Cylindrical Li-Ion Battery Cap Assembly for Sealing and Gas Venting
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Solution Overview
Problem
Cylindrical lithium ion secondary batteries face challenges in maintaining internal sealing while allowing safe release of internal gas pressure, as existing solutions do not effectively manage pressure thresholds to prevent overcharging and ensure safety.
Innovation Solution
A cylindrical lithium ion secondary battery design featuring a cap assembly with a top plate, middle plate, and bottom plate, where the top plate is deformable and includes a notch that ruptures at a predetermined pressure, allowing gas release without obstructing current paths, and adjustable breaking pressure through welding region location.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the cap assembly is made with a rigid structure to maintain internal sealing, then sealing reliability is improved, but the ability to release internal gas pressure is worsened
Solution Approach 1:
The cap assembly is divided into multiple plates (first plate, second plate, third plate) that can move relative to each other. The first plate can deform independently under pressure while the second and third plates maintain the sealing structure, allowing the system to both seal reliably and release pressure through controlled deformation of specific segments.
Solution Approach 2:
The cap assembly incorporates dynamic elements including a deformable first plate with a notch that can change shape under pressure, and plates connected by movable connections. This dynamic structure allows the cap to transition from a sealed state to a pressure-release state automatically based on internal pressure conditions.
2Object-generated harmful factors
If the cap assembly is designed to release gas pressure easily, then safety is improved, but internal sealing is worsened
Solution Approach 1:
Different regions of the cap assembly have different properties: the first plate is designed with a notch and deformable structure for pressure sensing and release, while the second and third plates maintain rigid sealing connections. This local differentiation allows simultaneous achievement of easy pressure release and reliable sealing in different parts of the same assembly.
3Object-generated harmful factors
If the top plate is made from soft aluminum to enable easy breaking, then gas release capability is improved, but structural strength is worsened
Solution Approach 1:
The cap assembly separates the function of pressure release (first plate with notch) from the function of structural support and sealing (second and third plates). The soft aluminum first plate can break or deform easily for gas release, while the other plates provide the necessary structural strength, resolving the contradiction between ease of breaking and overall structural integrity.
4Productivity
If the notch is positioned at the center of the top plate, then gas release efficiency is improved, but current path blocking is worsened
Solution Approach 1:
The notch is positioned asymmetrically at one side of the first plate rather than at the center, creating an offset between the gas release path and the electrical connection path. This asymmetric positioning allows gas to escape efficiently through the notch while the electrical current path through the center of the plate remains unobstructed, resolving the contradiction between gas release efficiency and current path integrity.
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 maintains internal sealing at lower pressures and safely releases gas at higher pressures, enhancing battery safety and capacity by using soft aluminum for the cap assembly, which easily breaks open when internal pressure reaches a specific threshold.
Implementation Method 1
When the internal gas pressure of the cylindrical can is larger than a predetermined first pressure and smaller than a predetermined second pressure, the top plate may be upwardly convexly deformed by the internal gas pressure, and the top plate may be electrically disconnected from the bottom plate
Implementation Method 2
When the internal gas pressure of the cylindrical can is larger than the predetermined second pressure, the notch may be broken, and the internal gas of the cylindrical can may then be released to the outside
Data Source
Figure 1A
Figure 1B
Figure 1C~2A
AI summary
Various embodiments of the present invention relate to a cylindrical lithium ion secondary battery. A problem to be solved is to provide a cylindrical lithium ion secondary battery which, when internal gas pressure is larger than predetermined first reference pressure (operating pressure) and is smaller than predetermined second reference pressure (breaking pressure) during overcharging, can maintain an internal sealing while a current path is blocked by a cap assembly. To this end, the present invention provides a cylindrical lithium ion secondary battery comprising: a cylindrical can; an electrode assembly received in the cylindrical can; and a cap assembly for sealing the cylindrical can, wherein the cap assembly comprises a top plate having a flat surface on which a notch is formed, a middle plate coupled to the top plate and including a first through-hole formed through the center thereof, and a bottom plate electrically connected with the electrode assembly, attached to the middle plate with an insulating plate interposed therebetween, and connected to the top plate through the first through-hole of the middle plate.