Slashdot Mirror
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."
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.
"Science flies us to the moon. Religion flies us into buildings." - Victor Stenger
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...)
No sig today...
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.
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".
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.
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.
"National Security is the chief cause of national insecurity." - Celine's First Law
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
http://m.earth.org.uk/
(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.