World's First Battery Fueled By Air 205
Hugh Pickens writes "The Telegraph reports on the revolutionary 'STAIR' (St Andrews Air) battery could now pave the way for a new generation of electric cars, laptops and mobile phones. The cells are charged in a traditional way but as power is used an open mesh section of battery draws in oxygen from the surrounding air that reacts with a porous carbon component inside the battery, which creates more energy and helps to continually 'charge' the cell as it is being discharged. The battery has a greater storage capacity than other similar-sized cells and can emit power up to 10 times longer. 'The key is to use oxygen in the air as a re-agent, rather than carry the necessary chemicals around inside the battery,' says Professor Peter Bruce of the Chemistry Department at the University of St Andrews. 'Our target is to get a five to ten fold increase in storage capacity, which is beyond the horizon of current lithium batteries.'"
Re:Any side-effects or drawbacks? (Score:3, Informative)
IANAC (chemist), but it sounds like what they are doing is take a reagent for the electrical reaction from the surrounding environment so they don't have to store it on board the battery -- thus freeing up additional weight/volume for the "charge" itself.
This might imply a problem with scale since you would need the infrastructure within the battery for safely extracting the reagent and, upon a recharge cycle, releasing it.
I wouldn't be surprised to see something like "DO NOT RECHARGE NEAR AN OPEN FLAME" written in huge letters all over the final product.
Re:Is it rechargable? (Score:4, Informative)
Well, given the summary (and the article it plagiarizes from) explicitly says:
Okay, sure, that's a little vague. 'course, if one were to actually go through the trouble of RTFA, you'd see this quote from the second article:
So, I would guess that, yes, it's rechargeable.
Lithium-oxygen, not carbon-oxygen (Score:4, Informative)
This coverage at The Register [theregister.co.uk] says they are lithium-oxygen batteries. The porous carbon matrix is for containing the chemicals and allowing the oxygen in during running and out during recharging.
Re:Powered by Air? (Score:3, Informative)
You're trying to be funny.
The Carbon's there only to help hold the catalyst in place along with allowing oxygen from the air into the system to react.
Li-Ion batteries are fueled by oxides (Lithium Cobalt Oxide...) in the battery. If I'm understanding this correct, the battery consumes ambient oxygen while it's discharging and produces it when it's being recharged.
So it is Carbon neutral as it doesn't put CO2 into the environment.
Re:Any side-effects or drawbacks? (Score:3, Informative)
Presumably the oxygen is going to released again when you recharge the battery. That's what recharging is, reversing the chemical reactions that took place during the discharge.
smells like hot air (Score:3, Informative)
creates more energy
Two problems here:
1. you can't create energy
2. reacting oxygen with some carbon substance is called combustion and while it does indeed burn, it doesn't make a battery
Re:Question (Score:3, Informative)
Yes, it would be extremely dangerous to use this near any source of ignition. At least, that is unless you had some kind of highly complex extraction [bizfriendmarketing.com] device [toolstation.com] to remove the oxygen build up.
Sigh. I had this serious reply written up explaining how you had it backwards - it removes the oxygen from the air etc etc ...
Then I clicked the links. Good thing, I would've earned a "whoosh" otherwise...
Re:Questions (Score:3, Informative)
So yeah, a lab experiment is all it really is at this point.
Re:smells like hot air (Score:3, Informative)
Thankfully, the Telegraph and Slashdot both being what they are, it's not a carbon-oxygen battery at all. It's lithium-oxygen with a porous carbon matrix storing the lithium but allowing the oxygen to flow into and out of the chamber.
The air flowing in is actually what causes the usable energy to be released, as it is released by the oxidation of the lithium. It is recharged in a cycle of de-oxidizing the lithium.
Re:What's the output? (Score:5, Informative)
Ok, second time I've had to do this; but, clearly the articles are pooorly written and do not describe the technology well, if at all.
It's a lithium-air battery in a carbon matrix. One electrode is lithium metal, one electrode is carbon. The oxygen, supplied by air and entering through the porous carbon electrode, reacts with the lithium to create lithium oxide. When the battery is recharged, the oxygen is liberated, returned to the atmosphere, and the lithium ions are returned to (plated on) the lithium metal electrode.
No CO2.
The output is electricity during discharge and oxygen during charging.
Re:Question (Score:3, Informative)
They consume carbon dioxide and release oxygen.
CO2 + 2 H2O + energy becomes CH2O + H2O + O2
Re:Any side-effects or drawbacks? (Score:5, Informative)
More informative article (Score:5, Informative)
There is next to no information in the first article... this one is much more informative:
http://www.theregister.co.uk/2009/05/19/lithium_oxygen_stair_battery/ [theregister.co.uk]
The concept (taking one of the reagents from air) is not new. There were zinc-air batteries for decades, and they are widely used. They have one of the highest energy densities of all types of commercially available batteries.
http://en.wikipedia.org/wiki/Zinc-air_battery [wikipedia.org]
Seems like four years ago somebody even figured out how to make them electrically rechargeable (before that, the usual method of recharge was to replace the zinc plates and remove oxide waste, which was facilitated by cell design).
http://www.eetimes.com/news/semi/showArticle.jhtml?articleID=164903727 [eetimes.com]
However, if those new batteries use carbon instead of zinc, they might have a higher theoretical upper bound on energy density. It looks like they're using graphite-lithium intercalate for the negative electrode (a standard thing), and the positive electrode is essentially a combined catalyst/adsorbent for Li2O2 which forms during electricity generation.
CnLi ---> Li+ + Cn + e
2Li+ + 2e + O2 --cat.-> Li2O2
Note that the first article is rather bogus: O2 does not "recharge" the battery, it is only a reagent.
I'm not familiar with the cost breakdown for the components of Li-ion batteries, but lithium seems like a major contributor, so this might not be much cheaper than the traditional Li-ion.
Re:Powered by Air? (Score:5, Informative)
Agreed. It's not even the first battery powered by air in this manner. As Taco ever heard of zinc-air batteries [wikipedia.org]? These are commonly used in, among other things, hearing aids.
Re:Your friendly neighbourhood environmental paran (Score:3, Informative)
You seriously underestimate the amount of oxygen in the Earth's atmosphere. Even massive forest fires do not change the global concentration of oxygen enough for anyone to notice.
Re:Is it rechargable? (Score:5, Informative)
Rechargeable zinc-air battery, 4 years ago:
http://www.eetimes.com/news/semi/showArticle.jhtml?articleID=164903727 [eetimes.com]
I wonder whether they managed to take it anywhere. rechargeable zinc-air would be cool, because there's much more zinc than lithium on Earth.
Re:Powered by Air? (Score:4, Informative)
Well, it's a lithium battery, that also includes an in-situ carbon fuel cell to replenish itself.
No, it is not. The carbon is only an adsorbent/catalyst matrix. Otherwise it would not be rechargeable. The first article contains misleading wording. Read the second one, or this one: http://www.theregister.co.uk/2009/05/19/lithium_oxygen_stair_battery/ [theregister.co.uk]
Re:Question (Score:3, Informative)
Re:Question (Score:5, Informative)
Addendum: the same amount of oxygen would be liberated when charging. It could be a problem if you decided to charge it in an air-tight box, but under normal conditions it won't be a problem.
Re:Hearing aids and Zinc-air batteries (Score:3, Informative)
Re:Question (Score:3, Informative)
Take a close look at your equation. See how energy is on the left, being used in photosynthesis? There's none on the left?
Plants metabolize sugars the same way you do, through respiration, consuming oxygen and releasing carbon dioxide. The difference is that they ALSO conduct photosynthesis, making those sugars they burn, instead of eating them. In general a plant will release more O2 than it uses because it stores away some of the extra carbon compounds in structural materials for the plant, fruit for you to eat, etc. but plants frequently consume more O2 than they use - at night, for example.
Try this page: http://en.wikipedia.org/w/index.php?title=Plant_respiration&redirect=no [wikipedia.org] [wikipedia.org]
and note that it redirects to the regular cellular respiration page. Plants conduct BOTH photosynthesis AND cellular respiration.
Re:Question (Score:3, Informative)
IIRC, it never worked like that. A mod point can only be spent once. If you mod somebody up, and then post in the same thread, the moderation disappears along with your mod point - you don't get it back.
Re:Question (Score:5, Informative)
I don't think it's that awesome. Air batteries (which are nothing new, BTW), tend to suffer from poor cycle lifes, poor power density, and very low efficiency. Often these "breakthroughs" aren't as impressive as they at first sound.
Now, that said, the other recent battery breakthrough -- on the Li-S front -- really does look as impressive as it sounds. I read through the paper on the research the other day as "light reading" at the dentist's office ;) Li-S's big problem has long been its really atrocious cycle life. It has great energy density, good power density, and very good efficiency, but the cycle life is a killer. And the variants they tried to improve cycle life really shot the energy density.
The reason it has these cycle life problems is because of how it works: you have sulfur in a carbon matrix (needs a conductive matrix because sulfur is an insulator) on one side of a separator film and metallic lithium on the other. The lithium ions migrate across the membrane and bond with the (insoluble) sulfur cathode to form (insoluble) Li2S; then, when running the cell in the other direction, the Li2S is split and the ions migrate back to the metallic anode. But there are intermediary reaction products -- various lithium polysulfides -- and these *do* tend to be very soluble. So, some of the polysulfides dissolve into the electrolyte, migrate across the membrane, and precipitate out on the other side and are rendered useless.
The new technique is pretty clever. They start by making a form of mesoporous carbon. This is made kind of like aerogel, via nanocasting, and it's covered in really deep pits. They then mill and then heat together the sulfur and carbon. The sulfur, having low surface tension, wicks into all of the pore space, with only a small amount of room left over to account for expansion. They then bake the composite at 155C, which boils all of the sulfur off the surface, leaving it only in the pits. So when the polysulfides form, they have a lot of trouble migrating out of the carbon.
That alone is a big improvement, but they took it a step further. The polysulfides are hydrophobic, so they bonded polyethylene glycol to the exposed surface of the carbon to make it repel the polysulfides. So now they have even more trouble migrating out of the pore space. To show how well they have them trapped, they took a traditional Li-S cathode and used a worst-case electrolyte -- something that loves to dissolve polysulfides. After 30 cycles, 96% of the sulfur was gone. With their cathode in the same worst-case situation, only 26% was lost.
In normal coin cells, their tests showed an initial capacity of around 80% of the theoretical maximum, falling about 15% in the first few cycles and then plateauing, nice and stable. The theoretical maximum for Li-S, if you discount everything but the sulfur, is 2,500Wh/kg (the best li-ion batteries on the market are 200Wh/kg). Now, obviously, you can't discount everything but the sulfur. The sulfur:carbon:lithium ratio, by weight, works out to something like 7:3:2. So, excluding the electrolyte, separator, and casing (which should be small components on large-format prismatic cells), they should get about 950Wh/kg. I imagine in a large format cell, they could probably get 800-850 -- over 4x the best current li-ion. Also, it's quite convenient that all of the raw materials are cheap and have low toxicities.
Re:O, not CO2? (Score:3, Informative)
Entropy is not a law that can or cannot be violated. It is a property of a system, like enthalpy, temperature, or pressure.
If you had said that the Second Law of Thermodynamics would be violated, then you might have a point.