In-line Sensor-based Process Control of the Calendering Process for Lithium-Ion Batteries

The calendering process is the final property-defining step in the manufacturing of electrodes for lithium-ion batteries. Calendering significantly affects mechanical properties by compacting the electrodes and increases the lithium-ion batteries’ volumetric energy density. The choice of calendering parameters is primarily based on empirical data, considering the final battery cell properties. The drive for increased energy densities and the corresponding high compaction rates results in an increased electrode defect and scrap occurrence. This leads to challenges in process control which are addressed in this paper by developing an agile and predictive sensor-based process control. Hereby an efficient determination of process parameters is enabled, resulting in a reduction of scrap and manufacturing costs. Applying in-line data acquisition for electrode thickness and surface topography allows real-time feedback of measurement data at the machine-product interface back into the calendering system control. Reliable data acquisition is established by integrating two sensor systems for coating thickness measurement (confocal sensors) and defect detection (laser triangulation sensor) in a cascaded arrangement, enabling real-time evaluation of the product properties achieved as a function of the process parameters. The associated potentials and challenges regarding a predictive analysis of machine and product behavior are addressed in this context. The experimental results demonstrate that the combination of both sensor systems offers the potential to establish an agile and innovative process control for the calendering process of lithium-ion batteries.