Meaning
Mechanical junctions where the electrical terminals exit the battery housing must maintain a gas tight and liquid tight barrier. The tab feedthrough seal prevents the ingress of oxygen and moisture which would otherwise react violently with the lithium salts. This component must also provide electrical insulation to prevent the terminals from shorting against a metal casing.
In pouch cells, this seal is formed by heat pressing the laminate around the tabs.
Material Compatibility
Selection of the sealing medium depends on the chemical nature of the electrolyte and the metal used for the tabs. A robust tab feedthrough seal often employs specialized polymers that adhere to both aluminum and copper surfaces. These materials must resist the mechanical stresses caused by the vibration and thermal expansion of the battery pack.
Failure Mode
Degradation of the seal is a primary cause of electrolyte leakage and subsequent cell failure. If the tab feedthrough seal is compromised, the electrolyte evaporates and the internal resistance of the cell rises sharply. This can be detected by a distinct odor or by the presence of salt crystals around the terminal area.
Inspection Protocol
Helium leak testing or vacuum decay methods verify the integrity of the junction during the assembly process. Every tab feedthrough seal is a critical point of failure that must be validated before the cell is integrated into a larger module. Advanced manufacturing uses infrared thermography to check the uniformity of the heat seal in real time.
