Slot Die Gap Profile for Uniform Battery Electrode Coating
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Solution Overview
Problem
The general slot die coating method for rechargeable battery electrodes results 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 the 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 general slot die coating method is used, then the coating process is simple and efficient, but the coating amount at edge portions is insufficient leading to resistance increase and safety deterioration
Solution Approach 1:
The patent applies local quality by creating different gap distances at different locations of the slot die. The gap distance is larger at edge portions and smaller at central portions, allowing the coating head to deliver appropriate amounts of active material slurry to each region. This local variation in gap distance compensates for the natural tendency of coating devices to deposit less material at edges, achieving uniform coating distribution across the entire electrode substrate surface.
Solution Approach 2:
The patent changes the geometric parameter of the slot die structure by varying the gap distance between the coating head and the electrode substrate. Instead of maintaining a constant gap distance, the design implements a gradient where the gap distance increases from the central portion toward the edge portions. This parameter change directly controls the coating amount, ensuring that edge portions receive sufficient active material to achieve the required face-to-face capacity ratio.
2Reliability
If the coating amount at edge portions is increased to ensure safety, then face-to-face capacity balance is improved, but the coating process complexity increases
Solution Approach 1:
The patent applies asymmetry by designing the slot die with an asymmetric gap distance distribution. The gap distance is intentionally made larger at the edge portions and smaller at the central portion, creating an asymmetric structure that compensates for the natural coating deficiency at edges. This asymmetric design simplifies the overall device structure while effectively addressing the safety concern related to insufficient edge coating.
3Manufacturing precision
If rheology control and spacer shape change are used to control coating flow, then coating amount distribution is improved, but the difference between sliding shape and active material amount persists
Solution Approach 1:
The patent applies preliminary action by pre-configuring the slot die with a specific gap distance distribution pattern before the coating process begins. The gap distance is designed to be larger at edge portions and smaller at central portions, which preliminarily determines the coating amount distribution. This preliminary structural configuration eliminates the need for complex real-time rheology control or spacer shape adjustments during operation, simplifying the coating process control while achieving uniform active material distribution.
Data Source
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AI summary
A coating device for an electrode substrate of a rechargeable battery includes: a roll that continuously supplies an electrode substrate; and a slot die that forms an active material coating portion at the electrode substrate. The roll and the slot die form a first gap between each other at a center of a width direction of the electrode substrate, and form a second gap that is greater than the first gap.