## Researchers at Rice University develop vanadium oxide-graphene materials for high power-density Li-ion batteries with ultrafast charging and discharging

##### 15 March 2013
 Rate capacities of VO2-graphene architectures with different VO2 contents, measured for 30 cycles at each selected rate from 1C to 190C. Credit: ACS, Yang et al. Click to enlarge.

A team from Rice University has developed vanadium oxide (VO2)-graphene ribbon materials that, when used as cathode materials in Li-ion batteries, enable ultrafast, “supercapacitor-like” charge and discharge rates with long cycle life while maintaining highly reversible capacity. In a paper published in the ACS journal Nano Letters, the researchers suggested that this “breakthrough in cathode materials with ultrafast charging and discharging capability...can significantly prompt the rapid development and applications of high-power lithium ion batteries.

With the single crystalline VO2-graphene ribbons as cathodes, a full charge or discharge is capable in 20 seconds. The electrodes retain more than 90% of the initial capacity after cycling more than 1,000 times at an ultrahigh rate of 190C, providing the best reported rate performance for cathodes in lithium ion batteries to date.

The achievement of high-rate capability, most important for high power density applications such as in electric vehicles, is known to be hindered by kinetic problems involving slow ion and electron diffusions in the electrode materials. An effective strategy to enhance current rates is by reducing the characteristic dimensions of the electrochemically active materials, since the diffusion time of lithium ions (t) is proportional to the square of the diffusion length (L) (t ≈ L2/D). In this regard, numerous nanoscale materials including nanowires, nanotubes, nanoparticles, nanosheets, and nanoribbons have been recently synthesized and demonstrated for improving electrochemical performance for lithium storage. However, only modest improvements in rate performances have been observed due to difficulties to simultaneously possess efficient ion and electron pathways in unmodified nanomaterials.

To further circumvent this problem, various three-dimensional (3D) architectures with high electrical conductivity have been employed to serve as current collectors for nanomaterials. Although some improvements in charging and discharging rates have been achieved with minimal capacity loss, these architectures commonly lead to the high-weight fraction of current collectors in electrodes, decreasing the overall energy density of batteries. Moreover, the complicated and limited approaches to fabricate such 3D architectures largely hamper their practical applications in lithium-ion batteries.

Here, we demonstrate a simple bottom-up approach for synthesizing vanadium dioxide (VO2) ribbons with thin, flexible, single-crystalline features simultaneously included with graphene layers as building blocks to construct 3D architectures.

—Yang et al.

The architecture of the material provides the following benefits, the researchers said:

1. Numerous channels for the access of electrolyte, facilitating rapid diffusion of lithium ions within the electrode material;

2. A short solid-state diffusion length for lithium owing to the thin nature of VO2 ribbons;

3. A high electrical conductivity of the overall electrode, based on the graphene network; and

4. The highest content of electrochemically active material within the electrode (up to 84% by weight).

The material enables rapid ion and electron diffusions—the kinetic requirements for ultrafast charging and discharging.

Vanadium oxide is known as a promising electrode material for both organic and aqueous lithium ion batteries owing to its high capacity, structure and electrode potential; however, it suffers poor cyclic performance as a result of high charge-transfer resistance. The use of graphene solves the electrical resistance problem with the VO2 electrodes, the researchers said.

In the study, they synthesized VO2-graphene architectures with various VO2 content (84%, 78%, and 68%). As examples of some of the test results, a very high reversible capacity of 415 mAh g−1 with stable cycle performance was achieved at 1C by VO2-graphene architecture with the VO2 content of 78%.

More remarkably, the VO2-graphene architectures exhibit ultrafast charging and discharging capability. For example, the VO2-graphene architecture containing 78% VO2 demonstrates reversible capacities as high as 222 and 204 mAh g−1 at the extremely high rates of 84C and 190C (corresponding to 43 and 19 s total discharge or charge), respectively. These high discharge−charge rates are 2 orders of magnitude greater than those currently used in lithium ion batteries. Moreover, even after 1000 cycles at the ultrahigh rate of 190C, both discharge and charge capacities are stabilized at about 190 mAh g−1, delivering over 90% capacity retention. To the best of our knowledge, such an excellent high-rate performance is superior to all existing cathode materials reported for lithium ion batteries.

—Yang et al.

Resources

• Shubin Yang, Yongji Gong, Zheng Liu, Liang Zhan, Daniel P. Hashim, Lulu Ma, Robert Vajtai, and Pulickel M. Ajayan (2013) Bottom-up Approach toward Single-Crystalline VO2-Graphene Ribbons as Cathodes for Ultrafast Lithium Storage. Nano Letters doi: 10.1021/nl400001u

Another dream that will never happen. Even the lateast lithium batteries are a complete flop, see the boeing 787 story. The mpg increase of electric hybrid car are not significant and cost a lot. When it's cold or very hot all batteries have big problem. these battery do not last more then one or two years before been degrading 50%. It's been the 300th miraculous battery finding that i read here over the years and yet no real good miraculous battery have show-up.

this week on local tv there was a prius owner that experienced catastrofic mpg this winter and very choppy driving. All his system was going havoc due to wear, cold and heat.

We seem to be accumulating materials capable of building the fabled "batacitor".

At a conservative (for this material) 50 C rating, a 2 kWh battery is capable of supplying or absorbing 100 kW.  This is enough for strong acceleration and decent regenerative braking in a Prius-sized vehicle; at a less-conservative 100 C, the battery could be downsized to 1 kWh.  The capabilities of hybrids would jump if this stuff was commercialized.

Lithium batteries are in their 22 year of production and make $billions a year in sales. Every mobile computer and cell phone uses lithium batteries. Some "complete flop". They could be used for HEV or PHEV, or rapid busbar charging bus. They might be very good for HEVs where you could get very good regenerative braking with quite a small battery. Also rapid charging buses lie the Arctic Whisper. or it may be just one of a series of "battery breakthroughs" that come to nothing. I think a battery like this is a bigger breakthrough than even an ultra-high capacity. If it can give us around 150-200 mile range with a 5 minute recharge then 99% of us could use it and be just fine. People who really need to drive long distance on a regular basis should stick with a good hybrid or diesel. The rest of us should be at least open to a vehicle like that. Not saying it's for everyone, but at least consider it as a viable option. "The electrodes retain more than 90% of the initial capacity after cycling more than 1,000 times at an ultrahigh rate of 190C" "ny uneducated a very high reversible capacity of 415 mAh g−1 with stable cycle performance was achieved at 1C " This is the best of many Rice battery specs. License the battery into mass production and change the world. So many uneducated hear some "bad battery" media story and don't realize their 'typing, talking and texting' on "bad batteries". Sooner or latter, governments may have to take a more active role to ensure that higher performance ultra quick charge batteries are effectively mass produced. 415 mAh/g is huge. The best li Ion batteries on the market give 4-500 Wh/kg and use the Argonne Labs developed cathodes. Those have only about 250 mAh/g gravimetric capacity. So this represents a 66% increase, but with greatly increased power.. Wonder how much vanadium would be needed for 1 billion EVs, where it's located, and how much of it is available at what price? How're we doing on mass producing graphene? Just sayin'. Machined metal and huge ICE/transmission part counts cost more each year, just as electronics and batteries cost less. 100% ICE doesn't meet emissions requirements. The best cost of ownership balance between 10 and 100% electric drive is the rolling question. Actually the mass production of graphene is doing quite well and the advances mirror or exceed the improvements in the batteries themselves. It cost$100 million for a gram of Graphene in 2008, now you can get it for a few hundred dollars. And the race is on for many fronts because they're making good progress and the potential uses are so huge.

Mannstein -

Go on Goggle maps to South-West Colorado, all around the town of Vanadium where bear creek Road runs into highway 145 and take a look around. We have tons of it here. This area is where Madam Curie's Radium mine is located also. I've been all through it.

(I have a Radium burn scar on my right forearm.)

I think Formula 1 should be funding this effort! They spend hundreds of millions of dollars a year on development and next year they go to a new formula with KERS where they can use 120kW and 4megajoules!

Throwing in a matching anode chemistry and running at ~5C, they could probably get about 400Wh/kg (~400Ah/kg * 3V is 1.2kWh/kg but the anode/cathode only weigh about 1/3 of the battery packaging so lets say 400Wh/kg for a pack) means they could put down about 25kg of these batteries and meet both the power and energy needs of the 2014 F1 cars.
That is compared to about 90kg of the current A123 batteries that some teams are using with 20kW/kg power ratings (but very low energy needs...by current regulations which are only 400kJ).

So you could probably use only 25% of the weight for the same power & energy needs in 2014 compared to current battery tech.

They produced a ribbon worth of the material. That means they have produced something interesting, but not ready for production.

TexasDesert,
Very true. But that is why I was thinking Formula 1. They can afford to pay top dollar for something like this and all 22 cars on the grid next year could be covered by not much more than lab samples :-)

The secret to perfecting and then scaling tech is to find those early adopters who have the money to spend and NEED your solution.

The more I think about it, the more a high power battery like this will bring the big breakthrough in EVs. This type of high power also means rapid charging with no degradation.

So a ~40kWh capacity which means paying for a cheaper battery which is also a lighter battery and using fast recharging stations as they become available and still allowing for a 125+ mile range.

One of my peers at work just bought a Ford Focus EV and he's already learning where the charging stations are around Atlanta so he can travel around without worrying. But if he had a 125+ mile range rather than a 70 mile range, he'd be plenty happy and not give it another thought.
Right now, he just runs a long extension cord out of one of the loading docks at work and charges it during the day if he thinks he's going to be running around a lot after work...plus I think he just likes getting free electricity since they think it's funny at work and let him charge for free LOL
No more gas OR electricity for him.

@DaveD

The CalBattery and Envia Systems batteries already get 400 to 525 Wh/kg. They use Argonne Labs cathodes, at 250 mAh/g and silicone composite anodes.

If the VO2 cathodes give 66% increased capacity over the Argonne labs cathodes, a battery with silicone anodes may get 7-800 Wh/kg. In current batteries, the cathode makes up a larger part of the mass of the battery, so the result could be more than 800 Wh/kg.

800 Wh/kg for a 200 kg battery would give 160 kWh battery. That's enough for about 480 miles. Li-Air would probably give about the same range, but currently they charge so slowly, it would take 4-5 days to charge it completely. The VO2 cathode battery could be charged overnight. Quick charging is good for locally driven cars with small batteries, where there are plenty of quick charging stations. But the VO2 cathode makes large capacity batteries possible for long-haul trucks, trains, and electric passenger airplanes.

Zhokova,
Actually, I agree with your assessment. I was taking worst case scenarios and even being conservative at that. I have always tended to be too optimistic on the battery/BEV front and then disappointed later when reality hits. Lately, I'm trying to come from the conservative side and be "pleasantly surprised". :-)

By the way, thanks for the post. You always have good numbers/thoughts.

It's just absurd when I read something like "Another dream that will never happen"

Scientific progress keeps on marching. Only a few years ago silicon nanowires and grapheme were first being tested for use in batteries. Now the silicon and grapheme composites work in real batteries.

The Argonne Labs cathode has been very successful in the last few years. Envia Systems announced they were sampling their 400 Wh/kg battery early last year, but now CalBattery is sampling their 525 Wh/kg battery. With a different company making a 25% improvement every year, how does anything actually get to the market before it becomes obsolete?

Spelled it wrong twice - graphene, not grapheme. Anyway, it's really phenomenal how important this material has become. Rice researchers are using it in the cathode and likely will use it in the anode when they make their own battery.

Zhukova,
I just realized that if these batteries really could achieve 800Wh/kg, that would be enough energy for a Formula 1 car to complete a Grand Prix with 200kg battery.
Considering they start a race by carrying over 140kg of fuel today, they could do that. Also, electric motors would be lighter and need smaller/lighter transmissions due to their wide, flat torgue bands and so the total car weight might be the same as today's 640kg.

Of course, I think Formula 1, or any high end racing will eventually go to all wheel drive if they become electric one day. They could take full advantage of the regen braking on the front wheels as that's where more of the energy is available for harvesting...and it would give better performance for acceleration and handling.

I think it's shocking. When you consider that gasoline has about 13,000 Wh/kg. But, when used in a ICE, which is only about 20% efficient, you get 13,000 x .2 = 2,600 Wh/kg. The BEV would be around 90% efficient, so at 700 Wh/kg, the net result is about 25% of the energy as gasoline for the same weight, which is very significant.

I also think the formula 1 car would be practical with such a battery. But you don't need the Formula 1 to get all that torque, you could just use an old Datsun 1200 like this one - http://www.youtube.com/watch?v=369h-SEBXd8

Oh yeah....the White Zombie! Cool stuff. But I'm starting to focus on things like the 200 mph Drayson experimental car and the Formula E series starting next year.

http://www.formulaeracing.com/?p=129

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