Superior Anode For Lithium-Ion Batteries Developed

RogerRoast writes "The anode is a critical component for storing energy in lithium-ion batteries. The Berkeley Lab (D.O.E) has designed a new kind of anode that can absorb eight times the lithium of current designs, and has maintained its greatly increased energy capacity after over a year of testing and many hundreds of charge-discharge cycles. According to the research published in Advanced Materials they used a tailored polymer that conducts electricity and binds closely to lithium-storing silicon particles, even as they expand to more than three times their volume during charging and then shrink again during discharge."

Comments

Subscription access only...

[Joce640k]

I couldn't see the main article because it requires subscription but how much extra capacity does this actually translate into? (Assuming it works...)

Re:Subscription access only...

[vlm]

Energy capacity (assuming constant voltage) is linear with stored charge.. stored charge is linear with quantity of active species, which is going up by a factor of 8, so I'd guess about 8 times.

Voltage is never constant under high discharge rates... lead acid "car" batteries are famous for covering their plates temporarily with gas (h2) and all batteries dump some fraction of their capacity into their internal resistance. For a good example try pulling 10 amps out of a giant deep cycle marine battery, then outta a nicad C size cell, then outta a pre-alkaline, pre-heavy duty zinc C size cell (think radio shack battery of the month club red battery).

expand to more than three times their volume during charging and then shrink again during discharge

Well, that's fairly terrifying word choice to anyone who did extreme stuff with prior battery techs. Expanding lead acid cell means the vent is clogged and you're about to get a large dose of flammable H2, corrosive electrolyte, and splintering plastic. Expanding lithium means its about to go kaboom. "Expand" is not a cool choice of words around battery people. Call it "volumetrically challenged" or something.

Re:Subscription access only...

[DamonHD]

What fraction of the entire cell is the anode, and thus how much 'sometimes unused' space has to be left for this anode when fully turgid, and thus by what fraction does this knock down Wh/l energy density, do you think?

Anyhow, it seems as if it might be quickly commercialisable and just needs a matching top-notch cathode! B^>

Rgds

Damon

Re:Subscription access only...

[Joce640k]

I'd guess about 8 times.

If that's true, and even if it only works out to six times in production then it almost solves the car battery problem. We can get about 100 miles with existing batteries and 600 miles is about as far as a normal person would want to drive in a day (ie. average 60mph for ten hours).

(I say "almost" because of the following posts...)

Re:Subscription access only...

[Anonymous Coward]

It's not the Lithium which is expanding. The silicon which stores the lithium expands and breaks into bits and pieces. That's the challenge in using Si as a Grahpite substitute in LIB.

Re:Subscription access only...

[Anonymous Coward]

"Expand" is not a cool choice of words around battery people. Call it "volumetrically challenged" or something.

In lithium-ion batteries, that's exactly what happens though. As lithium fills up the active material, there is a volume expansion. No gases are produced in li-ion batteries unless the electrolyte heats up, the problem with volume expansion is that it can form cracks in the material and reduce its mechanical and electrochemical integrity which usually results in high capacity fade with time (I guess these guys have figured it out though).

Re:Subscription access only...

[msauve]

Although you can't get to the paywalled article, there is a barely legible chart, which shows the specific capacity, in mAh/g, to be ~2200. Current Li-Ion batteries, which use a graphite based anode, have a specific capacity of ~350 mAh/g. So 2200/350= ~6 times the capacity.

Re:Subscription access only...

[DamonHD]

Hmm, I see a whole new slew of SPAM: "Need your anode volumetrically gifted? Feeling that your capacity is down or resistance to your action is going up, unlike you? Our new CiaLIaSi is for you!"

Rgds

Damon

Jaded

[drobety]

There has been many nice headlines over the months (years) about such and such new advances in battery technology. Surely it's nice, but now I am becoming jaded with such articles. Here is what I want now: "New AAA batteries lasting twice as long as those currently sold reach the market // blah blah ... as measured by independent testing ... blah blah"

Re:Jaded

[Anonymous Coward]

Not gonna happen any time soon. The energy density (per unit volume) of alkaline long-life cells is about 50% higher than any other viable technology we have available. It seems unlikely anything is going to revolutionise this technology. Almost all current research is targeted at improving lithium cells, which are the next best (lower density than NiMH, but that technology has severe limitations on longevity that are not going to go away). Lithium is better in terms of density per mass, but what it absolutely cannot give you is a longer-lasting battery in the same physical format as an alkaline cell.

What we might hopefully see in the near future is a lightweight battery that can survive many thousands of charge cycles (LiFePO4 is the best in this respect with reasonable energy density, but it still lacks in density compared to Li-ion technologies, so there is potential to improve these to match and get a better battery). Unfortunately, they're still talking in terms of hundreds of cycles here.

To make true electric vehicles a reality (which is IMO the most important target of battery research right now) what we need is a battery that will last >2000 cycles and carries >200Wh/kg. The technology here looks like it might more than exceed these energy density requirements[1] but with only a 650 cycle lifetime it would probably be too expensive for day-to-day use. We might see something that meets these targets in the future, but it isn't here yet.

[1]: the abstract of the paper doesn't mention cell voltage and describes density in terms of milliamp-hours, which leaves you having to guess about plausible voltages, but we could be looking at 400Wh/kg or more here, so similar to Li-S batteries but without the very low lifespan associated with them.

Re:Jaded

[Animats]

I am becoming jaded with such articles.

What's annoying are all these material science articles where someone has made a new material at lab-scale and this is immediately extrapolated to commercial products Real Soon Now. About one of those appears each week. This is one of the saner ones, though.

The Great New Material usually turns out to have some problem. It costs too much to make, it's too brittle, it won't work when hot or cold, it's too hazardous, or it has a short lifespan in the intended application. Sometimes this is overcome, but most of the time, not.

There's nothing wrong with having articles about this stuff, but writers should be clear on where they are in the range between "theoretical chemistry indicates this molecule would be insanely great" and "the product is shipping in volume".

Conceited?

[DamonHD]

Maybe *you* only want to know about things once they are no longer R&D and are just lumpen consumer goods available in your local B&M.

Others may like to know about research, both blue-sky and nearer commercialisation.

The fact is that batteries *have* improved vastly over recent time, but not possibly by quanta and in formats that excite you.

I'm rather impressed by the LiFePO4 battery that I have rigged up alongside my 2kWh of SLA gel to reduce cycling of the latter, at several times the energy density by volume and weight (and not that expensive). But I went and haggled and bought it straight off a vendor's R&D bench armed with the knowledge that it wasn't likely to turn up in consumer gear in that form, at least not for a year or two.

Rgds

Damon

Re:Conceited?

[DamonHD]

I do read NS, as it happens. I even write vaguely technical stuff for money sometimes.

But spending your effort to whinge about /.'s climate being the wrong shade of purple in the latter part of an autumnal afternoon in your backyard is just a waste of everyone's effort. Just don't read TFA/TFS/TFC and spare us your peccadilloes, please.

Rgds

Damon

Like more efficient solar panels

[ickleberry]

There are many improved versions of the Li-Ion battery that last longer (as in more cycles) but they never seem to reach the market. Yeah feck it you can buy loose 18650 LiFePO4 cells and even lithium based supercapacitors but name one phone or laptop a normal person can easily buy with anything other than the bog standard 400-500 cycle-then-dead Li-Ion battery?

I expect that the reason for this is quite sinister - Li-Ion batteries are used to enforce planned obsolescense, which is why standard cells are often packed into an overpriced proprietary plastic casing before sale. Manufacturers of consumer electronics don't want batteries that are still good after thousands of cycles. Apple also deserves a mention for pioneering the idea of packing the battery into the hard to open case of the phone/laptop itself, forcing 99% of the people who own these products to buy a new one as soon as the battery dies.

Re:Like more efficient solar panels

[vijayiyer]

Maybe instead of a vast conspiracy, it's because LiFePO4 batteries have a much lower energy density? They can be charged much faster, but would you carry a 200W power brick to take advantage of it?
Lithium based ultracaps have on the order of 10% of the energy density of Li-Ion batteries. Would you carry a laptop that lasted 30 minutes per charge?

Most people will have their batteries replaced if it every stops holding a charge. Seems like a fair tradeoff to have devices last 30% longer per charge.

Re:Like more efficient solar panels

[ickleberry]

Which has almost no or very little increase in durability over standard Li-Ion. The main advantage of them is that they can be made into a nice proprietary shape

Heat does negatively effect Li-Ion batteries, Ideally they are stored at a few degrees C and half-charged. There also seems to be a huge variation in the quality of these batteries. I know there are plenty of Nokia 6310i's around still on the original battery but my laptop battery from 12/2009 is already down to 57%

This part here is utterly false:

[Anonymous Coward]

(lower density than NiMH, but that technology has severe limitations on longevity that are not going to go away)

This isn't wrong, it's ridiculously wrong. NiMH batteries are used in the Toyota Prius, where almost all of them last for thousands of charge/discharge cycles. The *prototype* of all NiMH batteries lasted 500 c/d cycles and most modern NiMHs last on the order of 4000 cycles or more:

Interest grew in the 1970s with the commercialisation of the Nickel hydrogen battery for satellite applications. Hydride technology promised an alternative much less bulky way to store the hydrogen. Research carried out by Philips Laboratories and France's CNRS developed new high-energy hybrid alloys incorporating rare earth metals for the negative electrode. However, these suffered from the instability of the alloys in alkaline electrolyte and consequently insufficient cycle life. In 1987, Willems and Buschow demonstrated a successful battery based on this approach (using a mixture of La0.8Nd0.2Ni2.5Co2.4Si0.1) which kept 84% of its charge capacity after 4000 charge-discharge cycles. More economically viable alloys using mischmetal instead of lanthanum were soon developed and modern NiMH cells are based on this design.[9]

For comparison, lithium-ion batteries are often only rated for something like 200 c/d cycles, with the best commercial-grade lithium-ion batteries not rated for longer than 1000 c/d cycles.

Another thing that I'll never really see

[frovingslosh]

Sure, we all want this. And I realize I'm likely to get moded down, not because I'm saying anything wrong but because someone who saw the original story and was excited doesn't like hearing the truth. But I'm getting a bit tired of hearing about all of these advances in battery technology that never actually seem to make it to the marketplace, in spite of claims that the advance can quickly and easily be applied to current production techniques.. Of course if this stuff really panned out we wouldn't even need batteries, we would all be using those nano-particle based super capacitors that I read about here years ago.