Vacuum is also essential during the drying stage to remove even the smallest remaining amounts of solvents and moisture. Without vacuum, the drying process would need to be carried out at much higher temperatures and would last much longer. This would have a negative effect on the electrode quality. As soon as electrolytes are incorporated into subsequent process steps, vacuum takes on a safety aspect, since many of the electrolytes used are highly reactive and inflammable. High-quality vacuum is essential here. On the one hand, it lends purity to the process so that no particles or moisture can enter the cell during electrolyte filling and degassing. On the other hand, it provides a low-reaction environment without oxygen or humidity with which the electrolyte could react.
"The greatest challenge always lies in the gas mixture being pumped. In principle, everything that's pumped and processed is also transported by the vacuum pump. In battery production, this affects the solvents and electrolytes which tend to be toxic and can damage the pumps and possibly the pump oil," says Dr. Sina Weiss. "But very warm ambient temperatures and high humidity are, generally speaking, also circumstances that present us with challenges," she adds. This is where battery manufacturers are called upon to help, either by ensuring the correct cooling of the pump or by using condensers.