While electric car companies such as Tesla and Renovo, which recently came out of stealth mode to unveil the 1,000 lb-ft Renovo Coupe, are working on improving the capacity of their lithium-ion batteries, a group of researchers in Australia have developed a new technology that could eventually do away with batteries.
Researchers at the Queensland University of Technology (QUT) in Brisbane, Australia in cooperation with Rice University in Houston have come up with supercapacitors that can work with lithium-ion batteries to significantly improve a vehicle's electric power. The lightweight supercapacitors are made from a "sandwich" of electrolyte placed between two strong sheets of graphene, giving them a high power density that allows them to release energy in a much shorter period of time than conventional lithium-ion batteries.
"Vehicles need an extra energy spurt for acceleration, and this is where supercapacitors come in," says Ph.D. researcher Marco Notarianni of the QUT's Science and Engineering Faculty - Institute for Future Environments. "They hold a limited amount of charge, but they are able to deliver it very quickly, making them the perfect complement to mass-storage batteries."
Conventional supercapacitors currently available only have 28 watt-hours per kilogram, which is far less than the 200 watt-hours per kilogram held by the average lithium-ion battery. These graphene-based supercapacitors are not actually any better, demonstrating energy densities in the range of 8 to 14 watt-hour per kilogram. However, they have substantially higher power density and are made from flexible material that can be structured and molded to become part of the vehicle's body.
"Supercapacitors offer a high power output in a short time, meaning a faster acceleration rate of the car and a charging time of just a few minutes, compared to several hours for a standard electric car battery," says Notarianni.
Graphene's ability to yield means the supercapacitors could be embedded into vehicle's body panel - the roof, hood, floor and doors, to store energy that can be used to accelerate and supercharge the vehicle. In the future, the researchers plan to develop graphene-based supercapacitors that can store more energy than a regular lithium-ion battery, so that the car can do away with the lithium-ion battery and be powered entirely by supercapacitors.
"After one full charge this car should be able to run up to 500 kilometers - similar to a petrol-powered car and more than double the current limit of an electric car," says Dr. Jinzhang Liu, postdoctoral research fellow at QUT.
Other battery-powered devices, such as smartphones and tablets, are also expected to benefit from the technology. Dr. Liu says mobile devices can get a fast charge by placing a thin strip of graphene-based electrode on the back of the device.
The researchers believe their invention could be a game-changer in the energy industry because graphene is a cheap, environment-friendly material that can be easily produced, while the lithium used in lithium-ion batteries will remain expensive because of its relative scarcity.
The results of the study were published in the Journal of Power Sources and the Nanotechnology journal.
