Battery Cap Assembly Butt Welding for Height Reduction
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Solution Overview
Problem
Existing battery module designs face challenges in reducing height and ensuring strong connections between electrode terminals and connecting pieces, leading to low welding strength and reduced cycle life due to dimension tolerances and the need for thick electrode terminals for laser penetration welding.
Innovation Solution
A battery cap assembly with protruding electrode terminals and connecting pieces that allow for butt welding and laser penetration welding, reducing the height of the module and improving connection strength by using a cap plate with terminal holes and protrusions that facilitate secure attachment without increasing module height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If laser penetration welding is used to fix the connecting piece to the electrode terminal, then the welding strength is ensured, but the thickness of the electrode terminal must be not less than 2mm, which increases the height of the battery module
Solution Approach 1:
The patent transitions from vertical penetration welding (requiring thickness in the height direction) to lateral butt welding (utilizing the width dimension). The connecting piece is designed with protrusions that weld to the electrode terminal's upper surface, allowing sufficient welding area without increasing the terminal's protruding thickness, thus reducing battery module height while maintaining welding strength.
2Length of stationary object
If butt welding is used to fix the connecting piece to the electrode terminal, then the height of the battery module is reduced, but the dimension tolerances of secondary batteries make it difficult to attach the connecting piece accurately, leading to low welding strength
Solution Approach 1:
The connecting piece is designed with protrusions that preliminarily fit into corresponding recesses on the electrode terminal before welding. This preliminary mechanical interlocking ensures accurate positioning and alignment, compensating for dimension tolerance accumulations in secondary batteries, and provides a stable base for subsequent butt welding to achieve strong connections.
Solution Approach 2:
The patent introduces a specially designed connecting piece structure with protrusions and recesses that acts as an intermediary between the electrode terminal and the battery module assembly. This intermediary structure absorbs the dimension tolerance variations through its geometric design, ensuring consistent and accurate attachment across different battery units while maintaining reduced height.
3Strength
If the electrode terminal thickness is increased to ensure laser penetration welding, then the welding strength is improved, but the space occupied by the electrode terminal and connecting piece increases, reducing energy density
Solution Approach 1:
The patent shifts the welding approach from requiring thickness in the vertical dimension (laser penetration) to utilizing area in the horizontal dimension (butt welding of protrusions). This allows sufficient welding surface area for strong connections without increasing the protruding thickness of the electrode terminal, thereby reducing the space occupied and improving energy density.
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 reduces the thickness of electrode terminals and connecting pieces, enhances energy density, and increases the cycle life of the battery module by ensuring strong connections despite dimension tolerances, while minimizing heat damage and material usage.
Implementation Method 1
the connecting piece is generally fixed to an electrode terminal of the secondary battery by laser penetration welding
Implementation Method 2
the connecting piece also can be fixed to the electrode terminal by butt welding in the prior art
Data Source
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AI summary
The present invention provides a battery cap assembly, a secondary battery and a battery module. The battery cap assembly comprises: a cap plate, including a second terminal hole; a first electrode terminal, at least a part of which protruding above the cap plate; a second electrode terminal, including a second protruding portion protruding above the cap plate and a second base portion connected with the second protruding portion. The first electrode terminal is provided with a protrusion used for welding with a first connecting piece; the second protruding portion is used for welding with a second connecting piece to form a welding portion, and a projection of the welding portion in an up-down direction is positioned in a cross-section of the second base portion. The secondary battery comprises a case, an electrode assembly and the battery cap assembly. The battery module comprises the first connecting piece and the secondary batteries.