In the production of electrode foils for lithium-ion batteries, defects often occur due to inhomogeneous coatings. Together with partners from industry and research, Fraunhofer IPM and Fraunhofer ISIT have developed an optical inline measuring system that determines the material composition of electrode foils quantitatively and with depth resolution - directly on the production line. This should enable electrodes for lithium-ion batteries to be manufactured more cost-effectively and to a higher quality in future.
Electrode foils for Li-ion batteries consist of an active material (nickel-manganese-cobalt beads plus lithium), conductive additives and binders. These materials are applied as a suspension to an aluminum foil and then dried to form a thin layer of around 100 µm. It is not uncommon for the components of the suspension to separate during the drying process, so that the binder content is too low in some places. This impairs the adhesion of the overall layer. An optical inline measuring system developed by Fraunhofer IPM and Fraunhofer ISIT in the Q-LIB project together with the companies VARTA and OWIS now makes it possible to actively control the coating process with regard to the mixture. This reduces rejects in production and shortens the start-up time for the production of new formulations.
Inline measuring system with LIBS technology
The inline measuring system is based on laser-induced plasma spectroscopy (LIBS). LIBS is a laser spectroscopic method that can be used to determine the element-specific composition of a sample. The system determines the material distribution in the electrode foil point by point as 3D mapping. This allows both the correct mixing ratio of the components and their homogeneous distribution across the entire electrode volume to be detected. This enables quality control and regulation in real time. The challenge here was to measure the distribution not only on the surface, but also with depth resolution within the entire coating - at production speeds of around 20 m/min.
The measuring system was recently integrated into the laboratory system of an electrode production facility at Fraunhofer ISIT. There, electrode foils from VARTA Microbattery GmbH were successfully measured under real production conditions.
