Aluminum-Alloy Foil Composition for Thin Battery Current Collectors
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Solution Overview
Problem
Aluminum-alloy foils used as current collectors in power storage devices face a trade-off between high strength and high elongation, leading to breakage during manufacturing and battery operation due to reduced tensile strength and elongation with thinner foils.
Innovation Solution
An aluminum-alloy foil with a specific chemical composition (Fe: 1.0% to 2.0%, Cu: 0.1% to 0.5%, Mn: 0.05% or less, and Si: 0.01% to 0.6%) and a thickness of 20 μm or less, satisfying the condition El≥100×t/UTS, where El is elongation and UTS is tensile strength, to achieve both high strength and elongation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the foil thickness is reduced to improve battery capacity, then the weight and volume are reduced, but the tensile strength and elongation decrease causing breakage during manufacturing and operation
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition parameters (Fe: 1.0-2.0%, Cu: 0.1-0.5%, Mn: 0.05% or less, Si: 0.01-0.6%) and processing parameters (hot rolling temperature 350-500°C, cold rolling reduction ratio 90-98%, artificial aging temperature 100-200°C) to achieve the optimal balance between foil thickness and tensile strength, resolving the contradiction between thinning the foil and maintaining strength
Solution Approach 2:
The patent creates a composite microstructure within the aluminum alloy by combining multiple alloying elements (Fe, Cu, Mn, Si) that form different phases and precipitates, enhancing the strength of the thin foil through microstructural design rather than simply increasing thickness
2Quantity of substance
If the foil thickness is reduced to improve battery capacity, then the weight and volume are reduced, but the elongation decreases causing breakage during electrode manufacturing and battery operation
Solution Approach 1:
The patent simultaneously optimizes multiple parameters including chemical composition (Fe, Cu, Mn, Si content) and processing conditions (hot rolling temperature, cold rolling reduction, artificial aging) to achieve both high elongation and high strength in thin foils, ensuring reliability during manufacturing and operation
Solution Approach 2:
The patent creates local quality variations through controlled precipitate distribution and grain structure refinement, where the microstructure is optimized at the local level to provide both ductility and strength, preventing breakage while maintaining thin foil dimensions
3Strength
If the Fe content is increased to improve tensile strength, then the strength increases, but the resistivity increases reducing energy efficiency
Solution Approach 1:
The patent optimizes the Fe content parameter within a specific range (1.0-2.0%) and combines it with Cu (0.1-0.5%) and controls Mn (0.05% or less) to achieve the desired strength while minimizing resistivity increase through synergistic alloying effects and controlled precipitate formation
Solution Approach 2:
The patent creates a multi-phase composite structure where Fe-rich precipitates provide strength while Cu and other elements modify the matrix properties, achieving a balance between strength and electrical conductivity through compositional design
Data Source
AI summary
An aluminum-alloy foil that enables to satisfy both of high elongation and high strength even in the case of reducing the foil thickness. The chemical composition of the aluminum-alloy foil contains, in mass %, Fe: 1.0% or more and 2.0% or less, Cu: 0.1% or more and 0.5% or less, and Mn: 0.05% or less, the remainder being Al and unavoidable impurities. The aluminum-alloy foil has a foil thickness of 20 μm or less, and satisfies the relation El≥100×t/UTS. Here, t represents a foil thickness (μm), UTS represents a tensile strength (MPa), and El represents an elongation (%).