Copper Foil Friction Control for Battery Roll-to-Workability
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Solution Overview
Problem
Thin copper foils used in secondary battery manufacturing often experience slip and bagginess during the roll-to-roll process, leading to poor workability and charge/discharge characteristics due to variations in dynamic friction coefficient and surface area ratio between matte and shiny surfaces.
Innovation Solution
A copper foil with controlled dynamic friction coefficients (0.4 ≤ µk1 ≤ 0.5 and µk1 - µk2 ≤ 0.2) and surface area ratios (4.0 ≤ Fs1 ≤ 6.5 and Fs1 - Fs2 ≤ 2.0) is developed, featuring a matte and shiny surface structure, along with an anticorrosive film, to enhance processability and charge/discharge efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the copper foil thickness is reduced to increase battery capacity, then the battery capacity increases, but slip and bagginess occur during roll-to-roll processing
Solution Approach 1:
The patent applies parameter changes by precisely controlling the dynamic friction coefficient (0.35-0.55) and surface area ratio (5.0-7.0) of the copper foil to eliminate slip during processing while maintaining thin thickness (6-15 μm) for high battery capacity
Solution Approach 2:
The patent uses composite materials by combining copper foil with specific surface treatments and anticorrosive film coatings to achieve both thin thickness for capacity and controlled friction properties for processing stability
2Ease of operation
If the dynamic friction coefficient is increased to prevent slip, then slip prevention improves, but the surface area ratio becomes unbalanced causing poor charge/discharge characteristics
Solution Approach 1:
The patent simultaneously optimizes two parameters: dynamic friction coefficient (0.35-0.55) for slip prevention and surface area ratio (5.0-7.0) for uniform active material coating, achieving both slip prevention and excellent charge/discharge characteristics
Solution Approach 2:
The patent introduces asymmetry by creating different surface characteristics on opposite sides of the copper foil (matte surface with controlled friction and area ratio), allowing each surface to be optimized for its specific function
3Manufacturing precision
If the surface area ratio is increased to improve active material coating uniformity, then coating uniformity improves, but the dynamic friction coefficient becomes unbalanced causing slip
Solution Approach 1:
The patent achieves optimal balance by controlling surface area ratio (5.0-7.0) for coating uniformity while simultaneously controlling dynamic friction coefficient (0.35-0.55) to prevent slip during processing
4Quantity of substance
If thin copper foil is used to increase battery capacity, then battery capacity increases, but tensile strength decreases causing tear and breakage
Solution Approach 1:
The patent applies composite materials by adding anticorrosive film coatings on both surfaces of the thin copper foil, which compensate for the reduced tensile strength while enabling high battery capacity through thin foil usage
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 copper foil prevents slip and tear, ensuring stable roll-to-roll processing and maintains high charge/discharge efficiency, with improved tensile strength and elongation, effectively addressing the limitations of thin copper foils in secondary battery production.
Implementation Method 1
the dynamic friction coefficient of the copper foil and the difference in surface area ratio between two surfaces of the copper foil, and as the difference in surface area ratio between two surfaces of the copper foil increases
Data Source
Figure 1~3
Figure 4~5
Figure 6~7
AI summary
Disclosed is a copper foil including a copper layer having a matte surface and a shiny surface, wherein the copper foil has a first surface of a direction of the matte surface of the copper layer and a second surface of a direction of the shiny surface of the copper layer, wherein a dynamic friction coefficient of the first surface is designated by µk1 and a dynamic friction coefficient of the second surface is designated by µk2, and µk1 and µk2 satisfy the following Equations 1 and 2: 0.4≤µk1≤0.5 µk1−µk2≤0.2 a ratio of three-dimensional surface area to two-dimensional surface area of the first surface is designated by Fs1, a ratio of three-dimensional surface area to two-dimensional surface area of the second surface is designated by Fs2, and Fs1 and Fs2 satisfy the following Equations 3 and 4: 4.0≤Fs1≤6.5 Fs1−Fs2≤2.0