Battery Cover Sealing with Vacuum Pressing for Uniform Welding
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Solution Overview
Problem
Secondary battery manufacturing processes face issues of product deformation and non-uniform welding due to pressure applied in all directions and non-uniform pressing during the sealing and fixing of the cover to the main body casing.
Innovation Solution
A welding apparatus comprising a lower jig, upper jig, vacuum generating unit, and welding unit is used to create a negative pressure in the accommodation space, preventing cover swelling and ensuring uniform pressing, thereby using a laser welding unit to seal the main body casing and cover.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If resistance welding is used to join the tab extension to the current collector, then welding strength can be achieved, but internal stress concentrates at the weld boundary causing delamination and reduced battery reliability
Solution Approach 1:
The patent applies different joining methods to different regions of the tab extension. Resistance welding is used at the center portion where high strength is needed, while ultrasonic welding is used at the end portions where stress concentration would cause delamination. This local differentiation of joining quality prevents internal stress concentration at critical boundaries while maintaining overall welding strength.
2Reliability
If the entire tab extension is welded to the current collector, then electrical connectivity is improved, but stress concentration at weld boundaries causes delamination between the tab extension and current collector
Solution Approach 1:
The patent implements local quality by welding only specific portions (center and selected end regions) of the tab extension to the current collector, rather than the entire surface. This selective welding approach maintains sufficient electrical connectivity through the welded regions while avoiding continuous weld boundaries that would concentrate stress and cause delamination.
3Strength
If resistance welding is applied to the end portions of the tab extension, then welding strength increases, but internal stress at the weld boundary increases causing delamination
Solution Approach 1:
The patent applies asymmetric welding strategy where the center portion receives resistance welding for high strength, but the end portions receive ultrasonic welding instead. This asymmetric approach recognizes that end portions have different stress characteristics compared to the center, and uses the welding method (ultrasonic) that produces lower internal stress at boundaries, thereby preventing delamination while still providing adequate strength.
4Force
If ultrasonic welding is used instead of resistance welding, then internal stress at weld boundary is reduced, but welding strength may be insufficient for high-current applications
Solution Approach 1:
The patent merges two different welding methods (resistance welding and ultrasonic welding) into a single hybrid joining process. Resistance welding is applied at the center portion where high strength is critical for current carrying capacity, while ultrasonic welding is applied at the end portions where low internal stress is critical for preventing delamination. This combination allows both welding strengths and low internal stress to be achieved simultaneously in different regions.
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 apparatus prevents deformation and non-uniform welding by applying uniform pressure through negative pressure, ensuring precise welding and product integrity.
Implementation Method 1
an end portion of the tab extension is welded to the current collector by using an ultrasonic welding apparatus
Implementation Method 2
a center portion of the tab extension is resistance-welded to the current collector
Data Source
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AI summary
The present invention relates to a welding apparatus and a welding method for manufacturing a secondary battery, which are capable of preventing deformation of a product due to a pressure applied in all directions or non-uniform welding due to non-uniform pressing to a cover during a process of sealing and fixing the cover to an opening of a main body casing at the time of manufacturing a secondary battery.