Battery Module Weld Bead Geometry for Stable Tab-to-Bus Bar Joining
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Solution Overview
Problem
Current laser welding methods for battery modules often result in defects such as weak welding, non-uniformity, and the formation of intermetallic compounds that affect mechanical and electrical characteristics, leading to increased resistance and brittleness, particularly when joining dissimilar materials like aluminum and copper.
Innovation Solution
A battery module design featuring a bus bar with holes for electrode tabs, where the weld bead's metal concentration and height-to-width ratio are optimized within specific ranges to ensure stable and reliable electrical connections, minimizing defects and enhancing mechanical and electrical characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If laser welding is used to join dissimilar materials (aluminum and copper), then electrical conductivity and thermal conductivity are improved, but intermetallic compounds are generated that increase electrical resistance and reduce mechanical strength
Solution Approach 1:
The patent applies parameter changes by precisely controlling laser welding parameters (power, speed, focus position) to optimize the welding process. By adjusting these parameters, the patent achieves complete penetration welding that minimizes intermetallic compound formation while ensuring reliable electrical connection between dissimilar materials
Solution Approach 2:
The patent uses a guide pattern (marker) that is copied or replicated along the welding path to ensure consistent welding parameters and complete penetration. This guide pattern helps maintain uniform welding quality and prevents defects across the entire weld bead
2Reliability
If lap welding is used to join electrode tabs and bus bars, then electrical connection is achieved, but welding defects occur frequently leading to weak welding
Solution Approach 1:
The patent inverts the traditional lap welding approach by using complete penetration welding where the laser passes through the entire thickness of the workpiece. This inversion of the welding mode eliminates the accumulation of oxides and contaminants that cause defects in lap welding, resulting in stronger and more reliable welds
Solution Approach 2:
The patent utilizes phase transitions (melting and vaporization) of the material during laser welding to achieve complete penetration. The material transitions from solid to liquid and partially to vapor, allowing the laser to pass through and create a clean weld pool that solidifies into a strong bond without lap welding defects
3Reliability
If plating layers are formed on the bus bar to improve physical properties, then corrosion resistance is improved, but surface properties change causing non-uniform weld beads and defects
Solution Approach 1:
The patent applies preliminary action by forming a specific guide pattern (marker) on the bus bar surface before welding. This pre-formed pattern serves as a reference for the laser welding process, ensuring consistent welding parameters and uniform weld beads even on plated surfaces, thereby preventing welding defects
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 optimized weld bead configuration improves the mechanical and electrical characteristics of the battery module by reducing defects and ensuring consistent welding quality, even under varying conditions, thereby enhancing the reliability and performance of the battery module.
Implementation Method 1
laser welding is being used as the most common joining method
Implementation Method 2
weld bead... by melting and fusing the materials
Data Source
AI summary
A battery module including a plurality of battery cells each including an electrode tab and at least one bus bar comprising a plate connected to each of the electrode tabs via a weld bead, wherein the plate and the weld bead comprises a first metal at a particular concentration range and wherein the weld bead has particular dimensions.