Breakthrough In Use of Graphene For Ultracapacitors

Hugh Pickens writes "Researchers at the University of Texas at Austin have achieved a breakthrough in the use of a one-atom thick graphene for storing electrical charge in ultracapacitors. They believe their development shows promise that graphene could eventually double the capacity of existing ultracapacitors. 'Through such a device, electrical charge can be rapidly stored on the graphene sheets, and released from them as well for the delivery of electrical current and, thus, electrical power,' says one of the researchers. Two main methods exist to store electrical energy: in rechargeable batteries and in ultracapacitors, which are becoming increasingly commercialized but are not yet well known to the public. Some advantages of ultracapacitors over traditional energy storage devices such as batteries include: higher power capability, longer life, a wider thermal operating range, lighter, more flexible packaging and lower maintenance. Graphene has a surface area of 2,630 square meters, almost the area of a football field, per gram of material."

Comments

EEStor

[paul248]

Is this another factor of 2 on top of EEStor's still-unproven claims? How many more breakthroughs is it gonna take before something actually happens?

Re:EEStor

[smilindog2000]

No. This isn't even close to EEStor's claimed energy density. I personally put EEStor in the BS bucket a long time ago, but last week I found some very interesting news on wikipedia's EEStor page: competitors. It seems that several companies now have patents on materials they claim are similar in energy density to EEStor's claims. We may not get ultra-cheap batteries for electric cars any time soon, but at least the raw science seems to be real.

Re:EEStor

[JamesP]

Yeah, except there are also patents on glass pyramids that keep razors sharp, cures cancer or something like that. And don't forget the patents on playing with your cat with a laser pointer.

When people say anything can be patented, they're pretty much spot on.

advantages of batteries

[loshwomp]

Some advantages of ultracapacitors over traditional energy storage devices such as batteries include: higher power capability, longer life, a wider thermal operating range, lighter, more flexible packaging and lower maintenance.

By contrast, two advantages of batteries are 1) vastly higher energy density, and 2) the fact that they exist.

Re:advantages of batteries

[OldMiner]

I know you're trying to be cleverly ironic here, but you can buy ultracaps today. The higher power capability, swifter charging, longer life, wider thermal operation range, more flexible packaging, and lower maintenance are already there and have been for years along with the superior environmental characteristics. However, "lighter" isn't true yet, since the energy density of an ultracap is an order of magnitude lower than that for a dry cell. That's why a breakthrough such as in this article is such a big deal.

If grapheme could reliably be utilized to create the sort of energy density posited here, any application requiring large amount of batteries (such as electric cars) would benefit greatly. Unfortunately, since capacitors are more prone than dry cells to losing energy over time due to internal resistance, this won't eliminate the need for dry cells entirely.

Re:advantages of batteries

[loshwomp]

I don't see them replacing batteries at all, but augmenting them instead. Batteries are limited in the power they can absorb.

Yes, but the limit isn't especially limiting in practice. Power density is important, but any modern battery with sufficient energy density to be useful in the EV industry has plenty of power density. Some types of lithium cells (let's pick A123 since they're well known) have outrageous power densities (hence their use in power tools where you want high torque) but rather poor energy density, yet their energy density is an order of magnitude better than the best ultracaps.

Round trip energy efficiency for lithium type batteries is already on the order of 90%. Even if your hypothetical ultracap system were 100% efficient, you're only looking at an ~11% improvement. But of course your hypothetical system won't be anywhere near 100% efficient, and the cap voltage is dramatically higher and the discharge curve is different, so you have to account for additional power electronics losses involved in moving the charge back and forth between the battery system. And if you just doubled the complexity of your power electronics, you've added significant cost and weight.

In short, I'm an electric vehicle engineer, and I have yet to see a situation where adding caps makes more sense than adding more cells to the battery.

Re:Still...

[Anonymous Coward]

Mac users, however, will still be getting 1 1/2 hour of unbuttplugged life, tops :)

Re:How?

[Paradigm_Complex]

2D area vs mass. What that statement was trying to get across was that graphene is so thin that you could almost cover a football field with only a gram of it. Think of spreading cream cheese on a bagel. You only have a gram of cream cheese, though, so you have to spread very, very thin. Except the bagel is the size of a football field, so you have to spread it even more ridiculously thin: only an atom thick. Now instead of cream cheese it's carbon atoms.

graphene surface area

[metalcup]

I found this image from Nature magazine useful in imagining how 1 gm of graphene can have such a large surface area..

http://www.nature.com/nature/journal/v427/n6974/fig_tab/nature02311_F1.html

Re:How?

[m.dillon]

Yes, massively folded. Similar technology has been in used for many years to produce multi-Farad 'dime' capacitors, whos surface areas start around the size of a tennis court and go up from there.

These sorts of capacitors have very high capacitances (in the multiples, even tens of Farads) and a 20-50 year life span (or longer depending on how they are built), but also tend to only be able to be charged to fairly low voltages (3v, 5v, etc), and also have fairly high internal resistances (though this might be different for the newer Graphene-based caps), limiting the discharge rate.

This means they won't be replacing batteries any time soon, but the advances we're seeing are pretty cool.

We mostly use these things to run real time clock chips and provide backup power for static ram... i.e. very low current applications.

-Matt

Re:surface area of a football field

[Ihlosi]

If 1 gram of graphene has the surface area of a football field, what's the surface area of a football field of graphene?

One football field, of course. They're both units of area. Now, if you were to ask what the surface area of a VW-Beetle-equivalent of graphene is ...

Here's the deal

[Colin Smith]

Human resource usage expands to consume all available resource...

That is the history of humanity in one sentence. In fact, it can be generalized to all life.

 

Re:Here's the deal

[srussia]

Human resource usage expands to consume all available resource...

That is the history of humanity in one sentence. In fact, it can be generalized to all life.

Agree with your first statement. The difference, however, between humanity and other forms of life is that humans increase available resources in order to be able to expand usage.

Re:Here's the deal

[HungryHobo]

We don't seem to have expanded to use all oxygen yet, we don't seem to have used up all the salt water, both are freely available to a great many people.

Human resource usage expands to quite a high point but to assume it's infinite is a little presumptuous.

It was assumed that the human population would continue to increase exponentially but in some developed nations we're seeing a birth rates drop below 2 children per couple.

People multiply insanely when the chance of their children reaching adulthood is low, people try to obtain stupidly large amounts of resources when resources are scarce.
Average resource usage may not increase forever. It'll probably still has a way to go but I can see the average leveling out at some point.

Re:Here's the deal

[lisaparratt]

You think our atmosphere always had this much oxygen in it?

Re:Here's the deal

[HungryHobo]

No but the organisms which produced the oxygen first probably weren't the ones which needed it to survive, oxygen was waste, a poison to them.

Although there are animals and plants which by one means or another make more space for themselves to live in.

Re:Here's the deal

[TapeCutter]

Speaking of expanding..."Graphene has a surface area of 2,630 square meters, almost the area of a football field, per gram of material."... As a young man I plugged a large 12v capacitor into a 240v outlet because I thought....hmmm....if a 9v battery make that big a spark....Ten minutes later I had it screwed to a wooden booard with a domestic power cord attached....KABOOM!!!....my room was covered in sticky silvery confetti...you get where I'm going, graphene would go off like a fuel air bomb! All this leads me to the conclusing that .....

If you car has a graphene ultracapacitor, resources consume you! /sorry

Re:Here's the deal

[Joebert]

Yes, a lot of it was just hiding behind Hydrogen atoms, so you couldn't see it.

Re:Here's the deal

[pradeepsekar]

In microbiology, while trying to grow bacterial cultures, there is something called as the limiting resource - sometime the Glucose added to the culture, sometimes the nitrogen-nutrient added. And the culture grows till that nutrient is exhausted. Or it has exhausted the ability to dispose waste. Some nutrients remain unused, unless the mixture was so precisely balanced at the beginning.

Remove the bottleneck for growth, and the expansion will continue till the next bottleneck stops growth.

In our case, with our 'intelligence' we appear to be stretching all our resources to the extreme... till our growth is limited by food, water, land, and perhaps other resources like oil. Then we either have starvation (of food, or of oil or of whatever) or wars (that knock off population).

Re:Here's the deal

[NotBornYesterday]

What, doesn't everybody like that stuff?

Re:How?

[Diamo]

So why not just use toilet roll as a capacitor?

Re:Safety ?

[Genda]

That's one of the serious problems with any exceptionally high density energy storage technology. How do you keep the genie in the bottle, and protect the public from the critically stupid in our society.

There was a very cool design for a car whose power source was a high mass flywheel in a magnetic housing. You go to a power station, and the station would spin your flywheel up to some insane RPM rate. The possibility of using this in a hybrid vehicle meant you could get really excellent energy storage and return, it was very efficient.

The only drawback, was that if the bloody thing ever got out of containment, you had a death dealing juggernaut that would buzz-saw a swatch of destruction through the middle of wherever the now flying flywheel was pointed. Then some bright child imagined such a flywheel driven vehicle on a crowded freeway causing a chain reaction of thousands of other similar vehicle, and suddenly you pretty much have a scenario for mass destruction that looks like front row seats to Armageddon.

Whatever technology you finally pick, you'll need to make it very safe, or decide it's a Darwinian herd thinning tool.

Re:How?

[Ihlosi]

So why not just use toilet roll as a capacitor?

Because it doesn't have to layers that are insulated against each other?

However, if you're talking about two toiled rolls, soaked in electrolyte, with an insulator between them, rolled up and packaged nicely, then yes, you can use that as a capacitor (we'd all be thrilled about a capacity measurement and some pictures when you try it out, please?).

Graphene's properties

[JSchoeck]

Don't worry that the Graphene layer would rip. It's a very, very strong material and the connections between the atoms are strong conjugated double-bonds.
This is the same structure as in Carbon Nano Tubes and Fullerens (C60), just flat (and not cylindrically or spherically rolled up).

The problem to implement Graphene based technologies is rather the synthesis of it, since it's not yet easily possible to create a homogeneous Graphene layer on a large area (i.E. at my Applied Physics institute they create Graphene layers that are not even 1 mmÂ).

Re:How?

[Perf]

If you wanted a thin layer of carbon, wouldn't it be easier just to toast the bagel?

Re:Safety ?

[vivian]

Simple - mount it in a gimbal

Re:Safety ?

[Eivind]

More energy, true, but slower release-rate.

A battery has significant internal resistance, even if you short-circuit it the power-levels are limited. (high, but limited)

A capacitator can recharge significantly faster.

Put differently, the thing may only hold 10% of the energy in a battery. But if that energy is released a hundred times quicker, you're still looking at hell of a bang.

Re:Safety ?

[LehiNephi]

The flywheel has embedded permanent magnets. Coils surround it in the case, and spin up/down the flywheel in order to inject or extract energy. It's a brushless DC motor, essentially. Once you include magnetic bearings, you end up with something that can be encased in a near-perfect vacuum, eliminating all friction and giving rather impressive efficiency.

Large-scale systems of this sort are actually in use, just not inside vehicles. There are some electric train systems that use it to recapture energy from trains arriving in the station, and then assist trains as they accelerate out of the station.

Rule 34

[DrYak]

If his fetish is, say, truckers and fat mexican grannies with mustaches, do you still want to be the cameraman?

Must... resist... urge... to verify... Internet Rule 34....

Ghaaa !!! 22k+ pages found. The Google, it doesn't do nothing.

Re:Safety ?

[evilviper]

The only drawback, was that if the bloody thing ever got out of containment, you had a death dealing juggernaut that would buzz-saw a swatch of destruction through the middle of wherever the now flying flywheel was pointed.

Actually not.

The RPM rate is so high that flywheels get insanely hot as soon as the vacuum is broken, and it has to deal with friction from the air.

With metallic flywheels, this means it breaks apart, and you've got thousands of bits of white-hot magma flying through the air, in a straight line from the direction the flywheel was spinning. Of course your car is going to turned into swiss cheese, and the two cars directly in front/back of you are likely to get damaged as well, but it's not Armageddon.

With carbon-fiber flywheels, the flywheel material is completely incinerated instantly, and DOESN'T risk turning into such deadly projectiles. HOWEVER, you have to have a very good design to deal with the HUGE amount of unimaginably hot air now erupting out the top of the flywheel housing. Mount it properly, eg. externally, on the roof of your car, with a nice thick base-plate, and your vehicle quite quite likely wouldn't face any structural damage. Though, you can definitely expect to need a new coat of paint.

Or until we invent...

[clonan]

Or until we invent fertilizer (18th century)...for food
Or until we invent pesticieds/herbicides...for food
Or until we invent underground farming...for food
Or until we invent land reclimation...for land
Or until we invent skyscrappers...for land
Or until we invent seasteading...for land
Or until we invent lunar colonies...for land
Or until we invent large dams...water, food and power (oil)
Or until we invent water treatment...water
Or until we invent reverse osmosis distillation...water
Or until we invent atmospheric condensers...for water
Or until we invent nuclear fission...for power (oil)
Or until we invent fusion...for power (oil)
Or until we invent photovoltaics...for power (oil)
Or until we invent bio fuels...for power (oil)
Or until we invent direct CO2 conversion to hydrocarbons...for oil (from power)

and a big one is:

Or until we invent a trully good electrical battery, one that stores a lot of energy, has high power density, does not wear out, does not use environmentally harmfull components and is cheap (something like these graphene supercapacitors will be under mass production)...for oil

My point is simple. Humanity ran out of resources about 20,000 years ago. We are designed to be hunter/gatherers. The earth can only support a few million hunter/gatherer human beings. It was only through the invention of agriculture and other technologies that we are able to continue. While we will probably ALWAYS have some resource limitation (probably power) there are technologies that exist now that if used can prevent any Malthusian collapse for the indefinet future.

Re:Or until we invent...

[Rei]

Or until we invent a trully good electrical battery, one that stores a lot of energy, has high power density, does not wear out, does not use environmentally harmfull components and is cheap (something like these graphene supercapacitors will be under mass production)...for oil

Well, let's compare the modern automotive li-ions to see how well they meet your requirements:

* "A lot of energy" -- The automotive li-ions on the market are generally 90-110Wh/kg (not as good as the ~160Wh/kg for conventional li-ion). There are about a dozen different chemistries in the lab right now that offer 2x, 3x, or more energy density than this; I could go down the list if there was interest. Now, while this is notably less than gasoline, there's a couple factors that have to be considered, such as the fact that most of the energy in a battery goes into providing torque to the wheels, while only a tiny fraction of the energy in gasoline does (most gets wasted as heat). Secondly, batteries are heavy while electric motors are light; internal combustion engines are heavy while gasoline is light. It's an opposite paradigm; in a typical electric car equivalent, batteries are competing for the space and weight freed up by the lack of need for an internal combustion engine, transmission, and all of the supporting hardware, while the motor is about the same size and weight as a full fuel tank. As a result, to match a typical car in range for a given amount of weight, you need about 300Wh/kg. So, they're not a match for gasoline cars yet, but they very well could be in a few years. Even as it stands, it's not hard to get enough batteries to take you for two hours at highway speeds (general highway safety advice is that you're supposed to take a break every two hours or so).

* High power density: Already got this one licked. 100 kilograms of lithium phosphate batteries will give you up to ~250kw or so (335 electric horsepower, which due to the wider max power operating range, is more like a gasoline car with 500hp or so). 100 kilograms of titanate cells will give you 2-3 times as much. Even despite having far less research put into them, EVs are already challenging gasoline cars for speed records (esp. accel, but even top speed, such as with the Eliica). The motors and inverters are actually the limiting factor, not the power source.

* Lifespan: LiP and stabilized spinels will lose 20% capacity in ~7000 "gentle" cycles or so, while the titanates take tens of thousands to lose that much capacity. They also show little to no loss of capacity with age, as they resist lithium plating. By "gentle", this means a cooled pack, charge times of at least a couple hours, and discharge times of at least a couple hours. Under abusive conditions -- overheating, 5-20 minute charges, 5-10 minute (impossibly fast) discharges, etc, you'll get ~1000 cycles out of LiPs and spinels, more out of the titanates. Under a normal mix of fast and slow charging, with reasonable discharge times, you can expect a couple thousand cycles. For a car with 150 miles range, 1000 cycles = 150,000 miles, so a couple thousand cycles means around half a million miles. Adjust appropriately to your situation.

* Does not use environmentally harmful components: Two common types of batteries -- PbA and NiCd -- are highly toxic, and must be recycled to avoid serious environmental consequences. NiMH aren't great for the environment, and should be recycled, too, but they're not as bad as PbA and NiCd. Li-ion with a LiCoO2 cathode, like conventional li-ion and AltairNano's titanates, are minorly toxic; it's not as bad as NiMH, but it'd be best to recycle, and proper disposal is required in most places. LiP and spinel li-ion are nontoxic; the worst thing you can say about them is that their electrolyte is corrosive.

* Cheap: Current prices for LiPs in bulk straight from the manufacturers is about $0.50-$0.60Wh/kg, which most kinds of cars, is already low enough that the purchase price premium can be amortized into the car's operation

Re:EEStor AND Graphene

[clonan]

No, capacitors don't have to. In fact even the tiny capacitors you can get at radio shack hold enough power to fry most electronics if it were released at once.

Capacitors only release all the power they hold at once when they fail catastrophically...then they blow up.

However the output voltage of a cap is related to the energy they store so as the output voltage must be adjusted as the capacitor discarges to maintain usable voltage. By oncreasing the resistance in the circuit you can slow the discharge rate of a capacitor to usefull levels.