Microporous Membrane Winding Using Smooth Large-Diameter Core
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Solution Overview
Problem
Conventional microporous membranes used as separators in lithium-ion secondary batteries suffer from non-uniform thickness, which can degrade battery quality due to constriction during winding and misalignment issues, especially as membranes thin and winding lengths increase.
Innovation Solution
A microporous membrane winding process using a core with a specific outer diameter of 5 inches or greater and surface roughness of 3.0 μm or less, along with controlled thermal expansion coefficient, swelling rate, and alignment during winding, to achieve uniform membrane thickness and prevent deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a microporous membrane is wound around a core with conventional surface roughness, then the membrane undergoes constriction due to winding, but this transfers the core surface shape onto the membrane, causing deformation and thickness nonuniformity
Solution Approach 1:
The patent changes the surface roughness parameter of the core from conventional values to 3.0 μm or less, and sets the outer diameter to 5 inches or greater. These parameter changes reduce the constriction effect during winding and prevent deformation of the microporous membrane, thereby improving thickness uniformity while maintaining the necessary winding process.
2Quantity of substance
If the membrane thickness is decreased to increase battery capacity, then electrode utilization improves, but thickness nonuniformity becomes more significant and degrades battery quality
Solution Approach 1:
By changing the core parameters (outer diameter ≥5 inches, surface roughness ≤3.0 μm), the patent enables the use of thinner microporous membranes with improved thickness uniformity. The reduced constriction effect allows thin membranes to maintain their thickness consistency during winding, thereby increasing battery capacity without sacrificing quality.
3Productivity
If the winding-around length is increased to meet battery requirements, then productivity improves, but deformation of the microporous membrane becomes more serious
Solution Approach 1:
The patent changes the core surface roughness to 3.0 μm or less and outer diameter to 5 inches or greater, which reduces the constriction effect per unit length. This allows longer winding lengths to be achieved without accumulating significant deformation, thereby improving productivity while maintaining membrane quality.
4Ease of manufacture
If the core is fixed at a slight tilt during winding, then attachment is simplified, but winding misalignment and wrinkles appear in the unwound membrane
Solution Approach 1:
The patent addresses the alignment problem by specifying core properties (outer diameter ≥5 inches, surface roughness ≤3.0 μm) that reduce the sensitivity of the winding process to minor tilt angles. The larger diameter and smoother surface provide a more stable winding surface, reducing the appearance of misalignment and wrinkles even when slight tilts occur during attachment.
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 method ensures a microporous membrane with improved thickness uniformity, reducing battery capacity variations and enhancing the quality and safety of lithium-ion secondary batteries by minimizing constriction and misalignment during the winding process.
Implementation Method 1
when a microporous membrane is wound around a core, a phenomenon called 'constriction due to winding' occurs to the membrane because it contains micropores
Implementation Method 2
When a core of a microporous membrane winding swells or shrinks due to a change in temperature or humidity during transportation
Implementation Method 3
swelling rate due to humidity
Data Source
AI summary
A microporous membrane winding includes a microporous membrane wound around a core. The core has an outer diameter of 5 inches or greater, and has an outer surface with a surface roughness of 3.0 μm or less. A microporous membrane that is excellent in thickness uniformity and is favorably used as a separator for a lithium-ion secondary battery can be obtained from the microporous membrane winding.