Meaning
Manufacturing process used to hermetically close a battery pouch by applying heat and pressure while the internal environment is under negative pressure. This step, vacuum heat sealing, ensures that no air or moisture remains inside the cell and that any evolved gases are removed. A durable seal prevents the electrolyte from leaking and protects the internal chemistry from environmental contamination.
It is an important step in the assembly of soft-shell battery formats.
Seal Integrity
Fusion of the polymer layers on the pouch material creates a permanent barrier. During vacuum heat sealing, the heating elements must reach a specific temperature to melt the inner sealant layer without damaging the outer aluminum foil. Proper calibration of the dwell time and pressure prevents weak spots that could fail during the expansion and contraction of the cell.
Atmospheric Control
Removal of oxygen and water vapor is the primary reason for performing the seal under a vacuum. Even trace amounts of moisture can react with the electrolyte salts to form corrosive acids. By utilizing vacuum heat sealing, manufacturers ensure that the electrochemical environment remains stable for the life of the battery.
Production Yield
Automated inspection systems check the width and consistency of the seal after the process is complete. Inconsistent vacuum heat sealing can lead to high reject rates because a large leak can compromise an entire battery module. Optimized parameters allow for high speed production without sacrificing the long term reliability of the housing.
The machine logging of pressure and temperature for every cycle provides a data trail for quality audits.
