Lithium-Ion Battery Separator Coating for Fold-Resistant Winding
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Solution Overview
Problem
The small thickness and low rigidity of the separator in wound lithium ion batteries make them prone to folding during the winding and assembly process, leading to safety hazards and reduced yield, and can result in lithium precipitation due to insufficient electrolyte.
Innovation Solution
A separator with a base film coated on one or both surfaces, featuring a thicker edge portion with patterns that provide additional rigidity and accommodate electrolyte, reducing the likelihood of folding and lithium precipitation. The edge portion has a thickness ratio of 1.2 to 1.6 times that of the main body, and widths ranging from 10 mm to 20 mm, with patterns like stripe, grid, or pit shapes to store electrolyte and prevent stress concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the separator is made thin to reduce battery size, then the energy density is improved, but the rigidity deteriorates causing folding during assembly
Solution Approach 1:
The separator features a coating layer with different thicknesses in different regions: a first coating layer with greater thickness at the edge portion and a second coating layer with lesser thickness at the central portion. This local quality differentiation provides enhanced rigidity at the edges to prevent folding during assembly, while maintaining overall thinness for high energy density.
Solution Approach 2:
The patent introduces a width dimension to the coating layer thickness variation, creating a gradient structure where the coating thickness transitions from the edge toward the center. This dimensional approach allows the separator to maintain thin overall dimensions for high energy density while having locally thickened edges for structural support.
2Strength
If the separator thickness is increased to improve rigidity, then the folding resistance is improved, but the energy density deteriorates
Solution Approach 1:
Instead of uniformly increasing the separator thickness, the patent applies a coating layer with spatially varying thickness. The edge portion has greater thickness for rigidity, while the central portion remains thin to maximize active material volume and energy density. This local quality approach optimizes both mechanical strength and energy storage capacity.
3Reliability
If the edge portion thickness is increased to prevent folding, then the assembly reliability is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent controls the coating layer thickness as a continuous parameter that varies spatially across the separator surface. By adjusting the coating application parameters (such as dip coating speed, withdrawal angle, or spray pattern), the edge portion naturally receives greater coating thickness while the center receives less, achieving the desired thickness gradient through parameter optimization rather than complex multi-step manufacturing.
Data Source
AI summary
A separator includes a base film and a coating which covers a surface of the base film. The coating includes a main body and an edge portion arranged on the periphery of the main body. The edge portion has a greater thickness than the main body, and the edge portion is provided with several patterns arranged at intervals.