Electrolytic Copper Foil Microstructure for Thin High-Strength Collectors
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Solution Overview
Problem
Current methods for producing high-strength electrolytic copper foil for lithium-ion battery applications face challenges in achieving industrial-scale production due to low current densities and high costs, which are necessary for thinning copper foils and accommodating volume expansion of silicon materials, leading to inadequate tensile strength and thermal stability.
Innovation Solution
A method for manufacturing electrolytic copper foil with an average surface roughness of 3.50 μm or less, a twin grain boundary ratio of 35% or less, and high total grain boundary density, achieved through electrodeposition in a solution containing chloride ions and additives, with a wide operating temperature and current density range, enabling high-speed industrial production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the thickness of copper foil is reduced to increase energy density, then the energy density increases, but the tensile strength becomes insufficient leading to processing failures
Solution Approach 1:
The patent applies parameter changes by controlling the electrolyte composition (chloride ions 0.01-25.0 ppm, additives 0.01-75.0 ppm), temperature (20-60°C), and current density (20-80 A/dm²) to produce copper foil with optimized grain structure and surface roughness, achieving high strength at reduced thickness
Solution Approach 2:
The patent creates local quality differences through controlled grain boundary distribution, achieving high-angle grain boundaries with specific orientation relationships that provide localized strengthening mechanisms while maintaining overall foil thinness for high energy density
2Quantity of substance
If silicon material is used as negative electrode to increase energy density, then the theoretical energy density increases 10 times, but the volume expansion causes current collector rupture
Solution Approach 1:
The patent modifies physical parameters of the copper foil including surface roughness (Sz ≤ 3.50 μm), grain size (1.50 μm or less), and grain boundary density to enhance mechanical properties, enabling the current collector to withstand silicon's volume expansion during cycling
Solution Approach 2:
The patent creates a composite microstructure within the copper foil by controlling the distribution and orientation of high-angle grain boundaries, forming a multi-phase grain structure that combines ductility with strength to accommodate mechanical stress from silicon expansion
3Strength
If high proportion of nano-twins is used to strengthen copper foil, then the tensile strength increases, but the manufacturing becomes difficult for industrial mass production
Solution Approach 1:
The patent changes manufacturing parameters including current density (20-80 A/dm²), electrolyte temperature (20-60°C), and chemical composition (chloride ions, additives) to control grain boundary formation during electrodeposition, achieving high-strength foil through standardized industrial processes
Solution Approach 2:
The patent replaces mechanical strengthening methods with electrochemical control mechanisms, using electric current and electrolyte chemistry to directly control grain boundary formation and orientation during the electrodeposition process, eliminating the need for post-processing mechanical treatments
4Strength
If low current density is applied during electroplating to produce high-strength copper foil, then the twin grain boundary ratio increases, but the production speed decreases making mass production difficult
Solution Approach 1:
The patent optimizes the current density parameter to the range of 20-80 A/dm², which is sufficiently high to enable fast production speeds while still controlling the electrochemical deposition process to form the desired twin grain boundary structure and fine grain morphology
Solution Approach 2:
The patent employs periodic control of deposition parameters including current density cycles and temperature management during electrodeposition to consistently produce the target grain boundary structure at high production rates, maintaining quality uniformity across large-scale manufacturing
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 resulting copper foil exhibits high tensile strength, thermal stability, and fine grain structure, suitable for thin circuit boards and lithium-ion battery applications, facilitating increased energy density and capacity while maintaining durability.
Implementation Method 1
electrodepositing copper on the rotating cathode roll
Implementation Method 2
the electrolytic solution includes chloride ions in a range of from about 0.01 ppm to about 25.0 ppm and additives in a range of from about 0.01 ppm to about 75.0 ppm
Data Source
AI summary
Disclosed are electrolytic copper foils, characterized in that: an electrodeposited surface of the electrolytic copper foil has an average surface roughness (Sz) of 3.50 μm or less; the electrolytic copper foil has a twin grain boundary ratio of 35% or less, or a total grain boundary density of 3.50 μm−1 or more after heat treatment at 200° C. for 2 hours; the electrolytic copper foil is manufactured by electrodepositing in an electrolytic solution; and the electrolytic solution comprises 0.01 ppm to 25.0 ppm of chloride ion and 0.01 ppm to 75.0 ppm of an additive. Also disclosed are methods of manufacturing the electrolytic copper foils, and articles made therefrom. The articles include negative electrode current collectors of lithium-ion batteries or electrical double-layer capacitors, resin coated coppers, copper clad laminates, flexible copper clad laminates, various types of printed circuit boards, and the like.