Fast-Charging Lithium Batteries Disputed

24 June 2009—A new material enabling lithium-ion batteries to charge in just 10 to 20 seconds is either too good to be true or more than 10 times better than advertised.  Those are the battle lines in a dispute that’s been erupting since late May among battery researchers over whether the material has the potential to transform the usability of electric vehicles (EVs).

The fight began with a report in the journal Nature in March 2009 by materials scientists at MIT claiming an ultrafast-charging form of lithium-iron phosphate, the material employed as the positive electrode, or cathode, in the most promising lithium-battery design for EV applications. Leading the attack against MIT’s claim is a quartet of physicists from the United States, Canada, and France. They include University of Texas mechanical engineering professor John Goodenough, one of the original inventors of the lithium-iron-phosphate cathode. The principal argument in their critique, which was based on a close reading of the Nature report and published online by the Journal of Power Sources on 30 May, infers that the material actually demonstrates only rapid discharge. ”They can discharge at that rate but not charge,” says Alain Mauger, a physicist at the Université Pierre et Marie Curie in Paris.

Not true, replies MIT professor of materials science and engineering Gerbrand Ceder, who coauthored the report in Nature with his graduate student Byoungwoo Kang. Ceder says their tests of charging capacity retention after multiple charging cycles (Figure 3b in the Nature report) were performed with both rapid charging and discharging.

Jaephil Cho, a lithium-battery materials chemist at Korea’s Ulsan National Institute of Science & Technology, contacted by IEEE Spectrum for an independent reading of the Nature paper, says he finds the paper to contain ”high-quality data” and agrees that it shows both fast charge and discharge rates.

Ceder has submitted a written response to the Journal of Power Sources, which is considering it for publication. He says his group’s most recent research has pushed the technology even further. He says the new material’s best charging rates (albeit in very small laboratory cells) suggest the possibility of charging or discharging EV batteries in as little as a half second—about 15 times as fast.

Lurking behind the dispute is a fight over potentially valuable intellectual property rights. Lithium-iron-phosphate batteries for EVs are being commercialized because they are safer and more durable than most lithium-battery technologies. But ongoing patent disputes among the University of Texas, Montreal-based power utility Hydro-Québec (which has an exclusive license on Goodenough’s seminal patents), and innovative battery producers such as A123 Systems, based in Watertown, Mass., have complicated their development.

Ceder claims to have significantly altered the structure of lithium-iron-phosphate materials and says MIT is already selling licenses to use the technology—including an option to license taken by A123. However, his critics—two of whom are employed by lithium-iron-phosphate patent holders—question whether a novel structure is responsible for the improved mobility.

It could take years to sort out who’s right, and as both Ceder and his critics point out, these promising results in tiny laboratory cells may never revolutionize the charging practice for full-scale EVs. That’s because the power consumption required to rapidly charge an EV battery would place a major strain on power grids. A five-minute charge on a 15-kilowatt-hour battery—the scale of energy storage required in a plug-in hybrid vehicle—would require a whopping 180 kW of power. That means supplying the power needed to pull in your Chevy Volt or plug-in Prius for a quick charge would be like adding an entire office building to the grid.