David Carlstedt

David Carlstedt working on a structural battery cell in Chalmers composite lab.

​Photo: Marcus Folino

First to doctorate on structural batteries

​Structural batteries can both store energy and act as load-bearing materials in a construction. This technology opens the door to major energy savings and new innovations, but it also increases the complexity of the material's behavior. David Carlstedt, first at Chalmers to doctorate with focus on structural batteries, has studied the coupling effects between the various physical processes that occur in this material during operation.

During his doctoral studies, David Carlstedt was part of the research team that in 2021 was able to demonstrate a carbon fiber-based structural battery with unprecedented multifunctional properties. A lot of research has been done that lead to the breakthrough, and the work has taken place across several scientific disciplines and academic institutions. In the project one also wanted to develop a working prototype. David was part of a large interdisciplinary team that was commissioned to build and test such a prototype.

"I have probably built and tested close to 100 batteries over time. When one of them finally worked and showed values ​​that had never been measured before, at first, I had a hard time believing that it was correct. It was a really cool feeling when I understood that we had managed to produce such a good and unique structural battery,” says David.

Structural battery
A carbon fiber-based structural battery cell, with unprecedented multifunctional properties, is here seen lighting up a diode lamp. Image: David Carlstedt

Structural batteries have also been described as "mass-less energy storage". This can be explained by the fact that when the energy storage becomes part of the load-bearing structure, the weight and space previously taken up by the battery also "disappears". This in turn means less material consumption for the same type of construction, which leads to additional weight savings. Another advantage is that the structural battery is ductile and could be used to build, for example, car bodies, bicycle frames or aircraft.

"If you look at how a modern smartphone is constructed, it is, in addition to various electronics, basically one or more batteries with a protective and load-bearing material all around. If energy storage is instead integrated into the casing itself, it could be thinner and lighter, as well as enable new innovative design solutions. If you then apply this technology to vehicles and aircraft, you can make significant improvements in terms of efficiency, because weight plays such a crucial role in energy consumption during transport,” David explains.

Interfering physical processes - a challenge in structural batteries

The structural battery technology has many advantages, but it also has challenges. Crucial to understanding how a material or battery behaves is to be able to compute the physical equilibrium processes for electric charge, mechanical load, heat and mass transport. For example, to avoid overheating in a battery, you must be able to make exact calculations of the heating effects that occur.

To make calculations for physical balance in both batteries and construction materials separately, is well understood and has established calculation models. But if the battery and construction material become one and the same, the complexity increases when the different physical processes affect each other. This is called "coupling effects". In a structural battery, this means, among other things, that the electrochemical processes, which is the battery function itself, affect the load-bearing capacity, and that the mechanical loads in turn affect the electrochemical processes.

"In my research, I have studied different coupling effects between the physical processes and developed new calculation models that can be used to understand the behavior of the structural battery. We have applied and combined interdisciplinary methods. For example, we have used existing methods to solve complex mathematical problems as well as strategies for describing the physical processes and essential couplings. To some extent, there are such coupling effects in different structures in nature, but the material we use for the structural battery is unique in its kind. Therefore, there has been no need to address this particular problem before," David explains.

About the future

Leif Asp leads the research on structural batteries at Chalmers, and he has high hopes about further progress in the near future.

Leif Asp“A lot has happened in recent times, both in terms of scientific progress and interest. Now we have also trained our first doctoral student with a focus on structural batteries. Companies from all over the world have contacted us so there is a huge interest in this technology. We are already in a new project where we hope to be able to produce a structural battery that is about as strong as aluminum, and with a much higher energy density than with the current structural battery. We hope to be able to present the results within the next year,” says Leif Asp.

David Carlstedt has had Leif Asp as a supervisor during his doctoral studies, and he predicts a very bright future for David.

“We are very happy to be able to educate across disciplines in a project like this. David has gained an incredible experience of working in interdisciplinary contexts, and his knowledge will be highly sought after in both academia and industry,” says Leif.

After his doctoral studies, David will start working with structural simulations of batteries at Volvo Cars. David is very much looking forward to this exciting new assignment and believes he will make great use of his knowledge acquired during his doctoral studies. In the automotive industry, there is currently an extensive shift towards electric powered vehicles and batteries play a key role in this. David therefore sees this as a very exciting area to continue his journey in. He also speculates on future uses for structural batteries.

 David Carlstedt

“The electric power technology of the future may consist of several different types of solutions depending on the area of ​​application. In satellites and small aircraft, where low weight is highly sought after, one could imagine that our type of ductile carbon fiber-based structural battery would be a suitable solution. In an electric car, it is conceivable that certain parts of the body or interior are built with structural batteries to, for example, operate window lifts, sound systems or similar. What happens depends very much on how the industry decides to invest and develop this type of technology. Whatever happens, it will be very exciting to follow the development, and hopefully be a part of it,” says David.

David Carlstedt will doctorate on March 17, 2022 with the thesis Computational modelling of structural battery composites.

Text & photo: Marcus Folino

Read more about the structural battery

Page manager Published: Wed 23 Mar 2022.