Meaning
Sealing components placed at the junction where a battery terminal passes through the cell housing provide both mechanical isolation and environmental protection. The feedthrough gasket prevents the leakage of electrolyte while simultaneously blocking the ingress of moisture or oxygen from the external atmosphere. Polymeric materials such as perfluoroalkoxy or specialized rubbers are frequently selected for their chemical resistance and dielectric properties.
Failure of this seal leads to internal pressure loss or hazardous venting.
Chemical Resistance
Long-term stability in the presence of organic solvents and lithium salts is the most demanding requirement for the seal. A feedthrough gasket must withstand the aggressive nature of the electrolyte without swelling or degrading. Any loss of material integrity results in a path for gas escape.
Compression Requirement
Mechanical sealing force is maintained by the elastic deformation of the gasket material against the terminal and the lid. The design of the feedthrough gasket must account for the creep behavior of the polymer over the ten-year life of a typical battery system. Stress relaxation can reduce the contact pressure below the threshold required for a hermetic seal.
Manufacturers use accelerated aging tests to predict how the gasket will perform under thermal cycling.
Environmental Shield
Protection against external contaminants ensures the purity of the internal cell chemistry. The feedthrough gasket acts as the primary barrier against humidity. If moisture enters the cell, it reacts with the electrolyte to form hydrofluoric acid.
This reaction consumes lithium and damages the electrode surfaces.
