Battery Lid Welding Structure for Spatter-Free Hermetic Sealing
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Solution Overview
Problem
Hermetically-sealed power storage devices face issues with spatters from laser welding adhering to insulators, degrading insulation characteristics and creating sealing performance problems due to uneven solidified molten metal portions.
Innovation Solution
A power storage device design featuring a lid with an annular contact step and outer step portions, where the stopper is positioned radially inside the outer step portion, and the solidified molten portion is convexly shaped towards the outside, preventing spatters from adhering to insulators and ensuring uniform sealing by positioning the solidified molten portion entirely inside the lid's outer plane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the outer peripheral edge portion of the stopper is laser-welded with the liquid inlet circumferential portion of the lid, then the liquid inlet is sealed, but spatters scatter from the welded parts and adhere to the insulators, degrading insulation characteristics
Solution Approach 1:
The liquid inlet circumferential portion is segmented into multiple functional regions: a contact step portion for stopper placement, an outer step portion for welding, and a spatter reception portion positioned between them. This segmentation directs spatters away from insulators by providing a dedicated reception area that intercepts scattered metal droplets during laser welding.
Solution Approach 2:
The spatter reception portion acts as an intermediary element between the welding zone and the insulators. It intercepts spatters that scatter during laser welding, preventing them from reaching and adhering to the insulators, thus protecting the insulation characteristics while maintaining sealing performance.
2Reliability
If the outer step portion is provided to arrange the stopper radially inside, then sealing structure is enhanced, but a clearance is generated between the outer step portion and the outer peripheral edge portion of the stopper, causing uneven solidified molten portion
Solution Approach 1:
The outer step portion is designed with specific local geometric features including a radially inner surface and a thickwise lower surface that define a controlled clearance zone. This local structural quality ensures that the clearance between the outer step portion and the stopper's outer peripheral edge portion is uniform, allowing the laser beam to create a consistent molten portion that solidifies evenly around the entire circumference.
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 maintains preferable insulation characteristics by preventing spatter adhesion on insulators and ensures effective sealing by eliminating local thinness in the solidified molten portion, enhancing the overall performance of the power storage device.
Implementation Method 1
an outer peripheral edge portion of the stopper and a liquid inlet circumferential portion of the lid surrounding a liquid inlet are to be molten by a laser beam
Implementation Method 2
the outer peripheral edge portion of the stopper and a liquid inlet circumferential portion of the lid surrounding a liquid inlet are to be molten by a laser beam and are to be welded to each other
Implementation Method 3
a surface of the solidified molten portion is configured to: continue to an outer annular step surface of the outer step portion and a peripheral outward surface of the stopper; and form a convex shape toward a lid thickwise outside... spatters (molten metal droplets) could scatter from welded parts and adhere to various parts of the lid
Data Source
AI summary
A power storage device includes a lid of a case housing an electrode body and a stopper welded to a liquid inlet circumferential portion of the lid by energy-beam welding to seal the liquid inlet. An annular solidified molten portion made of metal, which has been once molten and then solidified, is positioned on a lid thickwise inside than a lid outer plane of the lid over the entire circumference, and has a surface which continues to an outer annular step surface and a peripheral outward surface and fomes a convex shape toward a lid thickwise outside.