Evolution Mechanism of Meniscus Formation for Lithium-Ion Battery Electrode Slot Coating with Substrate Heating Module Augmentation

Abstract

In the slot-die coating process for fabricating electrode films in lithium batteries, meniscus instability induces film defects in the coating bead region. This study introduces a substrate heating module into the coating process to investigate the forming mechanism of the coating meniscus and the evolutionary behavior of defects in the anode slurry during the non-isothermal coating process. Initially, the temperature-coating window was established based on the capillary number and minimum wet film thickness. Subsequently, the upstream meniscus position and shape, along with the wetting film edge effect, were investigated under varying coating conditions. Ultimately, the evolution of break-line and air entrainment defects was examined under diverse temperature conditions. The results indicated that regulating temperature at the upstream meniscus can expand the parameter boundaries of the coating window and reduce the apparent dynamic contact angle. The three regions of minimum thickness distribution of wetting films were altered due to the combined effects of coating gap and substrate temperature on slurry viscosity. Heavy edges can be mitigated by increasing the wetting film thickness due to an increase in substrate temperature. However, a narrow coating gap may enhance the flow rate of slurry at the edges of the wet film, consequently increasing edge height. It can be determined that three stages of defect evolution affected by the temperature involving break-line flow, bubble flow and transition flow based on experimental results.

Keywords: Slot-die coating, lithium battery, Temperature-coating window, Edge effect, Defect Evolution