Battery breakthrough promises phone, car revolution
March 12, 2009
Think of an electric car that can accelerate swiftly to cruising speed, laptop computers that can recharge in a couple of minutes rather than hours and a generation of super-miniature mobile phones.
That's the vision sketched on Wednesday by a pair of scientists in the United States, unveiling an invention that they say could lead to a smaller, lighter and more power-packed lithium battery than anything available today.
Current batteries made of lithium iron phosphate (LiFePO4) are good at storing large amounts of electricity but stumble at releasing it.
They are better at dispensing the power in a steady flow than at discharging it or gaining it in a sudden burst.
As a result, electric cars perform best when travelling along the motorway at a constant speed rather than when they are accelerating, and their batteries take hours to recharge when they run down.
Until now, the finger of blame has pointed at charged lithium atoms. These ions, along with electrons, move too sluggishly through the battery material before arriving at the terminal to deliver their charge -- or so it was thought.
But a pair of materials experts at the Massachusetts Institute of Technology (MIT) say the problem lies not with the ions but rather at how the ions gain access to nano-scale tunnels that riddle the material and transport the electrons to their destination.
Their solution was a lithium phosphate coating that, like a system of feeder roads, nudges the ions towards the tunnels. The ions then zip instantly down the tunnel entrance and to the terminal.
A small cellphone battery can be recharged in just 10 seconds thanks to the improved ion flow, they report in the British journal Nature.
In theory, a large battery that would be used to power a plug-in hybrid electric car could be recharged in just five minutes, compared to up to six or eight hours at present. But this would only be possible if a beefed-up electricity supply were available.
Unlike other battery materials, the tweaked LiFePO4 does not degrade as much when repeatedly charged and recharged. This opens the way to smaller and lighter batteries, which will not need such heft to deliver the same power, MIT said in a press release.
The invention, which was supported by US government funds, has already been licensed by two companies, MIT said.
Because the material involved is not new -- the difference is the way it is made -- "the work could make it into the marketplace within two to three years," it said.
The invention is the latest claimed advance in the quest to replace conventional electro-chemical batteries, which are heavy, lack energy density and take time to recharge.
Research in this field ranges from updated lithium-ion technology to hydrogen batteries and combinations of a battery with so-called ultracapacitors that harness exotic materials such as barium titanate to deliver a jolt.
Source: Associated Free Press