Battery Cap Assembly With Bimetal CID for Rapid Thermal Cutoff
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Solution Overview
Problem
Conventional cylindrical secondary batteries face safety issues due to internal short circuits during charging and discharging, leading to gas generation and potential explosion or rupture, necessitating improved structural safety measures.
Innovation Solution
A cap assembly incorporating a CID module with a bimetal deformation body that rapidly cuts off current when the battery temperature exceeds a deformation temperature, featuring a structure with multiple layers of differing thermal expansion coefficients and an insulating layer to ensure rapid disconnection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional CID device is used to cut off current when temperature rises, then safety is improved, but the response speed is slow and cannot rapidly cut off current
Solution Approach 1:
The patent changes the physical state and properties of the deformation body by using a bimetal structure with specific thermal expansion coefficients. The first deformation layer has a greater coefficient of thermal expansion than the second deformation layer, causing rapid deformation at the deformation temperature (70°C or higher). This parameter change enables the CID module to rapidly cut off current when temperature rises, resolving the contradiction between safety and response speed.
Solution Approach 2:
The patent employs a bimetal composite structure consisting of two deformation layers with different thermal expansion coefficients. This composite material approach creates a deformation body that rapidly changes shape at specific temperatures, enabling fast current cutoff. The combination of materials with different properties resolves the contradiction by providing both the safety function and the rapid response capability.
2Ease of manufacture
If the deformation body structure is simplified, then manufacturing is easier, but the reliability of current cutoff is reduced
Solution Approach 1:
The deformation body is segmented into multiple layers (first deformation layer and second deformation layer) with different thermal expansion coefficients. This segmentation allows each layer to be manufactured separately with standard processes, while the combination provides reliable rapid deformation at the deformation temperature. The layered structure resolves the contradiction between ease of manufacture and cutoff reliability.
Solution Approach 2:
By controlling the thickness parameters (first deformation layer thicker than second deformation layer) and thermal expansion coefficients of each layer, the patent achieves reliable current cutoff while maintaining manufacturability. The parameter optimization allows standard manufacturing processes to produce a component with predictable and reliable deformation behavior at 70°C or higher.
3Quantity of substance
If high capacity is realized in secondary batteries, then energy density is improved, but safety limitations increase due to internal short circuit risks
Solution Approach 1:
The patent introduces an intermediary mechanism (the bimetal deformation body) that acts as a mediator between the battery's thermal state and the current flow. When temperature rises due to internal short circuits or other issues, the deformation body deforms and physically separates the upper and lower plates, cutting off current. This intermediary mechanism provides enhanced safety for high-capacity batteries without reducing their energy density.
Solution Approach 2:
The patent replaces conventional mechanical CID mechanisms with a thermally-actuated bimetal deformation system. The deformation body uses thermal expansion differences to automatically trigger current cutoff when temperature rises, providing a more reliable and responsive safety mechanism for high-capacity batteries. This substitution resolves the contradiction by providing safety that scales with battery capacity.
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 cap assembly effectively prevents current flow by lifting the upper plate upon temperature rise, significantly enhancing safety by rapidly cutting off current and preventing internal pressure buildup.
Implementation Method 1
a first deformation layer and a second deformation layer are disposed in multiple stages, and the first deformation layer may have a greater coefficient of thermal expansion than the second deformation layer at the same temperature
Implementation Method 2
The deformation body may be formed of a bimetal that is deformed at the deformation temperature
Data Source
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AI summary
A cap assembly of the present disclosure includes a top cap; and a CID module provided below the top cap and cutting off a current when a temperature inside the secondary battery rises above the deformation temperature, wherein the CID module includes an upper plate provided below the top cap and having a protrusion; a lower plate provided below the upper plate and contacting only the protrusion; an insulating plate provided between the edge of the upper plate and the edge of the lower plate; and a deformation body that is provided between the upper plate and the lower plate and separates the protrusion and the lower plate so that the current does not pass therethrough by lifting the upper plate when a temperature of the secondary battery rises above the deformation temperature.