Quicker battery charge holds promise for plug-in cars

U.S. researchers have invented a battery that recharges ultra-quickly, opening the possibility of one day charging an electric car in the amount of time it now takes to fill up a gas guzzler.

The new lithium ion battery material has a special coating that allows it to charge and discharge dozens of times faster than existing lithium battery materials, according to a paper published in Thursday's issue of Nature.

That ability could make hybrid and plug-in hybrid vehicles more practicaland could be used to provide a back-up for wind and solar energy, the paper said.

In the case of a car, both the charging and discharging abilities are important, saidMassachusetts Institute of Technology graduate student Byoungwoo Kang, who co-authored the paper with engineering professor Gerbrand Ceder.

"The fast discharging means you can accelerate the car using the battery," Kang told CBCNews.ca Wednesday.

Currently, toaccelerate,a hybrid-electric vehicle relies heavily onits internal combustion engine.

Ceder said an uncoated lithium ion battery material similar to the new material has already been in use for transportation and power tool applications for about five years.

Such batteries can store a large amount of charge, but are quite slow at charging or discharging energy a problem that had been blamed on the speed of the lithium ions that help carry the charge across the battery.

During that process, the ions must leave one electrode, travel through an electrolyte, and lodge in "active" particles in the other electrode.

Calculationspointed the way

However, about five years ago, Ceder and his collaborators did some computer calculations and found the lithium ions could actually move extremely fast.

"That's not what we were seeing in batteries with these materials, so there had to be some other problem."

After further study, they concluded that the lithium ion could move quickly once it was inside the particles, but had trouble getting across the particle surface to an entry point.

"It's sort of like a big house with just one small door," he said.

Ceder andKang made small changes to the ingredients and processing used to make the particles so that they would form a coating that let lithium ions travel across the particle surface quickly.

Using the coated particles, they made a small battery that could charge or discharge in 10 to 20 seconds, compared to six minutes using uncoated particles.

Because an industrial practice already exists to make lithium batteries with the uncoated particles, Ceder estimated that batteries using the new materials may be for sale in two or three years.

Adding the coating isn't hard, Ceder said.

"It's created while the particles are synthesized. It's actually not even an extra step."

The technology has already been licensed to two companies: the Belgian materials company Umicore, which makes the lithium particles, and a battery manufacturer.

However, that doesn't mean people will necessarily be able to charge electric cars ultra-quickly right away. The paper points out that a five-minute charge-up would suck up electricity faster than an electrical outlet could provide it.