Dome-Shaped Safety Valve for Lithium-Ion Cell Pressure Relief
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Solution Overview
Problem
Existing non-resealable safety valves in lithium ion secondary cells are prone to variances in pressure activation and lack impact resistance, leading to potential cell burst or solution leakage due to inadequate stress concentration and vulnerability to external impacts.
Innovation Solution
A sealed cell design featuring a dome-shaped valve structure with a break groove located on the inner surface of the sealing plate, where the dome protrudes inward and the break groove is formed at its periphery, concentrating deformational stress and enhancing shearing force to reliably break at a predetermined pressure, while maintaining impact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sectionally-wedge-shaped grooves are provided in the sealing plate to enable gas release, then safety is improved, but the cell becomes vulnerable to impacts and solution leakage occurs
Solution Approach 1:
The invention uses a dome-shaped protrusion instead of flat grooves. The curved surface of the dome concentrates stress during internal pressure events, enabling reliable breakage at the groove location, while the rounded shape distributes impact forces more evenly during external impacts, preventing unwanted breakage from drops or shocks.
Solution Approach 2:
The dome-shaped protrusion creates localized stress concentration at its apex and along the groove, while the rest of the sealing plate maintains its structural integrity. This local geometric modification enables the safety function without compromising the overall impact resistance of the sealing plate.
2Reliability
If grooves are formed in the sealing plate to release internal pressure, then gas release is enabled, but stress concentration is insufficient causing variance in activation pressure
Solution Approach 1:
The dome-shaped protrusion with its curved surface concentrates internal pressure stress at the apex and along the groove location, creating a well-defined stress concentration zone. This geometric feature ensures consistent stress distribution during pressure events, leading to uniform activation pressure across different cells.
3Weight of moving object
If the sealing plate is made thinner to reduce cell weight, then weight is reduced, but impact resistance and structural integrity deteriorate
Solution Approach 1:
The dome-shaped protrusion adds local geometric complexity that enhances stress distribution and structural performance without significantly increasing overall material usage. The curved geometry provides mechanical advantage in distributing impact forces, maintaining impact resistance even in thinner sealing plates.
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 solution ensures reliable gas release at a specific internal pressure without unnecessary opening by external impacts, improving safety and impact resistance by concentrating stress on the break groove, thus preventing cell burst and solution leakage.
Implementation Method 1
the dome having at a periphery thereof a break groove for facilitating the breakage of the valve structure... concentrating deformational stress and enhancing shearing force to reliably break at a predetermined pressure
Implementation Method 2
the valve structure broken as soon as pressure inside the sealed cell reaches or exceeds a predetermined value so as to permit a gas inside the sealed cell to be released outside the sealed cell
Data Source
AI summary
A sealed cell having a safety mechanism is provided. The safety mechanism has a non-resealable valve structure formed in a sealing plate that seals the cell. The valve structure is broken as soon as the internal pressure reaches or exceeds a predetermined value so as to permit the internal gas to be released outside. The valve structure has at least one dome protruding toward the interior of the cell, which in turn has at the periphery thereof a break groove for facilitating the breakage of the valve structure. This makes the valve structure highly responsive to the internal pressure and causes to form a break-opened orifice of a sufficient area at the time of operation in response to the increased internal pressure. The valve structure is not unnecessarily broken by the impacts of, for example, dropping. As a result, the safety of the sealed cell is significantly improved.