Introduction
In the manufacturing process of energy storage devices, the uniform coating of cathode paste on aluminum foil is a key link. The coating quality directly affects the stability of the subsequent process and the performance of the final product. This article will systematically elaborate on the characteristics of slurry, coating process, influencing factors and detection methods, aiming to provide reference for relevant technicians.
Slurry characteristics
Cathode slurry is usually composed of active substances, conductive agents, binders, and solvents, and is a non-Newtonian fluid. The rheological behavior has a significant impact on the uniformity of coating. The relationship between the viscosity η and the shear rate γ of the slurry can be described by the power law model: η = Kγ^(n-1), where K is the consistency coefficient and n is the flow index. When n is less than 1, the slurry exhibits shear thinning properties, which is conducive to obtaining a uniform wet film during the coating process.
Coating process
Common coating methods include comma scraper coating, slit extrusion coating, etc. Comma scraper coating controls wet film thickness by adjusting squeegee clearance, substrate speed, and slurry feed. slit extrusion coating uses a precision pump to transport the slurry to the slit of the mold, and is coated on the surface of the aluminum foil under pressure. The process parameters need to be optimized according to the rheological properties of the slurry and the target coating volume.
Influencing factors
Coating uniformity is affected by multiple factors. The solid content, viscosity and stability of the slurry are the basic factors. Process parameters such as coating speed and drying temperature curve directly affect the leveling and curing process of wet film. The surface roughness, cleanliness and tension control of aluminum foil also have an effect on coating quality. Environmental conditions such as temperature and humidity need to be stable to reduce batch variations.
Detection method
Coating uniformity can be quantitatively evaluated by a variety of means. Online testing can use a β-ray thickness gauge to monitor the fluctuation of coating amount in real time. Offline analysis includes: measuring dry film thickness using a micrometer; The coating amount per unit area is calculated by the weighing method; The surface morphology and cross-sectional structure of the coating are observed by optical microscope or electron microscope. Statistical analysis of data such as calculating the standard deviation of coating amount is a common method for evaluating uniformity.
Technical highlights
To achieve uniform coating, several technical points need to be taken into account. First of all, the preparation of the slurry should ensure that the components are evenly dispersed and there is no agglomeration. Secondly, the aluminum foil needs to be properly treated before coating to enhance the wettability of the slurry. During the coating process, it is crucial to maintain a stable slurry supply and a constant substrate tension. The drying stage should adopt a segmented heating strategy to avoid surface crust or internal solvent retention.
Reference Standards
The relevant production process can refer to some technical specifications at home and abroad. For example, there are corresponding procedural documents for coating adhesion testing, thickness measurement methods, etc. These documents provide a basic framework for process parameter setting and quality evaluation.
Summary
The uniform coating of cathode slurry on aluminum foil is a systematic project involving materials, processes and equipment. Through an in-depth understanding of slurry rheology, precise control of coating and drying process parameters, and supplemented by scientific testing methods, the coating uniformity can be effectively improved and a good foundation for subsequent manufacturing links can be laid. Continuous process monitoring and data analysis are key to maintaining stable production.
References
1. Slurry characteristics: refers to the application of non-Newtonian fluids in the coating process.
2. Coating process: The principle description in the review literature of slit coating technology is synthesized.
3. Detection method part: General measurement technical data on coating quality characterization is cited.