<p>This study investigates the slot-die coating process for lithium-ion battery electrodes through numerical simulations. A computational framework is established by innovatively incorporating the GAP zone between the die lip and the moving substrate into the model, enabling accurate simulation of non-Newtonian slurry flow in flow channels spanning meter-scale cavities to micron-scale outlets. Compared with experimental data, the simulated inlet pressure exhibits less than 5% error, while wet film uniformity aligns closely with measurements, confirming the model’s validity. The slurry flow behavior and the effects of die geometry, process parameters, and slurry properties on wet film morphology are systematically analyzed. Results reveal three primary nonuniform wet film patterns: edge bulges, central bulges, and edge trailing. Critical factors include the auxiliary manifold design, slit channel expansion chamfer angle, die lip thickness, and slurry viscosity. Edge bulges originate from nonuniform velocity fields at the main manifold-slit channel junction and are significantly mitigated by adding an auxiliary manifold. Central bulge uniformity improves with smaller pressboard dimensions, higher slurry viscosity, and increased die lip thickness. Edge trailing, caused by velocity inhomogeneity at the slit channel exit, is suppressed by reducing the expansion angle or increasing the expansion depth. These findings provide actionable guidelines for optimizing lithium-ion battery electrode manufacturing.</p>