Structured battery could pave the way for lighter, energy-efficient cars

A newly developed structured battery could increase the driving range of an electric car by up to 70% on a single charge, halve the weight of a laptop and make a mobile phone as thin as a credit card.

Researchers at Chalmers University of Technology have made an advance in ‘massless energy storage’ with a device that functions as a battery as well as a load-bearing structure, reducing the weight and energy consumption significantly.

“We have succeeded in creating a battery made of carbon fibre composite that is as stiff as aluminium and energy-dense enough to be used commercially. Just like a human skeleton, the battery has several functions at the same time,” said Richa Chaudhary, Chalmers researcher and first author of a scientific article recently published in Advanced Materials.

Lower weight, reduced energy requirement

Research on structural batteries has been going on for many years at Chalmers, and in some stages also together with researchers at the KTH Royal Institute of Technology in Stockholm, Sweden. When Professor Leif Asp and colleagues published their first results in 2018 on how stiff, strong carbon fibres could store electrical energy chemically, the advance attracted significant attention.

Since then, the research group has further developed its concept to increase both stiffness and energy density. The previous milestone was reached in 2021 when the battery had an energy density of 24 watt-hours per kilogram (Wh/kg), which means roughly 20% capacity of a comparable lithium-ion battery, according to the researchers. Now it's up to 30 Wh/kg. While this is still lower than today's batteries, the conditions are quite different. When the battery is part of the construction and can also be made of a lightweight material, the overall weight of the vehicle is greatly reduced. Then, not nearly as much energy is required to run an electric car, for example.

“Investing in light and energy-efficient vehicles is a matter of course if we are to economise on energy and think about future generations. We have made calculations on electric cars that show that they could drive for up to 70% longer than today if they had competitive structural batteries,” said research leader Leif Asp, who is a professor at the Department of Industrial and Materials Science at Chalmers.

When it comes to vehicles, of course, there are high demands on the design to be sufficiently strong to meet safety requirements. There, the research team’s structural battery cell claims to have significantly increased its stiffness, or more specifically, the elastic modulus, which is measured in gigapascals (GPa), from 25 to 70. This means that the material can carry loads just as well as aluminium, but with a lower weight, according to the researchers.

Long road to commercialisation

From the start, the goal was to achieve a performance that makes it possible to commercialise the technology. In parallel with the fact that the research is now continuing, the link to the market has been strengthened — through the newly started Chalmers Venture company Sinonus AB, based in Borås, Sweden.

However, there is still a lot of engineering work to be done before the battery cells have taken the step from lab manufacturing on a small scale to being produced on a large scale for our technology gadgets or vehicles.

“One can imagine that credit card-thin mobile phones or laptops that weigh half as much as today, are the closest in time. It could also be that components such as electronics in cars or planes are powered by structural batteries. It will require large investments to meet the transport industry's challenging energy needs, but this is also where the technology could make the most difference,” said Asp, who has noticed a great deal of interest from the automotive and aerospace industries.

The latest advances in this area have been published in the article ‘Unveiling the Multifunctional Carbon Fibre Structural Battery’ in Advanced Materials. The research has been funded by the Wallenberg Initiative Materials Science for Sustainability (WISE) programme.

Image credit: Chalmers University of Technology | Henrik Sandsjö