Numerical and experimental investigation on the defect formation in lithium-ion-battery electrode-slot coating

Defect-free slot coating is important in the design and manufacturing of lithium-ion-battery electrodes. However, the defect formation in electrode-slot coating is not clearly understood because of the involvement and coupling of many parameters. Here, we investigate the defect formation mechanisms in electrode-slot coating by using numerical and experimental methodologies. Three defects, namely, striped, spotted, and irregular, are observed. The striped defect is related to downstream menisci contraction; however, the spotted and irregular defects are associated with the unstable development of the sawtooth dynamic contact line. In addition, three regions for the capillary number and minimum-thickness-based coating window are found, and the dominant force in each region is clarified. The results indicate that a higher maximum coating speed can be obtained for a lower coating gap, and the maximum coating speed of the underbite die configuration increases by 25.6% compared with that of the normal die configuration.