Pouch Sealing Structure Preventing Moisture Permeation
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Solution Overview
Problem
Pouch-type secondary batteries face issues with moisture permeation and electrolyte solution leakage, leading to deteriorated long-term storage stability and battery performance due to their soft container design and limited mechanical strength.
Innovation Solution
A pouch case with a first sealing portion where the upper and lower sheets are sealed, featuring a second sealing portion formed with an aluminum metal foil tape or an aluminum metal foil tape coated with an electrical insulator to prevent external moisture and electrolyte solution permeation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If pouch-type secondary batteries use a soft pouch as a container, then they can have various shapes and reduced volume, but they exhibit low mechanical strength and reliability leading to moisture permeation and electrolyte leakage
Solution Approach 1:
The pouch structure combines multiple materials with different properties: an inner layer (polyolefin) for thermal bonding and sealing, a metal layer (aluminum) for mechanical strength and barrier properties, and an outer layer (nylon) for protection. This composite structure maintains the flexibility and volume reduction benefits while improving mechanical strength and sealing reliability to prevent moisture permeation and electrolyte leakage.
2Quantity of substance
If the sealing portion width is decreased to accommodate higher capacitance electrodes, then battery capacitance increases, but sealing reliability deteriorates and external moisture permeation increases
Solution Approach 1:
The multi-layer composite pouch structure provides enhanced sealing capability with the inner polyolefin layer offering thermal bonding properties, the middle aluminum layer providing mechanical strength and moisture barrier, and the outer nylon layer adding protection. This composite construction maintains reliable sealing even when the sealing portion width is reduced to accommodate higher capacitance electrode assemblies.
3Ease of manufacture
If thermal bonding is used to seal the pouch, then the sealing process is simple and efficient, but the thermal-bonding portion becomes vulnerable to moisture permeation
Solution Approach 1:
The pouch uses a composite structure where the inner polyolefin layer provides thermal bonding capability for easy manufacturing, while the middle aluminum layer and outer nylon layer provide robust moisture and oxygen barrier properties. This combination allows simple thermal sealing processes while protecting against moisture permeation through the multi-layer barrier structure.
Solution Approach 2:
The middle aluminum layer acts as an intermediary barrier between the inner thermal-bonding layer and the external environment. It provides a moisture and oxygen barrier that protects the thermal-bonding portion from moisture permeation, while the thermal bonding process remains simple and efficient.
4Device complexity
If a single sealing layer is used, then the structure is simple, but it cannot effectively prevent moisture permeation and electrolyte leakage
Solution Approach 1:
The pouch employs a three-layer composite structure: an inner polyolefin layer for thermal bonding and sealing, a middle aluminum layer for mechanical strength and moisture/oxygen barrier, and an outer nylon layer for additional protection. This multi-layer composite design effectively prevents moisture permeation and electrolyte leakage while maintaining reasonable structural complexity.
Solution Approach 2:
The pouch structure is segmented into three functional layers, each performing a specific function: the inner layer handles sealing, the middle layer provides barrier and structural support, and the outer layer offers protection. This segmentation allows each layer to be optimized for its specific function, achieving effective moisture and leakage prevention.
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 additional sealing layer effectively prevents dielectric breakdown and electrolyte leakage, enhancing the insulating properties and long-term storage stability of the batteries, thereby improving their performance and reliability.
Implementation Method 1
a second sealing portion formed with an aluminum metal foil tape or an aluminum metal foil tape having at least one surface coated with an electrical insulator to prevent external moisture and electrolyte solution permeation
Implementation Method 2
an aluminum metal foil tape having at least one surface coated with an electrical insulator
Implementation Method 3
the upper sheet and a lower sheet are sealed, as shown in FIG. 2. However, the thermal-bonding portion of the pouch is vulnerable to permeation of external moisture
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
Disclosed is a pouch including a first sealing portion wherein an upper sheet and a lower sheet are sealed, and a second sealing portion present in a partial or entire region of the first sealing portion. The pouch further includes a second sealing portion present in a partial or entire region of the first sealing portion, thus efficiently preventing permeation of external moisture and leakage of electrolyte solution through the first sealing portion and enabling fabrication of batteries with improved capacitance maintenance and resistance increase.