Battery Cell Vent Structure for Internal Pressure Release
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Solution Overview
Problem
Secondary batteries, particularly lithium secondary batteries, experience swelling and heat generation due to repeated charging and discharging, posing risks of explosions or fires, necessitating effective control of internal pressure.
Innovation Solution
A battery cell design featuring a vent portion with a ring shape on the opposing surface, having a higher ten-point average roughness than adjacent areas, which changes shape based on internal pressure to manage pressure buildup, including a groove with reduced thickness and an equiaxed microstructure, formed by laser processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the internal pressure of the battery cell increases during charging and discharging, then the battery can store and release more energy, but the swelling phenomenon occurs leading to safety risks such as explosions or fires
Solution Approach 1:
A vent portion is formed in advance on the opposing surface of the case before pressure buildup occurs. This vent portion is positioned and structured to activate only when internal pressure exceeds safe thresholds, allowing preliminary preparation of a safety mechanism that does not interfere with normal energy storage operations but activates automatically when needed.
Solution Approach 2:
The vent portion converts the harmful effect of excessive internal pressure into a beneficial safety feature. When swelling and pressure buildup occur during charging/discharging cycles, the vent portion opens to release the excess pressure, transforming what would be a dangerous condition into a controlled pressure management mechanism that prevents explosions or fires while allowing normal energy operations.
2Reliability
If a vent portion is added to control internal pressure, then safety is improved, but the structural integrity and strength of the case may be compromised
Solution Approach 1:
The vent portion is designed with localized structural characteristics - it has a specific thickness that is less than or equal to one-sixth of the opposing surface thickness, and features a rougher surface texture (higher ten-point average roughness) compared to adjacent areas. This local differentiation allows the vent portion to be weaker and more compliant specifically where needed for pressure release, while the rest of the case maintains its full structural strength and integrity.
3Stress or pressure
If the vent portion thickness is reduced to allow pressure release, then pressure control is improved, but the overall strength of the opposing surface decreases
Solution Approach 1:
The vent portion thickness is specifically reduced to less than or equal to one-sixth of the opposing surface thickness only in the localized region where pressure release is needed. This creates a weak point that activates under pressure while the surrounding areas maintain full thickness and strength, allowing the structure to be both pressure-responsive and mechanically strong where required.
Solution Approach 2:
The vent portion is pre-formed with its reduced thickness and grooved structure during case manufacturing, creating a predetermined pressure relief pathway that requires minimal additional force to activate. This preliminary preparation ensures that when internal pressure builds up, the vent portion opens easily at the designed location without compromising the overall structural integrity of the thicker surrounding case material.
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 stability by safely releasing pressure through the vent portion, preventing explosions and fires, while maintaining electrical connectivity and minimizing physical damage to the cell structure.
Implementation Method 1
the shape of the vent portion may be changed based on internal pressure of the case. At least a portion of the vent portion may be opened when the internal pressure of the case increases.
Implementation Method 2
The vent portion may include a re-solidification layer formed by heating and solidifying a portion by using a laser.
Implementation Method 3
The vent portion may include a re-solidification layer formed by heating and solidifying a portion by using a laser.
Data Source
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AI summary
The present disclosure relates to a battery cell including a case including an opening formed in one surface and an opposing surface facing the opening, and accommodating an electrode assembly through the opening, a cap plate coupled to the case to close the opening, and a vent portion having a shape of a groove on the opposing surface, wherein a ten-point average roughness of a surface of the vent portion is greater than a ten-point average roughness of an area adjacent to the vent portion.