Fast-Charging Lithium Ion Batteries Tested

MIT engineers have developed a technique for creating fast-charging lithium ion batteries used in applications ranging from smartphones and mobile PCs to electric cars.

The technique described in the March 12 issue of Nature could dramatically shorten the amount of time it takes to recharge the batteries from hours to seconds. Lithium ion power supplies are slow to release and absorb power. While the former means the batteries can last for hours, the latter means they can also take hours to recharge.

The slow recharge is caused by the amount of time it takes lithium ions, along with electrons, responsible for carrying the charge to find a way into the battery material called lithium iron phosphate. The ions have to first find the tunnel entrances on the surface, a process that takes time.

MIT professor Gerbrand Ceder and graduate student Byoungwoo Kang created a new surface structure that allows the lithium ions to move quickly around the outside of the material, much like a beltway around a city. When an ion reaches a tunnel, it's instantly diverted into it.

Using their processing technique, the scientists made a small battery that could be fully charged or discharged in 10 to 20 seconds, rather than six minutes for a battery made with traditional materials.

Ceder said tests have shown that the new material also doesn't degrade as much when repeatedly charged and recharged. This could lead to smaller, lighter batteries because less material is needed for the same result.

"The ability to charge and discharge batteries in a matter of seconds rather than hours may open up new technological applications and induce lifestyle changes," Ceder and Kang said in their paper, which MIT disclosed Wednesday.

Because the battery material used isn't new and the only change is in the way it's made, Ceder believes the new processing technique could make its way into the marketplace within two or three years. One application could include the quick recharging of batteries in electric cars. However, that would be limited by the amount of power available to a homeowner through the electric grid.

The battery work was supported by the National Science Foundation and the U.S. Department of Energy. The new technique has been licensed by two companies, MIT said.

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