A team of researchers in Sweden has developed structural batteries made from carbon fiber composite, as strong as aluminum and with enough energy capacity for commercial use.
The breakthrough structural battery comes from Sweden’s Chalmers University of Technology, setting a new record with an energy density of 30 Wh/kg. While this figure pales compared to traditional lithium-ion rechargeable batteries (which have an energy density of 100–265 Wh/kg), it marks a significant step towards commercial viability.
How is this possible? The key lies in the battery’s dual functionality, expanding its range of applications. “We have succeeded in creating a carbon fiber composite structural battery that is as strong as aluminum and has enough energy density to be commercially viable,” explains Richa Chaudhary, a researcher at Chalmers and lead author of the study.
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What Are Structural Batteries?
Structural batteries are multifunctional devices capable of storing electrical energy while simultaneously bearing mechanical loads. This relatively new concept in energy storage emerged from the need to reduce the weight of batteries in electric vehicles. Lighter units with good capacity can improve the integration of energy storage in vehicles, helping to extend their range.
While most research focuses on increasing energy density (the amount of energy stored relative to weight), some studies have opted for multifunctionality, designing devices that can replace physical components within a system.
This is how structural batteries were born—rechargeable units that can reduce weight by up to 20% when used as vehicle load-bearing structures. But the potential doesn’t stop there. A structural battery could, for example, halve the weight of a laptop or make a cell phone as thin as a credit card.
Carbon Fiber for Both Electrodes
In this context, polyacrylonitrile-based carbon fibers are currently the best material for electrodes, offering a good balance between mechanical and electrochemical properties. They can serve as reinforcement, an electrical collector, and active material. However, until recently, carbon fiber was mostly used in multifunctional batteries at the negative electrode level.
Researchers Richa Chaudhary, Johanna Xu, Zhenyuan Xia, and Leif Asp from Chalmers University of Technology have taken this research to the next level. The team used carbon fiber for both the negative and positive electrodes, coating the latter with lithium iron phosphate and adding a thin cellulose separator. All components were then embedded in the structural battery’s electrolyte and polymerized to provide rigidity.
“Since carbon fiber conducts electrons, the need for current collectors made from copper or aluminum is reduced, which further lowers the overall weight,” explains the university. “Nor are conflict metals like cobalt or manganese required in the electrode design.”
The Best Multifunctional Structural Battery
The results are impressive: the structural battery composite demonstrates an energy density of 30 Wh/kg and a cycle stability of up to 1,000 cycles with nearly 100% coulombic efficiency. The elastic modulus—indicating the material’s ability to bear stress—exceeds 76 GPa, the highest value reported for these types of storage devices. In other words, the material can withstand loads similar to aluminum while being lighter.
“In terms of multifunctional properties, the new battery […] is the best ever made globally,” says Leif Asp, studying structural batteries since 2007. However, the team remains realistic about the future, acknowledging that much work is still needed before large-scale production can begin. The research was published in Advanced Materials.
