Vacuum sealing in battery manufacturing typically refers to the process of sealing pouch cells in a vacuum environment to ensure that no air (and especially no moisture) is trapped inside. For example, when finishing a pouch cell, the cell (with its liquid electrolyte) might be placed in a vacuum chamber to draw out any air, and then the pouch is heat sealed while under vacuum. This helps prevent any air or moisture from being present. Moisture reacts with electrolyte causing gas generation and excess air pockets can lead to poor stack. Vacuum sealing also ensures the pouch closely conforms to the cell stack, which is the design form factor of the cell.
In NOVONIX pilot line they vacuum seals pouch cells after filling them with electrolyte. They optimize sealing temperatures to ensure air or electrolyte leakage can occur. Prior to formation, the cells are made with an over-sized pouch. The formation process generates some gas, so after formation, the excess pouch material is removed in the dry room and the cells are vacuum sealed again. NOVONIX’s understanding of vacuum sealing is important to deliver high-quality test cells; any residual moisture or poor seal could skew test results by introducing side reactions or capacity loss that aren’t due to the active materials. Thus, their expertise ensures that when they evaluate a new chemistry, the packaging process isn’t a weak link.
