Notched Vent Member for Secondary Battery Safety
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Solution Overview
Problem
Conventional battery vents operate at high pressures, making it difficult to ensure safety when internal pressures are lower, as they only interrupt current flow at about 9 kgf/cm2, leaving batteries vulnerable to accidents like fires and explosions.
Innovation Solution
A cap assembly with a vent that includes a protrusion connected to the electrode assembly, featuring first and second circular notches and a third cross-notch, allowing it to operate at a lower pressure, thereby improving battery safety by interrupting current flow at a lower internal pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional vent is used that operates at high pressure (about 9 kgf/cm2), then the vent can interrupt current flow at high pressure, but it cannot ensure battery safety when internal pressure is lower
Solution Approach 1:
The vent member is divided into multiple notched portions (first circular notch, second circular notch, third cross notch) with different geometries and positions. Each notched portion can potentially deform at different pressure levels, allowing the vent to operate across a broader pressure range and improve adaptability while maintaining reliability through multiple failure modes
Solution Approach 2:
The vent member's structural parameters are modified by introducing multiple notches with varying depths, shapes, and locations. These parameter changes create different stress concentration points that deform at different pressure levels, enabling the vent to activate at lower pressures than conventional single-structure vents, thus expanding the operating pressure range while ensuring safety
2Reliability
If the vent operates only at high pressure (9 kgf/cm2), then the vent structure can be simpler, but battery safety is compromised at lower pressures
Solution Approach 1:
The vent member is segmented into multiple notched portions (first circular notch, second circular notch, third cross notch) with different geometries and positions. Each notched portion can potentially deform at different pressure levels, allowing the vent to operate across a broader pressure range and improve adaptability while maintaining reliability through multiple failure modes
Solution Approach 2:
The vent member's structural parameters are modified by introducing multiple notches with varying depths, shapes, and locations. These parameter changes create different stress concentration points that deform at different pressure levels, enabling the vent to activate at lower pressures than conventional single-structure vents, thus expanding the operating pressure range while ensuring safety
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 cap assembly effectively reduces the operating pressure to around 7-8 kgf/cm2, ensuring current flow is blocked even at lower internal pressures, enhancing battery safety and preventing potential accidents.
Implementation Method 1
When the internal pressure of the secondary battery reaches a predetermined level or higher, a current breaker, such as a vent, may be enabled to prevent current flow
Data Source
AI summary
A cap assembly for a battery and a battery incorporating the cap assembly. The cap assembly includes a plate that connects the electrodes of the bare cell of the battery. The cap assembly includes a vent member that includes a protrusion that is physically connected to the plate. Excess pressure within the bare cell results in the protrusion disconnecting from the plate thereby interrupting current. The vent further includes two circular notches, an inner notch and an outer notch. The vent further includes a cross notch that extends radially outward so as to intersect and extend beyond both the first and second notches. The notches are configured to release when the pressure within the bare cell exceeds a burst pressure.