Sealed Secondary Battery Current Cutoff Valve Spherical Cap Design
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Solution Overview
Problem
Existing sealed secondary batteries face challenges in actuating current cutoff mechanisms at low internal pressure, particularly in large batteries, due to the need for a larger pressure-receiving area and the associated manufacturing complexities and performance reductions.
Innovation Solution
A sealed secondary battery design featuring a current cutoff mechanism with a concavity comprising a sloped side wall and a spherical cap-shaped dome, where the sloped side wall tapers with a decreasing diameter from a ring-shaped flange to a thin portion, and the dome descends in a spherical cap shape, optimizing the pressure-receiving area and actuation pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the pressure-receiving area of the current breaking valve is increased to enable actuation at low internal pressure in large batteries, then the actuation pressure is reduced, but the manufacturing complexity increases and performance may be reduced
Solution Approach 1:
The current breaking valve employs a spherical cap-shaped dome instead of a flat or conical structure. This curved geometry provides a large pressure-receiving area that amplifies the internal pressure force, enabling actuation at low pressure levels. The spherical shape distributes stress evenly and creates mechanical advantage through its geometric properties, resolving the contradiction between low actuation pressure and manufacturing simplicity.
Solution Approach 2:
The current breaking valve is divided into distinct functional segments: a flange for electrical connection, a sloped side wall for structural support and gradual deformation, and a spherical cap dome for pressure sensing. This segmentation allows each part to be optimized independently while maintaining overall simplicity in manufacturing and assembly.
2Stress or pressure
If the current breaking valve is designed with a large pressure-receiving area, then the actuation pressure is reduced, but the height of the valve structure increases
Solution Approach 1:
The spherical cap dome achieves a large pressure-receiving area within a compact height by utilizing curved geometry. The dome's radius of curvature is optimized to provide sufficient surface area for pressure actuation while maintaining a compact profile that fits within the battery's height constraints.
Solution Approach 2:
The pressure-receiving surface is concentrated in the spherical cap dome region, which is specifically designed with large curvature radius to maximize pressure sensitivity. The flange and side wall portions maintain smaller dimensions for structural support and electrical connection, creating a non-uniform distribution of dimensions that optimizes both actuation pressure and overall height.
3Device complexity
If the current breaking valve structure is simplified to reduce manufacturing complexity, then the device complexity is reduced, but the ability to maintain proper contact and prevent conduction is compromised
Solution Approach 1:
The valve structure is segmented into a flange for electrical connection and a dome for pressure sensing, with each segment performing its specific function. This simple two-part design maintains reliability by ensuring the flange provides stable electrical contact while the dome responds to pressure changes, without requiring complex multi-component assemblies.
Solution Approach 2:
The electrical and mechanical properties of the current breaking valve are optimized by controlling material parameters and geometric dimensions. The thickness, diameter, and curvature radius are specifically selected to ensure the valve acts as a reliable switch that maintains contact under normal conditions and opens reliably when the spherical cap deforms under overcharge pressure.
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 allows for a low actuation pressure requirement, reducing manufacturing complexities and performance enhancements while maintaining sufficient height for proper contact and preventing conduction between the current breaking valve and current collector.
Implementation Method 1
the spherical cap-shaped dome has a sphere radius R of 30 mm or larger, but smaller than 100 mm... the larger the surface area of current breaking valve (i.e. surface area of the deformable portion (concavity) of current breaking valve, or 'pressure-receiving area' hereinafter) to which the battery's internal pressure is applied, the lower the battery's internal pressure (or 'actuation pressure' hereinafter) required to deform the current breaking valve
Data Source
AI summary
This invention provides a sealed secondary battery comprising a current cutoff mechanism. The current cutoff mechanism has a current breaking valve 30 comprising a sloped side wall 32A which tapers with decreasing diameter from the inner circumference of a flange 32 and a dome 32B descending in a spherical cap shape from the rim of sloped side wall 32A. The rotation axis L of sloped side wall 32A and the sloped side wall 32A form an angle θ to satisfy 60°≤θ≤75° while dome 32B has a sphere radius R of 30 mm or larger, but smaller than 100 mm. In a planer view along the rotation axis L, the outer circumference of dome 32B is located outside the outer circumference of a thin portion 76.