Anticorrosive Copper Foil for Silicon Anode Expansion Adhesion
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Solution Overview
Problem
The high volumetric expansion rate of silicon-based anode active materials in secondary batteries leads to separation from copper foils, reducing battery lifespan due to inadequate adhesive force and contact.
Innovation Solution
A copper foil with a Young's modulus of 37265 to 45111 MPa, a modulus bias factor of less than 0.12, and a maximum height roughness of 0.8 to 3.5 μm, coated with an anticorrosive film, is used as a current collector to enhance adhesion with active materials, preventing separation and ensuring efficient expansion and contraction during charging and discharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the surface roughness of the copper foil is increased to enhance adhesion with silicon-based anode active material, then the adhesive force between copper foil and active material is improved, but the copper foil's ability to accommodate volumetric expansion during charging and discharging is reduced
Solution Approach 1:
The copper foil is designed with non-uniform thickness distribution, having a first thickness in a first region and a second thickness in a second region. This local variation in thickness allows different regions to serve different functions: one region provides enhanced adhesion while another accommodates volumetric expansion during charging and discharging cycles
Solution Approach 2:
The copper foil's thickness is dynamically optimized to accommodate the dynamic volumetric changes of silicon-based anode active material during charging and discharging. The varying thickness distribution enables the foil to adapt to expansion and contraction forces without compromising structural integrity or adhesion
2Ease of manufacture
If a conventional copper foil is used as current collector for silicon-based anode, then the manufacturing process is simple, but the anode active material separates from the copper foil due to high volumetric expansion rate
Solution Approach 1:
The copper foil incorporates localized thickness variations with specific regions having different thicknesses. This structural differentiation enhances adhesion in critical areas while maintaining manufacturing feasibility through controlled rolling or stretching processes during production
3Strength
If the copper foil thickness is uniformly increased to prevent separation, then the adhesive strength and structural stability are improved, but the flexibility and charge-discharge efficiency are reduced
Solution Approach 1:
Rather than uniformly increasing thickness, the invention applies thickness enhancement only in specific regions where structural support and adhesion are most needed. Other regions maintain thinner profiles to preserve flexibility and enable efficient ion transport during charge-discharge cycles
Solution Approach 2:
The copper foil is effectively segmented into regions with different thickness characteristics. This segmentation allows the foil to simultaneously provide structural stability in load-bearing areas and maintain flexibility in areas requiring rapid ion diffusion and electron transport
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 with these specifications prevents separation from active materials, resulting in secondary batteries with high efficiency and excellent capacity retention rates, even with high expansion rate materials.
Implementation Method 1
An electrolytic copper foil is a copper foil formed by electroplating
Data Source
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AI summary
An embodiment of the present invention provides a copper foil which comprises a copper layer and an anticorrosive film placed on the copper layer, and has a Young's modulus of 3800 to 4600kgf/mm2 and a modulus bias factor (MBF) less than 0.12, wherein the modulus bias factor (MBF) is obtained by formula 1 below. [Formula 1] MBF = (maximum Young's modulus-minimum Young's modulus)/(average Young's modulus)