MIT's revamped Li-ion batteries fully recharge in seconds, not hours

Posted by Rick C. Hodgin

Cambridge (MA) - MIT engineers have developed a type of high-speed tunnel for transporting electrical energy through lithium iron phosphate, a well-known battery material. The discovery may yield lithium ion batteries that fully discharge and recharge in seconds, rather than hours, making batteries lighter, more powerful, and finally suitable for the all-electric vehicle that can be recharged in the same amount of time it takes to refuel the tank today.





The high-speed recharge/discharge battery technology is of particular interest to the automotive industry because, as it takes a few minutes to refuel an automobile today, future electric "gas stations" could allow all-electric vehicles to pull in and fully recharge in about the same amount of time, giving electric vehicles a much easier consumer acceptance due to their much greater feasible range.



The work has been led by Gerbrand Ceder, professor of Materials Science and Engineering, and will be reported in the March 12 issue of Nature magazine.

The material is not new, however the MIT researchers have changed the way in which it is made. Marketable products are believed to be possible within two to three years, though they have already constructed a battery prototype in the lab which functions as expected. In addition, the discovery has already received commercial interest and is being licensed.



Lithium Ion batteries are great at storing large quantities of energy. However, they are slow to receive the charge, and relatively slow to give it back off. While this gives them their longevity, it is also a problem for adoption in a wide array of applications which need faster discharge and recharge times.



About five years ago, Ceder and his colleagues made an important, surprising discovery. It had long been thought that lithium ions, along with electrons, moved too slowly through the lithium iron phosphate. However, MIT engineers discovered, through computer calculations, that the material's lithium ions should be moving extremely quickly. The search was then on to figure out why they're not.



In the end, the scientists discovered that they could indeed move quickly, but only if high-speed lanes, or tunnels, existed in the material. According to MIT's press release:


"Further calculations showed that lithium ions can indeed move very quickly into the material but only through tunnels accessed from the surface. If a lithium ion at the surface is directly in front of a tunnel entrance, there's no problem: it proceeds efficiently into the tunnel. But if the ion isn’t directly in front, it is prevented from reaching the tunnel entrance because it cannot move to access that entrance."



The team then began to create a new surface structure, one which allowed the lithium ions to move quickly around the outside of the material. The new technique was then applied to a real battery which demonstrated it could be fully charged or discharged in 10 to 20 seconds.



As an additional bonus, because of the revamped surface structure of the new material, it did not degrade as much over repeated discharge and recharge cycles, making the batteries last longer.



The end result is the possibility of creating smaller, lighter batteries (because less material is used to generate the same amount of electricity). And by being able to recharge them in seconds, a quick trip to a local communal "power station" will provide a full-up recharge in the same amount of time it takes to get a cup of coffee.



MIT's work was funded by the National Science Foundation via the Materials Research Science and Engineering Centers program and the Batteries for Advanced Transportation Program of the U.S. Department of Energy. The technology has also already been licensed by two currently undisclosed companies.