Slot Die Electrode Coating with Variable Gap Edge Uniformity
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Solution Overview
Problem
Conventional slot die coating methods for electrode substrates in rechargeable batteries result in uneven active material application, leading to increased resistance and safety risks due to imbalanced face-to-face capacity between positive and negative electrodes.
Innovation Solution
A coating device with a roll and slot die configuration that forms a first gap at the center and a second, larger gap at both ends of the electrode substrate, controlling the shape of the coating edge portion and the application amount of the active material to ensure uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional slot die coating method is used, then the coating process is simple and fast, but the coating amount at the edge portion is relatively small, leading to increased resistance and safety deterioration
Solution Approach 1:
The patent applies local quality by creating a non-uniform gap structure where the first gap at the center region provides standard coating thickness, while the second gap at the edge regions provides increased coating thickness. This local variation in gap size compensates for the natural tendency of coating material to be thinner at edges, achieving uniform coating distribution across the entire electrode substrate surface without compromising coating speed.
Solution Approach 2:
The patent employs asymmetry by designing the gap structure to be non-symmetric relative to the slot die, with deliberately different gap sizes at different positions. The first gap at the center and the second gap at the edges create an asymmetric coating path that counteracts the symmetric spreading of coating material, ensuring that edge portions receive adequate coating material to match the center region.
2Reliability
If the coating amount at edge portions is increased to maintain uniformity, then resistance is reduced and safety is improved, but the difference in application amount between central and edge portions becomes harder to control
Solution Approach 1:
The patent applies preliminary action by pre-establishing a specific gap structure before the coating process begins. The first gap and second gap are predetermined and fixed in the coating device design, allowing the coating process to proceed without real-time adjustment. This pre-configured asymmetric gap structure automatically compensates for edge effects, simplifying the coating control process while ensuring uniform coating distribution and reliable battery performance.
Solution Approach 2:
The patent utilizes parameter changes by varying the gap dimension parameter across different regions of the coating device. The gap size is changed from the first gap at the center to the second gap at the edges, creating a controlled gradient in the coating path. This parameter variation enables precise control over the coating amount distribution, ensuring uniformity across the electrode substrate while maintaining simple and reliable battery safety characteristics.
3Device complexity
If a uniform gap is maintained between slot die and electrode substrate, then the coating process is simple, but the face-to-face distance between electrodes becomes non-uniform, increasing resistance
Solution Approach 1:
The patent applies local quality by creating position-dependent gap characteristics, where the first gap at the center region and the second gap at the edge regions provide different clearance distances. This local variation in gap quality ensures that the coating material is deposited at appropriate thicknesses at each location, resulting in uniform face-to-face distance between positive and negative electrodes throughout the battery cell, thereby reducing resistance.
Solution Approach 2:
The patent employs another dimension by transitioning from a one-dimensional uniform gap concept to a two-dimensional variable gap structure. The gap size is no longer constant across the width of the electrode substrate but varies systematically from center to edge regions. This dimensional expansion in the gap design enables precise control over coating thickness distribution, achieving uniform electrode spacing and reduced resistance.
Data Source
AI summary
A slot die coating device includes: a roll configured to continuously supply an electrode substrate; and a slot die configured to form an active material coating portion on the electrode substrate. The roll and the slot die form a first gap between each other at a center in a width direction of the electrode substrate and form a second gap that is greater than the first gap.