Systematic Investigation of the Residence Time Distribution in a Twin-Screw Extruder for the Continuous Mixing Process of Electrode Slurry in the Battery Cell Production

Due to high scrap rates and manufacturing costs, battery cell production requires continuous process optimization. The potential for material efficiency is particularly high in electrode production, specifically in the mixing process. Challenges in the continuous mixing process are related to automation and traceability of material. As one of the most relevant parameters, the residence time of particles must be known, otherwise it is not possible to make a statement about the traceability of the slurry ingredients. Without knowledge of the residence time distribution (RTD), autonomous process control or traceability of battery cells and their components is not possible. The influence of process and material parameters on the RTD of the continuous mixing process in battery cell production is being systematically investigated. Based on a design of experiment, the mean residence time and the RTD are determined for a graphite-based anode slurry by manipulating the conductivity by adding a tracer. Special attention is given to the properties of the tracer as well as the tracer behavior within the mixing process. The influence of different parameters is analyzed based on the conductivity changes. It is shown that the parameters mass flow and solid content have the greatest influence on the RTD.