Progress made in building rechargeable lithium-air battery

Jul 20, 2012 by Bob Yirka report

(Phys.org) -- Researchers in the United Kingdom have taken another step towards proving that so named lithium-air (Li-O2) batteries might one day become practical. Up to now the problem has been using the technology to build a battery that uses oxygen and that can survive many charge-discharge-recharge cycles. Now Zhangquan Peng, Stefan Freunberger, Yuhui Chen and Peter Bruce of Saint Andrews in Scotland, have developed a way to build a lithium-air battery, using a gold electrode that, as they describe in their paper published in the journal Science, survived a hundred cycles with just 5% loss of power.

Traditional batteries are based on metal phosphate (or oxide) cathodes that serve as positive electrodes, carbon based that serve as negative electrodes and an electrolyte to move the ions between the two. With lithium air batteries, air is used as the cathode; oxygen reacts with lithium ions and electrons on the surface of the , forming lithium peroxide which leads to an electrical current being created during discharge. When recharging, everything happens in reverse resulting in oxygen being released back into the air. Up till now, the problem has been in preventing the cathodes and electrolytes from breaking down after repeated cycles of charging and discharging. To prevent that from happening, the UK team used a thin film of porous gold as the electrode.

That simple adjustment did indeed prevent the parts from decomposing, unfortunately, it’s not the solution to the problem, as using gold would not only be far too heavy, it would much too expensive for use in car batteries or consumer electronics. But as the researchers note, their work hasn’t resulted in a method of building lithium-air batteries for general use, but instead has shown that the technology itself works as hoped and that if another material can be used instead of gold, we might yet see the development of such batteries which could offer far more storage capacity than today’s offerings. Some have suggested that a phone with such a battery could be used for week without recharging, or that electric cars could finally start competing with gas guzzlers in the distance drivers could expect to travel before having to recharge.

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More information: A Reversible and Higher-Rate Li-O2 Battery, Science, DOI: 10.1126/science.1223985

ABSTRACT
The rechargeable nonaqueous Li-O2 battery is receiving a great deal of interest because theoretically its specific energy far exceeds the best that can be achieved with lithium-ion cells. Operation of the rechargeable Li-O2 battery depends critically on repeated and highly reversible formation/decomposition of Li2O2 at the cathode on cycling. Here, we show that this is possible, using a dimethyl sulfoxide electrolyte and porous gold electrode (95% capacity retention from cycles 1 to 100), whereas previously only partial Li2O2 formation/decomposition occurred and with limited cycling. Furthermore, we present data indicating that the kinetics of Li2O2 oxidation on charge is approximately 10-fold faster than on carbon electrodes.

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User comments : 6

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dschlink
not rated yet Jul 20, 2012
The primary advantage of higher energy storage would be in reducing the size of the battery, and hence the cost. Limited range is meaningless in a predominately urban environment. As more people own and operate electric vehicles without "getting stuck", the public will see this as the strawman that it is.
Eikka
1 / 5 (2) Jul 20, 2012
5% per 100 cycles is still way too much - it lasts only for 700-800 cycles before needing replacement, or no better than the cheapest lithium batteries on the market today.

As a car battery, you'd have to replace it as often as laptop batteries - every 3-4 years.

Some have suggested that a phone with such a battery could be used for week without recharging


I already have a phone that can be used for two weeks without recharging because it doesn't have stupid touchscreen-angrybirds-multimedia crap in it. It's just a phone.
Eikka
1 / 5 (2) Jul 21, 2012
Limited range is meaningless in a predominately urban environment.


http://www.statis...tistics/
Total number of commuters in the U.S. - 128.3 Million
Within City Commuters - 27.4 Million


In other words, for 78.6% of US commuters, range matters. Not only because of commuting but other daily business outside of the home-work-home route that require longer trips when you live outside of the city centers. The basic fallacy is that if you live near work, you never need to go any further than work, which is then used to argue that electric vehicles are sufficient for, say, 80% of the population. But that simply isn't true:

http://www.raeng....cles.pdf (page 25. figure 14.)

The average driver in the UK, with today's battery capacities, will find himself unable to drive the needed distance every once or twice a week on average. That's simply not acceptable.

Eikka
1.5 / 5 (2) Jul 21, 2012
For example, if I want to visit my friends the next town over, that's a 53 miles round-trip, plus 10 miles for work, plus a couple more miles for the groceries. That's pushing very close to the 73 miles that the Nissan Leaf got for the EPA estimated range, and in winter conditions it would simply not go the distance with the heaters on. Give it a couple years and the battery capacity starts to go down anyways.

That's what the reality of electric cars is. The batteries need to get better before they make any sense to the majority of the people.
yoatmon
not rated yet Jul 22, 2012
Why not stick to the subject of this discourse? You're anxiety about the range of an EV is not unbiased but it's not the theme of this blog.
The Li-air battery's electrodes must be designed with the right materials. Perhaps palladium would do the same job and be far cheaper than gold. Substituting one electrode with air automatically reduces the volume and mass of the complete battery. This would allow an icrease of a battery to around 100 kWh which should cut back range anxiety by 99% or even more.
BuddyEbsen
not rated yet Jul 30, 2012
if I want to visit my friends the next town over, that's a 53 miles round-trip, plus 10 miles for work, plus a couple more miles for the groceries. That's pushing very close to the 73 miles that the Nissan Leaf got


Then why not get a Tesla Model S, with a range of between 160 and 300 miles, depending on the model?

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