Negative-Electrode Terminal With Segmented Clad Portion
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Solution Overview
Problem
In lithium ion cells, excessive formation of intermetallic compounds at the bond interface between Al and Ni layers during welding leads to reduced bond strength and separation of the metal layers.
Innovation Solution
A negative-electrode terminal with a clad portion formed by bonding an Al layer and a Ni-Cu alloy layer, where the Ni-Cu alloy layer is embedded in the Al layer to prevent heat from reaching the bond interface, enhancing bond strength and reducing electrical resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the Al layer and Ni layer are bonded to each other over the whole surfaces to form a clad body, then welding between the lead and the clad body becomes easy due to resistance welding, but excessive formation of intermetallic compound occurs on the bond interface between the Al layer and the Ni layer, causing bond strength to lower and layers to separate
Solution Approach 1:
The bond interface between the Al layer and Ni layer is segmented into a stacked region and a connected region. The second metal layer (Ni layer) is positioned only in the stacked region and is not arranged in the connected region, which is the region actually connected with the cell terminal connecting plate. This segmentation prevents excessive intermetallic compound formation at the connection point while maintaining bonding strength in the stacked region.
Solution Approach 2:
Different regions of the clad body are given different structural characteristics. The stacked region has the second metal layer bonded to the first metal layer for strong bonding, while the connected region has only the first metal layer for optimal welding performance. This local differentiation allows each region to perform its specific function without the adverse effects of intermetallic compound formation.
2Ease of manufacture
If heat is applied during welding of the lead and clad body, then welding connection is achieved, but heat reaches the bond interface between the Al layer and Ni layer, causing excessive intermetallic compound formation
Solution Approach 1:
The connected region is separated from the stacked region, and the second metal layer is excluded from the connected region. This segmentation creates a heat isolation effect where the welding heat applied at the connected region does not directly reach the bond interface in the stacked region, preventing excessive intermetallic compound formation while still achieving welding connection.
3Area of stationary object
If the second metal layer is arranged in the connected region, then complete coverage is achieved, but heat during welding reaches the Al-Ni bond interface, causing intermetallic compound formation and layer separation
Solution Approach 1:
The coverage area of the second metal layer is segmented to be present only in the stacked region and absent from the connected region. This selective positioning maintains sufficient coverage for bonding purposes while preventing the harmful effect of heat-induced intermetallic compound formation at the welding connection point, thereby ensuring bond reliability.
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 inhibits excessive intermetallic compound formation, strengthens the bond between the Al and Ni layers, and reduces electrical resistance, making the connection more reliable and efficient.
Implementation Method 1
the Ni-Cu alloy layer is embedded in the Al layer to prevent heat from reaching the bond interface
Implementation Method 2
a clad portion formed by bonding an Al layer and a Ni-Cu alloy layer
Data Source
AI summary
A negative-electrode terminal for a cell in which separation between a first metal layer and a second metal layer hardly takes place is provided by suppressing excess formation of an intermetallic compound on a bond interface between the first metal layer and the second metal layer. This negative-electrode terminal for a cell includes a clad portion formed by bonding a first metal layer made of Al or an Al alloy and a second metal layer containing Ni and Cu and consisting of one or a plurality of layers to each other. The first metal layer includes a connected region connected with a cell terminal connecting plate and a stacked region adjacent to the connected region on the side of the same surface, while the second metal layer is bonded to the first metal layer in the stacked region and configured to be connectable to cell negative electrodes of cells.