Polyolefin Porous Film Protrusions for Battery Separator Peel Strength
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Solution Overview
Problem
Thinner polyolefin porous membranes used in battery separators face challenges with delamination during high-speed processing and assembly, leading to safety concerns and increased air permeation resistance when modified porous layers are laminated, which complicates the manufacturing process and reduces battery performance.
Innovation Solution
A polyolefin porous membrane with protrusions on both sides, ranging from 5 µm to 50 µm in size and 0.5 µm to 3.0 µm in height, irregularly disposed at a density of 3/cm² to 200/cm², is developed, allowing for exceptional peel strength with a modified porous layer, thereby preventing delamination and maintaining low air permeation resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the separator thickness is decreased to increase battery capacity, then the area for electrode and separator can be increased, but the membrane may deform in planar directions and delamination may occur during processing
Solution Approach 1:
The patent applies preliminary action by forming protrusions on the membrane surface before lamination. These protrusions are created during the membrane formation process itself, providing pre-established adhesion points that prevent delamination during subsequent high-speed processing and assembly operations.
Solution Approach 2:
The patent applies local quality by creating localized protrusions with specific dimensions (5-50 μm in size, 0.5-3.0 μm in height) at specific densities (3-200/cm²) on the membrane surface. This localized structural modification provides enhanced adhesion precisely where needed without affecting the overall thinness of the separator.
2Reliability
If a modified porous layer is laminated on the porous membrane to improve adhesion and heat resistance, then the functional properties are improved, but air permeation resistance increases significantly
Solution Approach 1:
The patent applies porous materials principle by maintaining the porous structure of the modified porous layer while controlling its formation process. The layer is formed with controlled porosity that allows adequate air permeation while providing sufficient adhesion through the protrusion structure, thus reducing air permeation resistance compared to conventional dense coatings.
Solution Approach 2:
The patent applies parameter changes by controlling the formation conditions of the modified porous layer, including temperature, humidity, and composition parameters, to achieve optimal balance between adhesion strength and air permeation properties. The specific parameters are optimized to prevent excessive air permeation resistance while ensuring reliable adhesion.
3Strength
If the resin in the modified porous layer is sufficiently permeated into the polyolefin porous membrane to improve adhesion, then the peel strength increases, but the air permeation resistance increases
Solution Approach 1:
The patent applies local quality by concentrating the resin permeation and adhesion enhancement at the localized protrusion sites rather than uniformly across the entire membrane surface. This localized adhesion strategy provides high peel strength through the protrusion anchor effect while leaving the bulk membrane porosity intact, thus minimizing the increase in air permeation resistance.
Solution Approach 2:
The patent applies partial action by achieving sufficient adhesion through localized resin permeation at protrusion sites rather than requiring complete or excessive permeation across the entire membrane. This partial permeation approach provides adequate peel strength (1.0-5.3 N/25 mm) while avoiding the harmful effect of excessive air permeation resistance that would result from complete permeation.
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
The membrane achieves high peel strength and prevents delamination during high-speed processing, maintaining low air permeation resistance and ensuring battery safety and performance, even when stored for extended periods.
Implementation Method 1
a polyolefin porous membrane comprising protrusions of polyolefin having a size (W) within a range of 5 µm ≤ W ≤ 50 µm and a height (H) within a range of 0.5 µm ≤ H
Data Source
Figure 1~2
Figure 3~4
AI summary
Considering that the battery separator of the present invention will require thinner materials and lower costs in the future, provided are a polyolefin porous membrane with exceptionally high peel strength between the polyolefin porous membrane and a modified porous layer, suitable for high-speed processing during slit processing and the battery assembly process, and suitable for laminating on a modified porous layer, and a battery separator obtained by laminating a modified porous layer on the polyolefin porous membrane. A polyolefin porous membrane comprising protrusions of polyolefin having a size (W) within a range of 5 µm ≤ W ≤ 50 µm and a height (H) within a range of 0.5 µm ≤ H and irregularly disposed on both sides of the polyolefin porous membrane in a density not less than 3/cm2 and not more than 200/cm2 per side, and the polyolefin porous membrane having a thickness of not more than 25 µm.