Elastomeric Lid Gasket for Lithium Cell Terminal Isolation
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Solution Overview
Problem
Lithium clusters can bridge between negative and positive polarity portions in lithium electrochemical cells, leading to premature discharge, especially in designs without a ferrule in the glass-to-metal seal, where a tight seal between dissimilar materials is difficult to achieve.
Innovation Solution
An electrochemical cell design featuring a glass-to-metal seal without a ferrule, where an elastomeric gasket contacts the inner surface of the lid and the sealing glass, and an insulator compartment is used to prevent lithium clusters from bridging to the terminal pin, ensuring electrical isolation and preventing internal loading mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ferrule is used in the glass-to-metal seal to ensure tight sealing, then sealing reliability is improved, but device complexity and manufacturing difficulty increase due to assembly of multiple dissimilar materials
Solution Approach 1:
The patent removes the ferrule component from the glass-to-metal seal assembly, extracting the problematic element that caused complexity in assembling dissimilar materials. The sealing glass directly contacts the lid without requiring a ferrule intermediary, simplifying the structure while maintaining sealing integrity through the elastomeric gasket compensation mechanism.
Solution Approach 2:
The patent changes the sealing mechanism from rigid mechanical interference (ferrule) to flexible elastomeric deformation. The elastomeric gasket is compressed between the sealing glass and lid inner surface, creating a tight seal through material deformation rather than precise mechanical fitting, thereby simplifying assembly of dissimilar materials.
2Reliability
If the elastomeric gasket is compressed to create a tight seal, then sealing effectiveness is improved, but the gap for lithium cluster formation increases
Solution Approach 1:
The patent introduces the insulator compartment as an intermediary barrier between the compressed elastomeric gasket and the cathode current collector tab. This intermediate insulating structure prevents direct electrical contact and blocks lithium cluster formation paths, resolving the conflict between sealing compression and lithium cluster prevention.
Solution Approach 2:
The patent adds a spatial dimension to the sealing solution by positioning the insulator compartment to extend radially outward from the gasket assembly. This creates a three-dimensional barrier system where the gasket provides radial sealing while the insulator compartment provides axial and radial electrical isolation, preventing lithium cluster bridging in multiple directions.
3Reliability
If the insulator compartment is positioned close to the sealing glass, then electrical isolation is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies local quality by providing electrical isolation only in the critical regions where lithium cluster bridging is most likely to occur. The insulator compartment is strategically positioned to cover the gap between the sealing glass and cathode current collector tab, rather than requiring uniform isolation throughout the entire cell structure, thereby reducing manufacturing precision requirements.
Solution Approach 2:
The elastomeric gasket serves as a beforehand cushioning element that compensates for manufacturing tolerances and assembly variations. By providing compliant sealing that can deform to accommodate dimensional variations, the gasket reduces the precision requirements for positioning the insulator compartment and other components.
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 effectively prevents lithium clusters from bridging to the positive polarity cathode components, thereby preventing premature discharge of the cell, even in designs without a ferrule, by creating a non-conductive barrier and maintaining a sufficient distance from the cathode current collector tab.
Implementation Method 1
an insulator gasket that covers a portion of the inner surface of a casing lid around the glass-to-metal seal (GTMS) to thereby form a physical barrier isolating the terminal pin from contact with lithium clusters in the vicinity of the GTMS
Implementation Method 2
The sealing glass electrically isolates the terminal pin from the lid so that the terminal pin is in a non-conductive relation with the casing
Implementation Method 3
the Li+ ions diffuse the short distance from the anode to the cathode and then within the pore structure of the cathode
Implementation Method 4
as long as a concentration gradient exists, deposition of lithium is thermodynamically favored in the region of higher lithium-ion concentration
Data Source
AI summary
A pulse dischargeable electrochemical cell, preferably of a Li/SVO couple, is described. To help prevent lithium clusters from bridging to the terminal pin extending below the casing lid and connected to the cathode current collector tab, an elastomeric gasket directly contacts the inner surface of the lid. The elastomeric gasket is preferably a unitary member comprising an O-ring gasket portion that contacts the sealing glass of the glass-to-metal seal (GTMS), and a sheet-shaped gasket portion connected to the O-ring gasket portion and that contacts the inner surface of the lid. The GTMS does not have a ferrule. Instead, the sealing glass seals directly to the lid and to the terminal pin. The elastomeric gasket resides between the lid and an insulator compartment, which is described in co-assigned U.S. Pat. No. 10,629,862 to Roy et al.