Laser Welded Lead Tab to Battery Case Preventing Spatter
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Solution Overview
Problem
The existing resistance welding process for connecting lead tabs to the case in lithium-ion rechargeable batteries results in weld spatter, leading to shorting and complex manufacturing, with low resistance between the case and lead tabs often resulting in defective welds.
Innovation Solution
A battery assembly with a conductive case and electrode assembly, where the lead tab is welded to the case from the outside using laser welding, with a larger cross-sectional weld area at the outer surface to prevent spatter entry and an insulating plate between the electrode assembly and the case to isolate the weld area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If resistance welding is used to connect lead tabs to the case, then electrical conductivity is improved, but weld spatter is produced which causes shorting and manufacturing complexity increases
Solution Approach 1:
The patent introduces a laser beam as an intermediary welding method instead of direct resistance welding. The laser beam acts as a mediator that melts and fuses the lead tab to the case without generating spatter, thereby maintaining electrical conductivity while eliminating the harmful spatter effect.
Solution Approach 2:
The patent replaces the mechanical resistance welding system with a laser-based thermal welding system. This substitution eliminates the mechanical contact and pressure required in resistance welding, thereby preventing spatter generation while achieving reliable electrical connection between the lead tab and case.
2Reliability
If resistance welding is used to connect multiple overlapping lead tabs, then electrical conductivity is improved, but manufacturing time increases and process complexity increases
Solution Approach 1:
The patent merges multiple welding operations into a single laser welding process. Instead of performing separate resistance welding operations for each lead tab, the laser beam can weld multiple overlapping tabs simultaneously or sequentially in one setup, reducing manufacturing steps and overall process complexity while maintaining conductivity.
Solution Approach 2:
The laser welding system provides universal applicability for welding different configurations of lead tabs (single or multiple overlapping tabs) using the same process parameters. This multi-functionality eliminates the need for different welding procedures for different tab configurations, simplifying the manufacturing process.
3Reliability
If resistance welding is used with low resistance materials, then electrical conductivity is improved, but weld quality deteriorates due to insufficient heat generation
Solution Approach 1:
The patent changes the welding parameter from resistance-based heat generation (which depends on material resistance) to laser-based thermal energy input. The laser beam delivers concentrated thermal energy that can effectively melt and fuse low-resistance materials without relying on their electrical resistance for heat generation, thereby achieving high weld quality regardless of the lead tab material's resistance.
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 reduces spatter and manufacturing complexity, ensuring safer and more effective welds with improved conductivity and reduced risk of electrode assembly damage.
Implementation Method 1
the at least one conductive element is welded to the inner surface of the case at a first location, wherein the weld is formed from the outside of the case
Data Source
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Figure 1C
AI summary
A rechargeable battery is provided. The rechargeable battery comprises an electrode assembly, a case housing the electrode assembly, at least one lead tab accommodated in the case to electrically connect the electrode assembly to the case, and a welded joint joining the lead tab to the case. In the rechargeable battery, the case is connected to the lead tab without producing any spatter within the case. The welded joint extends from an outer bottom surface of the case to the lead tab. The weld is formed from the outside of the case. The welding may be performed by laser welding. Further provided is a method for manufacturing the rechargeable battery.