Coating is the first core process in the manufacturing of lithium-ion battery electrodes, which refers to the process of uniformly and continuously coating electrode slurry on the surface of metal current collectors (positive electrode is aluminum foil, negative electrode is copper foil). Its core goal is to form an active material coating with uniform thickness, consistent surface density, and no defects, laying the foundation for the consistency, energy density, and safety of battery cells.

The standard workflow mainly includes the following steps:

Slurry transportation and preparation: The pre mixed uniform slurry is pumped through a pipeline to the material box of the coating machine. The material box is continuously stirred to prevent particle settling and ensure stable slurry concentration and viscosity.

Substrate unwinding and pretreatment: The metal foil material is drawn out from the unwinding shaft and maintained in stable transport through a tension control system. Some processes may clean or plasma treat the foil material before coating to enhance its wettability and adhesion with the slurry.

Precision coating and preliminary shaping: The foil is passed through a precision coating head (such as a slit extrusion die slot), and the slurry is continuously and uniformly extruded and transferred to the surface of the foil under pressure, forming a wet coating with a specific width and thickness. The thickness and width of the coating are precisely controlled by the mold gap, pump speed, and substrate walking speed.

Multi stage hot air drying and winding: The coated wet electrode sheet immediately enters a multi temperature zone hot air drying oven that is tens of meters long. Different temperature curves are set for each temperature zone based on the characteristics of the solvent, and the solvent is gradually dried to avoid surface peeling or cracking, forming a firm and smooth dry coating. Finally, the dried polarizer is wound by a winding shaft for use in subsequent rolling processes.

The core value of this process lies in determining the uniformity of the distribution of polar active substances. Accurately controlling the density and thickness of the coating surface is a prerequisite for ensuring the consistency of battery capacity; A high-quality coating without defects such as stripes, particles, or thick edges is the cornerstone for obtaining low internal resistance, high safety, and long cycle life batteries.