Pouch Battery Lead Film Structure for Seal-Preserving Gas Venting
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Solution Overview
Problem
Pouch-type secondary batteries face reduced lifespan due to internal gas buildup exceeding the casing's fusion strength, leading to premature release and gas discharge.
Innovation Solution
A secondary battery design featuring a lead film with high air permeability around the electrode lead, comprising an outer layer for adhesiveness and sealability and an inner layer with higher air permeability for effective gas discharge, integrated into a pouch-like casing to manage internal pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If energy density of the secondary battery is increased, then the amount of gases generated inside the battery is increased, but the casing fusion strength is exceeded leading to premature release and reduced battery life
Solution Approach 1:
The battery structure is segmented into distinct functional layers: the pouch-like casing provides containment, the lead film provides gas discharge pathways, and the electrode assembly provides energy storage. This segmentation allows each component to address specific functions, with the lead film specifically managing gas pressure to prevent casing failure while maintaining high energy density
Solution Approach 2:
The lead film acts as an intermediary component between the electrode assembly and the pouch-like casing. It provides a controlled gas discharge pathway that mediates the pressure buildup from high energy density electrodes, preventing direct transmission of excessive pressure to the casing and thereby extending battery life
2Object-generated harmful factors
If the pouch-type casing sealing is maintained to prevent gas discharge, then battery life is reduced, but if sealing is released to discharge gases, then internal pressure is relieved but battery life is significantly reduced
Solution Approach 1:
The harmful gas accumulation is extracted from the battery system through the lead film's gas discharge pathways. The lead film is specifically designed to allow gases to escape from the internal space while maintaining the overall sealing integrity of the pouch-type casing, thereby preventing pressure buildup without requiring complete seal release
Solution Approach 2:
The lead film introduces local quality variation in the battery structure by providing selective permeability at specific locations. The film allows gas molecules to pass through while maintaining sealing at other critical joints, creating localized gas discharge channels that relieve pressure without compromising overall battery integrity and lifespan
3Object-generated harmful factors
If a lead film with high air permeability is introduced to discharge gases, then gas discharge is effective, but the sealing integrity may be compromised
Solution Approach 1:
The lead film is strategically positioned and dimensioned to provide localized gas discharge functionality. By controlling the film's area, thickness, and permeability characteristics, the design achieves effective gas discharge at the molecular level while maintaining macroscopic sealing integrity at the casing connections and overall battery structure
Solution Approach 2:
The lead film utilizes composite material properties combining selective gas permeability with mechanical adhesion capabilities. The film's composite structure allows it to function as both a gas discharge pathway and a sealing element, maintaining stability of the battery's compositional integrity while enabling controlled gas release
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 effectively discharges gases generated inside the battery, enhancing its lifespan by preventing premature release and maintaining seal integrity.
Implementation Method 1
the inner layer includes a material having a higher air permeability as compared to the outer layer
Data Source
AI summary
Disclosed is a secondary battery including: an electrode assembly including electrode sheets and a separator interposed between the electrode sheets; a pouch-like battery casing in which the electrode assembly is received; an electrode lead connected to the electrode assembly and protruding out from the battery casing; and a lead film covering the electrode lead and interposed between the electrode lead and the battery casing, wherein the lead film includes an outer layer covering the electrode lead and an inner layer disposed inside of the outer layer, and the inner layer includes a material having a higher air permeability as compared to the outer layer.