrode could work safely in aqueous electrolyte and deliver two times more and compared to supercapacitors commercially available today.

The foam electrode was successfully cycled over 8,000 times with no fading in performance. The findings were outlined in a recently published paper, "Hydrous Ruthenium Oxide Nanoparticles Anchored to Graphene and Carbon Nanotube Hybrid Foam for Supercapacitors," in the journal Nature Scientific Reports.

The paper was written by graduate student Wei Wang; Cengiz S. Ozkan, a mechanical engineering professor at UC Riverside's Bourns College of Engineering; Mihrimah Ozkan, an electrical engineering professor; Francisco Zaera, a chemistry professor; Ilkeun Lee, a researcher in Zaera's lab; and other graduate students Shirui Guo, Kazi Ahmed and Zachary Favors.

Supercapacitors (also known as ultracapacitors) have garnered substantial attention in recent years because of their ultra-high charge and discharge rate, excellent stability, long cycle life and very high power density.

These characteristics are desirable for many applications including electric vehicles and portable electronics. However, supercapacitors may only serve as standalone power sources in systems that require power delivery for less than 10 seconds because of their relatively low specific energy.

A team led by Cengiz S. Ozkan and Mihri Ozkan at UC Riverside are working to develop and commercialize nanostructured materials for high energy density supercapacitors.

High capacitance, or the ability to store an electrical charge, is critical to achieve higher energy density. Meanwhile, to achieve a higher power density it is critical to have a large electrochemically accessible surface area, high electrical conductivity, short ion diffusion pathways and excellent interfacial integrity. Nanostructured active materials provide a mean to these ends.

"Besides high energy and , the designed graphene foam electrode system also demonstrates a facile and scalable binder-free technique for preparing supercapacitor electrodes," Wang said. "These promising properties mean that this design could be ideal for future energy storage applications."

Explore further: Silly Putty material inspires better batteries

More information: Paper: www.nature.com/srep/2014/14032… /full/srep04452.html

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User comments : 9

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boudreaux
3 / 5 (1) May 19, 2014
"ruthenium oxide anchored nanocarbon graphene foam architecture"

Hey! That would be a good name for a rock band!
Shakescene21
3 / 5 (3) May 19, 2014
Ruthenium is one of the rarest and most expensive elements on Earth. Perhaps this technology might be viable for high-end applications electronics or aerospace, but it can't supply hundreds of millions of electric vehicles.

I am much more impressed by researchers who can get good results from more common materials which can actually be used sustainably. It is usually hundreds of times more difficult to get good results from sustainable materials than from platinum-group metals, and but those researchers are the ones who'll solve the big problems.
Pejico
May 19, 2014
This comment has been removed by a moderator.
topkill
4 / 5 (1) May 19, 2014
Well, a quick check of spot prices for Ruthenium show it's only about $70/oz. It's rare, but seems to be one of those elements that's "rare" because there's not much demand for it so nobody is mining it much. So that doesn't seem to rule it out.

However, every time you see a breakthrough where they say "twice as much" rather than giving a solid measurement, you know it's most likely bullshit. Twice as much as WHAT? Just give us a damn real number.
Shakescene21
4 / 5 (1) May 19, 2014
@Topkill- Thanks for the correction. My guy is currently selling Ruthenium for $72/oz.
http://www.infomi...thenium/

I don't check on ruthenium prices very often, and when I last looked during the boom it was $860/oz, and it apparently reached $900/oz before collapsing, as shown in the price charts. At any rate the supply of Ruthenium is very thin and don't see how we can find enough of it to make supercapacitors for tens of millions of cars.
topkill
3 / 5 (1) May 19, 2014
@Shakescene21,
Yeah, I'm sure that it's rare enough to be a problem. But then again, I don't know if they use a nanogram or a kilogram to make a supercap with this new supercap formula LOL

Regardless, this is nothing more than another empty press release until they give us some real numbers about it's capacity. These "twice as good" without telling us what the baseline is a dead give away that it's not that good.

My favorite is every battery breakthrough that comes along is "twice as energy dense as normal lithium ion batteries"l. Of course, they forget to mention they are talking about the worst lithium batteries from 1992 that had less than 100Wh/kg and ignore the fact that today's batteries used by Tesla are already at 265Wh/kg! LOL Already better than whatever new "breakthrough" they are announcing.
Shakescene21
4 / 5 (2) May 20, 2014
@Topkill-- I looked up the full article and was pleasantly surprised that it wasn't pay-walled. They actually give some power numbers, but revise them downward in the "supplemental information" at the end. The bottom line: Maximum Energy Density = 131Wh/kg, Highest Power Density = 427 kW/kg.

So this doesn't seem to be a major "breakthrough" compared to the numbers you quote for Tesla's baatteries.
Liem
4 / 5 (2) May 20, 2014
On the contrary...considering these number it IS a breakthrough. supercapacitors used the have only 1/10 of batteries energy density. these numbers almost put them as a suitable replacement for batteries.
Do not confuse supercapacitors with batteries. They do not play in the same courtyard.
Supercapacitors can charge in seconds whereas batteries charge at best in minutes or realistically in hours. supercapacitors have also the advantage of vitually unlimited charge/discharge cycles.
Supercapacitors are suited for KERS when batteries are not.
The question is how long do these supercapacitors keep their charges.
FastEddy
4 / 5 (1) May 20, 2014
Ruthenium is one of the rarest and most expensive elements on Earth. ... I am much more impressed by researchers who can get good results from more common materials which can actually be used sustainably. It is usually hundreds of times more difficult to get good results from sustainable materials than from platinum-group metals, and but those researchers are the ones who'll solve the big problems.


Discovery, first, then optimization. (Although the search for "sustainability" may just cloud and confuse the efforts.)

Maybe you have a suggestion for a replacement for Ruthenium? ... Maybe something else in the "Iron group"?
topkill
not rated yet May 20, 2014
@Shakescene, Liem is right, this IS a huge breakthrough if they can get around the usual caveats (price/availability of materials, safety, etc). Those numbers would be by far the most impressive we've ever seen for a supercapacitor! Supercaps have very different usage characteristics than batteries. They last for 10's of thousands to even millions of cycles and you don't need the same energy density because if you run low, you can charge them literally in seconds instead of the many minutes-many hours of batteries! And they have much higher efficiency so you get much better regenerative braking.
I should apologize for my earlier skepticism. There are still some serious caveats to overcome to see something like this in production, but this has some great potential. Even if they end up using other elements that are more abundant than Ruthenium, at least they have a new class of materials to investigate.