Battery Exterior Weld Geometry for Crack-Resistant Sealing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The formation of acute-angled portions at the welding ends of laminated films in battery exterior bodies leads to reduced welding strength and increased risk of cracks, compromising sealability and gas ingress.
Innovation Solution
The exterior body design incorporates a curved portion at the end of the welding portion, which is formed by rounding acute-angled portions through external force application at a temperature exceeding the glass-transition point of the resin, ensuring the welding strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laminated films are welded to each other using conventional methods, then the welding process is simple and fast, but acute-angled portions are formed at the welding ends which reduce welding strength and increase crack risk
Solution Approach 1:
The patent applies curvature by forming a rounded shape at the end portion of the welding portion instead of an acute angle. Specifically, the end portion is formed with a radius of curvature of 0.5mm or more, which eliminates stress concentration points and prevents crack initiation. This curved geometry directly resolves the technical contradiction by maintaining welding strength while allowing for efficient welding processes.
Solution Approach 2:
The patent changes the geometric parameter of the welding end from an acute angle to a curved shape with a specific radius (0.5mm or more). This parameter change transforms the stress distribution at the welding end, preventing stress concentration that would lead to cracks. The modified geometry parameter ensures both welding strength and resistance to thermal expansion effects.
2Ease of manufacture
If the welding portion has an acute-angled end portion, then the welding process is easier to control, but cracks occur more easily under low-temperature conditions and welding strength is reduced
Solution Approach 1:
The rounded end portion with a radius of 0.5mm or more eliminates the acute angle that causes stress concentration. This curved geometry prevents crack initiation under low-temperature conditions while maintaining ease of welding control during the manufacturing process.
Solution Approach 2:
The patent preemptively forms a curved shape at the welding end before any cracking can occur. This pre-cushioning of the stress distribution prevents future crack initiation, especially under low-temperature conditions where material brittleness would otherwise cause cracking at acute angles.
3Loss of time
If resin projects to form a resin lump at the welding end, then the welding process is self-regulating, but acute-angled portions form on each side of the lump which reduce welding strength
Solution Approach 1:
Instead of allowing resin to form a lump with acute angles on its sides, the patent directly forms a controlled curved shape at the welding end. This eliminates the harmful acute angles that would form around the resin lump while maintaining the self-regulating benefit of resin flow during welding.
Solution Approach 2:
The patent extracts or removes the harmful acute-angled portions that would naturally form around a resin lump. By directly forming the curved end shape, the design eliminates the problematic geometry while preserving the beneficial resin flow characteristics during welding.
4Adaptability or versatility
If the exterior body is subjected to thermal expansion and contraction, then the battery can operate in varying temperature conditions, but cracks occur at acute-angled welding portions reducing sealability
Solution Approach 1:
The curved end portion with a radius of 0.5mm or more eliminates stress concentration points that would cause cracking during thermal expansion and contraction. This allows the battery to operate across a wide temperature range while maintaining sealability, as the curved geometry accommodates thermal stresses without initiating cracks.
Solution Approach 2:
The patent preemptively designs the welding end with a curved shape that cushions against future thermal stresses. This pre-cushioning prevents crack initiation during subsequent thermal cycling, ensuring long-term sealability and reliability in varying temperature conditions.
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 reduces the likelihood of crevices and cracks, enhancing the welding strength and durability of the battery exterior body, particularly in varying temperature conditions.
Implementation Method 1
applying external force to the planar body or the planar bodies such that an end portion of the welding portion on a content side is pulled to both sides in the second direction more strongly than that in a finished state of the exterior body
Data Source
AI summary
To ensure the welding strength (the T-peel strength) of a welding portion. An exterior body 3 of the present invention houses a content. The exterior body 3 has a welding portion 55 extending in a first direction X. At the welding portion 55, portions of a planar body or planar bodies (e.g., portions of a laminated film 3f or laminated films 3f) are welded so as to overlap with each other in a second direction Y perpendicular to the first direction X, the planar body or the planar bodies being the material of the exterior body 3. In a sectional view as viewed in a third direction Z perpendicular to the first direction X and the second direction Y, the welding portion 55 has, at an end portion on a content side, curved portions 58 recessed in a curved shape toward the side opposite to the content side.