Influence of electrode corrugation after calendering on the geometry of single electrode sheets in battery cell production

Calendering is an essential process step in battery cell production. By selective compaction of the material, the performance of the battery cell can be optimized. During processing, corrugations can occur in the machine direction, which are characterized in this article in relation to the material systems LiNi$_{0.8}$Mn$_{0.1}$Co$_{0.1}$O$_2$ (NMC811) and LiNi$_{0.6}$Mn$_{0.2}$Co$_{0.2}$O$_2$ (NMC622) as well as the rate of compaction and the web tension. It is shown that the corrugations are strongly dependent on the rate of compaction. The material system and the web tension show a weaker influence on the corrugation characteristics. Subsequently, single electrode sheets are cut from the coils and their geometry is investigated. It is shown that the corrugation hardly propagates further into the single electrodes, which is explained with the storage time of the electrodes. Rather, the coil bending strongly influences the electrode sheet geometry. It is shown that the position of the conductor tab also has an important influence.