NExBTL renewable diesel receives sustainability certification in Germany
Report: Honda planning to double hybrid sales in Japan to more than 20% next fiscal year

Graphene-based supercapacitor offers energy density comparable to NiMH battery, but with rapid charge and discharge

Graphenesupercap1
Ragone plot of graphene supercapacitor. Credit: ACS, Liu et al. Click to enlarge.

Researchers from Nanotek Instruments and Angstron Materials have developed a graphene-based supercapacitor that exhibits a specific energy density of 85.6 Wh/kg at room temperature and 136 Wh/kg at 80 °C (all based on the total electrode weight), measured at a current density of 1 A/g. These values are comparable to those of NiMH batteries, the researchers note, but the new supercapacitor offers the ability to be charged or discharged within seconds or minutes. A paper on their work was published online in the ACS journal Nano Letters.

These are the highest energy density values ever reported with carbon electrodes without the pseudocapacitance contributions from a conducting polymer or metal oxide, the authors said, further stating that “We believe that this is truly a breakthrough in energy technology.”

The group, led by Bor Jang of Nanotek Instruments, reported in 2006 that graphene can be used as a supercapacitor electrode material. Despite a number of efforts to improve the specific capacitance of graphene-based electrodes, however, results fell sort of the theoretical capacitance of 550 F/g due to the high tendency for graphene sheets to re-stack together.

The team determined that the best strategy to achieve a high capacitance in such graphene-based electrodes is to use curved graphene sheets rather than flat sheets to prevent the sheets from sticking to one another face-to-face. The curved morphology enables the formation of mesopores accessible to and wettable by environmentally benign ionic liquids capable of operating at a voltage >4 V.

With the total electrode weight of a supercapacitor system being typically one-fourth to one-half of the total system weight, the system-level specific energy of graphene-based supercapacitors can exceed 21.4-42.8 Wh/kg, which is comparable to that of a modern nickel metal hydride battery used in a hybrid vehicle. This breakthrough energy storage device is made possible by the high intrinsic capacitance and the exceptionally high specific surface area that can be readily accessed and wetted by an ionic liquid electrolyte capable of operating at a high voltage.

—Liu et al.

Resources

  • Chenguang Liu, Zhenning Yu, David Neff, Aruna Zhamu, and Bor Z. Jang (2010) Graphene-Based Supercapacitor with an Ultrahigh Energy Density. Nano Letters doi: 10.1021/nl102661q

Comments

DaveD

It is awesome to see this kind of progress. I'm trying to find data to get a good picture of capacitors/supercaps/ultracaps to check their progress... but is is almost impossible over time.

However, from the scant data I can find...capacitors have been following nearly a Moore's Law type curve for the last 20 years. And nobody really even noticed and there really wasn't a whole lot of research put into it compared to batteries and other fields.

As a couple of people pointed out, be patient because these are best case conditions and it usually takes about 5 years for things like this to show up in products.

I think the best use might be to put in about 5kWh of supercaps for short term commuting and regen braking/acceleration and then to team it with some high energy density batteries as a "range extender".

Think of what you can do on the battery front when you can ignore power density (and even cycle life to a degree) because the super caps handle power needs and reduce wear and tear on batteries. This allows batteries to focus on energy density and not have to make so many tradeoffs. Suddenly zinc chemistries make more sense as well as others.


SJC

The range extender idea may be a good one. Caps have a different voltage profile, but if they can be kept up with the lithium ion batteries then there is less stress on the batteries.

ToppaTom


Nanotek moved to the Dayton area in 2005 from North Dakota with two employees. In early 2010, the company had 16.

If something sounds too good to be true...

. . I probably IS too good to be true.

Nice scam.

kelly


""85.6 Wh/kg at room temperature and 136 Wh/kg at 80 °C"

Should one infer that performance continues to drop with ambient temperature?"

Room temperature = 21 C. In other words, the performance is stated to IMPROVE with higher temperature.

ToppaTom

"The best strategy is to use curved graphene sheets rather than flat".

Reminds me of the bathtub that would "never leave a ring" - it was square.

yoatmon

It's almost 4 years now that I predicted that Li-ion is just a hype and the true future is carbon; graphene is a particular molecular structure of carbon.

The described capacitor is designed with two parallel sheets of "curved" graphene and hence, limited in surface. The surface area can be increased tremendously by growing self assembling CNTs onto the graphene sheets. With such an increased surface, the achievable energy density can be more than 10x as high as presently. Once all possible improvements have been realized on this design, range anxiety will be no more than history.

For further info, google with:
"multiple walled CNTs grown on graphene sheets"

Reel$$

Interesting discussion yoatman. Looks like we can expect a new generation of wire conductors made from the very substance many fear... carbon.

In this case nano tubes grown into well-aligned atomic structures with excellent electrical properties.

kelly

ToppaTom, did you send them money? What was the 'nice scam amount?

Mannstein

Good news this might actually solve the impending lithium shortage problem.

ejj

@Mannstein: True. We are already supporting terrorist regimes with our oil consumption - last thing we need to do is support more countries that hate America...ie. lithium-rich Bolivia.

ai_vin

What lithium shortage problem?

creativforce

"Stealth mode" here we come. Bet this is the last we hear of it.

Mannstein

@ ai vin

Check out this BBC News Report at:

http://news.bbc.co.uk/2/hi/business/7707847.stm

to find out about the impending shortage.

ai_vin

Check out this; http://gas2.org/2008/10/13/lithium-counterpoint-no-shortage-for-electric-cars/

to find out about the Kings Valley mine in Nevada, a mine that’s now expected to produce 25 billion pounds of lithium carbonate. Enough lithium from an American source for almost 800 million EVs.

Canada has its own mine; http://www.canadalithium.com/s/QuebecLithium.asp

Stan Peterson

Once again Mankind's use of its specialized adaptation, his brain, helps him possibly live better.

Despite the nonsense that NiMH batteries were successful, they were only on the fringe of acceptability, for but a handful of committed people.

If and its a big if, practical Super caps can be fabricated and constructed, a composite cap & battery solution may become a practical way of producing a fast charging electro-chemical device.

Before you run off wildly, remember the last and continuing hustle, for a Super Capacitor, by the not-so-erstwhile lads in Texas.

kelly

Good luck Nanotek!

The comments to this entry are closed.