Secondary Battery Pouch Sealing Thickness Control
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Solution Overview
Problem
Lithium ion secondary battery pouch sealing processes often result in a thin polypropylene layer that is prone to damage, such as cracking, leading to insulation failure and pouch corrosion due to excessive bonding and deformation under external forces.
Innovation Solution
A method involving a bonding process that maintains a predetermined thickness of the polypropylene layer and a sealing process with increased pressure and temperature on the bonding area, creating a weak bonding part and a sealing part with distinct thicknesses to prevent cracking, while ensuring the pouch remains sealed and functional.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thermal fusion bonding is applied to seal the pouch, then the sealing function is achieved, but the polypropylene layer becomes excessively thin and prone to cracking
Solution Approach 1:
The patent applies different bonding forces to different regions of the pouch. The sealing area receives a first bonding force sufficient to create a strong seal, while the non-sealing area receives a second bonding force that is less than the first, preventing excessive thinning and cracking in regions where sealing is not required. This local differentiation resolves the contradiction by providing strong sealing where needed while maintaining layer integrity where sealing is not needed.
2Reliability
If excessive bonding force is applied to ensure sealing, then sealing reliability improves, but the polypropylene layer deforms and cracks under external force
Solution Approach 1:
The patent implements spatially differentiated bonding forces where the sealing area is subjected to higher bonding force to ensure reliable sealing, while the non-sealing area is subjected to lower bonding force to prevent deformation and cracking. This local quality approach allows the system to achieve high sealing reliability without causing harmful deformation in other regions.
Solution Approach 2:
The bonding area is segmented into a sealing area and a non-sealing area, each receiving appropriate bonding force. The sealing area is bonded with sufficient force to create a hermetic seal, while the non-sealing area is bonded with reduced force to maintain structural integrity and resist cracking under external forces.
3Ease of manufacture
If uniform bonding is applied across the entire pouch, then manufacturing simplicity is maintained, but the polypropylene layer thickness varies causing weakness in certain areas
Solution Approach 1:
The patent implements local quality by applying different bonding forces to different regions of the pouch. The sealing area receives higher bonding force to ensure proper sealing, while the non-sealing area receives lower bonding force to maintain uniform polypropylene layer thickness. This approach balances manufacturing precision with reasonable process complexity.
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 solution effectively minimizes polypropylene layer deformation and prevents cracking, thereby avoiding insulation failure and pouch corrosion, while maintaining the sealing function and durability of the battery.
Implementation Method 1
the polypropylene layer Z is used to bond an upper pouch 1a to a lower pouch 1b through thermal fusion
Implementation Method 2
a portion of the bonding area may be heated and pressed at a pressure greater than that applied to the other portion of the bonding area so as to be sealed
Data Source
AI summary
Provided are a secondary battery in which a sealing part is prevented from damaged by external force and a method for manufacturing the same. The method for manufacturing the secondary battery includes a preparation process of preparing a pouch in which an electrode assembly and an electrolyte are accommodated, a bonding process of bonding a bonding area disposed on a circumferential portion of the pouch by using a bonding device; and a sealing process of sealing a portion of the outside of the bonding area of the pouch that is bonded in the bonding process by using a sealing device.