The world of automotive has undergone a considerable transformation in the last decade, conditioned above all by emissions and pollution, which have opened the way to electric mobility.

But this mobility is full of challenges, so much so that its constant growth is slower than one would expect. One of the main reasons has to do with the batteries that move the electric carswith an autonomy that, in most cases, is usually limited, and that, in addition, takes a long time to recharge, not to mention public charging points and the difficulties of charging them outside the installation that one may have at home.

The batteries They are, let’s say, elements that are separate from the car, are manufactured separately and then integrated. They are very heavy and are usually placed on the floor of the vehicle and their only function, which is not a small one, is to provide energy, but they do not contribute to the resistance and rigidity of the body, rather they compromise it.

For this reason, the real challenge faced by the electric mobility for it to finish exploding, for the consumer to really bet on it, is directly related to the advancement of new batteries, and the industrial race is being fierce, especially in China, where they have the elements, or, rather, the rare earths, necessary to optimize them. Although in the United States and Europe they are also looking for efficient alternatives that do not depend on supplies from the Asian giant.

This is where an alternative arises that comes from our continent, from Sweden, and that precisely wants to change the indicated approach, that of heavy batteries that are installed in the lower part of the vehicle and that only provide energy.

In Davos, at the World Economic Forum, a project from the Chalmers University of Technology called a structural battery was presented, a carbon fiber composite material that can store electrical energy at the same time that it can support the mechanical load of the vehicle, that is, a battery that acts, in a certain way, as a chassis.

This technology could reduce the weight of a car by 25%, there would no longer be separate batteries, and the less weight, the more efficiency and more autonomy, up to 70% more according to research calculations.

structural battery

The structural batteries They aim to combine two functions, the ability to support the load and the ability to store energy, something that had not been done until now. The idea is to embed battery cells inside composite materials such as carbon fiber. A conventional battery adds weight and takes up space, but in this way, the total mass is reduced and mechanical resistance is not renounced, it can even be improved.

The comparison that the researchers themselves use is that of a human skeleton: just as bones support the body and at the same time produce blood cells, this material supports the weight of the car and stores energy at the same time. When the battery becomes part of the structure, its mass, in practice, “disappears”, hence the term “massless” energy storage.

The element used is carbon fiber as an electrode and as structural reinforcement at the same time. Carbon fiber is the negative electrode, where it also acts as a current collector and active material, which makes it possible to dispense with copper and silver and further reduce weight. In the latest version, the positive electrode is also carbon fiber, in this case coated with lithium iron phosphate, with a fiberglass fabric as a separator between the two. Thanks to this configuration, electrical energy can be stored while simultaneously withstanding mechanical stress.

It is worth putting the achievement in context: Chalmers has been at this since 2018, when Professor Leif Asp’s team demonstrated for the first time that carbon fiber could store energy, and has developed the work in different phases together with the KTH Royal Institute of Technology in Stockholm. The most recent leap, published in the journal Advanced Materials, multiplies the multifunctional performance of the first prototypes by ten.

Less weight and more space

If this idea is consolidated, we would be talking about a radical change in terms of what an electric car is today. If the batteries no longer have to be installed independently, space will be gained, and weight will also be reduced, since the structural battery itself would perform several functions at the same time. In fact, the weight could be reduced by 25%. And this implies more performance, and above all, more autonomy, since a lighter car does not need as much energy to move, and that is where we can find the most striking figure of this project, because they say that there would be 70% more autonomy.

And not only that, there would be more interior space, which could be used in many ways, to fit passengers better, for storage, or the designs of many of the current cars could be changed. The possibilities are many and varied.

The applications, in fact, go far beyond the car. The researchers themselves calculate that this technology could reduce the weight of a laptop by half or make a mobile phone as thin as a credit card, in addition to being interesting for electric bicycles, airplanes or satellites, precisely because of this weight saving.

The challenge of energy density

If there is something that still needs to be worked on with this new system, it has to do with the energy density, 30 watt hours per kilogram, a figure that is well below the 250 or 300 watt hours per kilogram that are capable of reaching the conventional lithium ion batteries that are installed in electric cars. Although researchers say that this difference is offset by the benefits of weight, space and autonomy.

These 30 Wh/kg represent around 20% of the capacity of a current lithium battery, but also, and this is important, a lower energy density translates into greater safety, an especially sensitive issue when the battery is at the same time the bodywork that protects the occupants.

The researchers insist that this difference is offset by the structural benefits of the system; by eliminating independent structural components and the battery casing itself, the balance of the entire system is much more favorable than the isolated energy density figure suggests.

Of course, it is advisable not to get too excited: it is still a laboratory development, and those responsible themselves recognize that there are still years to see it in a street car, with open challenges such as increasing energy density, industrializing the manufacture of carbon fiber and reducing its cost. Chalmers has created a spin-off company, Sinonus, to try to make precisely that leap from the laboratory to the market.

What is clear is that the industry has identified what is needed to drive growth. electric carbatteries, and for this reason, a multitude of projects and works are being carried out to promote this mobility.