Protective Copper Foil Plating to Prevent Curling in Thin Battery Electrodes
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Solution Overview
Problem
The challenge is to prevent curling, wrinkling, and tearing of copper foils during manufacturing and after salt spray testing, which affects the quality and capacity of secondary batteries, as thinner copper foils are more prone to defects and reduced workability.
Innovation Solution
A copper foil with a tensile strength index of 3.0 kgf/mm2 or less and an elongation index of 2.1% or less is developed, featuring a copper film with a protective layer, manufactured using a specific electrolyte composition and process that includes copper ions, sulfuric acid, chlorine, lead ions, arsenic, silver ions, hydrogen peroxide, and organic additives to enhance durability and prevent defects.
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 defects occur during manufacturing
Solution Approach 1:
The patent applies parameter changes by precisely controlling the electrolyte composition (copper ion concentration: 60-100 g/L, sulfuric acid: 50-150 g/L, temperature: 40-60°C) and electroplating conditions (current density: 20-50 ASD) to produce ultra-thin copper foils with optimized mechanical properties that prevent curling while maintaining thinness for high capacity
Solution Approach 2:
The patent creates a composite structure by forming a copper foil with controlled grain structure and surface morphology through electroplating, resulting in a composite material that combines ultra-thin thickness with enhanced mechanical strength and curling resistance
2Quantity of substance
If copper foil thickness is reduced to increase active material capacity, then battery capacity increases, but workability deteriorates due to curling
Solution Approach 1:
The patent changes physical parameters of the copper foil by controlling electrolyte composition and plating conditions to achieve a balance between thickness and mechanical properties, ensuring the foil remains flat and easy to handle despite ultra-thin dimensions
Solution Approach 2:
The patent applies preliminary action by pre-treating the copper foil surface during electroplating to establish optimal surface morphology and mechanical properties before the foil is used in battery manufacturing, preventing curling issues before they occur
3Quantity of substance
If copper foil is made thinner to increase capacity, then more active material can be included, but tensile strength and elongation become unbalanced causing deformation
Solution Approach 1:
The patent precisely adjusts electrolyte parameters (copper ion concentration, sulfuric acid content, temperature, pH) and electroplating parameters (current density, time) to control the copper foil's crystal structure and mechanical properties, achieving balanced tensile strength and elongation ratios suitable for ultra-thin foils
Solution Approach 2:
The patent applies local quality by creating specific surface morphology and grain structure characteristics in different regions of the copper foil through controlled electroplating, optimizing local mechanical properties to prevent deformation while maintaining overall thinness
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 effectively prevents curling, wrinkling, and tearing of the copper foil during and after the salt spray test, ensuring high workability and capacity retention in secondary batteries, while maintaining a balance between tensile strength and elongation to prevent deformation and delamination.
Implementation Method 1
forming a copper film by electroplating in an electrolytic bath
Implementation Method 2
forming a copper film by electroplating in an electrolytic bath, wherein the electrolyte includes copper ions at a concentration of 70 g/L to 100 g/L, sulfuric acid at a concentration of 70 g/L to 150 g/L
Data Source
AI summary
According one embodiment of the present disclosure, there is provided a copper foil including a copper film including 99.9 wt % or more of copper, and a protective layer formed on the copper film, wherein the copper foil has a tensile strength index of 3.0 kgf/mm2 or less, and an elongation index of 2.1% or less.