MIT Researchers Develop Lithium Battery Material For Ultrafast Charging
By John O'Dell March 12, 2009Could Lead to 5-Minute EV Recharging - If Power Delivery Systems Are Developed
Engineers at MIT have come up with a way to turn lithium iron phosphate, a common compound several hybrid- and electric-car battery developers are working with, into a super-expressway for electrical energy: a breakthrough that could dramatically reduce charging time for lithium batteries.
But while the process holds great promise for ultrafast recharging of cell phones, laptops and other small devices, don't hold your breath waiting for 5-minute recharging for electric cars.
EV or plug-in hybrid batteries made using the MIT process could take an ultrafast charge if one were avaialbe, but still needed is technology that could dramatically increase the amount of power a battery charger could draw from household and other electrical outlets.
The technology breakthrough, reported today by MIT and the journal Nature (subscription only), changes the way lithium iron phosphate is made, enabling it to absorb and release energy-toting lithium ions hundreds of times faster than before.
An example, provided by MIT researchers Byoungwoo Kang and Gerbrand Ceder, is that a common lithium cell about the size of an AA battery now takes about 6 minutes to charge while one made with the new process can be charged in as little as 9 second
Lithium batteries have very high energy densities - that's why they are being developed for use in electric and hybrid-electric vehicles: the energy density lets you drive at highway speeds for a long time.
But they are slow to absorb or discharge their energy, which is why automotive lithium batteries, so far, take a long time to recharge and don't provide a lot of acceleration power.
Ceder, who led the MIT research, said the team discovered that lithium ions move very quickly through the lithium iron phosphate material used in batteries but often don't have a route out into or out of the tunnels in the material's crystalline structure that permit that rapid movement.
The researchers' developed a new surface structure for lithium iron phosphate that enables lithium ions to travel around the outside of the material until they reach a tunnel opening and are diverted inside. The opposite occurs - the ions in the tunnels can immediately exit when they reach the terminus and jump onto the "expressways" that enable them to carry their electrical charge to the battery cathode.
Ceder says that he believes his team's work could make ultrafast rechargeable batteries for small devices commercially viable within three years.
Fast-charging for automotive battery packs, however, would require significantly more juice than is presently delivered to homes or to public charging stations.
John O'Dell, Senior Editor
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