What Does the Coating Process in Lithium-ion Battery Manufacturing Entail?

It is well known that the substrate for the positive electrode in lithium-ion batteries is aluminum foil, while the substrate for the negative electrode is copper foil. Following the coating process, these materials are transformed into rolls of positive and negative electrode sheets for use in subsequent manufacturing stages. The quality of these electrode sheets largely determines specific battery performance characteristics; therefore, electrode coating is a critical step in the overall battery manufacturing process!

Coating technology has evolved from early methods like dip coating and extrusion coating to state-of-the-art simultaneous double-sided coating—advancements aimed at enhancing the coating quality and performance of the electrode sheets. Producing reliable lithium-ion batteries typically requires high-quality, high-cost electrode coating equipment.

ACEY-HFC260 film coating machine is dedicated to the continuous coating process of cathode and anode electrode of lithium ion batteries, suitable for small-scale experiments in colleges and enterprises.

The general coating process flow is as follows: the coating substrate (metal foil) is unwound by an unwinding unit and fed into the coating machine. After the ends of the substrate are joined on a splicing table to form a continuous strip, the material passes through a traction unit into tension regulation and automatic edge-guiding systems. Once the running tension and alignment are adjusted, the substrate enters the coating unit. Inside the coating unit, electrode slurry is applied to the substrate in sections according to preset coating weight and uncoated gap length specifications. For double-sided coating, the system automatically tracks and aligns the second side based on the coating status and gap length of the first side. The wet coated electrode sheets are then conveyed into a drying tunnel; drying temperatures are set based on coating speed and thickness. After drying, the electrode sheets undergo tension adjustment and automatic edge-guiding before being wound into rolls for the next process step.

Electrode slurry coatings are relatively thick with high coating weights, resulting in a significant drying load. Currently, the industry widely employs hot-air impingement drying technology. Aluminum foil, used as the positive electrode substrate, is chemically highly reactive and prone to oxidation; however, a dense oxide film forms on its surface during manufacturing, preventing further oxidation. Because this surface oxide film is thin, porous, soft, and highly adsorbent, exposure to high-temperature and high-humidity environments can damage the film and accelerate the oxidation reaction. Currently, most manufacturing processes employ single-sided coating; while one side is being coated, the other remains fully exposed to hot air. The hot air temperature used for drying (in solvent-based systems) is typically around 130°C. If the moisture content in the hot air is not effectively controlled, the oxidation of the aluminum foil intensifies, compromising the adhesion between the cathode material and the foil—or, in severe cases, causing the material to delaminate.

To address the energy efficiency and aluminum foil oxidation issues associated with single-sided coating equipment, some leading companies have developed simultaneous double-sided coating technology. While this technology effectively resolves the oxidation challenge, the equipment is prohibitively expensive for many standard battery manufacturers.

In summary, the coating process for lithium-ion batteries is far more complex than a simple two-step sequence of "slurry application and drying." From substrate unwinding and double-sided alignment to hot-air drying and oxidation prevention, the selection of every process parameter is critical to the quality of the final electrode sheet. To achieve high performance, safety, and longevity in lithium-ion batteries, companies must continue to invest heavily in coating equipment, process technology development, and environmental control capabilities. As simultaneous double-sided coating technology matures, the process is expected to strike a better balance between cost and performance, thereby driving the entire lithium battery industry toward higher quality and lower energy consumption.

Acey New Energy is specialized in researching and manufacturing of high-end equipment for lithium-ion batteries. We can provide one-stop solution for lithium ion battery production line for cylindrical battery, coin cell, pouch cell.