Thursday, March 12, 2009

High Flow Battery Allows Quick In and Quick Out Flow of Electrons via Bypass Channels

MIT's Gerbrand Ceder has developed a new electrode for Lithium Ion batteries that should allow very rapid charging for cell phones and automotive batteries, for example, and very rapid discharging for laser weapons and race cars.
This level of power output would put these batteries on par with ultracapacitors, gadgets that can rapidly discharge power but can't carry much energy for their size, says John Miller, a vice president for systems and applications at Maxwell Technologies, a manufacturer of ultracapacitors, who wasn't involved in the research. The new batteries would store nearly 10 times as much energy as an ultracapacitor of the same size. The combination of small size and extreme power could make the batteries particularly useful for race cars, he says. (Starting this year, new Formula One racing rules will allow race cars to store energy from braking to deliver very brief jolts of acceleration.)

To improve the batteries, the researchers modified an electrode material called lithium iron phosphate to allow electrons and ions to move in and out of it much more quickly. The advance is based on computer models that Ceder developed in 2004. The models suggested a way to improve conductivity by directing lithium ions toward particular faces of crystals within the material.

To exploit this, Ceder included extra lithium and phosphorus. This helps form a layer of lithium diphosphate, a material known for its high lithium-ion conductivity. He says that ions encountering the material are quickly shuttled to faces that can pull them in, allowing for very fast discharging.

The fast-discharging materials may also recharge quickly, raising the possibility of cell phones that charge in seconds, Ceder says, but this would require expensive chargers. Ric Fulop, vice president of business development at A123 Systems, a battery maker based in Watertown, MA, that has licensed Ceder's new material, says that it could be useful for hybrids or for delivering the power needed for laser weapons. (Fulop notes that A123 is not developing batteries for the latter application.) _TechReview
Very interesting, if it pans out anywhere close to the numbers given in the article above. The new battery would provide much greater power density -- surge current -- but perhaps not significantly more energy density -- total energy storage.

In other words, this development will prove useful for many applications, but it does not seem to be the magic breakthrough that suddenly makes all-electric cars feasible for the masses. Of course, one cannot reliably predict when a breakthrough will happen. If a scientist five years from now discovers a battery that provides ten times the energy density of the best competing batteries, at one tenth the cost, Al Fin's predictions about the future of all-electric cars might have to be modified.

What is needed, is a fast-charging, high energy capacity, compact, lightweight, flexible, inexpensive storage battery, and we need it yesterday. In the real world, we work with what we have. Fast charging batteries for cars will make distributed charging stations far more practical, extending the effective range of electric vehicles. What we want, is batteries that can take you 1,000 miles between quick, cheap charges.

We will have to wait for that, but just knowing that scientists such as Ceder are working on the problem makes me feel better, somehow.



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