Koreans says graphene supercapacitors are ready for electric cars.

[LASooner]

http://nextbigfuture.com/2013/11/koreans-say-graphene-supercapacitors.html

 

NOVEMBER 14, 2013

Koreans say graphene supercapacitors are ready for electric cars

Conventional batteries take so long to charge that they cannot efficiently store braking energy. But now graphene supercapacitors that store almost as much but charge in just 16 seconds could do the job instead.

Now Santhakumar Kannappan at the Gwangju Institute of Science and Technology in Korea and a few pals say they have a solution based on the wonder material of the moment–graphene. These guys have built high-performance supercapacitors out of graphene that store almost as much energy as a lithium-ion battery, can charge and discharge in seconds and maintain all this over many tens of thousands of charging cycles.

The trick these guys have perfected is to make a highly porous form of graphene that has a huge internal surface area. They create this graphene by reducing graphene oxide particles with hydrazine in water agitated with ultrasound.

The graphene powder is then packed into a coin-shaped cell, and dried at 140 degrees C and at a pressure of 300/kg/cm for five hours.


Kannappan and co have measured the performance of their supercapacitor and are clearly impressed with the results. They say it has a specific capacitance of over 150 Farrads per gram can store energy at a density of more than 64 Watt hours per kilogram at a current density of 5 Amps per gram.

That’s almost comparable with lithium-ion batteries which have an energy density of between 100 and 200 Watt hours per kilogram.

Graphene is a promising material for energy storage, especially for high performance supercapacitors. For real time high power applications, it is critical to have high specific capacitance with fast charging time at high current density. Using a modified Hummer's method and tip sonication for graphene synthesis, here we show graphene-based supercapacitors with high stability and significantly-improved electrical double layer capacitance and energy density with fast charging and discharging time at a high current density, due to enhanced ionic electrolyte accessibility in deeper regions. The discharge capacitance and energy density values, 195 Fg-1 and 83.4 Whkg-1, are achieved at a current density of 2.5 Ag-1. The time required to discharge 64.18 Whkg-1 at 5 A/g is around 25 sec. At 7.5 Ag-1 current density, the cell can deliver a specific capacitance of about 137 Fg-1 and maintain 98 % of its initial value after 10,000 cycles, suggesting that the stable performance of supercapacitors at high current rates is suitable for fast charging-discharging applications. We attribute this superior performance to the highly porous nature of graphene prepared with minimum restacking due to crimple nature wrinkles and the improved current collecting method.

 

[corncobs]

Cool for thanks for sharing.

[trvlrschick]

I hope it comes out, but... they haven't actually MADE a battery. They need to put their money where their mouths are.

[acdii]

Two things come to mind, Leakdown, and weight. All storage devices leakdown over time, and capacitors are no different, in fact they tend to leakdown at a high rate. What would be good is if they started out like A123 and made small packs and marketed them to RC suppliers as the next generation packs. That would put the RC guys into a frenzy to be able to charge up a flight pack in minutes and fly all day, and give the company a profit stream to further develop them to larger storage units that can be used in cars and trucks.

 

Another thing to consider is, what is their flammability? Lion, Life, Lipo are all highly flammable when exposed to air, over charging, or over discharging(shorting). If these are far less likely to burst into a hot flame, then thats an additional plus.

[vangonebuy]

I believe caps will be a great option.

People have been testing cap batteries for a while.

 

 

This is one of my favorite testers.

 

I dont know how well caps will handle the cold though.

[acdii]

Caps make a really nice BANG when you overcharge them too, but man do they stink when they blow. You know those strobe lights on the wingtips of planes? I used to repair those, they have two large caps on them, and I have replaced a few blown ones due to overcharging because the trigger chip went bad. Nasty. How do they handle cold? How cold does it get at 40,000 feet? One of the tests that I had to do before sending them back was to deep freeze them and make sure they still fired off a strobe. It is a lot colder in that freezer than the cars will ever see, even in Alaska.

 

Oh and you never want to touch the leads when they have a full charge, unless you like getting knocked on your ass.