Pouch Cell Cap-Film Sealing Structure for Moisture and Venting Control
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Solution Overview
Problem
Existing secondary batteries face limitations in increasing battery capacity due to shape restrictions, moisture penetration, and poor structural stability, as well as challenges in controlling gas emission direction during abnormal conditions.
Innovation Solution
A secondary battery design featuring an electrode assembly surrounded by an exterior film and covered by a pair of caps, where the caps include a cover part, a connection part with a coupling portion made of specific resins, and a terminal part for electrical connection. This design enhances sealing strength, reduces moisture penetration, and controls gas emission direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a pouch cell is manufactured by molding a pouch film, then the battery can be assembled, but cracks occur in the pouch film and shape restrictions limit battery capacity increase
Solution Approach 1:
The invention divides the protective structure into two separate components: an exterior film that surrounds the electrode assembly and caps that cover the ends. This segmentation eliminates the need for complex molded pouch films, preventing cracks while maintaining ease of assembly. The exterior film and caps work together as a unified protective system without the structural limitations of a single molded piece.
Solution Approach 2:
The invention extracts the problematic molding process entirely from the battery structure. Instead of using a molded pouch film that requires complex shaping and is prone to cracking, the solution uses simple wraparound exterior film and separate caps. This extraction of the molding requirement eliminates shape restrictions and allows for easier manufacturing with improved reliability.
2Ease of manufacture
If a pouch film is used to surround the electrode assembly, then the battery structure is formed, but moisture penetrates from the outside
Solution Approach 1:
The invention employs composite material construction with the exterior film made from multiple layers including moisture barrier layers. The exterior film comprises layers such as polyethylene terephthalate (PET), nylon, aluminum alloy film, and polypropylene film, where the aluminum alloy layer specifically provides moisture barrier functionality. This composite structure maintains ease of manufacture while effectively preventing moisture penetration.
3Ease of manufacture
If the battery structure is simplified, then manufacturing is easier, but structural stability and sealing strength are insufficient to withstand internal pressure
Solution Approach 1:
The connection part uses composite material construction with multiple layers including a first layer (acid-modified polypropylene resin) and a second layer (non-stretched polypropylene resin). This composite structure provides both ease of manufacture through simple lamination and high sealing strength to withstand internal pressure generated during battery operation. The different resin layers complement each other's properties.
Solution Approach 2:
The invention applies local quality enhancement at the connection part between the cap and exterior film. The connection part uses specific resin compositions with controlled melt flow rates and melting points that are optimized for sealing performance. This localized material optimization ensures high sealing strength at the critical sealing interface while maintaining overall manufacturing simplicity.
4Ease of manufacture
If a traditional cup-molding design is used, then the battery can be assembled, but the venting direction cannot be controlled during abnormal conditions
Solution Approach 1:
The invention introduces asymmetry in the cap design by providing different structures at the first end and second end of the battery. The first cap includes a vent hole for controlled gas emission, while the second cap has a different configuration. This asymmetric design enables controlled venting direction during abnormal conditions while maintaining ease of manufacture through standard cap components.
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 design allows for increased battery capacity with reduced shape restrictions, improved structural stability, enhanced sealing strength to withstand internal pressure, and controlled gas emission direction during abnormal conditions, thereby improving safety and reliability.
Implementation Method 1
a coupling portion which is provided on an outer surface of the cover part and is coupled to the exterior film
Data Source
AI summary
A secondary battery and a battery pack including the same are provided. The secondary battery includes an electrode assembly extending in a first direction; an exterior film surrounding a portion of the electrode assembly; and a pair of caps covering a remaining portion of the electrode assembly, wherein each of the caps includes a cover part covering one side of the electrode assembly in the first direction; a connection part including a coupling portion which is provided on an outer surface of the cover part and is coupled to the exterior film; and a terminal part of which at least a portion is exposed to outside of the cover part and which is electrically connected to the electrode assembly, wherein the coupling portion of the connection part includes a first layer including a first resin and has an outer surface that couples to an inner surface of the exterior film and an inner surface that couples to an outer surface of the cover part.