Batteries now included
Mar 12th 2009
From The Economist print edition
The missing piece of the electric-car jigsaw has just turned up
IF YOU want to buy an electric car, you can. Tesla Motors, a firm based in San Carlos, California, will sell you a nifty open-top sports job for $109,000. Not cheap, admittedly, but cheap to run. Plugged in overnight, it can be refuelled for the equivalent of 25 cents a litre of petrol. The catch is, “plugged in overnight”. Tesla’s vehicles use standard lithium-ion battery cells. As any owner of a mobile phone or laptop computer knows, these take time to charge. If you use 6,831 of them, as a Tesla sports car does, that time does tend to drag on. Which is fine if you are not planning a long trip the following day, for a full charge will take you about 350km (220 miles). But it might cramp the style of anyone planning to bomb down from, say, Paris to Cannes, and who would therefore need to refuel on the way.
Gerbrand Ceder and Byoungwoo Kang of the Massachusetts Institute of Technology hope to change this, and thus help make the electric car a work-a-day consumer item, rather than a high-end boy’s toy. In this week’s Nature they have published the technical details of a new battery material that will, if all goes well, take the waiting out of wanting, at least when it comes to recharging.
Broadly speaking, there are two ways of storing electrical energy in a chemical system. One is a standard battery, in which the whole material of the electrodes acts as a storage medium. That allows lots of energy to be squirrelled away, but makes it relatively hard to get at—and so it can be released or put back in only slowly. The other way is called a supercapacitor. This stores energy only at the surface of the electrode. It is quick to charge and discharge, but cannot hold much energy. The great prize in the battery world has thus been a material that can both store a lot and discharge rapidly, and it is this that Dr Ceder and Mr Kang think they have come up with.
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