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Urea-reduced graphene oxide for high performance Li-ion capacitors

10 November 2012

Researchers from the Korea Advanced Institute of Science and Technology (KAIST) and SK Innovation have used urea-reduced graphene oxide (URGO) to build lithium ion capacitors (LICs) that deliver a specific energy density of approximately 106 Wh kgtotal−1 and a specific power density of approximately 4200 W kgtotal−1 with perfect capacity retention up to 1,000 cycles. These values are far superior to those of previously reported LICs and supercapacitors, they noted in a paper published in the journal ChemSusChem, and suggested that appropriately treated graphene can be a promising electrode material for LICs.

Lithium ion capacitors (LICs) have recently drawn considerable attention because they utilize the advantages of supercapacitors (high power) and lithium ion batteries (high energy). However, the energy densities of conventional LICs, which consist of a pair of graphite and activated carbon electrodes, are limited by the small capacities of the activated carbon cathodes. To overcome this limitation, we have engaged urea-reduced graphene oxide.

The amide functional groups generated during the urea reduction facilitate the enolization processes for reversible Li binding, which improves the specific capacity by 37% compared to those of conventional systems such as activated carbon and hydrazine-reduced graphene oxide.

—Lee et al.


  • Lee, J. H., Shin, W. H., Ryou, M.-H., Jin, J. K., Kim, J. and Choi, J. W. (2012), Functionalized Graphene for High Performance Lithium Ion Capacitors. ChemSusChem. doi: 10.1002/cssc.201200549

November 10, 2012 in Brief | Permalink | Comments (11) | TrackBack (0)


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"..deliver a specific energy density of approximately 106 Wh kgtotal−1 and a specific power density of approximately 4200 W kgtotal−1 with perfect capacity retention up to 1,000 cycles."

Isn't this better than many present batteries?

Also, and

The above 'drop in' components claim being several times better and cheaper.

Aren't 'pouch' batteries are just an anode, cathode, and electrolyte, so why must it take years to market 'drop in' component improved batteries?

Thousands of old and new devices await significantly better batteries or capacitors.

Meanwhile, the rest of the world doubles knowledge and transistor count during every two of the many battery 'years to market'.

I do not understand this article. It is too good to be truth. 10,6 Wh/kg for capacitor would be good. This would be better than Chevy Volt battery with 75 Wh/kg total effective.

This seems to be an energy density break through (about 10X) for super caps.

If true, these could be ideal for city e-buses (large and small), e-delivery city vehicles, Postal delivery e-vehicles, e-taxis, garbage e-trucks and many other applications requiring 1+ million cycles and much higher braking power recovery.

They will probably be peaked up to 200+ Wh/Kg by 2017 or so.

If this process ends up being 2x cheaper or more, you could essentially buffer power from the batteries.

Odds are the characterists of the potential voltage arent favorable in electronics, but if you use a large cap to supliment a large cheap and dense battery with low power output. Like Envia's you could have huge on demand power at tap.

Displacing the batteries also diplaces future cost liabilities from aging cells. Less risk for the OEM and owner.
Not to mention "fast charging" capabilities. Heck if they managed a way where there were a DCDC converter between the supercaps and the battery they could really charge fast, and have it charge the battery over time, even while your driving.--I probably should file a patent

For a PHEV or BEV application, the capacitor for the battery buffer would not need to be that large. A 1 kWh capacitor would be enough for a mid-size passenger vehicle.

Theoretically, the electrical energy required to accelerate a 4,400 lb. (2 tonnes) vehicle to 60 mph (27 m/s) is 200 Wh, probably 250 Wh with losses. Similarly, the energy available from regenerative braking from 60 mph to zero is 200 Wh theoretically.

At 85 mph, these Wh figures double.

So, with a dumb voltage controller that maintains the capacitor at half charge (500 Wh) so it can provide either acceleration or regenerative braking, a 1 kWh capacitor would satisfy the buffering needs in this case.

A smarter controller would adjust the charge level depending on vehicle speed, e.g., low charge at high and high charge at low speed. Then a smaller (and cheaper) capacitor than 1 kWh could be used.

In stop and go city traffic, a 10 to 20 Kg super cap like this one could do a lot to extend PHEVs/BEVs battery's range (and life) by recovering more braking energy and supplying acceleration energy 100++ times a day.

hmmm, I would wait these results to be confirmed, it is more than an order of magnitude better than anything reported so far, almost the EESTOR dream.

So let's see if it is real before speculating on wonderful applications..


Probably a good idea to wait before we get too excited. But I doubt anyone is as bad as EESTOR...those morons were special. LOL

Still, this is incredible if it's true. I've been trying for years to find a capacity growth chart for capacitors compared to batteries. From the little bit of evidence, that I CAN find, they've been growing on a curve as aggressive as Moore's law. But they started SO FAR behind batteries that nobody paid any attention.
If this is true, they may be worth looking at again. At least for certain applications they'd have an advantage already.

A 1 kWh capacitor would be enough for a mid-size passenger vehicle.
It depends if you're energy-limited or power-limited.  A capacitor rated to supply 100 kW at 4.2 kW/kg would require 24 kg of capacitors, which would store about 2.5 kWh at the 106 Wh/kg figure.  Regenerative braking power could easily peak at 100 kW or more (braking 1500 kg at 0.7 g at 100 km/hr dissipates an instantaneous power of 286 kW).

Getting the total braking power into the 40 kW range means low speed and gentle braking, conditions likely to be violated a lot by most drivers.

A 24kg pack would be 2.5kWh, and assuming regenerative power in/out per cycle is 240Wh, thats 10,000 starts and stops. At 8 years, 365 days a year, thats only 3 stops per day, probably not enough. Cycle life would need to get boosted, assuming the cycle life is linear with respect to depth of discharge (it might not be).

I was thinking about the cycle life as well. But I noticed they said "perfect retention after 1,000 cycles". Does that mean they haven't tested further yet? Did it drop to 80% after 2,000 cycles? Did it fall off a cliff?

Hard to tell without more info...but I'm a little skeptical as they don't say anything about longer cycles at all.

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