Analysis of side heavy edge reduction of battery electrode using high speed blade coating process

Abstract

Superelevation of the side edge, also known as heavy edge, is a defect that negatively affects Li-ion battery manufacturing and needs to be mitigated. In this study, we experimentally analyze heavy edge defects in battery anode slurry coatings. For this purpose, battery anodes are manufactured using a high-speed blade coating apparatus, and phenomenological observations of the heavy edge morphology development under process condition changes are conducted. The results indicate that the coating gap has the greatest effect on heavy edge defects, followed by the die lip length, whereas the substrate speed has the least effect. Furthermore, stress-strain modeling is employed to identify the heavy edge mitigation conditions regarding shear deformation by flows inside the coating gap and the subsequent viscoelastic response of the anode slurry. The model suggests a guideline for understanding the relationship between the heavy edge morphology and process conditions, a previously unexplored area. Furthermore, electrochemical analysis confirms that the defects can be minimized from a process point of view without degrading of the electrochemical performance. These results suggest a rudimentary understanding and research method for analyzing cross-web directional defects in the battery electrode manufacturing process from the perspective of the rheological properties of battery slurry.