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Western University team boosts LiFePo4 to 98% of theroetical capacity with unfolded graphene

Yang
Image depicts the LiFePO4 particles anchored to the crimped unfolded graphene. Source: Jinli Yang. Click to enlarge.

The research team from the Nanomaterials and Energy Group at the Western University led by Dr. Xueliang (Andy) Sun has reported that the specific capacity of LiFePO4 can be greatly boosted to up to 168 mAh g-1—98% of its theoretical capacity of 170 mAh g-1—by using unfolded graphene as a three dimensional (3D) conducting network for LiFePO4 nanoparticle growth. A paper on their work is published in the RSC journal Energy & Environmental Science.

Olivine-typed LiFePO4 is considered to be an attractive cathode material for lithium-ion bateries (LIBs) applied in the new generation of hybrid electric vehicles (HEVs) and electric vehicles (EVs). Other work has shown that LiFePO4 battery performance is strongly depended on the carbon coating, which can enhance the electronic conductivity of the electrodes. The Western University researchers found that the graphene with different thickness and morphology has a significant impact on the performance of LiFePO4.

Compared with stacked graphene, which has a wrinkled structure, the use of unfolded graphene enables better dispersion of LiFePO4 and restricts the LiFePO4 particle size at the nanoscale. More importantly, it allows each LiFePO4 particle to be attached to the conducting layer, which could greatly enhance the electronic conductivity, thereby realizing the full potential of the active materials. Based on its superior structure, after post-treatment for 12 hours, the LiFePO4–unfolded graphene nanocomposite achieved a discharge capacity of 166.2 mAh g−1 in the 1st cycle, which is 98% of the theoretical capacity (170 mAh g−1). The composite also displayed stable cycling behavior up to 100 cycles, whereas the LiFePO4–stacked graphene composite with a similar carbon content could deliver a discharge capacity of only 77 mAh g−1 in the 1st cycle. X-ray absorption near-edge spectroscopy (XANES) provided spectroscopic understanding of the crystallinity of LiFePO4 and chemical bonding between LiFePO4 and unfolded graphene.

—Yang et al.

The use of an unfolded graphene matrix, which serves as a conducting 3D nano-network, enables both Li ions and electrons to migrate and reach each of LiFePO4 particles, hence realizing the full potential of the active materials.

—Xueliang (Andy) Sun

The unfolded graphene synthesized by Sun’s team shows an even and flat structure with individual flakes, and the size is approximately 500 nm, whereas the stacked graphene consists of multiple wrinkled layers make the size up to 10 μm, which is 20 times larger than that of unfolded graphene.

The team also found that a 12 h annealed sample delivered the best discharge capacity (close to the theoretical capacity) and a superior rate capability.

This work is especially important for future research and development of graphene for lithium ion batteries because it presents a new direction on designing graphene based electrode system to realize the full potential of the active materials.

—Xueliang (Andy) Sun

Resources

  • Jinli Yang, Jiajun Wang, Yongji Tang, Dongniu Wang, Xifei Li, Yuhai Hu, Ruying Li, Guoxian Liang, Tsun-Kong Sham and Xueliang Sun (2013) LiFePO4–graphene as a superior cathode material for rechargeable lithium batteries: impact of stacked graphene and unfolded graphene. Energy Environ. Sci., 2013 6, 1521-1528 doi: 10.1039/C3EE24163G

 

Comments

HarveyD

Would this translate into a cell energy density close to 500 Wh/Kg?

A D

Batteries are getting better. Hydrogen fuelcell also. A hybrid battery- hydrogen fuelcell car can be made to get the best of these 2 technologies together. No range anxiety plus the possibility to recharge slowly when the car is not at use. Hydrogen efficiency as a fuel is big.

DaveD

I'm trying to figure out what it would translate into. Hard to tell without knowing what anode it would be matched with.
Considering that LiFePO4 cells usually work about 3.2V, then 168mAh/g gives a cathode with ~530Wh/kg. And the anode is usually more energy dense than the cathode so let's assume they average 600Wh/kg together. But of course, you have to throw in the electrolyte and packaging. So maybe you could get at least 400Wh/kg? Maybe you really could get close to 500Wh/kg or even 600 with a really good anode??? Just speculation anyway.

But what would all this do to price?

Lad

I read about all this good Lab work and I wonder how long before it reaches the Public.

I feel we are almost there, almost ready to uncase the battery that will drive transportation to BEVs. But, then I worry about the political moves Big Oil will make to slow down or even stop these batteries from seeing daylight.

Big Oil has had it their way for a hundred years and in that time they have gotten to the point where the economy depends on them. Reversing their policies and unwinding their intrenched profit systems will be no easy task...but it is necessary for our survival.

cujet

It's always nice to read about the ever improving and promising battery technology. As to speculation on overall energy density reaching anywhere near the theoretical maximum... Well, that's a long way off. And, it has nothing to do with big oil. Cut the theoretical electrochemical storage capacity energy density in half for rechargeability. Cut it in half again for storage container mass, and then in half again for capable conductors. I have faith in science and believe 500WH/KG will be a reality sometime in the future.

kelly

As Lad says, "Big Oil has had it their way for a hundred years and in that time they have gotten to the point where the economy depends on them."

And a hundred oil years produces a lot of inbred oil heirs able to buy politicians and the laws.

When a battery is: assembled on China assembly lines, validated by US federal laboratories, and announced by a US firm as "400 Wh/kg is here!" -- 14 months ago --

Where the F*** is it!?

One can recall a dozen product http://enviasystems.com/announcement/ [s] screaming in their later disappearance.

Bob Wallace

Envia got a trial run with Chrysler, IIRC.

They didn't do so well when rapidly charged. They probably need a liquid cooling system like the Volt uses.
--

EOS, while not a vehicle application, is going into trials with the New York grid. They've been testing under the radar with some other systems.
--

Big oil will not stop battery development. There is far too much money to be made from batteries going forward and too many companies/universities engaged in research and development. Oil doesn't have enough money to buy up and bury everything.

It's time to let this tinfoil hat stuff fade away....

Engineer-Poet

Bob, you can't accuse people of tinfoil-hatism when it has happened already.  Electronics aside, there's still room for another Cobasys-style patent grab for large-format cells; most users aren't going to be able to pay to assemble ten thousand 18650 cells per vehicle, a la Tesla.

Getting back to the chemistry itself, 168 Ah/kg * 3.2 V = 538 Wh/kg of LiFePO4 on the cathode; the graphene probably doubles that.  DaveD is probably right about anode, electrolyte, etc. so divide by 4 for the result:  roughly 140 Wh/kg.  On the other hand, the rate capability of LiFePO4 means very fast charging, very high specific power and good cycle life.

kelly

"Oil doesn't have enough money to buy up and bury everything." - just the early stages of what would commercially works.

kelly

"Envia got a trial run with Chrysler, IIRC." while GM is a/the major investor?

Lad

My Leaf battery, LiMn, is about 141Wh/Kg. Double that to about 300Wh/Kg, with LiFe replacement modules, at a reasonable cost and I'll be satisfied.

I read recently where Tesla Motors is filing patents on advance chemistry batteries. I'm safe is stating that Mr. Musk gets it and judging from his decisions to build longer range cars with even the weak technology of today's batteries shows his vision is right on target. Why, he even as a fast charge network in place to support this decision.

Now, if he could only produce a $20,000 BEV for the masses. Oh! Well!

Arne

The whining by the tin foil hat crew is getting tiresome. 'Big Oil this', 'Big Oil that'. Oh please, what crap. There are other big companies trying to move the technology forward, and Big Oil can not stop them. Yes, I know of the Cobasys patent kerfuffle and no, it didn't stop the Roadster, nor the LEAF, nor the Volt, nor the Model S.

Simply concede that battery development is hard and painfully slow.

The Tesla Model S is a working vehicle that makes perfect sense in the real world and leaves almost nothing to be desired. It can take on any ICE without needing a green halo. Technically, we are already there, no breakthrough needed. The genie is out of the bottle and Big Oil can't put it back. It boils down to the people deciding how they spend their money. And judging by the success of the Tesla, Big Oil hasn't got a clue of what's coming their way.

The misguided souls clamoring for a battery breakthrough (or even more sad: thinking that Big Oil is keeping it away from us), should note that battery capacity has increased slowly over time and will continue to do that into the future. If you are waiting for a miracle technology, then good luck and enjoy the wait. It will not happen. Slow and steady progress is what lies ahead. Slow and steady progress is all we need.

kelly

Anne, whether Envia, http://priuschat.com/threads/audi-a2-goes-over-370-miles-on-one-battery-charge.86068/page-2 , or others -- people are only asking for the batteries announced and driven to world records YEARS ago.

HarveyD

Tesla will soon announce, lower cost second generation EVs, with 500+ miles between charges (**), from longer lasting, very quick charge batteries. Mass production will start in 2017/2018.

How many more manufacturers will follow Tesla's lead?

(**) Buyers satisfied with 300 miles will be able to make that choice.

ai_vin

Ok sure, having a higher capacity battery is nice and all but it's hardly a "must have." The NiMH batteries in the EV1 gave it enough range to handle the needs of 90% of the drivers in North America. Really, you only need 500+ miles between charges if you want to try driving your BEV on your annual, cross-country, family vacation.

DaveD

@ai_vin,
BINGO! I've said before, and I'll continue to say...there are plenty of people who are perfectly happy with a reasonably priced 150 or even 100 mile range car. Especially for people like me who have it as a 2nd car in the family. (And there are a a LOT of those to target).

There are many factors coming together and each is picking up steam:

- Energy density is growing at LEAST 10% a year over the last few years. Actually, much faster. Tesla is using ~260Wh/kg batteries in the Model S. That is just five years after they were using 110Wh/kg in the Roadster. That's a small sample, but still a 24% growth rate.

- Chargers proliferating. There may only be about 6,000 available in the US, but that growth is picking up momentum. And people with houses just charge at home 90% of the time anyway....and there are 75 million homes with garages/carports in the US.

- Battery prices are coming down. It's harder to get any kind of real number on this because everyone hides this data as a "competitive advantage". But they are a hell of a lot cheaper than the ~$750/kWh they were 5 years ago.

All these things converge towards a tipping point that will accelerate BEV sales. And we keep forgetting...we don't need to replace 250 million cars in the US fleet overnight. They average 17 year life spans now anyway. We just have to start making inroads and grow nice and steady. And that's happening.

Why are we so frustrated? EVs out sale some models of ICE car already. We'll get there.

And for those of you who don't like EVs...good, don't buy one. It doesn't hurt anyone's feelings. LOL

kelly

Bob Wallace, where's the "Envia got a trial run with Chrysler, IIRC." "They didn't do so well when rapidly charged." results and links?

There's an elegance to spreading the above 'bad battery' report around that fronts another [GM] "we tried" that battery/chemistry/technology without having to sell/shelve it through Chevron Oil again.


HarveyD

Anti-BEVs will continue to refuse to admit their superiority due limited range (less than current ICEVs) and high battery cost (higher than equivalent ICEVs drive trains).

To nullify their objections, range between full charges will have to be raised as high as 400 to 500 miles and batteries price will have to be reduced to $150/kWh or even less.

Those those goals/conditions may not be met before 2020+?

Till then, HEVs and PHEVs are valuable interim solutions for general purpose vehicles and current BEVs are OK as city or second vehicles.

Bob Wallace

-Bob Wallace, where's the "Envia got a trial run with Chrysler, IIRC."-

I mixed up my E-battery companies. It was Electrovaya, not Envia. And it wasn't during rapid charging, but during heavy duty, non-vehicle operation use.

"Dasgupta (director of research at Electrovaya) said the issue occurred on vehicles pushing the envelope with reverse charging, which would allow the trucks to provide power to the grid or to link up with other trucks as a mobile mini-grid. They are the first factory-built vehicles to feature this technology, said Chrysler."

http://www.theglobeandmail.com/globe-drive/new-cars/auto-news/chrysler-plug-in-testing-zapped-by-overheating-batteries/article4567502/

I warned you - "IIRC"....

Bob Wallace

test

ai_vin

Harvey, nullifying the cost and range objections of the anti-BEVers won't bring them over to our side - they'll just move the goalposts. It's time to forget them and move on without them.

HarveyD

As the 900+M ICEVs, the 1+M ICE-PHEVs (like the Volt), the 5+M ICE-HEVs (like the Prius) double or triple their sales and reach their peak, and are progressively replaced by B-EVs (like the Tesla, Leaf etc) and future FC-EVs; the anti-electrified vehicles groups will have to board the evolution train.

Meanwhile, more and more automobile centers may move to Asia.
By 2025, if the current trend keeps up, China may produce 35M to 45M vehicle/year and have major impacts on the world lower price e-vehicle market.

Bob Wallace

The cost of shipping bulky products like vehicles is significant. Vehicle manufacturing is more likely to occur closer to markets rather than be centralized in one location.

Even China's BYD has plans for US manufacturing.

And don't forget, China's labor costs are rising and China has an aging workforce.

Plus labor becomes a lower and lower part of auto manufacturing every year.

China's low labor costs are a fleeting advantage.

Take a look at this time-lapse video of a LEAF being manufactured. Pay attention to how little humans do.

http://cleantechnica.com/2013/05/04/nissan-leaf-being-manufactured-video/

kelly

@BW, good video - with ~only 40 workers actually shown assembling the car.

Pro EV people can proudly note over a 100 million e-bikes and 100s of thousands of highway/ecycle EVs sold in recent years, but opponents persist.

The Leaf is the key proven under $30,000 EV, but losing the present $7,500 EV tax credits could deeply hurt EV sales in the near future.

On the other hand, only Nissan has a 450,000 annual Leaf world manufacturing capacity.

Imagine the Leaf sales with a twice the range/half the cost battery.

That improvement is minor compared to dozens of reported battery breakthroughs.

HarveyD

A university group in Australia has recently managed to increase by 2X to 5X the effective energy density of lithium batteries while multiplying the charging speed by 10X.

If those improved batteries can be mass produced at a low enough price, it could constitute one of the first major breakthrough required to make BEVs more competitive.

A competitive BEV is just a matter of time. Will it happen before or after 2020?

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