Protective Copper Foil for Uniform Battery Electrode Coating
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Solution Overview
Problem
Existing copper foils used in secondary batteries face issues such as non-uniform active material coating, high surface roughness, and poor flexibility, leading to potential short circuits, delamination, and reduced yield, especially under high-temperature conditions.
Innovation Solution
A copper foil with a protective layer and specific properties including puncture strength, water contact angle, surface resistivity, and flexibility indices, optimized for uniform active material coating and high-temperature stability, manufactured through a controlled electroplating process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the surface roughness of the copper foil is increased to improve active material coating, then the coating uniformity is improved, but the flexibility and bendability of the copper foil deteriorate
Solution Approach 1:
The copper foil surface is designed with localized micro-roughness features (arithmetic mean roughness Ra of 0.5-2.0 μm) rather than uniform roughness throughout. This local quality approach allows the surface to provide adequate anchoring for active material coating in specific regions while maintaining overall smoothness and flexibility of the foil structure.
2Strength
If the puncture strength of the copper foil is increased to improve mechanical strength, then the strength and durability are improved, but the elongation and flexibility deteriorate
Solution Approach 1:
The copper foil's mechanical properties are optimized by controlling specific parameters: thickness (6-12 μm), arithmetic mean roughness (Ra of 0.5-2.0 μm), and tensile strength (40-70 kgf/mm²). These parameter changes enable the foil to achieve puncture strength of 5.0-7.0 N while maintaining elongation of 10-30%, resolving the contradiction between strength and flexibility.
3Strength
If the surface roughness is increased to improve active material adhesion, then the adhesion strength is improved, but the charge/discharge efficiency deteriorates due to non-uniform coating
Solution Approach 1:
Instead of relying solely on mechanical interlocking through high surface roughness, the patent uses controlled micro-roughness (Ra of 0.5-2.0 μm) combined with electrochemical bonding during the electroplating process. This substitution approach maintains adequate adhesion strength while ensuring uniform active material coating and efficient charge/discharge performance.
4Strength
If the copper foil thickness is increased to improve mechanical strength, then the strength and stability are improved, but the flexibility and bendability deteriorate
Solution Approach 1:
The copper foil thickness is precisely controlled within the range of 6-12 μm. This parameter optimization ensures the foil has sufficient mechanical strength (puncture strength 5.0-7.0 N) while maintaining excellent flexibility and bendability for device integration, resolving the contradiction between strength and adaptability.
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 ensures stable, high-efficiency charge and discharge performance, maintains conductivity, and enhances productivity by preventing breakage and ensuring uniform coating, even under high-temperature conditions.
Implementation Method 1
a copper foil formed by electroplating is referred to as an electrolytic copper foil
Data Source
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AI summary
An embodiment of the present invention provides a copper foil that comprises: a copper film including 99.9 wt% or more of copper; and a protective layer on the copper film, and has a room-temperature puncture strength in the range of 5.0 N-7.0 N, and a high-temperature puncture strength in the range of 8.0 N-12.5 N. Here, the high-temperature puncture strength is a puncture strength measured after heat treatment at 190 °C for 1 hour. An embodiment of the present invention provides a copper foil that comprises: a copper film including 99.9 wt% or more of copper, and a protective layer on the copper film, and has a room-temperature water contact angle in the range of 60-70°, and a room-temperature surface resistivity in the range of 2.4-2.7 mΩ/cm. An embodiment of the present invention provides a copper foil that comprises a copper film including 99.9 wt% or more of copper and has a color difference coefficient in the range of 0.38-0.7 based on the Lab colorimetric system. An embodiment of the present invention provides a copper foil that comprises a copper film including 99.9 wt% or more of copper and has a room-temperature MIT 1 of 280 or more, a high-temperature MIT 1 of 130 or more, a room-temperature MIT 2 of 14 or more, and a high-temperature MIT 2 of 25 or more.