Battery Tab Compaction Layout for Crack-Resistant Ultrasonic Welding
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Solution Overview
Problem
Existing battery cells face issues with cracks at the connecting portion between tab sheets and terminal posts, leading to reduced conductive yield rate and connection strength, which affects the reliability of the battery.
Innovation Solution
The tab sheets are configured with a higher compaction degree in the first area and a lower compaction degree in the second area, with the edge of the connecting portion located in the first area, allowing for reduced pulling stress and improved deformation during welding, thus enhancing the connection strength and reducing cracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the tab sheets are uniformly compacted, then the connection strength is improved, but cracks appear at the connecting portion edge
Solution Approach 1:
The patent applies different compaction degrees to different areas of the tab sheets. The first area (connecting portion edge) has a first compaction degree, while the second area (inner portion) has a second compaction degree that is lower than the first. This local differentiation allows the edge to have sufficient strength for connection while the inner area maintains flexibility to reduce stress concentration, thereby preventing cracks.
2Productivity
If the tab sheets are highly compacted, then the conductive yield rate is improved, but pulling stress increases causing cracks
Solution Approach 1:
The patent differentiates compaction by location: the first area at the connecting portion edge achieves high compaction (first compaction degree) to ensure good electrical connection and high conductive yield rate, while the second area in the inner portion maintains lower compaction (second compaction degree) to reduce pulling stress and prevent crack formation during welding.
3Strength
If the tab sheets are uniformly welded, then the connection is strong, but the pulling stress at junctions causes cracking
Solution Approach 1:
The patent implements non-uniform welding compaction where the first area at the connecting portion edge receives higher compaction (first compaction degree) for strong welding connection, while the second area in the inner portion receives lower compaction (second compaction degree). This gradient structure allows the welded junction to accommodate thermal expansion and contraction stresses, reducing pulling stress concentration that would otherwise cause cracks.
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
This configuration improves the conductive yield rate and connection strength at the tab portion-terminal post junction, enhancing the reliability of the battery cell by minimizing cracks and ensuring effective electrical conductivity.
Implementation Method 1
an ultrasonic welding head (400) used for processing a gathered portion (722). A welding surface (9) of the ultrasonic welding head (400) includes a first surface portion (91) and a second surface portion (92), the first surface portion (91) protrudes from the second surface portion (92)
Data Source
AI summary
A battery cell includes a case, a terminal post, and an electrode assembly. The terminal post is provided with ten cases. The electrode assembly includes an active material coating portion provided in the ten cases, and a tab portion electrically connected to the active material coating portion and the terminal posts. The tab portion includes multiple tab sheets. The multiple tab sheets are stacked and connected to form a gathered portion. The gathered portion has a first area and a second area. A compaction degree of the multiple tab sheets in the first area is greater than that in the second area. A connecting portion is formed at a position of the gathered portion used for being electrically connected to the terminal post. At least part of an edge of the connecting portion on the gathered portion is located in the first area.