Electrolytic Copper Foil Surface Control Against Curling and Tears
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Solution Overview
Problem
Existing electrolytic copper foils used in secondary batteries face challenges such as curling, tearing, and wrinkling during manufacturing, particularly when thin, which affects the production of high-capacity and high-quality batteries.
Innovation Solution
The electrolytic copper foil is designed with specific parameters including valley mean roughness (VMR) of 0.8 to 12.5, (220) texture coefficient (TC(220)) of 0.49 to 1.28, tensile strength of 25 kgf/mm² to 51 kgf/mm², and width direction weight deviation of 3% or less, along with a surface roughness of 2.5 μm or less and a protective layer comprising chromium, silane, or nitrogen compounds, to prevent curling, tearing, and wrinkling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If copper foil thickness is reduced to increase active material capacity, then battery capacity increases, but curling and edge defects occur during winding
Solution Approach 1:
The patent applies parameter changes by optimizing the valley mean roughness (VMR) to a specific range of 0.5 to 1.5, which fundamentally alters the surface morphology parameters of the copper foil. This controlled surface roughness modification enables the foil to maintain structural integrity and prevent curling while achieving thin thickness (6 μm or less), thereby resolving the contradiction between increasing capacity and maintaining reliability.
2Quantity of substance
If copper foil is made thinner to increase the number of current collectors, then battery capacity increases, but manufacturing difficulty increases due to curling and tears
Solution Approach 1:
The patent changes the surface morphology parameters by controlling VMR within 0.5 to 1.5 during the electrolytic copper foil manufacturing process. This parameter optimization prevents edge curling and tearing, making thin foils (6 μm or less) manufacturable through standard winding and rolling processes, thus resolving the manufacturing difficulty while increasing the number of current collectors.
Solution Approach 2:
The patent applies preliminary action by pre-modifying the surface morphology of the copper foil during manufacturing to achieve the desired VMR range before the foil enters subsequent manufacturing processes. This preliminary surface treatment ensures that the foil maintains its flatness and integrity throughout winding, rolling, and active material coating, preventing defects before they occur.
3Quantity of substance
If copper foil thickness is reduced to increase active material density, then battery capacity increases, but edge tears and wrinkles occur during rolling and coating processes
Solution Approach 1:
The patent changes the surface morphology parameters by precisely controlling the valley mean roughness to 0.5 to 1.5, which modifies the surface structure to prevent stress concentration at edges. This enables thin foils to withstand rolling and coating processes without developing tears or wrinkles, maintaining edge quality while increasing active material density.
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 solution enables the production of stable, high-capacity secondary batteries with improved manufacturing efficiency and extended lifetime by preventing defects in the electrolytic copper foil during processing, ensuring uniform coating and adhesion of active materials.
Implementation Method 1
an electrolytic copper foil... manufactured by electroplating
Data Source
AI summary
An embodiment of the present disclosure provides an electrolytic copper foil, which comprises a copper layer and has a valley mean roughness of 0.8 to 12.5, a texture coefficient of (220) face (TC(220)) of 0.49 to 1.28, a tensile strength of 25 to 51 kgf/mm2, and a weight deviation in lateral direction of 3% or less.