Slot die coating window for a uniform fuel cell ink dispersion

Abstract

The continuous roll‐to‐roll slot die coating technique has shown great potential for fuel cell electrode fabrication. It is essential to determine the particulate coating window to obtain a defect‐free film of uniform thickness and uniform particle dispersion. For this dual‐purpose, an additional upper operating limit has been proposed via a “flow field analysis scheme” that combines analysis and simulation. In this analysis, the fundamentals of flow pattern transition (Poiseuille–Couette–bubbly flow) behind coating limits are clarified. The Couette flow is advantageous for uniform shear rate and dispersion. Furthermore, phase‐field simulations systematically investigate the effect of fluid and geometrical parameters and quantitatively present the flow limit with explicit expression. Results reveal that the slope of the upper limit is inversely correlated with shear‐thinning index n while proportional to the coating gap H. Combining the bubble entrainment boundary, lower n and H are favorable for a larger particulate coating window.

Control of Meniscus Formation Using an Electrohydrodynamics Module in Roll-to-Roll Systems for the Stable Coating of Functional Layers

“…Once the reservoir is filled, it is ejected from the coater lip through the gap of the shim plate and used to coat the conveyed web. The thickness of the coating layer formed by the ink ejected from the coater lip can be predicted using a continuous equation [ 40 , 41 ]. When the law of conservation of mass is applied to the coater lip illustrated in Figure 3 c, the following equation is obtained: where indicates the mass of the control volume, denotes the flow rate of the fed ink, denotes the width of the coated layer, indicates the thickness of the coated layer, and indicates the speed of the web transferred through the backup roll from the bottom of the slot-die coater.…”

“…Once the reservoir is filled, it is ejected from the coater lip through the gap of the shim plate and used to coat the conveyed web. The thickness of the coating layer formed by the ink ejected from the coater lip can be predicted using a continuous equation [40,41]. When the law of conservation of mass is applied to the coater lip illustrated in Figure 3c, the following equation is obtained:…”

Analysis of the Influence of Inlet Position on the Transverse Homogeneity of Slot Coating

“…Slot coating is a kind of coating method. It is commonly used in the production of high performance materials [1,2]. The performance of the material depends mainly on whether the coating is uniform, which requires a good transverse uniformity in the coating process.…”

“…The governing equations they used were 2D steady momentum conservation equation and the continuity equation. Pan et al [1] clarified the fundamentals of flow pattern transition (Poiseuille-Couette-bubbly flow) behind coating limits. And they also used phase-field simulations to systematically investigate the effect of fluid and geometrical parameters and quantitatively presented the flow limit with explicit expression.…”