Optimized battery electrodes with primer layers by simultaneous two-layer slot-die coating

Multi-layer coating is a promising method for optimizing the properties of battery electrodes. This study examines the simultaneous coating of anodes with a primer layer without the necessity of a second coating and drying step, as it is the case for sequential coating processes. The primer layer is used to concentrate the binder in proximity to the substrate, thereby enhancing the adhesion strength of the electrode. Two systems comprising anode and primer, differing in rheological properties, are selected for coating investigation. It is demonstrated that the viscosity ratio of the multi-layer coating has a pronounced effect on coating suitability. In a two-layer system, the viscosity ratio also changes with shear rate due to the possibly different shear thinning properties. This results in the observation that combinations with strong viscosity ratios might only be stable in specific coating speed ranges. In contrast, combinations with moderate viscosity ratios exhibit a reduction in stable process windows as the viscosity ratio between the top and bottom layer increases. A mechanical characterization of the adhesion strength of dried and calendered electrodes demonstrated a notable enhancement in adhesion strength when a primer was utilized. In addition, capacity retention tests revealed that the electrochemical properties were not adversely affected by the primer.