The growing demand for batteries, driven by the progress in electric vehicles and renewable energy sources, highlights the urgent necessity for efficient manufacturing and improved research in battery technologies. To facilitate the transition of innovations to an industrial Technology Readiness Level (TRL), the Fraunhofer Research Institution for Battery Cell Production (Fraunhofer FFB) is strategically ramping up its pilot line and establishing a dedicated battery research factory.

One key challenge encountered during this ramp-up is the “Heavy Edge” phenomenon, where the wet film is thicker at the edges than at the centre of the electrode. This defect leads to inhomogeneous stress distribution during the calendering process, ultimately causing cell failures. The coating and drying processes are essential in battery production, as they greatly influence the quality and performance of electrodes. Therefore, the aim of this study is to identify the critical parameters responsible for this defect and to implement effective solutions to ensure consistent, high-quality electrode production with the new pilot line.

Initial tests revealed that the defect was mainly caused by uneven slurry coating and rapid over-drying of the electrodes. Based on these findings, a second Design of the Experiments (DoE) was implemented to evaluate the impact of slot-die positioning, adjustments in the shim thickness and temperature distribution in the hot-air ovens. Measurements were performed using an inline laser line sensor based on laser triangulation, enabling precise distance calculations in the micrometre range. The systematic adjustment of these parameters led to significant qualitative and quantitative improvements: the height difference at the heavy edges was successfully reduced on both sides of the electrode.

In conclusion, this study demonstrates that by systematically adjusting the critical coating and drying process parameters, the heavy edge phenomenon can be overcome, enabling the production of high-quality electrodes. By incorporating these optimized parameters, high-performance and reliable battery cells can be consistently manufactured.