When lithium-ion batteries become damaged or destabilised (or if they are faulty), they can present a fire risk. While the risk in electric vehicles (EVs) is currently estimated at around one in 12 million, as more and more electric cars are made, combustion incidents will become more frequent. Scientists at the Technical University of Braunschweig (TU Braunschweig) have therefore set out to increase the safety of these batteries by developing new kinds of current collectors.

In the “Polysafe” project the TU’s Battery LabFactory Braunschweig (BLB) is working together with two Fraunhofer institutes and several commercial partners and it is funded by the Federal Ministry for Economic Affairs and Energy with EUR 4 million over the next three years.

At the moment, current collectors for EVs are made from thin metal foil that is highly conductive. The project will focus on making aluminium or copper-polymer polymer composite collectors that inhibit the thermal runway and stop them from catching fire. Basically, when a critical temperature is reached, the polymer melts and the current is interrupted preventing short circuiting.

The feasibility of the metal-polymer collector has already been demonstrated by two of the project partners - Von Ardenne GmbH and Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology (FEP) in an earlier project called “PolyCollect”. PolySafe will build on their findings with specific application-oriented evaluation. It will try out different formats (e.g. round cell or pouch cell) and battery designs according to the function of the application and investigate how the new metal-polymer collectors can be integrated into current production processes.

The other partners in the project are Brückner Maschinenbau GmbH & Co. KG, Fraunhofer Institute for Surface Engineering and Thin Films (IST) and Varta Microbattery GmbH.