Your Next Electric Car May Not Even Need a Battery

Scientists discover a way to make a car's doors, hood, and roof generate electricity.

(Photo: Adam Berry/Getty Images)

Nov 11, 2014· 2 MIN READ
Hannah Hoag reports on the environment, global health, science, and science policy for Nature, Discover, Wired, and others.

In the years ahead, an ultrathin substance made of cheap carbon materials could be wrapped around electric cars to power them. No battery needed.

Researchers at Queensland University of Technology in Australia and Rice University in Houston have developed a flexible supercapacitor that could be embedded in an electric car’s doors, hood, and roof to charge the battery or even replace it.

Nunzio Motta, an engineer at QUT, and his colleagues wanted to create environmentally friendly materials that store and produce electricity. They developed an electrolyte sandwich with newfangled bread—a film made of graphene and carbon nanotubes.

Supercapacitors are energy-storage devices that charge and discharge hundreds to thousands of times faster than a battery. They’re also more durable—they can run through more charge-discharge cycles before degrading. But instead of storing energy in a chemical reaction like a battery does, supercapacitors store power in an electric field.

Tesla Motors chief executive Elon Musk has said that the breakthrough in electric cars will come from supercapacitors, not batteries.

“Supercapacitors can be combined with regular batteries to dramatically boost the power of an electric car, providing an extra energy spurt for acceleration,” said Motta.

Supercapacitors are already in use. Hybrid electric buses in China use them to quickly turn on the engine and reduce the load on the battery. At this year’s Goodwood Festival of Speed in Chichester, England, the Toyota TS040 hybrid carried a supercapacitor that gives its motor an extra kick when needed.

So what’s the holdup for the rest of us?

It’s been tough to design supercapacitors that are strong, inexpensive, and able to store enough energy for everyday applications.

Most hybrid vehicles have batteries because supercapacitors can’t yet store the same amount of energy, pound for pound. The energy density of supercapacitors is still one-tenth of that of a lithium-ion battery, said Motta. The new material he and his colleagues created, however, is more power dense and energy dense than graphene, which won its creators the 2010 Nobel Prize in Physics.

“Our research is set to find the right material based on carbon so that supercapacitors are cheap enough and can be easily embedded in the car body,” said Motta.

The discovery means that it is possible to produce supercapacitors with just carbon materials, which could cut the cost of the devices.

Graphene is a flexible, conductive form of carbon that can be as thin as one carbon atom. By adding carbon fibers and polymers to the supercapacitor sheet, Motta and his colleagues strengthened the structure of the film. Overall, the film is less than one micron thick—about half the length of a bacterium.

“Our supercapacitors are bendable, which means they can be adapted to many shapes,” said Motta. “This is a step towards meeting the challenge of powering an electric car.”

The goal, said Motta, is to create a device that stores more energy than a lithium-ion battery—and releases it faster—to be able to power a car for up to 310 miles. It could also be used to store energy generated from solar- or wind-power installations.

Motta said real-life applications could be on the market in as soon as five years—if the technology attracts investors who can provide the financing to take it to the next stage.