How to choose a lithium battery coating machine

In the production process of lithium batteries, the coating stage is an extremely important pre-processing step, which has a direct and profound impact on the performance and quality of the batteries. The uniformity of coating directly affects the consistency of battery capacity. If the coating is not uniform, the chemical reaction rates of different parts of the battery will be inconsistent, leading to local overheating and rapid capacity degradation during charging and discharging, significantly shortening the battery's lifespan.

Understanding the lithium battery coating machine

(1) What is a lithium battery coating machine

The lithium battery coating machine is the core equipment in the pre-processing stage of lithium battery manufacturing. Its main function is to precisely and uniformly coat the slurry containing positive and negative electrode active substances, conductive agents, and binders onto copper foil or Aluminum Foil and other metal substrates, and then dry and solidify to form electrode sheets, directly determining the battery's energy density, consistency, and safety.

Its working process includes four units: unwinding, coating, drying, and rewinding. The substrate is corrected and tension-controlled before entering the coating unit. The coating thickness is adjusted by an extrusion or transfer coating head (the mainstream extrusion precision reaches ±0.3 μm), and then the solvent is removed by a hot air or infrared drying system. Finally, it is wound into an electrode sheet roll.

(2) The uses of the lithium battery coating machine

Firstly, the positive and negative electrode sheets of lithium batteries need to form a uniform active substance coating on copper foil (negative electrode) or aluminum foil (positive electrode), and the core purpose of the coating machine is to precisely and uniformly coat the slurry containing active substances, conductive agents, and binders onto the substrate surface through a precisely controlled coating head, forming a coating that meets the thickness requirements - this step is the basis for the battery to store and release electrical energy. If the coating is missing or not uniform, the battery will not be able to work properly.

Secondly, the coating machine can adjust the coating pressure, speed, and coating thickness (with an accuracy of ±0.3 μm) to ensure the uniformity and consistency of the electrode sheet coating. This precision control directly affects the battery's energy density (the coating thickness determines the active substance content per unit volume), charging and discharging efficiency (avoiding uneven reactions caused by overly thick coatings), and safety (preventing local overheating due to differences in coating thickness). For example, the high requirements for coating precision in power batteries are to ensure the safety and range of electric vehicles.

Coating material characteristics

(1) Material types

The common coating materials for lithium batteries include positive and negative electrode slurries. They have different special requirements for the coating machine. The positive electrode slurry usually contains cobalt oxide, nickel cobalt manganese oxide, etc. as active substances, as well as conductive agents and binders, and its composition is complex, with extremely high requirements for the uniformity and precision of coating. Because the coating quality of the positive electrode material directly affects the battery's energy density and charging and discharging performance, if the coating is not uniform, it will lead to a decrease in battery capacity, shortened cycle life, and other problems. Therefore, when choosing a coating machine, it is necessary to consider whether the equipment can precisely control the coating amount and thickness of the slurry to ensure the uniform distribution of the positive electrode material on the electrode sheet. The negative electrode slurry is generally composed of graphite and other materials, and its viscosity and fluidity are different from the positive electrode slurry. During coating, it is necessary to ensure that the negative electrode material can fully adhere to the copper foil and maintain good consistency. This requires the coating machine to have a suitable coating method and feeding system that can adapt to the characteristics of the negative electrode slurry and ensure the quality and stability of the coating.

(2) Drying characteristics

Some coating materials are thermally sensitive and have special requirements for drying temperature, humidity, and drying time. For example, some slurry containing organic binders is prone to decomposition or deterioration at high temperatures, affecting the battery's performance. For such thermally sensitive materials, a coating machine with controllable drying temperature and air speed needs to be selected, and the drying system should be able to achieve precise temperature control to avoid damage to the material during drying. In addition, based on the characteristics of the materials, appropriate drying methods can be selected, such as hot air drying and infrared drying. Hot air drying uses hot air to blow dry the coated electrodes, which is suitable for most conventional materials.

Pay attention to key performance parameters

(1) Coating accuracy

Coating accuracy is one of the core indicators for evaluating the performance of lithium battery coating machines. It plays a decisive role in the consistency and quality of lithium batteries. The coating accuracy of lithium battery electrodes is usually measured in micrometers (μm), and the error must be controlled within a very small range. Generally, high-precision coating machines can control the coating thickness error within ±1 μm or even lower. This is like creating a precise work of art, where every detail must be without any deviation to achieve a perfect effect.

High-precision coating machines have many significant advantages. Firstly, they can ensure the high uniformity of the coating thickness of the battery electrodes, allowing the active substances and electrolyte to fully contact during charging and discharging, and the reaction to be more uniform, thereby improving the capacity consistency and stability of the battery. For example, in the application of electric vehicles, a battery pack with high capacity consistency can ensure the smooth power output of the vehicle during driving, avoiding excessive power fluctuations and improving driving safety and comfort. Secondly, high-precision coating helps to increase the energy density of the battery. Precise control of the coating thickness can distribute the active substances reasonably within a limited space, fully exerting the energy storage capacity of the battery, and extending the battery's range.

(2) Coating speed

Coating speed is closely related to production efficiency and is one of the key factors affecting the production efficiency of enterprises. In lithium battery production, the coating speed is usually measured in meters per minute (m/min). A higher coating speed means that more coating operations can be completed in a unit of time, thereby increasing production efficiency and reducing production costs. For example, on large-scale lithium battery production lines, if the coating speed of the coating machine can increase from 50 meters per minute to 80 meters per minute, the output will increase significantly in the same production time, better meeting the demand for lithium batteries in the market.

(3) Drying methods and efficiency

Drying is an important step in the lithium battery coating process. Common drying methods include hot air drying and infrared drying, each with its unique characteristics and application scenarios.

Hot air drying uses hot air to blow dry the coated electrodes, which is a relatively common and widely used drying method. Its principle is to use the convective effect of hot air to transfer heat to the slurry on the electrode, causing the solvent to evaporate rapidly. The advantage of hot air drying is that the equipment cost is relatively low, the operation is simple, and it is suitable for most conventional lithium battery coating materials. It can meet the needs of large-scale production to a certain extent and is an economical and practical choice for some slurry with not particularly strict requirements for drying temperature and speed. For example, for some common lithium battery negative electrode materials, hot air drying can effectively remove the solvent and ensure the quality of the electrode. However, hot air drying also has some limitations. Due to the uneven temperature distribution of the hot air, it can easily lead to inconsistent drying levels of the electrodes, affecting the consistency of battery performance. Moreover, the efficiency of hot air drying is relatively low and the drying time is long, which may affect the production rhythm.

Choosing a lithium battery coating machine is a complex and crucial decision that requires comprehensive and in-depth consideration from multiple aspects. Starting from a clear understanding of one's own needs, based on factors such as production scale and coating material characteristics, precisely determine the type of equipment required, laying the foundation for subsequent choices. Pay attention to key performance parameters, such as coating accuracy, speed, drying method and efficiency, tension control, etc. These parameters directly determine the working quality and production efficiency of the coating machine and are the core indicators for evaluating the quality of the equipment. Assess the quality and brand of the equipment, by understanding the reputation and reviews of well-known brands, as well as examining the manufacturing process and material selection of the equipment, to ensure that the selected coating machine has reliable quality and stability.