Pouch Battery Lead Sealing Using an Expanded Pouch Section
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Solution Overview
Problem
The sealing strength of pouch-type secondary batteries is compromised by the protrusion of leads, leading to potential electrolyte leakage and reduced durability, especially as battery capacity increases and size decreases.
Innovation Solution
An expansion part is formed on the pouch where the lead protrudes, increasing the sealing area by bonding the expansion part to the lead and lead film, which is thermally fused to enhance the sealing performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the battery is miniaturized to increase capacity density, then the battery size is reduced, but the sealing area at lead protrusion portions is reduced leading to lower sealing strength
Solution Approach 1:
The sealing structure is segmented into multiple portions: a first sealing portion formed by thermal fusion at the pouch edge, and a second sealing portion formed by bonding the expansion part to the lead and lead film. This segmentation allows each sealing portion to contribute to overall sealing strength, compensating for the reduced total sealing area in miniaturized batteries.
Solution Approach 2:
The expansion part is pre-formed on the pouch surface at the lead protrusion position before sealing. This preliminary structure provides an extended bonding area that compensates for the reduced sealing area caused by miniaturization, ensuring adequate sealing strength is achieved during the subsequent sealing process.
2Volume of moving object
If the sealing area is reduced due to miniaturization, then the battery size is reduced, but the reliability is lowered due to potential electrolyte leakage
Solution Approach 1:
The sealing function is divided into two independent sealing portions: thermal fusion sealing at the pouch edge and bonding sealing at the expansion part. This segmentation ensures that even if one sealing method is compromised, the other maintains sealing reliability, preventing electrolyte leakage in miniaturized batteries.
Solution Approach 2:
The expansion part is specifically positioned at the lead protrusion portion where sealing is most critical. This local enhancement of sealing structure at the vulnerable lead exit point maintains high sealing reliability despite overall battery miniaturization and reduced total sealing area.
3Duration of action of stationary object
If thermal fusion is applied to seal the pouch, then the pouch is sealed, but the lead protrusion area has insufficient sealing strength
Solution Approach 1:
The sealing system is segmented into thermal fusion sealing for the pouch body and bonding sealing for the lead protrusion area. The bonding sealing method using expansion part is specifically applied at the lead protrusion position where thermal fusion alone is insufficient, providing enhanced sealing strength at this critical location.
Solution Approach 2:
The expansion part acts as an intermediary element between the pouch and the lead. It provides an additional bonding interface that mediates the sealing connection at the lead protrusion area, supplementing the thermal fusion sealing and ensuring adequate sealing strength where the lead exits the pouch.
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 enhanced sealing area reduces the likelihood of electrolyte leakage and lead damage, improving the overall sealing performance and reliability of the battery.
Implementation Method 1
a sealing process of applying heat along an edge of the pouch to seal the pouch in a state in which the electrode assembly and the lead are mounted in the pouch, and the pouch is closed, wherein, in the sealing process, the sealing is performed so that the expansion part is bonded to the lead
Data Source
AI summary
The present invention provides a secondary battery, in which an electrode assembly is embedded in a pouch, and a lead electrically connected to the electrode assembly has one side protruding to the outside of the pouch, the secondary battery comprising: the pouch in which the electrode assembly is embedded, and sealing is performed along an edge thereof; the lead having one end connected to the electrode assembly and the other end protruding to the outside of the pouch; and a lead film disposed between the lead and the pouch and adhering to each of the pouch and the lead when the sealing of the pouch is performed, wherein an expansion part expanded by a predetermined length along a longitudinal direction of the lead is formed on the pouch, and the lead film has an area so that the entire expansion part is accommodated therein.