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Swedish researchers report rapid advances in the development of so-called massless electricity storage systems. This includes batteries that combine structural components with energy content.
First of all: the massless structural battery developed by the Swedish scientists should not be confused with the approach pursued by Tesla, among others, of using batteries in a sandwich construction as structural components, for example as a floor assembly.
The structural battery, which is jointly developed by Chalmers University of Technology and the KTH Royal Institute of Technology, has nothing to do with ordinary battery technology. The massless energy storage of the Swedes look like ordinary components for the respective purpose, which have been expanded to include the possibility of storing energy.
Carbon fibers lead to higher stiffness
Research has been carried out on the structural battery for years. Successes were communicated rather sparsely. The project is supported by the European Commission’s Clean Sky II research program and by the US Air Force.
While it was possible in the past to develop cells that had either good mechanical or good electrical properties, project leader Leif Asp, professor at Chalmers University, can now announce a breakthrough.
With the current generation of the structural battery, it was “possible to use carbon fibers to design a structural battery that has both competitive energy storage capacity and rigidity,” said Asp Gigapascal offer. This means that the energy density is still well below that of conventional lithium batteries.
The key difference to earlier prototypes is that carbon fibers are used as the negative electrode, while an aluminum foil coated with lithium iron phosphate serves as the positive electrode. The carbon fiber acts as a host for the lithium and thus stores the energy. The mechanical properties are equally influenced by carbon fiber and aluminum foil.
The two electrode materials are kept separated by a glass fiber fabric in a structural electrolyte matrix, whereby it is the task of the electrolyte to transport the lithium ions between the two electrodes of the battery. In addition, they should transfer the mechanical loads between the carbon fibers and other parts.
Project starts in next phase
Although this is already working quite well, the research project will move on to the next phase. This consists of using carbon fibers in the positive electrode as well and doing without the aluminum foil.
Project manager Asp estimates that in this way an energy density of 75 watt hours per kilogram and a rigidity of 75 gigapascals should be achieved. This would make the structural battery about as strong as aluminum, but much lighter. And the energy density then slowly reaches values at which it starts in a conventional lithium battery.
As a first step, Asp sees great potential for smartphones, laptops and electric bicycles, which can be made much lighter and more compact thanks to the structural battery. The Swedish researchers are also looking at use in electric cars, for example.
The new technology should be available in around two years for use in comparatively small devices.
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