Secondary Battery Cap Welding Recess for Flush Side Sealing
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Solution Overview
Problem
Surface unevenness caused by welding beads on the cap assembly of secondary batteries can lead to connection failures at the positive and negative electrodes, affecting the reliability and performance of the battery module.
Innovation Solution
Incorporating a welding recess at the side portion of the cap assembly and the battery can, allowing for top surface welding and preventing weld beads from protruding, thus maintaining a uniform size and preventing connection failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If top surface welding is used to join the cap assembly to the battery can, then the bonding strength is improved, but the surface unevenness increases due to protruding weld beads
Solution Approach 1:
The cap assembly is designed with a welding recess at the peripheral portion, creating a localized depression area specifically for receiving weld beads. This local structural modification allows the welding process to maintain strong bonding while containing the surface unevenness within the recess area, preventing protrusion onto the outer peripheral surface.
Solution Approach 2:
Instead of treating the weld bead protrusion as a harmful defect to be eliminated, the invention converts it into a beneficial feature by designing the welding recess to intentionally accommodate the weld beads. The previously harmful protruding beads are now contained within the recess, transforming the welding process outcome from a defect into a controlled structural feature that maintains both strength and surface uniformity.
2Reliability
If welding is performed on the battery can and cap assembly, then the sealing reliability is improved, but the alignment complexity increases due to surface unevenness
Solution Approach 1:
The welding recess creates a localized area with different surface characteristics compared to the rest of the cap assembly. This local modification provides a defined zone for welding operations, making it easier to align and position the cap assembly relative to the battery can during the welding process, thereby reducing overall alignment complexity while maintaining sealing reliability.
3Shape
If the cap assembly width is reduced to fit within the battery can width, then the surface uniformity is improved, but the electrode terminal connection area is reduced
Solution Approach 1:
The cap assembly is segmented into different functional zones: a peripheral portion with the welding recess for sealing purposes, and an inner portion with electrode terminals for electrical connection. This segmentation allows the peripheral area to be optimized for surface uniformity while the inner connection area maintains sufficient size for electrical connectivity, resolving the contradiction between surface uniformity and connection area.
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 implementation of a welding recess ensures a uniform size of the secondary battery after welding, enhances the stability and yield of the battery, and reduces alignment complexity in battery modules, thereby improving the overall performance and density of the battery cells.
Implementation Method 1
a side weld joining a side portion of the welding end of the battery can to a side portion of the cap assembly
Data Source
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AI summary
A secondary battery (500), comprising: a battery can (100) having an opening (O) to expose an accommodating space to the outside, a can width (Dcan) in a first direction, and a can length in a second direction crossing the first direction; an electrode assembly (EA) in the accommodating space, and comprising a positive electrode plate (A), a negative electrode plate (C), and a separator (S) between the positive electrode plate (A) and the negative electrode plate (C); a cap assembly (200) electrically connected to the positive electrode plate (A) and the negative electrode plate (C), and having a welding recess (WR) at a peripheral portion of the cap assembly (200), the cap assembly (200) being joined to a welding end (WE) of the battery can 100 via the welding recess (WR) to seal the accommodating space; and a side welding unit (300) joining a side portion of the welding end (WE) of the battery can (100) to a side portion of the cap assembly (200), a surface of the side welding unit (300) being located at a same level as or a level lower than that of an outer peripheral surface (101) of the battery can (100).