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ANL team demonstrates improved Li-O2 performance with iron-nitrogen-carbon composite cathode material

2 October 2012

Shui1
Discharge/charge voltage profiles of Li−O2 cells using α- MnO2/XC-72 and Fe/N/C as cathode catalysts. Credit: ACS, Shui et al. Click to enlarge.

A team at Argonne National Laboratory (ANL) has demonstrated improved performance of a rechargeable Li−O2 battery when an iron−nitrogen−carbon (Fe/N/C) composite is used as the cathode catalyst.

In side-by-side studies reported in the Journal of the American Chemical Society, they found that such a catalyst could reduce overpotentials during both discharge and charge processes when compared with the benchmark metal oxide catalyst, such as α-MnO2 or high-surface-area carbon. (High overpotentials in discharge and charge result in low efficiences, and are one of the known obstacles needing resolution for the commercialization of Li-air batteries.)

Shui2
Cycling performance of cells with catalysts Fe/N/C and carbon black (BP) as cathode catalysts. Current was 0.05 mA with duration of 5 h. Credit: ACS, Shui et al. Click to enlarge.

Detailed studies also suggested that the chemically modified carbon selectively promoted the decomposition of lithium peroxide over that of the electrolyte. This improved selectivity led to an enhanced battery lifespan under controlled cycling (decomposition of the electrolyte harms lifespan), with 50 discharge−charge cycles achieved.

The study, concluded the team, emphasizes the importance and promise of developing efficient electrocatalysts for Li−O2 battery application, particularly those that can promote the oxygen evolution reaction through better mass and electronic transfers.

The rechargeable Li−air battery represents an attractive energy storage device for electric vehicle applications due to its high theoretical energy storage capacity. The use of an active cathode catalyst would reduce both discharging and charging overpotentials by facilitating the oxygen reduction reaction (ORR) during discharge and the oxygen evolution reaction (OER) during charge, thereby increasing the overall energy storage efficiency.

...From a rational design point of view, an ideal cathode catalyst in the Li−O2 battery should have highly active catalytic centers densely populated over the support surface, with minimum separation between individual sites, to achieve maximum interaction with the solid precipitate, such as Li2O2. The active sites should also be easily accessible to the electrons necessary to complete the electrochemical reactions. One such material is the transition metal−nitrogen−carbon composite prepared by thermolysis of transition metals (Fe, Co, etc.) ligated by nitrogen-containing organic compounds over high-surface-area carbon support.

For example, iron−nitrogen−carbon (Fe/N/C) catalysts have been synthesized and studied extensively as low-cost alternatives to Pt for ORR in both acidic and alkaline fuel cells. Significant improvements in performance and durability have been reported recently for the Fe/N/C material, rendering it a benchmark for the nonprecious metal catalysts in fuel cell application. Nonetheless, the nature of the active site and catalytic mechanism involved remain to be fully understood. One representative Fe/N/C catalyst is the material prepared by pyrolysis of supported iron(II) acetate and 1,10-phenanthroline that has demonstrated excellent activity toward ORR in the aqueous phase. Since it is low-cost and easy to make, it is particularly attractive if such a catalyst can be used in promoting cathodic reactions in the Li−O2 battery.

—Shui et al.

The team synthesized an atomically dispersed Fe/N/C composite to study its role in controlling the ORR during Li–O2 battery charging with the use of a tetra(ethylene glycol) dimethyl ether-based electrolyte.

In addition to finding that Li–O2 cells using Fe/N/C as the cathode catalyst showed lower overpotentials than α-MnO2/carbon catalyst and carbon-only material, they found that gases evolved during the charge step contained only oxygen for Fe/N/C cathode catalyst, whereas CO2 was also detected in the case of α-MnO2/C or carbon-only material—presumably generated from electrolyte decomposition.

Resources

  • Jiang-Lan Shui, Naba K. Karan, Mahalingam Balasubramanian, Shu-You Li, and Di-Jia Liu (2012) Fe/N/C Composite in Li–O2 Battery: Studies of Catalytic Structure and Activity toward Oxygen Evolution Reaction. Journal of the American Chemical Society doi: 10.1021/ja3042993

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Comments

Another encouraging not so minor step in lithium batteries evolution? Over 440 mAh/g for more cycles is good news.

"The rechargeable Li−air battery represents an attractive energy storage device for electric vehicle applications due to its high theoretical energy storage capacity." Not true. There is higher energy density based on the comparison of the cathode material only. Indeed, the volume of lithium air will be larger than traditional lithium ion, because you need an air manifold and cathode catalyst support structure. Li-air may be fine for stationary storage, because of the potential to be lower cost (although there are no real manufacturing processes yet), but highly unlikely to be used in cars.

Li-air is like the new fuel cell technology in that it is very unlikely to be a cost effective product for the appication that is stated as it's place of commercialization. Fuel cell vehicles are nice in that they were never really going to be cost effective, because of the issues with hydrogen, but it sounded good, and so the car companies and the government could hold that out there as the way of the future, yet knowing that they would never reach the future. Well, that's what Li-air is. The promise of the future with no real path forward that allows for action not to be taken now.

Li ion battery technology is already capable enough,safe enough,and cost effective enough. Nearly all of the bad press around the EVs is faked up garbage, mistatement of facts, and intentional misinterpretations. However, the powers that be hold out hydrogen fuel cell cars and Li-air batteries as the future solution because those will only happen way into the future, if at all, and thus do not threaten the industries that exist.

Republican or Dmocrat, they all protect the oil companies, and screw the consumer. Our leaders are creeps.

brotherkenny:
Thank god we have you to correct all those know-nothings at Daimler, Toyota, Hyundai etc!
Who would have guessed that they don't understand basic engineering, let alone the scientists at the DOE who tested them for years!

A lot depends on the maximum current the Li-Air battery can provide. Other Li-Air batteries provide such low current, you need one with a very large capacity to get 100 hp out of it. In one of my other posts, I calculated that a 1,000 mAh/g capacity cell would give a 400 mile\200 kg car battery. It would have a large volume,so you wouldn't be able to put one in a Mini Cooper. A 100 mile, 30-40 hp battery might be better as long as it comes with a high-current secondary battery for acceleration.

It would probably take more than a day to charge it up, but only once in 2-3 weeks for most cars. In that case, 50 cycles is convenient, if the cost is right. Most of the time it would be discharged only 5-10% per day, so it would probably last more than a couple years. 500 mAh/g doesn't seem worth the effort considering the lifetime.

Dave - some things work, but they don't work well enough to be players.

It's a horse race between EVs and FCEVs. EVs have huge lead when it comes to "fuel" cost and infrastructure in place.

FCEVs are rounding the first turn. EVs are coming down the home stretch.

Fuel cells are a pie in the sky diversion. I agree. I don't think Lithium air is in this category though.

Good observations BW...FCEVs may be more suited to heavy long long vehicles (trucks, buses, locomotives etc). Adequate infrastructures could be limited to about 100 large hydrogen facilities located at major highway intersections. Potential suppliers would fight to get the appropriate permits because it would be huge profit making endeavors.

Railways can run on electricity. No conversion loss that way. The Trans-Siberian system is 100% electric and runs a distance equal to crossing the US twice. Hauls a tremendous amount of freight.

Improve our rail system. Make trucks the "last mile" from rail siding to door. We can build 100 mile range electric 18 wheelers - someone's already done that.

Build high speed rail and get rid of long distance buses. Use "100 mile" electric buses to connect HSR to smaller towns. Doing battery swaps ever 100 miles would not be a problem for long distance buses, just work the swaps into normal passenger stops.

Hydrogen just throws energy away. Why waste 40% of the electricity we generate? And there's a big infrastructure cost that's avoidable, both the extra 40% electricity generation and all the electricity -> hydrogen -> electricity stuff.


BW:
You are arriving at conclusions such as that hydrogen throws away 40% of energy based on batteries we don't have, compared to just one way of generating hydrogen, eletrolysis, that is not much used at the moment.

The real world facts are that running a car using batteries powered by the present grid or running one on hydrogen reformed from natural gas are around equally efficient, with the difference being that hydrogen can power a bigger vehicle far longer and faster than is possible with batteries.

We know that fuel cells can be greatly improved and cost reduced without any fundamental breakthroughs, which is not the case for batteries.

So you are comparing technologies with totally different performance technologies, making massively favourable assumptions regarding the one you happen to fancy whilst ruling out similar breakthroughs in the one you don't, such as that it may be possible to generate hydrogen in a whole host of ways which do not incur the efficiency penalties you assume.
There is the possibility of using energy from resources which would otherwise, without storage, be thrown away, as is planned for peak wind, aside from alternatives such as sunlight direct to hydrogen.

You carry out a similar process in your comments on railways.
It is very expensive to electrify railway lines, and in the real world the lesser used ones won't be.
Have you any idea of the huge cost of relocating industry to use railway lines, and building the lines to service them?
That would make the cost of providing hydrogen for transport look trivial, that's for sure.

And the sole criteria is not energy efficiency. There is a 40% efficiency penalty involved everytime people climb into a car with just one passenger, and of course even more when they travel on their own.

I really am giving up arguing about it, and leaving it for the facts on the ground as hydrogen is rolled out to speak for themselves, as the counter arguments seem to have all the hallmarks of people on hobby-horses, focussing on single issues, ignoring the reams of studies done on how things work and relative costs, making any assumption needed to favour their pet projects whilst making the most unfavourable assumptions possible about the alternative, and on, and on.

Bob, BEV cars have sold extremely badly, and not many are prepared to accept the range limits.
Maybe you think they should, and maybe you think that they should just rip up half the industrial and commercial facilities in the country and spent any amount on running electrified rail lines to them, but it aint' gonna happen.


Devenmart,

What is the point converting natural gas into hydrogen instead using natural gas directly in fuel cell? Are still there some people on earth dreaming about free hydrogen?

The efficiency of using natural gas in a combustion engine is roughly the same as petrol.
A fuel cell is 2-3 times as efficient at point of use.
The Toyota small SUV for instance gets a confirmed 68mpge in real world driving conditions.
Even with a 30% loss in energy in conversion and compression you use a lot less natural gas in a FCEV.

In addition a FCEV is all electric.
This means that the engineering needed to combine FCEV's with a large, plug in battery pack is trivial, unlike the complex duplicate systems needed in the Volt, and which would be needed in a NG plug in car.

So fuel cell technology enables battery cars to reach their potential, and overcomes range limitations completely, while allowing the possibly greater efficiency of batteries depending on the assumptions to do what they are best at, commute on plug in power.

I should have added that unlike NG cars, fuel cell cars are zero pollution at point of use.
The devastating consequences of air pollution are only now becoming clear.

'On average, air pollution is cutting human lives by roughly eight months and by about two years in the worst affected regions, such as industrial parts of eastern Europe, because it causes diseases such as lung cancer and cardiovascular problems.'

http://news.yahoo.com/breathing-european-air-shortens-lives-report-083906676.html

Of course not all of this pollution is from cars, and NG cars are far cleaner than petrol ones, but they still emit substantial amounts of pollution.

Bear in mind that the average 8 months loss of life is just that, an average, and city dwellers will do far worse.

I should have also said that it is only reforming losses that need to be taken into account in comparing NG and fuel cell vehicles, as both have to be compressed.

This differs from comaring battery and FCEVs where compression losses should be taken into account, as the gas is burned without compression to produce electricity at the power station.

BW... have to agree with you about electrified trains. Our local rail tracks owner (CN-CP) is fighting hard to stop electrification of tracks in common use for suburban trains. This is an example of how far the lack of common sense can go. Those tracks will have to be re-nationalized (as they were up to 30-40 years ago) before they can be electrified. CN-CP figured that they can make more $$$$ by systematic objection than by collaboration. Monetary gain has become the prime mover, not common sense nor people well being.

FCEV/EV=NO combustion=NO smog=NO oil.

"We know that fuel cells can be greatly improved and cost reduced without any fundamental breakthroughs, which is not the case for batteries."

I'm not convinced that fuel cells will improve and get cheaper and that batteries won't.

In fact, the Electrovaya battery that Chrysler was testing would give us significant range improvement. It would require an cooling system something like is used in the Volt. That is a 170 to 210 Wh/kg battery. The Leaf battery is 120 Wh/kg.

The Envia battery has already been tested by a US Navy lab and they have confirmed 400 Wh/kg. They are working to get their cycle life higher. Right now they have a "90,000 mile" battery based on a 200 mile range EV.

Battery prices are largely economy of scale issues.

"It is very expensive to electrify railway lines, and in the real world the lesser used ones won't be."

I wonder which would be more expensive, stringing a wire over existing rail tracks or building the infrastructure to generate, store and dispense hydrogen.

Both technologies would require some modification to engines. Many are already hybrid electrics so in one case you'd have to replace the diesel engine with fuel cells and hydrogen storage. With electrification you could just add a pickup to bring power into the engine and leave the existing diesel in place as backup.

"Have you any idea of the huge cost of relocating industry to use railway lines, and building the lines to service them?"

Heavy industry is already located along rail lines.

My suggestion was to use battery powered large trucks to move from rail to factory/warehouse "the last 100 miles". Move the long distance shipping to rail and turn trucks in to shuttles.

"And the sole criteria is not energy efficiency. There is a 40% efficiency penalty involved everytime people climb into a car with just one passenger, and of course even more when they travel on their own."

Business decisions take efficiency into account. Try selling your board of directors on a solution that will raise your 'fuel' costs by 40% per year.

Yes, EVs/PHEVs have sold poorly. But they have sold better in their first year on market than did Toyota and Honda hybrids. Ranges will improve, prices will drop, people will move past their hesitancy of the unknown.

"I should have added that unlike NG cars, fuel cell cars are zero pollution at point of use."

That does not help if we are still extracting natural gas from under the ground. We need to leave that carbon safely sequestered. We shouldn't even be talking about long term use of NG, at best it's a bridge that we can use for a little while and then we should tear it down.

Both EVs and FCs are zero pollution at point of use.

Both Batteries and Hydrogen tanks can be filled directly or indirectly with electricity.

All the electricity can be produced cleanly and cheaply enough.

The main differences is that:

1. Electricity is available most everywhere to recharge batteries, with a simple 220 VAC low cost outlet in most cases.

2. Hydrogen will have to be made and stored at the hydrogen distribution sites/stations. Those facilities will be costly but doable.

3. In principle, FCs can have longer range than EVs, specially for heavy vehicles.

4. Both Batteries and FCs cost will go down with time.

5. BEVs are inherently more efficient than FCVs.

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