Battery Collector Cladding Material Warping Prevention
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Solution Overview
Problem
Existing battery collector cladding materials face issues with warping due to differences in thermal expansion coefficients between aluminum and copper foils, leading to convex and concave warps during rolling and cooling, and increased contact resistance due to insufficient active material penetration on roughened stainless steel surfaces.
Innovation Solution
A cladding material with a two-layer structure of Al-based and Cu-based alloys, where the Al layer's thickness is limited to no more than 35% of the total thickness, or a three-layer structure with a high Young's modulus core layer, to reduce warping and enhance active material contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the aluminum foil thickness ratio is increased to about 67% in a two-layer cladding structure, then the ease of manufacture is improved, but the manufacturing precision deteriorates due to remarkable warping during rolling and cooling
Solution Approach 1:
The patent changes the thickness ratio parameter of the aluminum layer from the conventional 67% to 30-70%, which balances the plastic deformability and thermal shrinkage between the two layers, thereby preventing remarkable warping during rolling and cooling processes while maintaining ease of manufacture
Solution Approach 2:
The patent uses a composite two-layer structure of aluminum-based and copper-based foils with optimized thickness ratios. This composite structure leverages the complementary properties of both materials to reduce warping while maintaining manufacturability
2Manufacturing precision
If a stainless steel collector with roughened surface is used to prevent warping, then the manufacturing precision is improved, but the contact resistance increases due to insufficient active material penetration
Solution Approach 1:
The patent applies different surface properties to different parts of the collector structure. The aluminum-based layer provides a relatively smooth surface for good contact, while the copper-based layer provides high electrical conductivity. This local differentiation resolves the contradiction between preventing warping and ensuring low contact resistance
Solution Approach 2:
The composite two-layer structure combines aluminum-based and copper-based foils, where the aluminum layer provides structural stability and the copper layer provides excellent electrical conductivity and contact properties, thereby achieving both low warping and low contact resistance
3Manufacturing precision
If the aluminum foil thickness is increased to prevent warping during cooling, then the manufacturing precision is improved, but the weight of the battery collector increases
Solution Approach 1:
The patent optimizes the thickness ratio parameter of the aluminum layer to 30-70% of the total thickness, which is sufficient to prevent warping during cooling without excessive weight increase. This parameter optimization balances manufacturing precision and weight reduction
Solution Approach 2:
The patent uses a thin copper-based layer (30-70% thickness ratio) that compensates for the aluminum layer's thermal shrinkage, allowing the use of thinner overall material while maintaining dimensional stability, thereby reducing weight while preventing warping
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 warping and reduces contact resistance by ensuring flexible Al and Cu layers maintain close contact with active materials, improving the battery collector's structural integrity and performance.
Implementation Method 1
the aluminum foil more easily plastically deformable than the copper foil
Implementation Method 2
thermal shrinkage of the aluminum foil having a large thickness remarkably influences at the time of the cooling after the heat treatment, since the thermal expansion coefficient of the aluminum foil is larger than that of the copper foil
Implementation Method 3
the thermal expansion coefficient of the aluminum foil is larger than that of the copper foil
Data Source
AI summary
This cladding material for a battery collector consists of a cladding material having a two-layer structure formed by bonding a first layer arranged on a first surface and constituted of an Al-based alloy and a second layer arranged on a second surface and constituted of a Cu-based alloy to each other by rolling. The ratio of the thickness of the first layer to the total thickness of the first layer and the second layer is not more than 35%.