Small Cylindrical Battery Valve Ring Protrusions
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Solution Overview
Problem
Small cylindrical lithium-ion secondary batteries face challenges in releasing internal pressure safely due to increased stress concentration on valve members, leading to potential bursting, especially when the battery size is reduced, as the through-hole area ratio increases, compromising the ring's strength and valve member's ability to cleave at normal pressure.
Innovation Solution
A cylindrical lithium-ion secondary battery design featuring a ring with linear ridge line protrusions inside a through-hole, a sheet-like valve member, and a sealing body that ensures the valve member cleaves at a predetermined pressure, maintaining sufficient mechanical strength and sealability, even with a battery case outer diameter of 10 mm or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the battery size is reduced to meet wearable equipment requirements, then the compactness and portability are improved, but the valve member area decreases leading to insufficient stress concentration and inability to cleave at normal pressure
Solution Approach 1:
The invention applies local quality by creating protrusions with specific geometric features (pointed tips, predetermined angles) at localized positions within the through-hole. These protrusions concentrate stress locally on the valve member at critical points, enabling reliable cleavage even when the overall valve member area is reduced due to smaller battery size. The local geometric modification compensates for the reduced scale.
Solution Approach 2:
The protrusions are pre-formed on the ring structure before assembly, creating predetermined stress concentration points. This preliminary action ensures that when internal pressure increases, the stress is immediately concentrated at the protrusion tips, facilitating reliable valve member cleavage at normal operating pressures despite the reduced battery size.
2Reliability
If the through-hole area is increased to ensure sufficient protrusion size for cleavage, then the valve member cleavage capability is improved, but the ring strength decreases due to increased opening area ratio
Solution Approach 1:
Instead of increasing the overall through-hole area, the invention uses local quality by adding protrusions with specific geometric features (pointed tips, predetermined angles) at strategic locations within the through-hole. This concentrates stress locally on the valve member, enabling effective cleavage without requiring a larger through-hole area, thus maintaining ring strength.
Solution Approach 2:
The protrusions are designed with asymmetric geometric features (pointed tips rather than rounded edges, specific angle configurations) that create optimal stress concentration patterns. This asymmetric design maximizes the cleavage effect at the valve member while minimizing the required through-hole area, preserving ring structural integrity.
3Reliability
If multiple circular holes are used to form the through-hole to create protrusions, then the protrusion formation is improved, but the manufacturing complexity and deformation risk increase
Solution Approach 1:
The invention uses a single through-hole with protrusions that have curved or rounded tips rather than multiple circular holes. This simplifies the manufacturing process by requiring only one drilling operation, while the curved protrusion geometry still achieves the necessary stress concentration effect for reliable valve member cleavage.
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 effectively releases internal pressure at a normal pressure, ensuring the battery's safety by maintaining valve member sealability and strength, preventing bursting in small battery sizes, with optimal protrusion arrangement and material selection.
Implementation Method 1
stress is concentrated on the valve member at the tip of the protrusions when the internal pressure increases
Data Source
AI summary
A small cylindrical lithium-ion secondary battery provided with a safety mechanism that enables internal pressure to be released when an anomaly occurs. The battery includes an electrode group formed of a positive electrode and a negative electrode that are wound or stacked with a separator interposed therebetween, an electrolytic solution, a battery case that contains the electrode group and the electrolytic solution, and a sealing body. The battery case has an outer diameter of 10 mm or less. The sealing body includes a ring having a through-hole and includes a sheet-like or film-like valve member disposed such that the valve member covers the through-hole of the ring, and a safety mechanism that causes the valve member to cleave when the internal pressure reaches a predetermined pressure is disposed therein. The ring includes protrusions formed of linear ridge lines that protrude toward an inside of the through-hole.