Asymmetric Copper Foil Surface Control for Battery Roll-to-Roll Workability
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Solution Overview
Problem
Thin copper foils used in secondary battery manufacturing often experience slip and bagginess, leading to poor workability and charge/discharge characteristics due to high dynamic friction coefficients and uneven surface area ratios, which hinder continuous roll-to-roll processing and electrode production.
Innovation Solution
A copper foil with a matte and shiny surface, controlled dynamic friction coefficients (0.4≤μk1≤0.5 and |μk1−μk2≤0.2), and surface area ratios (4.0≤Fs1≤6.5 and |Fs1−Fs2≤2.0), along with a tensile strength of 40 kgf/mm2 or more, is developed, incorporating an anticorrosive film and specific organic additives in the electroplating process to enhance processability and battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the copper foil thickness is reduced to about 10 μm or less to increase battery capacity, then the battery energy density is improved, but the dynamic friction coefficient increases causing frequent slip between roll and copper foil
Solution Approach 1:
The patent applies parameter changes by controlling the dynamic friction coefficient to be within 0.05 to 0.15 and the surface area ratio difference between two surfaces to be 2.0 or less. These parameter optimizations prevent slip during RTR processing while maintaining the thin foil structure for high capacity batteries.
Solution Approach 2:
The patent implements local quality by creating different surface characteristics on each side of the copper foil. One surface has a higher surface area ratio than the other, with each surface having controlled friction coefficients. This asymmetric surface treatment prevents slip while ensuring uniform active material coating on both surfaces.
2Reliability
If the dynamic friction coefficient is high to prevent slip, then the copper foil stability is improved, but the bagginess and tear of copper foil occur frequently
Solution Approach 1:
The patent optimizes the dynamic friction coefficient to a specific range (0.05 to 0.15) that is low enough to prevent bagginess and tear but sufficient to prevent slip. This precise parameter control resolves the contradiction between stability and harm prevention.
Solution Approach 2:
The patent converts the potential harm of low friction (which would cause slip) into a benefit by precisely controlling it to an optimal range. The friction coefficient is maintained at levels that are sufficient for process stability but low enough to prevent deformation and tearing of the thin copper foil.
3Reliability
If the surface area ratio difference between two surfaces is large to control friction, then the slip prevention is improved, but the uniformity of active material coating deteriorates
Solution Approach 1:
The patent sets the surface area ratio difference between two surfaces to be 2.0 or less, optimizing this parameter to maintain both slip prevention and coating uniformity. This parameter control ensures that active material is evenly distributed while preventing friction-related defects.
4Quantity of substance
If the copper foil thickness is reduced to increase battery capacity, then the energy density is improved, but the charge/discharge characteristics deteriorate due to slip and bagginess
Solution Approach 1:
The patent controls the dynamic friction coefficient and surface area ratio parameters to prevent slip and bagginess in thin copper foils. This ensures that the reduced thickness does not compromise charge/discharge characteristics, maintaining both high capacity and reliable electrochemical performance.
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 prevents slip and tear, improves workability, and maintains excellent charge/discharge characteristics, ensuring high-capacity secondary battery performance and stability during the roll-to-roll process.
Implementation Method 1
a copper layer formed by electroplating
Data Source
AI summary
Disclosed is a copper foil including a copper layer having a matte surface and a shiny surface, wherein the copper foil has a first surface of a direction of the matte surface of the copper layer and a second surface of a direction of the shiny surface of the copper layer, wherein a dynamic friction coefficient of the first surface is designated by μk1 and a dynamic friction coefficient of the second surface is designated by μk2. A ratio of three-dimensional surface area to two-dimensional surface area of the first surface is designated by Fs1, a ratio of three-dimensional surface area to two-dimensional surface area of the second surface is designated by Fs2.