New charging method could greatly reduce battery recharge time

Mar 11, 2010 by Lisa Zyga report
This figure shows the fraction of non-intercalated lithium ions per time, with the different colors representing different amplitudes of the applied oscillating field (A = 5 kCal/mol). The denominator in the exponential is the average intercalation time in nanoseconds, showing that a larger amplitude field speeds up ion intercalation. Credit: Hamad, et al.

(PhysOrg.com) -- Part of the headache of having to constantly recharge batteries is not just how often they need to be charged, but also the time it takes to charge them. In a new study, researchers have proposed a charging method that could greatly reduce the charging time of lithium-ion batteries, which are used in everything from electronic devices to electric vehicles. The new method uses an additional oscillating electric field (besides the charging field) that should be capable of charging a lithium-ion battery in a fraction of the time compared with traditional methods.

Researchers Ibrahim Abou Hamad from Mississippi State University and coauthors have developed the new charging method thanks to revolutionary developments in molecular dynamics simulations. In their study, the researchers simulated the battery-charging process by simulating the intercalation (i.e. “insertion”) of lithium ions into the battery’s graphite . Although intercalation is just one part of the charging process (along with diffusion), it dominates the charging time.

In the charging process, lithium ions first diffuse within the battery’s until they reach the graphite anode. At this interface, ions must overcome an energy barrier in order to be intercalated into the anode.

In their simulations, Hamad and his team found that an additional oscillating electric field can lower this energy barrier, enabling lithium ions to intercalate more quickly into the anode. The oscillating field also increases the diffusion rate, which helps further reduce the overall charging time, albeit to a lesser extent.

Specifically, when the scientists applied an oscillating square-wave field with a frequency of 25 GHz and an amplitude of 5 kCal/mol to the graphite sheets in the anode, the lithium ions intercalated into the sheets within an average time of about 50 nanoseconds. By changing the amplitude of the oscillating wave, the researchers found that they could further improve charging time by lowering the energy barrier and speeding up intercalation. Their simulations showed that the dependence of the intercalation time on the amplitude is exponential, meaning that a small increase in amplitude leads to a large increase the intercalation speed, which offers the potential for very fast charging times.

In the future, the researchers plan to further investigate the new method, including analyzing how changing the frequency of the oscillating field effects the charging time. They noted that the new method might provide an increase in battery power densities, as well.

Explore further: Experiment with speeding ions verifies relativistic time dilation to new level of precision

More information: Ibrahim Abou Hamad, M. A. Novotny, D. Wipf, and P. A. Rikvold. “A new battery-charging method suggested by molecular dynamics simulations.” Available at arxiv.org. Doi: 10.1039/b920970k.
via: Technology Review

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4 / 5 (1) Mar 11, 2010
Could this be modified to work with say a lead acid battery?
antialias_physorg
4 / 5 (1) Mar 12, 2010
If this does not affect the number of duty cycles negatively then that's a pretty neat discovery.
broglia
3 / 5 (1) Mar 12, 2010
Method proposed applies a 25GHz signal to a battery, which is impractical at large scale. The problem is huge capacitance of porous electrodes, which are behaving like giant capacitor.

But maybe even lower frequencies could work in sufficient way. After all, the charging with AC component is used widely, as it decreases the tendency to formation of dendrites in certain batteries.
chandram
3 / 5 (1) Mar 12, 2010
Interesting but appear a bit impractical, as it requires 25 Ghz oscillatory field along with the normal reverse dc charging field. The prescription also needs theoretical justification.
joefarah
5 / 5 (2) Mar 12, 2010
Altairnano's Lithium Titanate batteries can charge as fast as you can feed power to them (e.g. Charge an auto in 10 minutes). Let's get this technology to be mainstream. See www.altairnano.com
Royale
3.7 / 5 (3) Mar 12, 2010
I want supercapacitors! Lets concentrate on them, then we don't have to worry about batteries any more!
El_Nose
Mar 12, 2010
This comment has been removed by a moderator.
Yevgen
3.5 / 5 (4) Mar 12, 2010
It is well known that battery impedance in overall decreases with temperature. Mostly it is because of the decrease in activation energy of electron transfer, increase of diffusion rate and increase of ion mobility.

Applying 25 GHz Ac has probably only one real effect - it is heating the battery. That is why it reduced impedance and increases charging rate. They should measure the battery impedance and compensate it for temperature and they will see that there is no difference if you heat it with 25 GHz AC or just with a thermal chamber.

Now, heating the battery (while decreasing impedance and
therefore increasing charging rate) is not without consequences. It is well known that it accelerates battery degradation. For example cycle life at 25C is 3 times longer than that at 60C. Heating during charge is
specially harmful, that is why new Japanese charging standard specifically requires to reduce charging rate at higher temperatures.

Regards,
Yevgen
Parsec
1 / 5 (1) Mar 12, 2010
I want supercapacitors! Lets concentrate on them, then we don't have to worry about batteries any more!


Why? Super capacitors have their own problems, not least of which is low capacity, and the ability to discharge instantly when shorted (the technical term is the kaboom factor). Note that the kaboom factor goes up with the capacity.
Nartoon
not rated yet Mar 13, 2010
Right, batteries never short out and go kaboom.
seneca
not rated yet Mar 13, 2010
Right, batteries never short out and go kaboom.
Only theoretically, because currently the energy density of batteries is 30 - 50 times higher, then at the case of supercapacitors.

http://www.youtub..._TBzD49Y
antialias
not rated yet Mar 13, 2010
Supercapacitors are not comparable to batteries. They have entirely different applications.

Supercapacitor: low power density; able to accept (and donate) energy quickly; voltage is dependent on energy stored.

Battery: high power density (about a factor of ten higher per unit weight than supercapacitors); able to accept (and donate) energy slowly; voltage stays roughly the same until battery is nearly empty.
NeilFarbstein
not rated yet Mar 14, 2010
The Altair nano batteries are garbage that lost all of the charge after two days. The method detailed above doesn't lower the cost of batteries but it will have applications in battery vehicles.
akkuJukka
not rated yet Mar 18, 2010
The method mentioned in this article has nothing to do with the temperature of the cell components. There's even greater news to us in the documented procedure mentioned. There's a lot of data about how Lithium cells behave in various operating environments. This discovery made in MSU actually explains plenty of odd things that so far have gone by with question marks. You need very large cells to even notice these things. I believe we are now at the verge of new Lithium battery implementation methods at many applications. Very good news indeed !
El_Nose
not rated yet Mar 18, 2010
my previous comment was taken down by physorg

ummm.. you still have to charge a capacitor


and its still true -- i felt a couple earlier poster missed the point that u STILL have to charge the capacitor and that is 4*RC so the bigger the capaitor the longer it takes to charge to close to full capacity -- I didn't feel i needed to explain further - but since it was POINTLESS VERBAIGE I decided to clarify for the psyorg moderator because they didn't understand that the article is about short charge times in a battery and previous posts could inspire unique responces.