Electrolytic Copper Foil Surface Control for Battery Capacity Retention
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Solution Overview
Problem
Lithium secondary batteries face rapid capacity degradation due to repeated charge and discharge cycles, leading to short lifetimes and frequent replacements, which is inconvenient for consumers and wasteful in resources.
Innovation Solution
An electrolytic copper foil with specific surface characteristics, including peak density, texture coefficient, and surface roughness, is developed to enhance adhesion with active material layers, maintaining a high capacity retention rate by forming a copper layer with matte and shiny surfaces and protective layers, and a manufacturing method involving electroplating with controlled electrolytic solutions and filtration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electroplating methods are used to produce copper foil, then manufacturing cost and process simplicity are maintained, but capacity retention rate deteriorates due to rapid degradation after repeated charge and discharge cycles
Solution Approach 1:
The copper foil manufacturing process is segmented into multiple electroplating stages with different electrolyte compositions and parameters. Each stage deposits copper layers with specific crystal orientations and surface properties, collectively achieving the desired texture coefficient and surface roughness for high capacity retention
Solution Approach 2:
Manufacturing parameters including electrolyte temperature, current density, electrolyte composition, and plating time are precisely controlled and varied during different plating stages. These parameter changes enable control over crystal growth orientation and surface morphology, achieving the specified texture coefficient ≤1.32 and surface roughness 0.5-2.7 μm
2Strength
If copper foil with high surface roughness is produced to increase adhesion, then adhesion strength improves, but surface quality deteriorates affecting battery performance
Solution Approach 1:
The electrolyte temperature is controlled within 20-40°C and current density within 2-10 A/dm² during electroplating. These parameter ranges promote controlled crystal growth that develops surface roughness for adhesion while maintaining surface uniformity and quality suitable for battery applications
3Strength
If copper foil with low texture coefficient is produced to improve adhesion, then adhesion strength improves, but crystal structure control becomes more difficult
Solution Approach 1:
The electroplating process is divided into multiple stages, each targeting specific crystal orientation development. Intermediate XRD measurements are performed between stages to monitor texture coefficient progression, enabling stepwise control of crystal structure to achieve TC(220) ≤1.32
Solution Approach 2:
X-ray diffraction (XRD) analysis is used to measure the texture coefficient during and after electroplating. This feedback information on crystal orientation is used to adjust subsequent plating parameters, ensuring the texture coefficient remains within the target range for optimal adhesion
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 ensures a high capacity retention rate of 80% or more after 500 charge and discharge cycles, minimizing consumer inconvenience and resource waste by maintaining battery performance over a longer period.
Implementation Method 1
forming a copper layer by applying electricity between a positive electrode plate and a rotating negative electrode drum which are disposed in an electrolytic solution
Implementation Method 2
preparing an electrolytic solution by dissolving 75 g/L of copper sulfate and 100 g/L of sulfuric acid in 1 L of water
Data Source
Figure 1~2
Figure 3~4A
Figure 4B
AI summary
Provided are an electrolytic copper foil capable of improving a capacity retention rate of a secondary battery, an electrode including the same, a secondary battery including the same, and a method of manufacturing the same. The electrolytic copper foil, which includes a first surface and a second surface opposite the first surface, comprises a copper layer including a matte surface facing the first surface and a shiny surface facing the second surface, and a first protective layer on the matte surface of the copper layer, wherein the first surface has a peak density (PD) of 3 to 110, a texture coefficient [TC(220)] of a (220) plane of 1.32 or less, and a surface roughness (Rz) of 0.5 to 2.7 µm.