Battery Safety Vent Notch Structure for Controlled Pressure Relief
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Solution Overview
Problem
Existing secondary batteries face challenges in ensuring safe pressure relief without premature venting or deformation of the safety vent, particularly in maintaining the desired breaking pressure and preventing electrolyte leakage.
Innovation Solution
The secondary battery design incorporates a cap assembly with a safety vent featuring a main notch and a sub-notch, where the sub-notch has a smaller depth than the main notch, strategically positioned to ensure controlled breakage and maintain the desired pressure relief while reducing the risk of cracking or deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single deep notch is used in the safety vent, then the safety vent can break at the desired pressure, but the safety vent may deform or crack prematurely before reaching the breaking pressure
Solution Approach 1:
The single deep notch is divided into multiple notches (first notch, second notch, third notch) with different depths arranged in a circular pattern. The shallower notches prevent premature deformation while the deeper notches ensure breaking at the desired pressure, thus resolving the contradiction between reliability and strength.
Solution Approach 2:
Different regions of the safety vent are given different notch depths to perform different functions. The shallower notches (first and second notches) provide structural support and prevent premature deformation, while the deeper notch (third notch) ensures breaking at the target pressure, applying local quality differentiation to resolve the strength-reliability contradiction.
2Stress or pressure
If the notch depth is increased to ensure breaking at higher pressure, then the breaking pressure is maintained, but the safety vent becomes more prone to cracking and deformation
Solution Approach 1:
The pressure relief function is segmented across multiple notches with different depths. The shallower notches (first and second notches at 30-70% depth) resist cracking and deformation, while the deeper notch (third notch at 80-100% depth) ensures breaking at the required pressure, thus maintaining pressure while reducing harmful factors.
Solution Approach 2:
The shallower notches are designed to engage first and provide structural reinforcement before the deeper notch reaches its breaking point. This preliminary action of the shallower notches prevents premature cracking and deformation, allowing the system to safely reach the desired breaking pressure.
3Strength
If a shallower single notch is used to prevent deformation, then the safety vent maintains structural integrity, but it cannot break at the desired high pressure
Solution Approach 1:
The notch system is segmented into multiple levels: shallower notches (first and second notches) maintain structural integrity and prevent deformation, while the deeper third notch ensures breaking at the desired high pressure. This segmentation resolves the contradiction between strength and pressure achievement.
Solution Approach 2:
Different local regions (notches) are assigned different depths to serve different functions. The shallower notches provide structural support and prevent deformation, while the deeper notch locally concentrates stress to achieve breaking at the target pressure, thus resolving the strength-pressure contradiction.
Data Source
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AI summary
A secondary battery includes an electrode assembly; a case that accommodates the electrode assembly; and a cap assembly that is coupled to an upper portion of the case, the cap assembly including a cap up, a safety vent below the cap up, and a cap down below the safety vent and electrically connected to the electrode assembly, wherein the safety vent includes a main notch and a sub-notch adjacent to the main notch, and the sub-notch has a depth that is smaller than a depth of the main notch.