Thermal wrinkling in anode production: Defect analysis and mitigation strategies

With the increasing demand for electric vehicles, roll-to-roll manufacturing systems have emerged as a promising approach for the large-scale and cost-effective production method of Li-ion batteries. However, this process poses unique challenges, including web wrinkle defects, referring to undesired folds, creases, or distortions that occur in the flexible, thin substrate composed of copper film during anode production. Web wrinkles can occur because of strain deviation in the cross-machining direction due to the application of nonuniform tension and the differences in geometrical and material properties. This study analyzed the thermal effects on formation of web wrinkles with respect to operating conditions (coating thickness, web speed, and web tension) and suggested guidelines for battery anode production to ensure optimal operating conditions through a series of simulations followed by experimental verification. A simulation-based analysis was performed, and a copper film and anode material were utilized for experimental verification. Excessive wrinkling was observed in cases with low coating thickness, low operating speed and high operating tension. The results indicate the effect of thermal conditions on web wrinkling and the adjustment of operating conditions required to mitigate defects such as wrinkling.