Cylindrical Lithium Battery Venting to Prevent Side Rupture
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Solution Overview
Problem
Large cylindrical lithium secondary batteries face safety issues due to increased heat and gas generation, leading to potential fire or explosion risks, especially when used in battery packs, as conventional venting mechanisms can cause side rupture and flame spread.
Innovation Solution
The battery design includes a configuration where the electrode assembly is ejected through the first end portion of the battery can when internal pressure exceeds 21 kgf/cm², with a distance from the farthest end of the electrode assembly to the second end portion being at least 1.25 times the distance between the end portions, and features a vent portion that ruptures at specific pressures to release the electrode assembly without side rupture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the cross-sectional area of the battery is increased to release heat and gas, then the heat release capability is improved, but the volume increases and the heat generation increases proportionally more, leading to increased explosion risk
Solution Approach 1:
The battery can is pre-designed with a vent portion that will rupture at a predetermined pressure threshold. This preliminary structural arrangement ensures that when internal pressure builds up during thermal runaway, the vent portion ruptures first to eject the electrode assembly, preventing side rupture and flame spread before they can occur.
Solution Approach 2:
The battery structure is segmented into distinct functional zones: the vent portion at a specific end for controlled rupture, the electrode assembly that can be ejected, and the side walls that are protected from rupture. This segmentation allows the battery to release pressure through a controlled mechanism rather than uncontrolled side rupture.
2Object-generated harmful factors
If conventional vent portions are used to release gas, then gas release is achieved, but side rupture of the battery can occurs leading to flame spread in battery packs
Solution Approach 1:
The harmful electrode assembly is extracted from the battery can through the vent portion when internal pressure increases. By ejecting the electrode assembly through the pre-designed vent portion, the system removes the source of further heat generation and gas production, preventing side rupture and flame spread to adjacent batteries.
Solution Approach 2:
The internal pressure that would normally cause dangerous side rupture is converted into a beneficial force that ejects the electrode assembly through the vent portion. The harmful pressure buildup is thus transformed into a controlled ejection mechanism that enhances safety by removing the thermal runaway source.
3Quantity of substance
If the battery is designed for high capacity with large volume, then energy storage is improved, but the amount of heat and gas generated increases, increasing fire or explosion risk
Solution Approach 1:
The battery is pre-configured with a vent portion and ejection mechanism that will activate at predetermined pressure levels. This preliminary arrangement ensures that when high-capacity operation leads to thermal runaway and pressure buildup, the system automatically ejects the electrode assembly to stop further heat and gas generation.
Solution Approach 2:
The battery system performs self-protection by using its own internal pressure buildup to trigger the ejection of the electrode assembly. The system automatically detects thermal runaway conditions through pressure increase and self-corrects by ejecting the harmful electrode assembly, eliminating the need for external intervention.
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 design prevents side rupture and local flame occurrence, reducing the risk of fire spread within the battery pack and improving overall safety by allowing controlled ejection of the electrode assembly, thereby enhancing the safety of individual batteries and the vehicle they power.
Implementation Method 1
wherein at least a portion of the electrode assembly is ejected through the first end portion of the battery can when an internal pressure within the battery can is 21 kgf/cm 2
Data Source
Figure 1a
Figure 1b
Figure 2
AI summary
This lithium secondary battery may comprise a battery can, an electrode assembly and an electrolyte contained in the battery can, and a cap plate configured to seal the battery can. The battery can may include a first end and a second end opposite to the first end. The lithium secondary battery is configured such that, if the internal pressure of the battery can is 21 kgf/cm2 or higher, at least a part of the battery assembly is discharged through the first end of the battery can. After a part of the battery assembly is discharged through the first end of the battery can, the distance from an end of the electrode assembly located farthest from the battery can to the second end of the battery can is at least 1.25 times the distance between the first end and the second end of the batterv can.