Battery Module Bus Bar Welding for Crack-Resistant Cu-Al Joints
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Solution Overview
Problem
Current secondary battery welding methods, particularly laser welding of dissimilar materials, face challenges in achieving high welding quality and reliability due to the formation of intermetallic compounds, which lead to brittleness and increased electrical resistance, and are prone to cracks, affecting long-term battery performance.
Innovation Solution
A secondary battery module design featuring a weld bead with controlled concentration deviation and morphological symmetry, formed by laser welding of aluminum and copper components, where the concentration deviation is less than 5 wt% and the weld bead has a bilaterally symmetrical structure, minimizing intermetallic compound formation and ensuring stable mechanical and electrical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If laser welding is used to join aluminum electrode tabs and copper bus bar, then electrical connection and thermal conductivity are improved, but intermetallic compounds form causing brittleness and increased electrical resistance
Solution Approach 1:
The patent applies parameter changes by precisely controlling laser welding parameters (power, speed, focus position) to optimize the welding process. This control prevents excessive intermetallic compound formation while ensuring adequate electrical connection, resolving the contradiction between electrical reliability and mechanical ductility
Solution Approach 2:
The patent implements local quality by creating a weld bead with controlled composition gradient. The weld bead contains a specific distribution of aluminum and copper with limited intermetallic compound formation in critical regions, providing both electrical conductivity and mechanical flexibility locally
2Productivity
If conventional laser welding is used for dissimilar materials, then joining speed and productivity are improved, but weld quality consistency and crack suppression are worsened
Solution Approach 1:
The patent implements feedback control by monitoring weld bead morphology and composition in real-time during the welding process. This feedback mechanism allows dynamic adjustment of welding parameters to maintain consistent weld quality and prevent crack formation while preserving high welding speed
Solution Approach 2:
The patent applies dynamics by making the welding process adaptive and controllable. The welding parameters can be dynamically adjusted based on material variations and process conditions, ensuring consistent weld quality across different production batches while maintaining high productivity
3Quantity of substance
If high energy density is pursued in battery design, then battery capacity is improved, but welding reliability and long-term battery performance are worsened due to increased brittleness and crack susceptibility
Solution Approach 1:
The patent creates a composite weld bead structure combining aluminum and copper with controlled intermetallic compound distribution. This composite structure provides both the electrical conductivity needed for high capacity batteries and the mechanical flexibility required for long-term reliability, preventing crack propagation during battery operation
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 significantly improves the mechanical and electrical properties of the weld bead, suppressing crack formation and enhancing the long-term reliability and stability of the battery module by maintaining uniformity and tensile strength, thus ensuring reliable electrical connections.
Implementation Method 1
the electrode tab inserted into the hole and the plate are joined to each other by a weld bead, one or more of the weld beads are included
Data Source
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AI summary
Provided is a secondary battery module including: a plurality of battery cells including electrode tabs; and a bus bar connected to the plurality of electrode tabs so that the plurality of battery cells are electrically connected to each other, wherein the bus bar includes a plate having a plurality of holes formed therein, each of the electrode tabs of the plurality of battery cells is inserted into at least a part of the plurality of holes of the plate, the electrode tab inserted into the hole and the plate are joined to each other by a weld bead, one or more of the weld beads are included, and the weld bead has a concentration deviation (△C) satisfying the following Equation 1: ConcentrationdeviationΔC<5wt% wherein the concentration deviation (△C) refers to a difference between an average copper concentration (C1) of a left side and an average copper concentration (C2) of a right side based on a center line of the hole in a section of the weld bead in a thickness direction of the plate.