Negative Electrode Layer Structure for End-Slope Lithium Control
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Solution Overview
Problem
The inclination of the end portion of the negative electrode active material layer in lithium secondary batteries leads to insufficient capacity, charge and discharge efficiency, and reduced life characteristics due to lithium precipitation and inadequate lithium intercalation.
Innovation Solution
A negative electrode design featuring a first active material layer with inclined side portions and second active material layers on these sides, where the second layers' height is 40% to 95% of the first layer's height, ensuring even distribution and preventing lithium precipitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a negative electrode active material layer is coated on a negative electrode current collector using slurry, then the negative electrode active material layer can be formed, but the end portion forms an inclination due to fluid characteristics of the slurry, causing insufficient capacity and lithium precipitation
Solution Approach 1:
The negative electrode active material layer is divided into a first negative electrode active material layer and a second negative electrode active material layer. The first layer addresses the inclination problem by being disposed at a specific angle (15° to 45°) relative to the current collector, while the second layer provides additional capacity compensation. This segmentation allows each layer to perform its specific function optimally.
Solution Approach 2:
The first negative electrode active material layer is specifically disposed at an inclination angle of 15° to 45° relative to the current collector surface, creating a local quality difference that compensates for the fluid-induced inclination. This localized angular adjustment ensures uniform lithium distribution at the end portions without affecting the overall electrode structure.
2Quantity of substance
If the negative electrode active material layer is coated to achieve desired capacity, then the end portion inclination causes lithium precipitation and decreases charge and discharge efficiency
Solution Approach 1:
The negative electrode active material layer is segmented into two distinct layers: the first layer provides the primary loading capacity, while the second layer specifically addresses the end portion deficiency. This segmentation enables the electrode to achieve both high loading amount and high charge-discharge efficiency by distributing active material strategically.
Solution Approach 2:
The first negative electrode active material layer is disposed at an inclination angle before the second layer is added, preliminarily compensating for the expected fluid-induced inclination. This preliminary action ensures that when the electrode is assembled, the end portions will have sufficient active material to accept lithium uniformly, preventing lithium precipitation and maintaining high charge-discharge efficiency.
3Manufacturing precision
If the negative electrode active material layer is coated uniformly, then the end portion inclination is avoided, but the manufacturing process becomes more complex
Solution Approach 1:
Instead of making the entire electrode structure complex to achieve uniformity, the invention applies a localized solution: the first negative electrode active material layer is disposed at a specific inclination angle (15° to 45°) only where needed to compensate for fluid-induced inclination. This local quality approach maintains manufacturing simplicity while achieving the desired uniformity in lithium distribution and preventing end portion defects.
Data Source
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AI summary
The present invention provides a negative electrode comprising: a negative electrode current collector; a first negative electrode active material layer disposed on at least one surface of the negative electrode current collector and including a first negative electrode active material; and a second negative electrode active material layer including a second negative electrode active material, wherein the first negative electrode active material layer includes side portions partitioned on both sides thereof and a central portion partitioned off from the side portions, the side portions have an inclination toward a surface of the negative electrode current collector, the second negative electrode active material layer is disposed on at least a portion of the side portions, and the maximum height of the second negative electrode active material layer with respect to the surface of the negative electrode current collector is equal to or less than the maximum height of the first negative electrode active material layer.