Laser Welded Battery Lead Joint Strength and Sputtering Control
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Solution Overview
Problem
Laser welding between the lead and the sealing plate in sealed secondary batteries is affected by sputtering due to variations in fabrication processes, leading to potential short circuits caused by foreign substances, which can result in a reduced joint strength and reliability.
Innovation Solution
A sealed secondary battery design where a lead is laser-welded to a sealing plate using a laser beam with a spot diameter smaller than the lead's thickness, employing deep penetration keyhole welding and continuous scanning with a fiber laser to maintain joint strength and reduce sputtering, with a welded portion having a penetration depth greater than the bead diameter and a linear shape for stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If resistance welding is used to join the lead to the sealing plate, then joint strength is improved, but sputtered substances are generated causing contamination and potential short circuits
Solution Approach 1:
The patent replaces resistance welding (mechanical/electrical system causing sputtering) with ultrasonic welding (acoustic vibration system). The ultrasonic vibration joins the lead to the sealing plate without melting, thereby eliminating sputtered substances while maintaining joint strength.
Solution Approach 2:
The patent utilizes the phase transition of metal particles during ultrasonic welding, where acoustic energy causes localized heating and melting at the interface without bulk melting. This allows joining without the extensive sputtering that occurs in resistance welding.
2Object-generated harmful factors
If ultrasonic welding is used to join the lead to the sealing plate, then contamination by sputtered substances is avoided, but joint strength is reduced
Solution Approach 1:
The patent optimizes ultrasonic welding parameters including vibration amplitude (3-10 μm), frequency (20-40 kHz), and welding time (0.1-2 seconds) to achieve sufficient joint strength. By carefully controlling these parameters, the patent maintains joint strength comparable to resistance welding while avoiding sputtering.
3Productivity
If laser welding is used to weld aluminium lead to aluminium sealing plate, then welding speed is improved, but sputtering increases due to high thermal conductivity
Solution Approach 1:
The patent replaces laser welding (thermal process causing sputtering in aluminium) with ultrasonic welding (acoustic process). This substitution eliminates the thermal conductivity issue that causes sputtering in laser welding of aluminium, while maintaining high welding speed and productivity.
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 configuration ensures a stable and reliable joint between the lead and the sealing plate, reducing sputtering and maintaining joint strength even with variations in fabrication processes, thereby enhancing the reliability of sealed secondary batteries.
Implementation Method 1
a lead extending from one of the positive and negative electrode plates in the electrode group is laser-welded to the sealing plate with application of a laser beam
Implementation Method 2
Joining by ultrasonic welding, instead of resistance welding, does not cause melting as caused by the resistance welding
Data Source
AI summary
An electrode group 4 formed by stacking or winding a positive electrode plate 1 and a negative electrode plate 2 with a separator 3 interposed therebetween, is housed in a battery case 5. An opening of the battery case 5 is sealed with a sealing plate 10. A lead 11 extending from one of the positive and negative electrode plates in the electrode group 4 is laser-welded to the sealing plate 10 by application of a laser beam 12 having a spot diameter smaller than a thickness of the lead 11.