Fraunhofer FEP has introduced a roll-to-roll production process for manufacturing metal-on-polymer current collectors intended for lithium-ion batteries. Using electron beam evaporation, copper and aluminum layers up to 1 µm thick per side are deposited onto 12 µm PET films over roll widths up to 60 cm. These composite current collectors match the electrical conductivity and thickness of conventional metal foils while offering reduced weight and added safety.
During the development, the research team optimized parameters including web speed, substrate pretreatment and metal evaporation rates. A gas-cooled drum supplied by VON ARDENNE GmbH minimized thermal load on the polymer substrate, maintaining film integrity and productivity. Project manager Claus Luber noted that balancing layer thickness with electrical conductivity was critical to meet battery production requirements.
In safety tests, the polymer substrate acts as a built-in fuse: if a short circuit occurs, the polymer melts and breaks the current path, preventing thermal runaway. This feature addresses fire risks associated with lithium’s flammability and reactivity during overcharge, damage or overheating.
As part of the PolySafe project funded by the German Federal Ministry of Education and Research (BMBF), the new process was scaled to semi-industrial levels. The resulting metal-on-polymer collectors were integrated into pouch cells by project partner TU Braunschweig’s Battery LabFactory. Electrochemical testing showed that cells with composite collectors achieved performance and cycle stability comparable to cells using conventional metal foils across various charge and discharge rates.
The successful demonstration under semi-industrial conditions lays the groundwork for industrial adoption of metal-on-polymer current collectors. By reducing collector weight and enhancing inherent safety, the process offers a pathway to higher energy density and lower fire risk in next-generation lithium-ion batteries. Industry stakeholders can leverage these findings to further refine battery designs and manufacturing processes.
Source: Fraunhofer Press Release
