Researchers at the Fraunhofer Institute for Electron Beam and Plasma Technology (FEP) have developed a roll-to-roll manufacturing process for producing metal-on-polymer current collectors – lightweight composite structures that replace conventional metal foils in lithium-ion batteries.
The technique applies copper and aluminum layers onto both sides of PET substrates via electron beam evaporation, delivering conductivity and thickness comparable to traditional foil collectors, while introducing enhanced safety features such as thermal shutdown capabilities. In the event of a short circuit, the polymer substrate melts, interrupting current flow and mitigating thermal runaway.
This breakthrough is part of the PolySafe project, funded by Germany’s Federal Ministry of Education and Research (BMBF). Project lead Claus Luber noted the challenge of balancing conductivity, mechanical integrity and heat control – overcome by precise tuning of parameters including web speed, surface pretreatment, and the use of a gas-cooled drum from VON ARDENNE to ensure substrate stability.
Production results:
- Copper: Up to 1μm per side on 12μm PET film; compact layers achieved without wrinkling.
- Aluminum: Similarly applied via two-stage process; films remained smooth and suitable for electrode integration.
Partner TU Braunschweig fabricated pouch cells using Fraunhofer’s coated films and validated their electrochemical performance. Results confirmed comparable cycle stability and charge/discharge behaviour to conventional reference cells.
Fraunhofer FEP’s scalable process marks a promising step toward lighter, safer, and more energy-dense lithium-ion batteries – offering manufacturers a semi-industrial production pathway for next-generation current collector designs.
Image: Electron beam evaporated copper-coated polymer film for use as a metal-on-polymer current collector for battery cells. © Fraunhofer FEP, Finn Hoyer
