Cap Assembly Vent Member Notch Design for Battery Safety
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Solution Overview
Problem
In conventional secondary batteries, when the vent member breaks due to internal pressure, it can contact the cap, leading to current flow and a decrease in battery reliability due to arcs between the vent member and underlying elements.
Innovation Solution
The cap assembly features a vent member with radial notches and reinforcement parts that protrude to a predetermined height, preventing contact between the broken vent member and the cap, or using additional notches that fold the vent member to avoid contact with the cap.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the vent member breaks due to internal pressure to release gas, then gas venting function is achieved, but the broken vent member contacts the cap causing current flow and arc discharge
Solution Approach 1:
The vent member is divided into multiple notched sections that can independently break and fold. When internal pressure exceeds the threshold, the notches break sequentially, allowing the vent member to fold back and away from the cap, preventing contact and maintaining electrical insulation while still venting gas effectively.
Solution Approach 2:
The vent member is designed to move from a flat configuration to a three-dimensional folded structure when broken. The notches enable the vent member to fold back along its length, changing its spatial orientation and moving it away from the cap in the radial direction, thus preventing contact while maintaining the venting function.
2Strength
If the vent member is made strong to prevent breakage, then structural integrity is maintained, but gas cannot be vented when internal pressure exceeds threshold
Solution Approach 1:
The vent member has non-uniform structural properties: the notched regions are designed with lower strength to break at a predetermined pressure threshold, while the overall structure maintains sufficient strength to contain pressure below the threshold. This local variation in strength allows controlled breakage at specific points while maintaining overall structural integrity.
Solution Approach 2:
The notches are pre-formed in the vent member during manufacturing, creating predetermined weak points that will break at a specific pressure threshold. This preliminary preparation ensures that when internal pressure exceeds the threshold, the vent member breaks in a controlled manner rather than catastrophically, allowing safe gas venting.
3Object-generated harmful factors
If the vent member breaks completely to vent gas, then gas release is achieved, but the broken pieces contact the cap causing arcs and current flow
Solution Approach 1:
The vent member transitions from a static rigid structure to a dynamic folded structure when broken. The notches enable the vent member to flex and fold back upon breaking, changing its position dynamically to move away from the cap, thereby preventing contact and arc discharge while maintaining the venting function.
Solution Approach 2:
The notched structure acts as an intermediary mechanism between the pressure-induced breakage and the final position of the vent member. The notches control how the breakage propagates and direct the folded segments away from the cap, mediating the transition from broken state to safe retracted position without direct contact.
Data Source
AI summary
A cap assembly and a secondary battery having the same which can prevent current from flowing out of the battery by preventing contact of a broken vent member with a cap. The vent member is broken due to an internal pressure of the secondary battery greater than a predetermined level. The cap assembly includes a vent member having a plurality of notches formed in a radial direction from the center of the vent member and a plurality of reinforcement parts formed between the notches. The cap assembly may include a vent member having a plurality of notches formed between two adjacent notches so that the vent member folds when the internal pressure of the secondary battery is too great.