Batteries That Double As Structure Could Change How Your EV, Phone and Laptop Are Designed

How carbon fiber could turn car bodies into power sources.

A battery usually sits inside a machine like dead weight. It stores energy, but it does not help a car drive straighter, an aircraft stay aloft, or a phone survive a fall. Now, a team of researchers in Sweden has built a battery that does all of that at once.

I know you must be scratching your head right now, but that’s because you haven’t heard of structural batteries. These are batteries that serve at least two purposes: storing electrical energy like a traditional battery and providing mechanical strength as a load-bearing component, essentially making the device’s chassis or frame its power source.

Engineers at Chalmers University of Technology have created a structural battery that performs up to ten times better than earlier versions of its kind. The advance brings engineers closer to what they call “massless” energy storage, where batteries no longer add weight because they are the structure. Instead of hiding energy inside a heavy box, the battery becomes the box.

When the Battery Becomes the Body

Today’s electric vehicles carry their batteries like backpacks. In some models, the battery alone accounts for roughly a quarter of the car’s total weight, without strengthening the vehicle at all. That extra mass demands more energy, more materials, and more cost.

Structural batteries flip this logic. They integrate energy storage directly into materials that already need to be stiff and strong. In principle, a car door, a bike frame, or even a satellite panel could store electricity while holding everything together.

This idea is not new. The first attempt dates back to 2007, when researchers tried to embed batteries into layered composite materials. Those early designs ran into a stubborn trade-off. They were either mechanically strong but electrically weak, or good at storing energy but too soft to carry loads.

“Previous attempts to make structural batteries have resulted in cells with either good mechanical properties, or good electrical properties. But here, using carbon fibre, we have succeeded in designing a structural battery with both competitive energy storage capacity and rigidity,” said Leif Asp, a professor at Chalmers and leader of the project.

Carbon fiber really was key here. Already prized in aerospace and high-end vehicles for being light and strong, certain types of carbon fiber can also store lithium ions, the same charge carriers used in lithium-ion batteries. That means the fiber can act as a structural beam and as part of the battery’s electrode.

In the new design, carbon fiber serves three roles at once: it bears loads, conducts electricity, and stores energy chemically. This multifunctional approach avoids extra copper wiring and redundant support materials, cutting weight even further.

Strength and Safety

The structural battery reported by the Chalmers and KTH Royal Institute of Technology team reaches an energy density of about 24 watt-hours per kilogram. That is roughly 20 percent of a conventional lithium-ion battery. On its own, that number may sound modest.

But you have to look at the broader context. This battery also has a stiffness of around 25 gigapascals, comparable to many common construction materials. It can genuinely replace parts of a structure, not just tag along. When engineers account for the weight savings across an entire vehicle or device, the trade-off starts to look attractive.

The researchers describe this balance in detail in their 2021 peer-reviewed paper, where they report an “energy density of 24 Wh kg⁻¹ and an elastic modulus of 25 GPa,” a combination that “outperform[s] all previous structural battery materials reported in the literature.”

Lower energy density also brings an unexpected benefit: safety. Batteries with lower concentrations of stored energy are generally less prone to overheating and fires.

Inside the battery, layers of carbon fiber and lithium iron phosphate-coated aluminum are separated by a thin glass fiber fabric. A solid structural electrolyte holds everything together, transferring both mechanical loads and lithium ions.

A 2024 upgrade aimed to replace the aluminum foil with carbon fiber in the positive electrode as well. That kind of change could push energy density toward 75 watt-hours per kilogram and stiffness toward 75 gigapascals, roughly matching aluminum while weighing far less. Let’s not talk about costs for now, although you can expect quite a hefty increase.

Recent all-carbon-fiber designs now reach around 30 Wh/kg, while maintaining or exceeding the mechanical stiffness of aluminum. In some configurations, researchers report elastic moduli above 70 GPa along the fiber direction, putting these batteries squarely in the realm of serious structural materials.

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The Future of Structural Batteries

Newer structural batteries have now survived hundreds to nearly a thousand charge–discharge cycles with very little capacity loss. That matters because, in a structural component, degradation is not just an electrical problem. It can become a mechanical one.

Despite this progress, one number has not changed dramatically. Structural batteries still fall far short of conventional lithium-ion cells, which commonly exceed 200 Wh/kg. That gap remains large, and no one in the field pretends otherwise. The wager is that removing the weight of the battery pack itself can outweigh the lower energy density of the cells embedded in the structure.

Asp is optimistic about where this could lead. “The next generation structural battery has fantastic potential. If you look at consumer technology, it could be quite possible within a few years to manufacture smartphones, laptops or electric bicycles that weigh half as much as today and are much more compact,” he says.

Longer term, the vision extends to electric cars, aircraft, and satellites designed around structural batteries from the start. That would represent a shift not just in battery technology, but in how engineers think about energy, materials, and form. Structural battery composites were highlighted as a top emerging technology in 2025 by the World Economic Forum.

As Asp puts it, “We are really only limited by our imaginations here.”

The findings appeared in the journal Advanced Energy and Sustainability Research.