Elastomeric Lid Gasket for Lithium Cluster Isolation in Li/SVO Cells
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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 an insulator compartment is positioned between the electrode assembly and the lid to prevent lithium clusters from bridging to the terminal pin, ensuring a non-conductive relation 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 a tight seal, then sealing reliability is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent removes the ferrule component from the glass-to-metal seal assembly, simplifying the structure while maintaining sealing reliability through the elastomeric gasket that directly contacts the lid inner surface and provides the necessary seal without requiring additional ferrule components
Solution Approach 2:
The patent changes the sealing mechanism from a rigid ferrule-based seal to a flexible elastomeric gasket seal, allowing the sealing interface to deform and adapt to surface irregularities, thereby achieving reliable sealing without the complexity of a ferrule
2Ease of manufacture
If dissimilar materials (metal lid and polymeric insulator) are used to reduce weight and complexity, then ease of manufacture is improved, but sealing reliability deteriorates due to difficulty in achieving a tight seal
Solution Approach 1:
The patent uses a flexible elastomeric gasket as a thin film barrier between the metal lid and polymeric insulator compartment. The elastomeric material can deform to accommodate the dissimilar materials interface, creating a reliable seal that prevents lithium cluster migration while maintaining the benefits of dissimilar material construction
Solution Approach 2:
The patent employs a composite sealing solution combining elastomeric material with the metal lid and polymeric insulator components. This composite approach leverages the advantages of each material - the rigidity of metal, the insulation properties of polymer, and the sealing capability of elastomer - to achieve both ease of manufacture and sealing reliability
3Reliability
If the elastomeric gasket extends to the periphery of the lid to maximize isolation, then reliability is improved, but device complexity increases
Solution Approach 1:
The elastomeric gasket is positioned specifically at critical locations where lithium cluster migration is most likely to occur - around the glass-to-metal seal and along the inner surface of the lid near the insulator compartment. This localized placement provides maximum isolation effectiveness without requiring the gasket to extend uniformly across the entire lid periphery, thereby reducing complexity
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 cases where a tight seal between the metal lid and polymeric insulator compartment is not possible, ensuring reliable operation of implantable medical devices.
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 electrode assembly including all of the positive polarity portions are physically segregated from the negative terminal comprising the anode leads connected to the casing in a primary lithium electrochemical cell
Data Source
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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 sheetshaped 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. Patent No. 10,629,862 to Roy et al.