## 3D self-assembling nanostructure for cathodes enables very rapid charge and discharge without sacrificing capacity; potential for EVs

##### 21 March 2011
 (a) Cross-sectional SEM image of an MnO2 cathode. (b) Lithiated MnO2 cathode. Zhang et al. Click to enlarge.

Researchers at the University of Illinois at Urbana-Champaign have developed a self-assembling three-dimensional nanostructure for battery cathodes (Li-ion and NiMH) that allows for faster charging and discharging without sacrificing energy storage capacity. Their findings are published in the journal Nature Nanotechnology.

The bicontinuous nanoarchitecture consists of an electrolytically active material sandwiched between rapid ion and electron transport pathways. The team achieved rates of up to 400C and 1,000C for lithium-ion and nickel-metal hydride chemistries, respectively (where a 1C rate represents a one-hour complete charge or discharge), enabling fabrication of a lithium-ion battery that can be 90% charged in 2 minutes.

This system that we have gives you capacitor-like power with battery-like energy. Most capacitors store very little energy. They can release it very fast, but they can’t hold much. Most batteries store a reasonably large amount of energy, but they can’t provide or receive energy rapidly. This does both.

—Paul Braun, a professor of materials science and engineering

Braun’s group wraps a thin film into three-dimensional structure, achieving both high active volume (high capacity) and large current. They have demonstrated battery electrodes that can charge or discharge in a few seconds, 10 to 100 times faster than equivalent bulk electrodes, yet can perform normally in existing devices. This kind of performance could lead to phones that charge in seconds or laptops that charge in minutes, as well as high-power lasers and defibrillators that don’t need time to power up before or between pulses.

Braun is particularly optimistic for the batteries’ potential in electric vehicles. Battery life and recharging time are major limitations of electric vehicles. Long-distance road trips can be their own form of start-and-stop driving if the battery only lasts for 100 miles and then requires an hour to recharge.

If you had the ability to charge rapidly, instead of taking hours to charge the vehicle you could potentially have vehicles that would charge in similar times as needed to refuel a car with gasoline. If you had five-minute charge capability, you would think of this the same way you do an internal combustion engine. You would just pull up to a charging station and fill up.

—Paul Braun

All of the processes the group used are also used at large scales in industry so the technique could be scaled up for manufacturing.

They key to the group’s novel 3-D structure is self-assembly. They begin by coating a surface with tiny spheres, packing them tightly together to form a lattice. Trying to create such a uniform lattice by other means is time-consuming and impractical, but the inexpensive spheres settle into place automatically.

Then the researchers fill the space between and around the spheres with metal. The spheres are melted or dissolved, leaving a porous 3-D metal scaffolding. Next, a process called electropolishing uniformly etches away the surface of the scaffold to enlarge the pores and make an open framework. Finally, the researchers coat the frame with a thin film of the active material.

The result is a bicontinuous electrode structure with small interconnects allowing the lithium ions to move rapidly; a thin-film active material, so the diffusion kinetics are rapid; and a metal framework with good electrical conductivity.

The group demonstrated both NiMH and Li-ion batteries, but the structure is general, so any battery material that can be deposited on the metal frame could be used.

We like that it’s very universal, so if someone comes up with a better battery chemistry, this concept applies. This is not linked to one very specific kind of battery, but rather it’s a new paradigm in thinking about a battery in three dimensions for enhancing properties.

—Paul Braun

The US Army Research Laboratory and the Department of Energy supported this work. Visiting scholar Huigang Zhang and former graduate student Xindi Yu were co-authors of the paper.

Resources

• Huigang Zhang, Xindi Yu & Paul V. Braun (2011) Three-dimensional bicontinuous ultrafast-charge and -discharge bulk battery electrodes. doi: 10.1038/nnano.2011.38

### Comments

It is a good thing that not many charging stations have been deployed so far because when these batteries appear, they would have to be replaced completely tin order to deal with 2-5 minutes of full charges on 20kwh batteries.

OK, so very fast charging - excellent.
Good for cars, especially regenerative braking.
However,
How many charge/discharge cycles ?
If > 3600, we have something.
(You could charge the car every day for approx 10 years).
With something that can charge in < 3 minutes, you could really hop along an "electric highway" in 100 mile jumps.
Something you can't do now.

It could also work well for buses where you do inductive charging at stops / terminii.
If you can charge at 100C, you could charge for a 10 minute run in 6 seconds (!) - or more likely, 30 seconds.
I am not sure how such a high current would go with inductive charging, but it would be worth investigating.

This is an incredible breakthrough. Two statements in particular mean this is not some lab curiosity, but rather a real world application waiting to happen:

"All of the processes the group used are also used at large scales in industry so the technique could be scaled up for manufacturing."

"We like that it’s very universal, so if someone comes up with a better battery chemistry, this concept applies. This is not linked to one very specific kind of battery"

This is the kind of breakthrough where a 100-150 mile range becomes less of an issue. Yes, it would be nice to have it be 300 miles...but if you can refill in 2 minutes, then you might be willing to trade off the extra $4,000-$5,000 in battery costs and weight.

I never drive more than 150 miles in a day. Ignoring the cost issue, I would never want an extra 200-300lbs of batteries in my car that I didn't need anyway.

1000 C is a recharge in 3.6 s. Unbelievable.

A 20 kWh battery typical of the first-gen mass ev's would would absorb a whopping 20 MW. Unbelievable.

Even if reality is 10x worse than promised, it still remains unbelievable.

These are outstanding claims, so are these:

http://news.stanford.edu/news/2008/january9/nanowire-010908.html 10X better

up to 1,000 times more powerful, 10 times longer-lasting and cheaper than traditional batteries http://www.today.colostate.edu/story.aspx?id=2849

http://www.gizmag.com/lithium-ion-battery-breakthrough-mit/11244/ promises 100-fold boost in performance
.....
Years and years have passed since these announcements, but I haven't found any 10X better - rather less 100X or 1000X better - batteries to buy.

What is impeding these huge improvements? Are top schools/researchers lying? Are there more classic NiMH GM/Chevron type collusions? Even a 5 times better range or recharge time improvement would firmly shift light vehicles to electric power.

This article is the clincher. Claims self-assembly, no extra material cost, over a magnitude(s?) reduction of charge time for ANY battery chemistry!!

This advance needs to be implemented and kept from 'big business' patent burial.

I agree with Kelly. This is exactly the kind of thing you never hear from again. May be some kind of government taskforce should investigate what ever happened to all those energy breakthroughs that promised so much but were never heard from again.

This could be a major win-win breakthrough for electrified vehicles if it is ever produced. A small unit would benefit current HEVs (and PHEBs/BEVs) since it could recover much more braking energy.

However, a 500 Km range 70 Kwh battery to recharge in about 6 minutes would use energy at the rate of 700 Kwh. Depending on voltage available, it would take rather high current to handle it. Very heavy duty DC to DC chargers may be a strong possibility for highway fast charging stations.

I see really big potential everywhere for this innovation. In the short term, I see a really big impact for HEVs. Imagine what a generation III Prius could do with a li-ion battery that would have 4x the effective energy and power density (conservatively).

Seeing that this method "applies to all chemistries" imagine what it could do with a lithium titinate chemistry!

Along EV lines, http://www.hybridcarblog.com/hyundai-sonata-hybrid-delayed-due-to-gov-regulations/

Here a fine, high gas mileage, \$25,000USD vehicle can't be sold because a (LAZY, IGNORANT?) EPA can't figure out what extra noise should be added? Whether extra noise can be switched off? It may take years for a EPA ruling?

This 'Bush logic' has to END.

kelly - let's try to keep the politics out of these boards, please. i'm sure even you have seen a simple statement like yours get whacked out of the ballpack after the treehuggers and neo-cons start hammering each other.
but when you're talking about the government taking so long to pass what should be easy legislation, i also get angry. but then i step back and realize it isn't the people in those bureaus who are to blame, regardless which president appoints them. it's the endless line of lawyers and lobbyists who push/pay the bureaucrats to do their bidding.
nobody likes the idea of getting fired because you butted heads with your boss' idealogies or influences. if you can skirt the lobbyists and lawyers you can usually get quite a lot accomplished.
of course, i think you can. haven't really ever seen it myself...

okay, besides all that, this is another of those technologies that sound promising but usually fail once they get to Real World scenarios. the one-size-fits-all approach seems workable this time, however.
it would be nice to see if this pans out beyond the lab, though...

If this technology doesn't pan out, another will. With all the battery R & D going on worldwide, many research groups will come out with superior e-storage units in the next 10 years or so. Meanwhile, current technologies will improve gradually. However, breakthroughs are required for future higher performance electrified vehicles.

Might be the breakthrough that battery industry needs, fast charging with limited capacity might be the path of least resistance to battery powered car after all, instead of high capacity battery but slow to recharge.

But don't forget that ultimately once you have solved the power issues that allows fast charge and discharge you are limited by the self-heating of the battery when you charge it too fast. It should still allow pretty fast charging though

MIT researchers already did this two years ago. http://www.greencarcongress.com/2009/03/mit-researchers.html

The article predicts their invention could be on the market within 2-3 years. Theirs uses a similar concept, nano-sized structures. But the lifetime isn't very good. the voltage drops to 2.0 volts after about 100 charge cycles. But they get 3-400C charging rate. What's the lifetime of the UIUC battery?

sheckyvegas,

The EPA is taxpayer funded government department created by politics. When the EPA has had years dealing with hybrids, yet still somehow manages to stall the US assembled Sonata hybrid - Bush-league logic is a mild comment.

But it's that kind of logic that's crushed batteries and EVs over a decade.

I was just looking the similarities to natural solution to maximize contact/reaction surface at http://en.wikipedia.org/wiki/Intestine#Structure_and_function

Villi are vaginations (folds) of the mucosa and increase the overall surface area of the intestine...

CelsoS, wouldn't nanowire arrays be more similar to villi than this 3D self-assembling nanostructure?

May be Kelly, but I was just leaving a link to start a "brainstorming".

Those natural structures are kind of recursive themselves and still quoting from the same text:

Microvilli are present on the epithelium of a villus and further increase the surface area over which absorption can take place.

Similar idea is scientifically explored in fractals (http://en.wikipedia.org/wiki/Fractal_dimension). A structure based on the H-fractal (http://en.wikipedia.org/wiki/File:H_fractal2.png) could have interesting properties of convenient conductivity of both electrons and heat at each section while allowing an optimization of surface/reaction area.

Zhukova

these people might have slam a duck with this but they have no clue how much time it takes to bring a breakthrough from the lab to mass production, when it comes to a new material like this, 10 years is more like a realistic number...

Zhukova...10 years was the time required to design, build, train, launch astronauts to the moon and back.

Mass production of a breakthrough technology e-storage unit should not take much more than 5 or 6 years unless lobbies and master speculators gang together to stop or delay it.

If we do not do it, China will do it.

Treehugger, this process is just a different electrode coating process - in a decades produced three element component sold in the billions!!

Also this week, http://www.greencarcongress.com/2011/03/pnnl-team-finds-that-new-electrolyte-mix-increases-energy-storage-capacity-of-vanadium-redox-batteri.html

So it took over TWENTY YEARS to use two common acids instead of one for a 70+% battery improvement?

Electronics would still be land line telegraph at the battery chemistry "breakthrough" and "implementation" rate!!

Maybe something else is going on..

Good point kelly. Why is battery R&D going at turtle pace? What is braking it?

Harvey

That is the right question, I know it is frustrating, but when you compare battery development and train and rocket you are comparing apple and oranges. Development of systems based on assembly of subsystems is fast, development of new material is slow, again look around you, new material always emerge at a turtle pace, qualifying a new material takes time,and also often requires retooling of industry at large scale, which means heavy investment, so before pouring big money investors want o make sure the new material is ready...
But Kelly has a point here it is not about new material but a new way to assembly existing material so it might go faster in that case, but still it requires to develop mass production tools and who knows how long it can take.

"But don't forget that ultimately once you have solved the power issues that allows fast charge and discharge you are limited by the self-heating of the battery when you charge it too fast. It should still allow pretty fast charging though"

I really dont think there is much need for super fast charging outside of a handful of rest-stops along the hwys, but this lowers the self heating of the battery as it charges or discharges (much lower internal resistance) and lower heat means longer life.. and that is important.. we need batteries that last the usual life of a car (10-15 years) without capacity degradation.

It should also improve the power output of the batteries at extremely low temperatures..

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