Pouch Cell Vent Member Layout for Directed Thermal Gas Venting
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Solution Overview
Problem
Conventional secondary batteries face challenges in directing gas discharge during thermal propagation, leading to potential fire hazards due to uncontrolled gas release.
Innovation Solution
A secondary battery design with a vent inducing region having a narrower width than the sealing portion, incorporating a vent member made of linear low-density polyethylene with a specific comonomer content, which melts at elevated temperatures to facilitate controlled gas discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a wound type separator is used to improve electrolyte retention and prevent internal short circuits, then battery safety and reliability are improved, but the manufacturing complexity and difficulty of handling increase
Solution Approach 1:
The separator is divided into multiple independent wound layers, each contributing to different functions: the first wound separator provides primary separation and electrolyte retention, while the second wound separator adds an additional safety layer. This segmentation allows each layer to be optimized independently for its specific function, improving overall reliability while maintaining manufacturing feasibility through standardized winding processes
Solution Approach 2:
A protective film is introduced as an intermediary layer between the positive electrode and the separator. This film acts as a mediator that prevents direct contact and potential short circuits between the electrode and separator, especially during abnormal conditions. The protective film simplifies the overall system by providing a dedicated safety component that doesn't require complex modifications to the existing separator structure
2Quantity of substance
If the battery capacity is increased to meet higher energy demands, then energy storage capability is improved, but the risk of internal short circuits and thermal runaway increases
Solution Approach 1:
The battery is divided into multiple smaller battery packs, each with its own independent separator and protective film. This segmentation limits the potential impact of a short circuit to individual packs rather than affecting the entire battery system. Each pack can be optimized for higher capacity independently, allowing the overall battery to achieve high energy storage while maintaining safety through modular isolation
Solution Approach 2:
The protective film and dual separator structure are installed beforehand to prevent short circuits before they can occur. These safety components are positioned in advance to intercept potential failure modes, such as electrode deformation or separator puncture, before they can lead to thermal runaway. This prior cushioning allows the battery to be designed with higher capacity without proportionally increasing short circuit risk
3Reliability
If the battery pack size is increased to provide cushioning space, then safety margin is improved, but the overall device volume and weight increase
Solution Approach 1:
The protective film and separator functions are merged into a integrated safety structure. The protective film is positioned adjacent to the separator, creating a combined safety barrier that provides both short circuit prevention and thermal insulation without requiring separate dedicated spaces. This merging allows the safety margin to be achieved within the existing battery pack volume rather than requiring additional cushioning space
Solution Approach 2:
The protective film is nested between the positive electrode and the separator, utilizing the existing inter-layer space rather than requiring additional external volume. The dual separator structure is nested within the battery pack architecture, with each separator layer contributing to safety while maintaining compact overall dimensions. This nesting approach provides safety margins without increasing the external battery pack volume or weight
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 enhances safety by enabling directed gas discharge, reducing the risk of fire by ensuring controlled venting during thermal events.
Implementation Method 1
The porous polymer outer layer is configured to contact the electrolyte and provide capillary action to retain the electrolyte
Implementation Method 2
The porous polymer outer layer comprises a hydrophilic inorganic filler dispersed in a polymer matrix
Implementation Method 3
the porous polymer outer layer provides capillary action to retain the electrolyte and prevent internal short circuits
Data Source
Figure 1
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Figure 4~5
AI summary
Disclosed herein is a secondary battery having a vent member. The secondary battery may include an electrode assembly; an electrode lead attached to the electrode assembly; a case including an accommodation portion for accommodating the electrode assembly and a sealing portion containing a sealant resin and formed to seal the electrode assembly; a lead film formed to surround a part of an outer surface of the electrode lead and interposed between the electrode lead and the case; and a vent member containing a linear low-density polyethylene having a comonomer with a carbon number of 6 or more, wherein the sealing portion has a vent inducing region including the vent member, and a width of the vent inducing region is smaller than a width of the sealing portion other than the vent inducing region.