By Irina Slav
Imagine an electric car that’s lightweight and fast, and can go for hundreds of miles on a single charge. This car would not have a battery pack to weigh it down. Its batteries would be part of its body. Structural batteries have been around at least since the 2000s when the U.S. military designed the first ones out of carbon fiber, which is a conductive material. It is also notoriously lightweight, and things can be built from it, including car bodies.
Tesla’s Elon Musk announced at the company’s Battery Day it was going to start incorporating the batteries into the chassis of the cars. It was time to do away with the “skateboard” pack and mold the battery cells into the body of the vehicle. Musk called it revolutionary. Scientists who have been working on structural batteries for years must have rolled their eyes.
“He’s essentially doing something that we did 10 years ago,” Emile Greenhalgh, a materials scientist at Imperial College London and the Royal Academy of Engineering Chair in Emerging Technologies, told Wired. “What we’re doing is going beyond what Elon Musk has been talking about. There are no embedded batteries. The material itself is the energy storage device.”
Greenhalgh is one of the researchers pursuing the path of structural batteries that are not a separate object from the car they are put in but rather a component of it because the battery is essentially the material, from which the body—or any other part—is made.
Structural batteries most simply consist of two layers of carbon fiber polymers, one with a negative and the other with a positive charge for anode and cathode, and with an insulation layer of fiberglass between them. The material can be used to build the whole body of a car, theoretically.
Designing an actual working structural battery has been challenging. In 2018, the Smithsonian Magazine reported on one such project, from the Chalmers University of Technology, led by professor Leif Asp. For all the promise structural batteries held, the project team found it hard to make a working one.
“The carbon fibers that are available on the market, they have been made for structural applications or made for electrical applications,” Asp told the Smithsonian Mag at the time. Asp, Greenhalgh, and others are still working on developing a composite material that can do both but, according to Greenhalgh, the research took a while to get enough funding to progress. This year, the two scientists and their team even completed a project that aimed to develop structural batteries for aircraft.
Hypothetically, structural batteries could jeopardize the future of “normal” lithium-ion batteries—a technology that carmakers have spent millions upon millions on. GM is building a whole new battery plant in Ohio, and it will not be producing structural batteries. In Europe, Volkswagen is adapting one part of a factory complex in Germany to start producing EV batteries from 2024. The stakes that major carmakers have placed on the electrification of transport are high.
Yet structural batteries seem to need more work. Asp, Greenhalgh, and a team of other scientists in 2013 completed a three-year project dubbed Storage that resulted in the successful incorporation of a commercial lithium-ion battery into a structural component of a Volvo. The battery was small, though, and could only power the air-conditioning system, the stereo, and the lights when the engine was off for a short time. It will probably be a while before they live up to the promise—but what a glorious promise it is, for cars made up of batteries instead of having batteries installed in them.