Secondary Battery Pouch Forming Process for Durability
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Solution Overview
Problem
The durability of pouch-type secondary batteries is compromised when forming cups of varying depths, leading to potential cracking and limitations in increasing battery capacity due to constraints on the internal space volume.
Innovation Solution
A method involving a two-step forming process for the pouch, where initial concave portions are formed and then the first cup's depth is increased beyond the initial constant depth, allowing for a greater volume while maintaining pouch integrity through specific depth ratios and curved inter-area design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the depth of the cup formed in the pouch is increased to accommodate larger electrode assemblies for higher capacity, then the battery capacity increases, but minute cracks occur in the pouch and durability deteriorates
Solution Approach 1:
The forming process is segmented into two distinct stages: a first forming step that creates initial cups of constant depth, and a second forming step that selectively increases the depth of only the first cup. This segmentation allows the pouch to be formed without excessive stress that would cause cracking, while still achieving the required depth for high capacity batteries.
Solution Approach 2:
The first forming step performs preliminary action by creating initial cups of constant depth before the second forming step increases the depth of the first cup. This preliminary formation at constant depth allows the pouch material to be properly positioned and stress-distributed before deeper forming occurs, preventing crack formation.
2Volume of stationary object
If two cups of equal depth are formed in the pouch according to related art, then the manufacturing process is simple, but the internal space volume is insufficient for high capacity requirements
Solution Approach 1:
The invention introduces asymmetry into the cup formation process by making the first cup deeper than the second cup. While this may seem to increase complexity, it actually achieves the volume increase goal more efficiently by utilizing the available pouch depth asymmetrically, allowing the first cup to extend deeper to provide additional internal space for the electrode assembly.
Solution Approach 2:
The invention changes the depth parameter of the first cup from the initial constant depth to a final greater depth through the second forming step. This parameter change allows the internal space volume to be increased without changing the pouch dimensions or material, simply by adjusting the forming depth parameter of the first cup.
3Ease of manufacture
If the pouch is folded between two cups to accommodate the electrode assembly, then the battery can be manufactured, but the area between the cups becomes a vulnerable area prone to whitening and cracking
Solution Approach 1:
The invention applies local quality by making the first cup deeper than the second cup, which changes the distribution of stress and material thickness in the inter-area. The increased depth of the first cup provides better support and reduces the vulnerability of the folding area, preventing whitening and cracking while maintaining ease of manufacture.
Data Source
AI summary
Disclosed is a method for manufacturing a secondary battery.According to the present invention, a problem of weakening durability of a pouch, which may occur in a process of forming cups having different depths in the pouch may be solved.