High-Elongation Copper Foil Through Local Grain Refinement
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Solution Overview
Problem
The demand for thinner copper foils for secondary batteries has increased, but thinner foils exhibit weaker mechanical strength and lower elongation rates due to increased plastic anisotropy and bamboo-like microstructures formed during heat treatment.
Innovation Solution
A method of manufacturing copper foil with a high elongation rate by controlling its microstructure, involving the preparation of a plating solution with copper ions, conductivity additives, a plating inhibitor, and a plating accelerator, and electroplating the copper foil on a substrate while preventing the formation of bamboo-like microstructures through local grain refinement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the copper foil is made thinner to increase battery capacity, then the battery capacity increases, but the mechanical strength and elongation rate of the copper foil decrease
Solution Approach 1:
The invention applies local quality by creating a dual-phase microstructure where the surface layer has fine grains (0.5-5 μm) providing high strength and elongation, while the interior maintains larger grains for ductility. This local differentiation of grain sizes at different depths resolves the contradiction between thin foil strength and overall mechanical performance.
Solution Approach 2:
The invention uses preliminary action by adding specific additives (polyethylene imine and gelatin) to the electroplating solution before deposition to control nucleation and grain growth during the plating process. This preliminary chemical preparation ensures the formation of the desired fine-grained surface structure and dual-phase microstructure, preventing bamboo-like structure formation from the outset.
2Strength
If heat treatment is applied to improve mechanical properties, then defects are eliminated, but bamboo-like microstructure forms increasing plastic anisotropy
Solution Approach 1:
The invention prevents bamboo-like structure by creating local quality differences in grain size throughout the foil thickness. The surface layer has fine grains while the interior has larger grains, which disrupts the uniform grain growth that causes bamboo-like structure during heat treatment, thereby maintaining microstructure uniformity while improving mechanical properties.
Solution Approach 2:
The invention applies preliminary action by pre-forming a controlled dual-phase microstructure during electroplating before heat treatment occurs. The additive-controlled nucleation and grain growth during plating creates a microstructure that is resistant to bamboo-like transformation during subsequent heat treatment, preventing the worsening of plastic anisotropy.
3Strength
If recrystallization method with heat treatment is used to improve mechanical properties, then defects are eliminated, but elongation rate does not effectively increase due to plastic anisotropy
Solution Approach 1:
The invention uses local quality by establishing a depth-dependent grain size distribution where the surface layer (0-10 μm from surface) has fine grains (0.5-5 μm) for high elongation, while the interior has larger grains. This local differentiation ensures that during heat treatment, the surface layer maintains fine grains that prevent stress concentration and enhance elongation rate, directly resolving the contradiction between mechanical property improvement and elongation maintenance.
4Productivity
If conventional electroplating is used to manufacture thin copper foil, then production efficiency is maintained, but bamboo-like microstructure forms reducing reliability
Solution Approach 1:
The invention applies preliminary action by incorporating specific additives (polyethylene imine at 10-50 ppm and gelatin at 5-20 ppm) into the electroplating solution before deposition begins. These additives control the nucleation and grain growth kinetics during the electroplating process itself, pre-forming a dual-phase microstructure that prevents bamboo-like structure formation during subsequent heat treatment, thereby maintaining reliability while preserving production efficiency.
Solution Approach 2:
The invention uses parameter changes by modifying the electroplating solution composition with specific additives and controlling their concentrations within precise ranges. This changes the electrochemical parameters during plating to control grain nucleation and growth, forming the desired microstructure that prevents bamboo-like structure formation during heat treatment, thus improving reliability without sacrificing productivity.
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 method achieves a copper foil with an elongation rate per unit thickness of 0.6%/μm or more, improving mechanical properties and preventing stress concentration during deformation, thus enhancing the reliability of secondary battery products.
Implementation Method 1
manufacturing the copper foil by immersing a substrate in the plating solution and applying an electric current to the plating solution to electroplate the copper foil on a surface of the substrate
Implementation Method 2
The local grain refinement region may be formed by an interaction between the plating inhibitor and the plating accelerator
Implementation Method 3
Recrystallization of the copper foil may occur in the local grain refinement region
Data Source
AI summary
The method of manufacturing a copper foil with a high elongation rate includes: preparing a plating solution by mixing a copper ion, an additive for improving conductivity, a plating inhibitor, and a plating accelerator; and manufacturing the copper foil by immersing a substrate in the plating solution and applying an electric current to the plating solution to electroplate the copper foil on a surface of the substrate.