Battery Tab Laser Welding with Clad Material
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Solution Overview
Problem
In battery packs with film sheathed batteries, the intensity of the laser used for bonding tabs to clad material is weakened due to dispersion, leading to unreliable bonding between the tabs and the clad material.
Innovation Solution
A method involving the use of a clad material interposed between the tabs, with lasers applied from both sides to ensure reliable bonding, where the same kind of metals are in contact, and the laser beams are directed perpendicular and parallel to the principal surfaces to achieve strong bonding without forming brittle compounds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a laser is applied from one side to bond tabs to clad material, then the bonding process is simple, but the laser intensity is weakened due to dispersion, leading to unreliable bonding
Solution Approach 1:
The patent applies laser beams from both the front and back sides of the clad material simultaneously, transitioning from a single-sided welding approach to a dual-sided approach. This dimensional change in the welding process allows the laser to effectively bond tabs to the clad material on both surfaces, overcoming the laser intensity weakening issue while maintaining bonding reliability.
2Reliability
If lasers are applied from both sides to bond tabs, then bonding reliability is improved, but the device complexity increases
Solution Approach 1:
The welding process is segmented into two independent welding operations: one from the front side and one from the back side. Each laser welding operation can be independently controlled and optimized, allowing the system to achieve reliable bonding while managing complexity through modular, separable welding steps rather than a single complex simultaneous operation.
3Reliability
If tabs of different metals are connected through clad material, then electrical connection is achieved, but brittle compounds may form at the interface
Solution Approach 1:
The clad material structure is designed with local quality variations, where the intermediate layer is specifically composed of metal elements that match the tabs being connected (e.g., Al for Al tabs, Cu for Cu tabs). This local matching of material properties at the interface prevents the formation of brittle intermetallic compounds while maintaining excellent electrical connection reliability across different metal types.
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
This method effectively bonds the tabs to the clad material from both sides, enhancing the bonding strength and preventing the formation of brittle metals or increased conductive resistance, thus improving the reliability and efficiency of the battery pack assembly.
Implementation Method 1
applying a laser from one of directions crossing the principal surfaces of the positive electrode tab and the negative electrode tab and the clad material thereby bonding one of the tabs to the clad material
Implementation Method 2
bonding one of the tabs to the clad material, while applying another laser from the other direction thereby bonding the other of the tabs to the clad material
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
Provided is a method for welding positive electrode tab (2) and negative electrode tab (3) of battery pack (5A) configured by stacking a plurality of single cells (1) each of which has positive electrode tab (2) and negative electrode tab (3) drawn outward and formed of metals different from each other in kind. In this welding method, clad material (6) is disposed between positive electrode tab (2) of second single cell (1B) and negative electrode tab (3) of first single cell (1A). Next, with a laser welder, focal point (F2) is aimed at interface (8) between negative electrode tab (3) and clad material (6), and laser (L2) is applied thereto from the side of negative electrode tab (3). Then, focal point (F1) is aimed at interface (7) between positive electrode tab (2) and clad material (6), and laser (L1) is applied thereto from the side of positive electrode tab (2).