Lithium Battery Safety Vent Pressure Reduction Design
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Solution Overview
Problem
Conventional lithium secondary batteries face safety issues due to the fragility of their safety vents, which can rupture upon impact, leading to electrolyte leakage and potential explosion when subjected to external forces like drops or large pressures.
Innovation Solution
The design incorporates insulation and terminal plates with vent holes that correspond to the safety vent on the cap plate, where the insulation plate vent-hole is between 30% to 70% of the safety vent's area, allowing pressure reduction and preventing direct electrolyte impact on the safety vent, while ensuring efficient gas release during malfunctions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the safety vent is made larger to improve gas release efficiency, then the gas venting capability is improved, but the safety vent becomes more fragile and prone to rupture upon impact
Solution Approach 1:
The safety vent structure is segmented into multiple functional zones: a large upper groove for gas venting and a smaller lower groove for impact resistance. This segmentation allows each zone to optimize its function - the upper groove provides large opening for gas release while the lower groove maintains structural integrity against impact forces.
Solution Approach 2:
Different regions of the safety vent are given different properties - the upper surface has a larger cross-sectional area for gas venting efficiency, while the lower surface has a smaller cross-sectional area for impact resistance. This local quality differentiation resolves the contradiction between venting capability and impact strength.
2Speed
If the safety vent is positioned closer to the electrode assembly to improve gas release efficiency, then the gas venting speed is improved, but the safety vent becomes more vulnerable to electrolyte impact during drops
Solution Approach 1:
The lower groove acts as an intermediary protective structure between the electrolyte and the safety vent. When the battery is dropped, this groove absorbs and dissipates the impact energy of the electrolyte before it can reach and rupture the safety vent, while still allowing gas to pass through the venting path.
3Strength
If the cap plate thickness is increased to strengthen the safety vent, then the impact resistance is improved, but the manufacturing complexity and material usage increase
Solution Approach 1:
Instead of uniformly increasing cap plate thickness, the design segments the safety vent into grooves of different depths and cross-sectional areas. This allows localized strengthening where needed while maintaining overall structural efficiency and reducing unnecessary material usage.
Solution Approach 2:
The design changes the geometric parameters of the safety vent - creating grooves with specific depth, width, and cross-sectional area ratios. These parameter optimizations provide enhanced impact resistance through structural geometry rather than simply increasing material thickness, thereby reducing manufacturing complexity.
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
This configuration reduces the risk of safety vent rupture upon impact, allowing for controlled pressure release and maintaining battery integrity by minimizing direct electrolyte contact with the safety vent, thus enhancing the safety and reliability of lithium secondary batteries.
Implementation Method 1
it can be destroyed by a pressure of gas created due to overcharge and full discharge of the secondary battery or by overheating of the secondary battery, thereby exhausting the gas from the secondary battery and preventing an explosion
Implementation Method 2
The vent holes allow electrolyte in a dropped lithium secondary battery to pass through a thereby and undergo pressure reduction, preventing rupture of the safety vent by the electrolyte
Data Source
AI summary
A lithium secondary battery having a cap assembly including a cap plate, an insulation plate and a terminal plate. The insulation plate and the terminal plate each have a predetermined vent hole corresponding to a safety vent formed on the cap plate so that if the secondary battery is dropped, an electrolyte passes through the vent-holes and undergoes a pressure reduction, thereby preventing fracture of a safety vent by the electrolyte while allowing gas to be exhausted upon battery overcharge, full discharge or by overheating.