Meaning
Electrical conductor isolation is achieved by melting a glass collar between a metallic pin and a surrounding outer metal body. For battery cells designed for long-term storage or extreme environments, a glass to metal feedthrough provides a highly robust, hermetic seal that prevents electrolyte leakage and moisture ingress. This component serves to maintain the internal chemistry without degradation.
Hermetic Sealing
Chemical compatibility between the molten glass and the metal components is established through controlled surface oxidation during the heating process. The glass to metal feedthrough relies on either a matched expansion seal, where the metal and glass have similar thermal expansion coefficients, or a compression seal, where the outer metal ring shrinks tightly around the glass. Compression seals are generally more robust and can withstand higher pressures.
They are widely used in specialized cylindrical lithium batteries.
Sourcing Quality
Procurement specifications for aerospace and grid-scale cells demand helium leak rates below ten to the minus nine standard cubic centimeters per second. When purchasing a glass to metal feedthrough, sourcing managers must verify the corrosion resistance of the pin metal against highly reactive battery chemistries. Stainless steel and specialized nickel-iron alloys are common choices because they resist both external atmospheric moisture and internal lithium-ion electrolyte attacks.
Failure Mode
Mechanical stresses from terminal torque or thermal cycling can induce micro-cracks in the glass insulator. Such cracks allow ambient moisture to slowly diffuse into the cell, destroying the lithium salt and generating hydrofluoric acid. These failures cannot be easily repaired once the battery pack is assembled.
Therefore, sourcing contracts should include mechanical pull tests and thermal shock resistance requirements for all feedthrough shipments.
