On Tuesday A123 Systems, a Massachusetts-based maker of lithium-ion batteries, said it had an improved battery that would provide better performance over a wider range of temperatures and, more important, last as long as the car it powers.
Great news, if true. A123 is in dire financial straits, and it could use a technological shot in the arm to attract the investment in needs to stay afloat. All the more reason to take its claims for its “Nanophospate EXT” technology with a grain of salt.
A long-lasting battery would be big news because in any pure-electric car, and in most plug-in hybrid cars, the battery pack is the single greatest expense. For many drivers, the prospect of having to replace it is a deal-breaker.
“Say you want the car to go for 150 000 miles [240 000 kilometers]—that’s perhaps 500 cycles,” says chemical engineer Venkat Srinivasan, the head of battery technology at Lawrence Livermore National Laboratories. “That by itself may not sound like a big problem, but I also have to do it over the 10 to 15 year expected life of the car, and that is a problem. It’s hard to simulate the passage of that much time! To do so, we often raise the temperature to increase speed of chemical reactions; obviously, this is all guesswork.”
Srinivasan adds that he knows nothing of A123’s secret sauce. However, he notes that a lot of people in the business are also trying to find ways to stabilize the battery so as to extend its life.
In 2007, when we first wrote about A123, the company was just six years old and still on its venture-capital training wheels. Its great ambition was to be chosen as a supplier to the first generation of electric-drive vehicles to use lithium-ion batteries, notably the Chevrolet Volt. However, A123 didn’t get the Volt contract, and its other great hope, the Fisker Karma, turned sour when A123 had to recall potentially defective battery packs. Meanwhile, the entire electric-vehicle market ended up growing slower than many proponents had said it would.
A123 has always championed a battery chemistry based on cathodes made of iron phosphate. There are many alternatives, including cobalt dioxide and manganese oxide spinel. The advantage of iron phosphate is its stability and, therefore, safety. That was quite a selling point some years ago, when lithium-ion designs were causing laptop computers to burst into flame.
As writer John Voelcker explained in our 2007 article, the bonds between the iron, phosphorus, and oxygen atoms are stronger than those in the competing chemistry, based on cobalt and iron, making it harder to detach the oxygen molecule through overcharging. That way, if for some reason the battery should overheat, it would be much less likely to catch fire.
To compensate for the relatively poor conductivity of iron phosphate, A123’s engineers added traces of other elements. They also structured the cathodes on the nanoscale, a proprietary idea meant to let molecules in the cathode rearrange themselves faster when taking up or relinquishing lithium atoms. Not only would that increase the battery’s power, it would subject it to suffer less physical stress and thus keep it working through a greater number of charge-discharge cycles.
We’ll see if what they’ve come up with now can do better.
Philip E. Ross is a senior editor at IEEE Spectrum. His interests include transportation, energy storage, AI, and the economic aspects of technology. He has a master's degree in international affairs from Columbia University and another, in journalism, from the University of Michigan.