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May 26 2025Lithium-ion battery positive electrode ceramic edge coating: Why is there always a problem of cross-linking?
In lithium-ion battery manufacturing, coating the edge of the positive electrode with a ceramic layer is an important process to improve battery safety and electrical performance. However, during the coating process, the problem of material mixing between the ceramic and the dressing area occurs frequently, which directly affects the battery yield and consistency. This article analyzes the root causes of material mixing from four dimensions: slurry characteristics, material adaptation, process parameters, and equipment operation, and explores optimization directions.
1. Slurry properties
The viscosity, solid content and thixotropy of lithium-ion battery slurry directly affect the coating uniformity. If the slurry viscosity is low (such as the NMP solvent ratio is not controlled), insufficient surface tension can easily lead to uncontrolled edge diffusion and blurred boundaries between the ceramic layer and the dressing area. In addition, slurries with poor thixotropy are difficult to quickly restore viscosity under the shear force of the coating head, resulting in edge accumulation. For example, lithium iron phosphate battery slurry has a higher density of active materials, so it is necessary to accurately control the rheological properties of the slurry to avoid stratification.
2. Chemical Compatibility of Ceramics and Slurry
The compatibility of ceramic coatings (such as alumina) with lithium-ion battery cathode slurries is critical. Alumina may react weakly with the solvent NMP to form a gel material, change the local viscosity, and cause abnormal flow. In addition, the polarity difference between ceramics and active materials may lead to interface stratification, especially in lithium iron phosphate battery systems, where the ceramic composition and dispersion process need to be optimized to reduce interface stress.
3. Process parameters
When the coating speed exceeds 8m/min, the slurry does not have enough time to spread on the current collector, and it is easy to diffuse to the edge and form a string of materials. At the same time, if the scraper gap is too large, it is easy to cause "edge collapse", and if it is too small, the slurry will be squeezed out due to excessive shear force. For example, lithium-ion batteries used in energy storage systems require higher coating accuracy, and it is necessary to dynamically adjust the pump speed to match the coating speed to ensure edge uniformity.
4. Equipment and Operation
Insufficient equipment sealing or pressure fluctuations in the buffer tank can cause slurry leakage and affect edge stability. During operation, deviations in the parallelism of the coating head may cause unilateral accumulation, and changes in temperature and humidity (such as high temperature accelerating solvent volatilization) can significantly change the rheology of the slurry. Especially in the large-scale production of energy storage systems, environmental control and equipment maintenance are the core links in the prevention and control of cross-materials.
Positive electrode ceramic coating technology is the key path for lithium-ion batteries to move towards high safety and long life, but the problem of cross-linking needs to be solved in a coordinated manner from multiple dimensions including slurry design, material adaptation, process refinement and equipment stability.
Positive electrode ceramic coating technology is the key path for lithium-ion batteries to move towards high safety and long life, but the problem of cross-linking needs to be solved in a coordinated manner from multiple dimensions including slurry design, material adaptation, process refinement and equipment stability.
