Aluminum Cathode Foil Composition for High-Temperature Strength
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Solution Overview
Problem
Current battery foils, particularly cathode current collector foils, face challenges in maintaining mechanical properties at high temperatures, leading to issues such as plastic deformation, wrinkles, and breakage during battery production, especially in high-temperature applications like racing car batteries.
Innovation Solution
A thin aluminum foil with a specific chemical composition and a unique manufacturing process, including hot rolling, cold rolling, and foil rolling without intermediate or final annealing, to achieve high tensile strength and thermal stability, featuring controlled intermetallic particle size and density for improved mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the aluminum foil undergoes cold rolling with high thickness reduction to increase tensile strength, then the tensile strength increases, but the electrical conductivity decreases significantly
Solution Approach 1:
The patent changes the chemical composition parameters of the aluminum alloy by precisely controlling the content of alloying elements (Fe: 0.01-0.6 wt%, Si: 0.01-0.2 wt%, Cu: 0.01-0.2 wt%, Mn: 0.01-0.05 wt%, Mg: 0.01-0.05 wt%, Ti: 0.01-0.05 wt%, Zn: 0.01-0.1 wt%). This compositional parameter adjustment allows achieving tensile strength ≥220 MPa while maintaining electrical conductivity ≥50% IACS, resolving the contradiction between strength and conductivity that would otherwise require extreme cold rolling.
2Loss of substance
If the aluminum foil is heated to high temperatures for solvent evaporation during battery manufacturing, then the solvent is removed, but the mechanical properties of the foil deteriorate causing deformation and breakage
Solution Approach 1:
The patent applies preliminary heat treatment (annealing) during the foil manufacturing process before the battery production stage. This preliminary action optimizes the microstructure and mechanical properties of the aluminum alloy foil in advance, creating a material that can withstand the subsequent high-temperature solvent evaporation process (heating to 80-100°C) without undergoing plastic deformation or breakage, thus preventing production interruptions.
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 results in an aluminum foil with tensile strength of 245-275 MPa and elongation of 2.5-4.6%, maintaining mechanical integrity at elevated temperatures up to 70°C, suitable for high-temperature battery applications.
Implementation Method 1
Iron (Fe) as an alloying element was chosen to increase the strength of the aluminum alloy through solid solution and intermetallic formation of Al-Fe and Al-Fe-Si intermetallics
Implementation Method 2
the formation of Al-Fe, Al-Fe-Si intermetallic particles in aluminum alloys is inevitable and does not have a negative effect on the mechanical properties of the aluminum alloy
Implementation Method 3
the tensile strength of 261MPa was achieved after cold rolling in which the entire thickness reduction is 98.3% or more
Data Source
Figure 1~2
AI summary
The invention relates to a battery foil (current collector) comprising an aluminum alloy, with the following composition: Si: 0.1 - 0.2wt-%, Fe: ≤ 0.6wt-%, Cu: 0.1 - 0.2wt-%, Mn: 0.03 - 0.05wt-%, Mg: 0.0 - 0.05wt-% Zn: 0.0-0.1wt-% Ti: 0.0 - 0.05wt-%, with 3-4 times as much Fe as Si, with at least 4 times as much Cu as Ti, wherein the aluminum alloy may have impurities of Cd with a max 20ppm, Pb with a max 100ppm and Hg with a max 5ppm, the sum of Pb, Hg, Cd and CrVI being ≤100ppm, the others (not mentioned) individually <0.05 wt-% and the sum of the others ≤0.15 wt-%, with the rest of the alloy being Al, and, wherein the battery cathode foil has intermetallic phases having an average diameter length of 0.5µm or more and their number density being on average 1.3×104particles/mm2 or more.