Battery Module Bus Bar Welding for Low-IMC Tab Joints
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Solution Overview
Problem
Existing secondary battery modules face challenges in achieving high welding quality and reliability due to the formation of intermetallic compounds during laser welding of dissimilar materials, leading to brittleness, cracks, and increased electrical resistance, which affects the long-term reliability and safety of the batteries.
Innovation Solution
A secondary battery module design featuring a weld bead with a concentration deviation of less than 5 wt% and morphological symmetry, formed by laser welding of aluminum electrode tabs into copper bus bars, which minimizes the formation of intermetallic compounds and ensures excellent mechanical and electrical properties, thereby improving welding reliability and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If laser welding is used to join aluminum electrode tabs to copper bus bars, then electrical conductivity and thermal conductivity are improved, but intermetallic compounds form causing brittleness and cracks
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 ensures consistent weld bead geometry and minimizes intermetallic compound formation, resolving the contradiction between achieving strong joints and avoiding brittleness
Solution Approach 2:
The patent replaces mechanical joining methods with laser welding, using optical energy instead of mechanical force. This substitution enables precise control of the joining process, achieving reliable electrical and thermal conductivity while maintaining mechanical strength through controlled heat input that minimizes harmful intermetallic compounds
2Productivity
If conventional laser welding is used for dissimilar materials, then joining efficiency is improved, but weld bead symmetry and concentration uniformity deteriorate
Solution Approach 1:
The patent implements feedback control by monitoring weld bead geometry and copper concentration distribution in real-time during the welding process. This feedback enables dynamic adjustment of laser parameters to maintain consistent weld quality and concentration uniformity, resolving the contradiction between high productivity and manufacturing precision
Solution Approach 2:
The patent utilizes parameter changes by optimizing laser power, welding speed, and focal position to achieve both high joining efficiency and precise control of weld bead characteristics. These parameter optimizations ensure symmetric weld beads with uniform copper concentration distribution
3Ease of manufacture
If welding parameters are not optimized, then manufacturing complexity is reduced, but crack formation and welding quality increase
Solution Approach 1:
The patent applies preliminary action by pre-establishing optimized welding parameter sets and procedural guidelines before production. This preparation includes determining optimal laser power, speed, and focus parameters, as well as setting up monitoring systems, thereby simplifying the manufacturing process while ensuring high reliability without requiring complex real-time decision-making
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 enhances the mechanical and electrical properties of the weld bead, suppressing crack formation and ensuring stable welding quality, thus improving the long-term reliability and safety of the battery module.
Implementation Method 1
laser welding of aluminum electrode tabs into copper bus bars
Implementation Method 2
the electrode tab inserted into the hole and the plate are joined to each other by a weld bead
Implementation Method 3
the weld bead has a concentration deviation (ΔC) satisfying the following Equation 1... one or more of the weld beads are included, and the weld bead has a concentration deviation (ΔC) satisfying the following Equation 1
Data Source
AI summary
Provided is a secondary battery module including: plurality of battery cells including electrode tabs; and 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 plate having plurality of holes formed therein, each of the electrode tabs is inserted into at least part of the plurality of holes of the plate, the electrode tab inserted into the hole and the plate are joined by a weld bead, one or more of the weld beads are included, and the weld bead has concentration deviation (ΔC) satisfying the following Equation:Concentration deviation (ΔC)<5 wt %,(ΔC) is difference between average copper concentration of left side and average copper concentration of right side based on center line of the hole in a section of the weld bead in a thickness direction of the plate.