Carbon fiber structural battery
Automakers seem to be in agreement that the ‘skateboard’ location for heavy battery packs—low and wide beneath the passenger floor—is the ideal layout for electric vehicles.
Decades from now that might not be the case. Researchers in Sweden have examined the possibility of using the vehicle shell as a battery casing itself—with the carbon-fiber body shell as an electrode.
“If all these functions were part of a car or aircraft body, this could reduce the weight by up to 50 percent,” said Leif Asp, the professor of material and computational mechanics researching these potential dual roles of carbon fiber at Chalmers University of Technology.
The authors of the accompanying paper underscore the potential for the strategy to provide ‘mass-less’ energy storage.
McLaren Monocage II carbon fiber monocoque structure
There are some hurdles even if the scheme does work out. For instance, the type of carbon fiber that works best for the electrode treatment—with the lithium-ion mechanism being studied—has a lower stiffness than that used in airplanes and cars. So some of it would need to be thicker. And sophisticated modeling and manufacturing techniques would be needed to provide a consistent level of orientation and symmetry.
The strategy leaves open plenty of other wider questions, like how it would contend with current battery-pack issues, such as cooling and collision safety. Asp notes that the lower energy density of such a structural battery would make it inherently safer.
Such a strategy could potentially raise a vehicle’s center of mass and make it inherently less stable, however.
It also may be cost prohibitive—requiring not just an entire body to be made of carbon fiber composite, but also varying materials and textures to achieve the right symmetry and strength. In an industry where ubiquitous cell formats are one of the keys to getting per-kwh pricing down, the cost factors alone may keep this idea from ever getting past the drawing board in the foreseeable future.