In the model above, the car roof has been replaced by a structural battery. (Credit: Emilia Lundgren / Chalmers University)
Today’s electric car batteries are quite heavy. For instance, the weight of the Nissan Leaf’s 24 kW·h lithium ion battery is 648 lbs (294 kg). If some parts of the car’s body could simultaneously function as a battery, significant weight reductions would be possible. In a recently completed EU/FP7-funded project on structural batteries Prof. Patrik Johansson from the Chalmers University of Technology investigated materials that can store and deliver energy and also carry a load.
“We have investigated materials that can store and deliver energy and also carry a load. The idea is neither to make the best energy storage nor the best construction material. But the compromise, the ‘multi-functionality’, is really unique,” says Patrik Johansson.
The scientists’ goal is to create a structural battery that can replace the traditional 12 V battery and can be charged from an outside source. Structural batteries are not yet likely to be able to provide enough energy to power an electric car.
Structural batteries are made as laminates and are extremely strong.
“This is a composite of glass fibers and carbon fibers. It is moldable as any composite. Within there is a special electrolyte, not a liquid, but based on a gel polymer matrix. In our research group we have foremost investigated the transport properties of this kind of electrolytes,” explains Patrik Johansson.
Structural batteries can double as various car parts. For example, the Volvo Car Corporation, a partner in the project, managed to replace a metal plenum chamber cover with a lighter composite material that can store energy.
“With this basic idea we avoid the battery being solely a ‘burden’ for the vehicle, says Patrik Johansson. This conceptual thinking we keep in mind for future projects,” says Patrik Johansson.
“It is not at all for sure that the final implementation will be in vehicles. Vehicles have very tough demands on safety, cost, and recycling. But there are perhaps other niches in the future, unknown to us at present. It is the basic idea and the concept itself that is cool!”
