Cu-Clad Battery Terminal Recess to Prevent Al Layer Exposure
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Solution Overview
Problem
The exposure of the Al layer to the surface of the recess, which needs to be composed of a Cu layer, can lead to a deterioration in electrical characteristics due to the Al layer being elongated more than the Cu layer and forming gaps when in contact with the electrolyte, especially at the thinned side wall of the recess.
Innovation Solution
A battery terminal is designed with an Al layer made of an Al alloy containing a high content of Al and Mn or Mg, diffusion bonded with a Cu layer, ensuring a hardness greater than pure Al, reducing the elongation of the Al layer during press working and preventing exposure to the electrolyte, while maintaining conductivity at 30% IACS or more.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If pure Al layer is annealed to soften it for press working, then press workability is improved, but the Al layer becomes too soft and elongates more than the Cu layer, causing exposure and breakthrough to the surface
Solution Approach 1:
The patent changes the material parameter of the Al layer from pure Al to Al alloy containing Mn or Mg, which fundamentally alters the hardness characteristics. This alloying allows the Al layer to maintain higher hardness even after annealing, preventing excessive elongation while still enabling press working. The conductivity is maintained at 30% IACS or more despite the alloying.
Solution Approach 2:
The patent creates a composite structure where the Al layer is made of Al alloy (not pure Al) and is diffusion-bonded with the Cu layer. This composite approach allows combining the benefits of Al (lightweight, conductivity) with improved mechanical properties from alloying, while the diffusion bonding ensures strong interlayer adhesion and prevents delamination during pressing.
2Ease of manufacture
If the Al layer is softened by annealing, then the Cu layer can be pressed to form the recess, but the softened Al layer breaks through the Cu layer and is exposed on the surface
Solution Approach 1:
By changing the Al layer from pure Al to Al alloy with Mn or Mg content, the hardness parameter is fundamentally altered. The alloyed Al layer maintains higher hardness after annealing, which prevents breakthrough through the Cu layer during pressing while still allowing the Cu layer to be formed into the recess shape.
Solution Approach 2:
The patent performs diffusion bonding between the Al alloy layer and Cu layer before press working. This preliminary bonding action creates a strong interface that prevents delamination and controls the deformation behavior during subsequent pressing, ensuring the Al layer does not breakthrough the Cu layer.
3Reliability
If pure Al is used in the Al layer, then conductivity is high, but hardness is low causing excessive elongation during pressing
Solution Approach 1:
The patent optimizes the composition parameters of the Al layer by adding Mn or Mg to create an Al alloy. This composition change simultaneously improves hardness (preventing excessive elongation) and maintains conductivity at 30% IACS or more, resolving the trade-off between strength and conductivity.
Solution Approach 2:
The patent applies different material qualities to different layers: the Al layer is made of Al alloy with specific Mn or Mg content to achieve the right balance of hardness and conductivity, while the Cu layer maintains its inherent high conductivity and ductility. This local optimization allows each layer to perform its specific function effectively.
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 Al layer exposure and gap formation, maintaining electrical characteristics by ensuring the Al layer does not break through the Cu layer, thus preserving the conductivity required for the battery terminal.
Implementation Method 1
an Al layer made of an Al alloy containing a highest content of Al and a second highest content of Mn or Mg and having a conductivity of 30% IACS or more, and a Cu layer made of Cu are diffusion bonded to each other in a stacking direction
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A negative electrode terminal (battery terminal) (10) includes a flange (12) in which an Al layer (41) made of an Al alloy containing a highest content of Al and a second highest content of Mn or Mg and having a conductivity of 30% IACS or more, and a Cu layer (42) made of Cu are diffusion bonded to each other in a stacking direction, a shaft (11) extending from the flange in the stacking direction of the Al layer and the Cu layer, and a recess (13) at an end of the shaft on a side of the Cu layer, including a surface composed of the Cu layer.