Li-on battery breakthrough?

[Geo]

http://nanotechwire.com/news.asp?nid=5413

Stanford researchers have found a way to use silicon nanowires to reinvent the rechargeable lithium-ion batteries that power laptops, iPods, video cameras, cell phones, and countless other devices.

The new version, developed through research led by Yi Cui, assistant professor of materials science and engineering, produces 10 times the amount of electricity of existing lithium-ion, known as Li-ion, batteries. A laptop that now runs on battery for two hours could operate for 20 hours, a boon to ocean-hopping business travelers.

Yet reading the rest of the article, it seems more like the discovery helps long-term battery life than performance, so I'm a little unsure.

The electrical storage capacity of a Li-ion battery is limited by how much lithium can be held in the battery's anode, which is typically made of carbon. Silicon has a much higher capacity than carbon, but also has a drawback.

Silicon placed in a battery swells as it absorbs positively charged lithium atoms during charging, then shrinks during use (i.e., when playing your iPod) as the lithium is drawn out of the silicon. This expand/shrink cycle typically causes the silicon (often in the form of particles or a thin film) to pulverize, degrading the performance of the battery.

Cui's battery gets around this problem with nanotechnology. The lithium is stored in a forest of tiny silicon nanowires, each with a diameter one-thousandth the thickness of a sheet of paper. The nanowires inflate four times their normal size as they soak up lithium. But, unlike other silicon shapes, they do not fracture.

Maybe it does both? Or maybe it improves performance while making battery life acceptable for the use of silicon?

 

[LunchBox]

great news for me i hate having to charge my laptop or cell phone almost everyday :/

although i wonder, since the silicone expands, would it explodes if someone (like myself) would accidentally over charge it

 

[Simon F]

although i wonder, since the silicone expands,

I think you meant silicon though one of the uses of silicone is, indeed, expansion related.

Just to bring this back on topic, one would assume that even if, at first, it did not increase the storage, as it would degrade more slowly, over time it would seem to have better performance than standard Lithium ion cells.

 

[AlNom]

Why not explore carbon nanotubes.

 

[Sxotty]

Geo I don't know if you looked at the actual data anytime, but the cycles for the cell was minuscule. Like 20% degradation in 10 cycles or some ridiculous thing like that. I read about this before Christmas break, but thought there was no point in posting it since the performance was so incredibly terrible.

 

[Geo]

See, that's why I put articles here sometimes, so somebody who actually understands what's going on can interpret them.

Now, could you switch to english for that, please?

 

[digitalwanderer]

I think it means they wear out too fast, if my geekspeak translator is working correctly.

 

[AlNom]

Which part did you want explained

(maybe I'm just spewing out the same stuff exactly ?)

The initial implementation of silicon in Li batteries as described in the article was poor -> the silicon structures that are meant to contain the higher amount of Lithium would get damaged upon further charge/recharge cycles. So the Si-Li battery might have a great charge capacity at first, but subsequent usage would degrade the storage capacity greatly. i.e. one would have to replace the battery every so often with heavy use.

The new implementation makes use of structural mechanics - the interleaved silicon nanowires - to prevent destruction from expansion/contraction. Presumably it's the spacing between nanowires that prevent the silicon from destroying itself when they expand - there's room. From what I understand, the silicon in the original implementation is a bulk material of sorts, so there is no room for expansion. At the nanoscale, you're also dealing with the high surface area to volume ratio, increasing the capacity to store Lithium.

So this new battery has both the higher charge capacity (than C-Li) and a better sustainability of that capacity with subsequent charging/recharging.

 

[Blazkowicz]

the breakthrough I want to see would make batteries cheap, non toxic/made from sober materials and with a very long life cycle (cycle charges).

 

[Geo]

Okay, AlS, I was able to follow that. . . so what is Sxotty pointing at to say it really ain't so?

And the sustainability issue. . . how does it compare to traditional Li-on batteries? I.e. is it just better on that point that the first Si-Li batteries, or actually roughly comparable or better to traditional Li sustainability?

 

[AlNom]

Hm... I'm not sure. They indicate that they solve the structural issues, but they made no comparison at all for charge sustainability. Since the major issue was the structural integrity of the silicon, it seems like it should be fine.

Maybe Sxotty is referring to the original silicon-lithium implementation

edit: here's a neat paper on carbon-lithium and recharging.
http://ieeexplore.ieee.org/iel5/6201/16562/00836110.pdf

edit2: bugger, it's only one page of it!

edit3: here's a patent that uses carbon nanofibres.

http://www.patentstorm.us/patents/6503660-description.html

 

[AlNom]

From the patent:

Also, the performance of lithium ion secondary batteries, such as the charge/discharge capacity, voltage profile and cyclic stability strongly depends on the microstructure of the carbon anode material, which in this invention are graphitic carbon nanofibers comprised of graphite sheets.

I would guess the discharging and recharging place a great deal of stress on the crystal lattices, which may change or deform, resulting in a lower capacity. (this is just guessing from what I recall of some course a few years back though. )

To get some sort of comparison, we might have to look at the respective lattice strengths of nanosilicon and nanocarbon or just carbon - how much energy it would take to bust them or change them so that the material's ability to latch onto lithium ions is reduced.

 

[_xxx_]

Okay, AlS, I was able to follow that. . . so what is Sxotty pointing at to say it really ain't so?

And the sustainability issue. . . how does it compare to traditional Li-on batteries? I.e. is it just better on that point that the first Si-Li batteries, or actually roughly comparable or better to traditional Li sustainability?

The biggest problem with batteries is that they're getting old pretty fast when steadily being drained/recharged. This prolongs the life of the battery if I got it correctly (didn't bother reading it all).

 

[Mariner]

I've just encountered this interview which provides more info. I don't think it has been posted in this thread before now?

Sounds very encouraging, even considering that fact that the discovered of these types things tend to 'big up' the potential.

 

[Sxotty]

Okay, AlS, I was able to follow that. . . so what is Sxotty pointing at to say it really ain't so?

And the sustainability issue. . . how does it compare to traditional Li-on batteries? I.e. is it just better on that point that the first Si-Li batteries, or actually roughly comparable or better to traditional Li sustainability?

Yeah, sorry for not responding earlier. But when I read it, they said yay we fixed the expansion contraction issue, but their results were still absolutely horrid.

Looking at A123 systems LiFePO4 batteries for example they say they have 4000 cycles at 100% DoD (depth of discharge). And btw 4000 cycles means that you have no more than 20% degradation over that period. That is the general definition (lifetime is ended after 20% degradation). From what I recall they still had a similar degradation in 10 cycles.

There is one thing though, it may be the cell they produced was built by a grad student to test one thing and completely sucked in other ways. A

From mariners link

In the study you published, how many cycles did you run on your cells?

In the paper, we showed 10. If you read the supplementary, we also have the data in there up to 30. And in the lab right now we are testing more and more cycles. It looks like it’s going up and up and up.

That is ridiculously small, 30 cycles? It is just silly. In the paper there was significant degradation in those 10 cycles, but perhaps it has a plateau or something. I don't mean to disparage it too much, but it isn't at this moment something that is changing the game.

If you want something that might change the game sooner I say look at this stuff another interesting development is http://www.greencarcongress.com/2008/01/lockheed-martin.html

Ultra Caps could be really cool.

 

[AlNom]

Thanks for the link.

 

[Sxotty]

Oh another separate thing, (that is why another post) a lot of times these patents are somewhat bogus.

For example there is wide speculation that there is no difference between the high energy lithium chemistries really. In other words they have different processes that yield the same results and the patents that specify how the results are achieved are wrong. (In other words it was a side effect of what they did not their goal.) Like saying we built a zeppelin and pumped hydrogen in it to make it look shiny, and the other group put hydrogen in it for another random reason and then they say our zeppelin floats b/c it is shiny (instead of b/c they filled it was a lighter than air gas).

 

[Mariner]

One thing to think about is that even if degredation in capacity is worse than current technology, if capacity is a factor of 10 higher in the first place it could still be a net gain surely? Say capacity was down to 50% after 1,000 cycles, then it would still be much, much higher than the current technology. It wouldn't be too much of a disaster if your laptop battery started off running for 30 hours but still could manage 15 hours on a single charge several years later.

Regarding the Ultra-cap stuff (specifically EEStor), it is a good sign that Lockheed are investing in them as I know many have been very sceptical about their claims before now. If EEStor's technology can meet their claims it will be a pretty fantastic advance but, again, I note slippage in their self-quoted deadlines - not sure if they've even demonstrated the technology in public yet, have they?

This interview with a Lockheed dude seems to indicate they think EEStor is the real deal:

http://www.gm-volt.com/2008/01/10/lockheed-martin-signs-agreement-with-eestor/

 

[Sxotty]

Regarding the Ultra-cap stuff (specifically EEStor), it is a good sign that Lockheed are investing in them as I know many have been very sceptical about their claims before now. If EEStor's technology can meet their claims it will be a pretty fantastic advance but, again, I note slippage in their self-quoted deadlines - not sure if they've even demonstrated the technology in public yet, have they?

This interview with a Lockheed dude seems to indicate they think EEStor is the real deal:

http://www.gm-volt.com/2008/01/10/lockheed-martin-signs-agreement-with-eestor/

Yeah, I thought EEstor was bogus myself, but it certainly gives great credence to them.

One thing to think about is that even if degredation in capacity is worse than current technology, if capacity is a factor of 10 higher in the first place it could still be a net gain surely? Say capacity was down to 50% after 1,000 cycles, then it would still be much, much higher than the current technology. It wouldn't be too much of a disaster if your laptop battery started off running for 30 hours but still could manage 15 hours on a single charge several years later.

And if you lose 20% in 10 cycles which they did Mariner at first, that is just way to fast. They are competeing against 20% in 4000 cycles, and they will not give 10x the power density as it said, that is the best case which will not happen.

[

 

[LunchBox]

I think you meant silicon though one of the uses of silicone is, indeed, expansion related.

Just to bring this back on topic, one would assume that even if, at first, it did not increase the storage, as it would degrade more slowly, over time it would seem to have better performance than standard Lithium ion cells.

lol the extra "e" does make a lot of difference