Meaning
Thermal treatment process removes volatile contaminants and trapped gases from materials by heating them in a low-pressure environment. Performing vacuum hot outgassing ensures that battery components like housings or current collectors are free from moisture and organic residues. The combination of heat and vacuum lowers the boiling point of contaminants, allowing them to escape from the surface and the bulk of the material.
This procedure is critical for maintaining the purity of the electrolyte after the cell is sealed.
Vapor Removal
Kinetic energy of the absorbed molecules increases with temperature until they overcome the binding forces of the substrate. During vacuum hot outgassing, these molecules are pulled away by the vacuum pump system. This prevents the formation of gas bubbles inside the finished battery.
Surface Decontamination
Elimination of water vapor and oxygen from the surface of metallic foils prevents the formation of insulating oxide layers. Subjecting a part to vacuum hot outgassing improves the adhesion of the electrode coating to the current collector. This step reduces the internal resistance of the electrochemical cell.
Pressure Boundary
Effectiveness of the treatment depends on the ultimate vacuum level and the duration of the heating cycle. Reaching a specific torr level during vacuum hot outgassing indicates that the majority of the volatile species have been removed. If the pressure rises again after the pump is valved off, it suggests that the material is still releasing gas.
Mass spectrometry can be used to identify the specific types of molecules being released. This monitoring ensures that only clean components enter the assembly line.
