## New high-power supercapacitor electrode material offers power density of up to 990 kW/kg

##### 09 January 2011
 The power performance of the SWNH/SWNT composite electrode surpasses other nanocarbon electrodes. Credit: ACS, Click to enlarge.

Researchers at Japan’s National Institute of Advanced Industrial Science and Technology (AIST) and Japan Science and Technology Agency (JST) have developed a novel high-power composite material for supercapacitor electrodes.

The material, featuring a unique meso-macro pore structure engineered through the utilization of single-walled carbon nanotubes (20 wt%) as scaffolding for single-walled carbon nanohorns (80 wt%), offers a high maximum power rating of 990 kW/kg and 396 kW/L. A paper on their work was published in the journal ACS Nano.

The single-walled nanohorn/single-walled nanotube (SWNH/SWNT) composite electrode also exhibited durable operation (6.5% decline in capacitance over 100,000 cycles) as a result of its monolithic chemical composition and mechanical stability, the team found.

Compared with another high-power electrode made from single-walled carbon nanotubes, the composite electrode had a lower surface area (280 vs 470 m2/g from nitrogen adsorption), and a higher meso-macro pore volume (2.6 vs 1.6 mL/g from mercury porosimetry). This enabled the composite electrode to retain more electrolyte, ensuring facile ion transport, and hence achieving a higher maximum power rating.

The maximum power rating of the SWNH/SWNT composite electrode (990 kW/kg) was almost twenty times higher than the estimated maximum power performance (~50 kW/kg) of the only previous report on SWNH electrodes, and more than twice that of the SWNT Bucky paper (400 kW/kg) examined here. Comparison of the performance of the composite electrodes with other nanocarbon electrodes showed that while the composite electrodes have been operated only at 2.5 V, their maximum power rating still surpassed other nanocarbon electrodes.

The only electrode (nanocarbon based or otherwise) reported having a higher maximum power (3.2 MW/kg, 16 kW/l vs 0.99 MW/kg, 396 kW/l for the composite electrodes) was composed of a sparse MWNT forest electrode (density of 0.005 g/cm3). Sparse CNT forest electrodes naturally have higher power performance as essentially individual CNTs within the forest are immersed in an almost infinite sea of electrolyte, i.e., infinite supply of ions. Here, our composite material has achieved a similar power performance, by tailoring the pore structure to optimize electrolyte retention yet having a density eighty times that of the sparse CNT forest.

Resources

• Ali Izadi-Najafabadi, Takeo Yamada, Don. N. Futaba, Masako Yudasaka, Hideyuki Takagi, Hiroaki Hatori, Sumio Iijima, Kenji Hata (2011) High-Power Supercapacitor Electrodes from Single-Walled Carbon Nanohorn/Nanotube Composite. ACS Nano Article ASAP doi: 10.1021/nn1017457

OMG!!! I guess we can build rail guns for real now. Maybe we can just "throw" payloads into space...assuming we can do so without crushing them under the acceleration LOL

Too bad that batteries and super capacitors capabilities have not been combined yet. It would make the perfect BEV storage unit.

If this proves economical, it adds a powerful new capacity to EVs.

If the energy density was sufficient the Formula 1 boys would be interested.

Harvey may be on to something, if they can combine a high energy density design with a super capacitor in the same device, they have the best of both worlds without trying to find the magic chemistry for both high energy and high power in one battery.

A supercap buffer would help cut peak charge / discharge demands on a battery pack during operation, and would allow more braking energy to be captured.

~30kW of motor power and ~1.4kWh of battery capacity are enough to double a vehicles MPG. If a supercapacitor bank was used with the ablitity to over rate the motor / generator for a short period of time it could recover, then deliver as much as 100kW

The CSIRO here in Australia have already developed the UltraBattery, which regular GCC readers will probably remember. It combined a supercap with a lead acid battery, so I guess the principle has been proven. It would be good to see the best of both combined into one system.

I do remember the UltraBattery developed by CSIRO. IIRC, they used a led-acid battery along with an ultra-capacitor.

A power density of 990kw/kg is pretty awesome. The ultra high cycleability is even more awesome. Current energy densities are sufficient for BEVs. What's needed is a reduction in cost and/or an increase in cycleability that would allow said batteries/ESUs to be financed.

I wish this could be combined with what is being done with zinc batteries .. lithium is probably too expensive to make a more efficient battery like the Ultrabatter

Off the top of my head I recall the Nissan Leaf using 4.4kg of lithium carbonate. Seems like lithium has been trading in the $10/kg range this year. Less than$100.

Just for comparison a catalytic converter for an ICEV can contain 3 to 7 grams of platinum which sells for more than $60 per gram.$180 to \$420.

"OMG!!! I guess we can build rail guns for real now"

Man portable railguns and solid state multi kw lasers!.. more effective EMP devices that can be delivered by small drones or fired from cannons.

Wait a minute!, who developed this supercapacitor?

Thanks for the info Bob, one of the targets for car fuel cells is not to use more platinum than the average catalytic converter. This make sense to me.

"Too bad that batteries and super capacitors capabilities have not been combined yet. It would make the perfect BEV storage unit."
They are here:
A Battery-Ultracapacitor Hybrid:
http://www.technologyreview.com/energy/27045/?nlid=3982

"Wait a minute!, who developed this supercapacitor?"

Oops. Well, at least it wasn't the Chinese LOL

EEStor...:(

The trade-off. The supercap-Li-On combo has less than 1/3 the energy density than an all lithium battery storage unit. Paired systems extend the life of the lithium battery but reduce e-range of both PHEVs and BEVs. Could be an acceptable compromise for city traffic PHEVs and e-tools but would limit BEV range too much and would be counter productive.

New supercaps and lithium batteries with higher energy density capability may solve the problem.

@biff,
There are other advanced developed lithium ,Strucural Capateries that is a lithium - any integrated with a "structural capacitive element" that is the capacitor is a "structural - or as we know it as charged plates physical electron storage, component as opposed to the 'plastic' battery that is housed in the forementioned integrated package.
Although it is unclear if any but the CSIRO product is availble to the public.
It is ironic that CSIRO dont have an Oceania distributer yet so you cant but that (here) either.

Even small changes in carbide chlorination temperature can affect the average pore size and pore-size distribution of resulting carbon, Skeleton says, with reproducible results.
Christene

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