High-speed slot-die coating of primer layers for Li-ion battery electrodes: model calculations and experimental validation of the extended coating window depending on coating speed, coating gap and viscosity

Abstract

AbstractIn the battery industry, very thin primer layers are used to improve electrode adhesion on substrates or act as blocker layers to prevent corrosion in case of aqueous cathodes. For these material configurations, high-speed coating is mandatory to ensure the economic viability of the process. One way to realize high-speed coating is a set-up including a slot die and a vacuum box to stabilize the coating bead. Knowledge and prediction of the coating window of thin wet film thicknesses is crucial to design the production process. Therefore, the influence of coating gap and viscosity of shear-thinning fluids on the coating window is investigated with the help of various model fluids. In addition, a prediction model for the calculation of the coating window for high-speed slot-die coating with vacuum box is developed. This model is shown to be valid for the prediction of the coating window for the investigated material systems and coating gaps over the investigated range of coating speeds up to 500 m min−1. For a material system, which corresponds to a real material system for adhesive primer coatings, it is possible to reach a target wet film thickness of 20–25 µm. This would correspond to a layer thickness of 0.5 µm for a solid content of 2–2.5 wt%.