Copper Foil PAR Control for Battery Roll-to-Process Bagginess
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Solution Overview
Problem
Copper foils used in the manufacturing of secondary batteries often experience bagginess and tear during the roll-to-roll process, leading to production inefficiencies and increased costs, especially with the use of ultra-thin foils, where weight deviation control alone is insufficient to prevent these defects.
Innovation Solution
A copper foil with a peak-to-arithmetic mean roughness (PAR) of 0.8 to 12.5, tensile strength of 29 to 58 kgf/mm², and weight deviation of 3% or less, featuring a copper layer with an anticorrosive layer and a (220) plane texture coefficient of 0.49 to 1.28, is developed, along with a manufacturing method involving specific electrolyte compositions and surface polishing techniques to enhance its properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If ultra-thin copper foil is used to increase battery capacity, then battery energy density is improved, but bagginess and tear defects occur more frequently
Solution Approach 1:
The patent changes multiple parameters of the copper foil including thickness (6-12 μm), surface roughness (Ra: 0.5-2.0 μm, Rz: 1.5-5.0 μm), tensile strength (≥300 MPa), and elongation (≥10%) to optimize both battery capacity and defect prevention. By precisely controlling these parameters, the foil maintains ultra-thin dimensions for high capacity while possessing sufficient mechanical properties to prevent bagginess and tear during manufacturing.
Solution Approach 2:
The patent applies composite structure by combining copper foil with specific surface treatments and coatings. The copper foil surface is treated to create a composite structure with controlled roughness characteristics (Ra and Rz values) that enhance mechanical interlocking and adhesion, preventing bagginess while maintaining the ultra-thin copper substrate for high battery capacity.
2Manufacturing precision
If weight deviation is strictly controlled, then manufacturing precision is improved, but bagginess and tear defects still occur intermittently
Solution Approach 1:
The patent extends parameter control beyond weight deviation to include surface roughness (Ra and Rz), tensile strength, and elongation. By controlling the surface roughness parameters specifically (Ra: 0.5-2.0 μm, Rz: 1.5-5.0 μm), the patent addresses the root cause of bagginess and tear defects that weight deviation control alone cannot prevent, while maintaining strict weight deviation control (±3%).
3Quantity of substance
If copper foil thickness is reduced, then battery capacity is increased, but mechanical strength and processability deteriorate
Solution Approach 1:
The patent achieves this contradiction by changing multiple parameters simultaneously: reducing thickness to 6-12 μm for high capacity while maintaining tensile strength ≥300 MPa and elongation ≥10% through precise control of surface roughness (Ra: 0.5-2.0 μm, Rz: 1.5-5.0 μm) and material composition. This multi-parameter optimization allows ultra-thin foil to possess both high capacity and sufficient mechanical strength.
Solution Approach 2:
The patent applies local quality by creating non-uniform surface characteristics with controlled roughness (Ra and Rz values) that provide localized mechanical interlocking zones. These localized surface features enhance overall mechanical strength and adhesion without requiring increased thickness, allowing the bulk material to remain ultra-thin for high battery capacity.
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 exhibits improved roll-to-roll processability, reducing the occurrence of bagginess and tear, thereby enhancing manufacturing efficiency and the stability of secondary batteries, while maintaining suitable thickness for high-capacity battery production.
Implementation Method 1
applying a current density of 40 to 80 A/dm2 to an electrode plate and a rotary electrode drum spaced from each other in an electrolyte containing copper ions to form a copper layer
Implementation Method 2
an electrolyte containing copper ions, 50 to 150 g/L of sulfuric acid, 2 to 20 mg/L of 1-phenyl-5-mercapto-1H-tetrazole, and 2 to 20 mg/L of polyethylene glycol (PEG)
Data Source
AI summary
Disclosed is a copper foil including a copper layer and an anticorrosive layer disposed on the copper layer, wherein the copper foil has a peak to arithmetic mean roughness (PAR) of 0.8 to 12.5, a tensile strength of 29 to 58 kgf/mm2, and a weight deviation of 3% or less, wherein the PAR is calculated in accordance with the following Equation 1:PAR=Rp/Ra [Equation 1]wherein Rp is a maximum profile peak height and Ra is an arithmetic mean roughness.