Electrolytic Copper Foil Grain Control for Battery Adhesion
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Solution Overview
Problem
Current copper foils used in lithium batteries face challenges such as high manufacturing costs, difficulty in producing wide-width foils, contamination from lubricating oils affecting adhesion with active materials, and decreased capacity due to thick current collectors, which also struggle with volume changes and heat phenomena during charging and discharging.
Innovation Solution
An electrolytic copper foil with specific resistivity of 1.68 to 1.72 µΩ·cm and grain mean diameter of crystallites between 0.41 to 0.80 µm, providing high tensile strength and elongation percentage, along with controlled surface roughness to ensure strong adhesion and uniform active material layers, is developed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If rolled copper foil is used as current collector, then manufacturing cost is reduced and wide width fabrication is enabled, but adhesion with active material is degraded due to lubricating oil contamination
Solution Approach 1:
The invention extracts and eliminates the harmful lubricating oil component from the copper foil surface by using an electrolytic purification process, thereby removing the source of adhesion degradation while maintaining the cost advantages of rolled copper production
Solution Approach 2:
The invention changes the surface chemical composition parameters of the copper foil by controlling the electrolytic purification process, specifically adjusting the electrolyte composition and processing conditions to achieve optimal adhesion properties without compromising manufacturing efficiency
2Strength
If current collector thickness is increased to improve mechanical strength, then resistance to volume change and heating is improved, but capacity per volume of lithium battery is decreased
Solution Approach 1:
The invention changes the microstructural parameters of the copper foil, specifically controlling the grain size to 0.41-0.80 μm through electrolytic processing, which dramatically improves strength properties allowing thin foils to achieve the mechanical strength previously only available in thick foils
Solution Approach 2:
The invention enables the use of ultra-thin copper foil (6-12 μm) as a flexible yet strong current collector, replacing traditional thick rigid foils, thereby maximizing the active material volume while maintaining sufficient mechanical strength through controlled grain structure
3Quantity of substance
If copper foil thickness is reduced to increase capacity per volume, then more active material can be accommodated, but mechanical strength and elongation resistance are degraded
Solution Approach 1:
The invention fundamentally changes the grain size parameter of the copper foil to an ultra-fine range (0.41-0.80 μm), which activates grain boundary strengthening mechanisms that provide exceptional strength-to-thickness ratios, enabling thin foils to outperform traditional thick foils in mechanical strength
4Quantity of substance
If copper foil thickness is reduced to improve capacity per volume, then space for active material is increased, but adhesion with active material and resistance to volume change are degraded
Solution Approach 1:
The invention optimizes the surface grain structure parameters of the thin copper foil, creating a controlled microtopography and chemical composition at the surface that enhances mechanical interlocking and chemical bonding with active material particles, thereby improving adhesion despite reduced thickness
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 electrolytic copper foil enhances the mechanical strength and elongation properties of lithium batteries, improving their high-rate capability and life characteristics by effectively managing volume changes and heat, while maintaining uniform charging and discharging.
Implementation Method 1
A copper foil is generally used as a current collector of a medium and large lithium battery
Implementation Method 2
a grain mean diameter of a crystallite as calculated from the electron backscattering diffraction pattern from 0.41 to 0.80 μm
Data Source
Figure 1
AI summary
Disclosed is an electrolytic copper foil having specific resistivity of 1.68 to 1.72 µΩ • cm and a grain mean diameter of a crystallite less than 0.41 to 0.80 µm.