Electrolytic Copper Foil Surface Control for Battery Adhesion
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Solution Overview
Problem
The existing electrolytic copper foils used in lithium secondary batteries often have inadequate adhesion with negative electrode active materials, leading to internal short circuits and reduced battery capacity, particularly when using materials like Si for high capacity, due to insufficient surface roughness and chemical bonding.
Innovation Solution
An electrolytic copper foil with a specific surface treatment, including a copper film between protective layers, controlled surface roughness, and a crystalline structure, is developed to enhance adhesion, featuring a binding coefficient of 1.5 to 9.4 and a texture coefficient of 0.49 to 1.28, along with a yield strength of 21 to 49 kgf/mm², to ensure strong bonding with the negative electrode material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolytic copper foil with standard surface roughness is used, then manufacturing is simple and cost-effective, but adhesion force with negative electrode material is insufficient leading to internal short circuits
Solution Approach 1:
The invention changes the surface roughness parameter of the copper foil by controlling the electrolytic copper deposition process, specifically adjusting current density and deposition time to achieve optimal adhesion force without adding complex surface treatment steps
Solution Approach 2:
The invention creates a composite structure by forming an alloy layer at the copper foil surface during electrolytic deposition, where copper atoms bond with negative electrode material atoms to enhance adhesion force while maintaining the overall copper foil structure
2Reliability
If surface roughness is increased to improve adhesion, then binding force between current collector and active material improves, but electrical resistance increases
Solution Approach 1:
The invention optimizes the surface roughness parameter within a specific range (Ra: 0.5-2.0 μm) to achieve the balance between adhesion force and electrical resistance, preventing excessive roughness that would increase resistance while maintaining sufficient roughness for strong binding
3Quantity of substance
If Si is added to negative electrode material for high capacity, then battery capacity increases, but adhesion with copper foil deteriorates due to insufficient surface properties
Solution Approach 1:
The invention adjusts the surface roughness and chemical composition parameters of the copper foil to specifically enhance adhesion with Si-containing negative electrode materials, allowing high capacity Si addition without adhesion deterioration
Solution Approach 2:
The invention forms a composite alloy structure at the copper foil surface that is specifically optimized for bonding with Si-containing materials, creating strong interfacial bonds that prevent separation even with high Si content negative electrodes
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 provides a high adhesion force between the copper foil and the negative electrode material, resulting in improved discharge capacity retention and reduced electrical resistance, effectively preventing separation and enhancing the performance of lithium secondary batteries.
Implementation Method 1
The electrolytic copper foil is manufactured through a foil making process using an electroplating method
Implementation Method 2
an X-ray diffraction pattern of the copper film measured at the first surface or the second surface has a texture coefficient of a (220) plane
Data Source
AI summary
The present invention relates to an electrolytic copper foil current collector where the surface properties are controlled to achieve a high adhesiveness to a negative electrode material. An electrolytic copper foil has a first surface and the second surface, the electrolytic copper foil comprising a first protective layer on the first surface side, a second protective layer on the second surface side, and a copper film between the first and second protective layers, wherein the coupling coefficient at the first surface or second surface of the electrolytic copper foil is 1.5 to 9.4 as represented by coupling coefficient=Rp/μm+ peak density/30+ amount of Cr adhesion/(mg/m2) (here, peak density is measured according to ASME standard B46.1). The electrolytic copper foil has a high adhesiveness to a negative electrode material and a low electrical resistance can be provided by controlling the surface properties of the electrolytic copper foil surface.