Concepts for the Reduction of Longitudinal Wrinkles During Calendering of Battery Electrodes

"Many potential customers are currently still discouraged from buying an electric car because the prices are significantly higher than their
expectations. Important cost drivers are the high amount of energy required to produce the battery cell as well as high material costs. These costs
can be reduced by minimizing scrap in manufacturing, because less energy and material is wasted. The calendering process step is a rolling
process in which the coating of an electrode is compacted. Among many other positive effects, calendering is a necessary process step to increase
the volumetric energy density. However, calendering can also generate defects in the electrodes caused by the high mechanical stresses due to
high line loads during compaction. One such defect is the formation of longitudinal wrinkles that form at deflection rollers. They lead to scrap
and, in the worst case, to web tears that cause process interruptions. This paper presents two material-independent concepts to reduce longitudinal
wrinkling during calendering. One contributing factor is the deformation of the electrode during calendering. Therefore, the aim is to minimize
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the deflection of the electrode out of the plane, so that the web can hit the deflection roller straighter and longitudinal wrinkling is reduced. The
first concept involves the implementation of additional rollers and the second concept realizes a lateral stretching movement. This paper also
shows the implementation of prototypes, first results and recommendations for an optimization. Finally, further concepts can be developed on
the basis of these findings in order to reduce scrap and thus energy wastage and production costs. Consequently, a more sustainable and resilient
electrode manufacturing will be enabled. The material-independent approaches will also allow for the implementation in the electrode production
of new and sustainable battery concepts."