Negative Electrode Pattern Coating to Prevent Layer Dragging
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Solution Overview
Problem
The existing methods for preparing negative electrodes in rechargeable lithium batteries face challenges in accurately coating active material layers, leading to issues like dragging of the coating portion during the pattern coating process, which can result in electrode instability and potential fires.
Innovation Solution
A method involving the simultaneous coating of a first and second negative active material layer composition on a current collector, with specific capillary numbers ranging from 0.25 to 1.50, to prevent dragging and ensure uniform coating, thereby maintaining electrode stability and preventing the formation of regions with only the second active material layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single negative active material layer composition is coated on the current collector, then the coating process is simple, but dragging of the coating portion occurs leading to non-uniform active material layer formation
Solution Approach 1:
The single-layer coating process is segmented into two sequential coating steps: first coating a first negative active material layer composition, then coating a second negative active material layer composition. This segmentation allows each layer to be optimized independently, preventing dragging while maintaining process simplicity.
Solution Approach 2:
The invention changes the parameters of the coating composition by using two different negative active material layer compositions with distinct properties. The first composition has different solid content, viscosity, or capillary number characteristics than the second composition, allowing the first layer to provide a stable base that prevents dragging of the second layer, thereby achieving uniform active material layer formation.
2Productivity
If the coating speed is increased to improve productivity, then more active material can be coated per unit time, but dragging of the coating portion becomes more severe
Solution Approach 1:
The first negative active material layer is coated in advance to create a stable foundation layer. This preliminary action prepares the surface with appropriate adhesion and flow characteristics, allowing the second layer to be coated at higher speeds without dragging, thus improving productivity while maintaining coating uniformity.
Solution Approach 2:
The invention uses a composite structure of two different negative active material layer compositions. The first composition acts as a base layer with properties optimized for adhesion and drag prevention, while the second composition provides the final active material layer. This composite approach enables higher coating speeds without sacrificing uniformity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively prevents the dragging of the coating portion, ensuring uniform active material layer formation and enhancing the stability and performance of the negative electrode, reducing the risk of electrode deterioration and fires.
Implementation Method 1
coating a first negative active material layer composition having a capillary number of about 0.25 to about 1.50 on the current collector and coating a second negative active material layer composition having a capillary number of about 0.28 to about 1.50 on the first negative active material layer composition
Data Source
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AI summary
Disclosed are a method of preparing a negative electrode for a rechargeable lithium battery and a rechargeable lithium battery including the negative electrode, and the method of preparing the negative electrode comprises preparing an active material layer on a current collector so that a coating portion in which an active material layer is formed and an uncoated region in which an active material is not formed are alternatively arranged, wherein the coating portion in which the active material layer is formed is performed by coating a first negative active material layer composition having a capillary number of about 0.25 to about 1.50 on the current collector and coating a second negative active material layer composition having a capillary number of about 0.28 to about 1.50 on the first negative active material layer composition.