A pre-calendering process to reduce the corrugations and wrinkles of ultra-thin electrodes

The formation of surface irregularities during electrode calendering remains a critical challenge. Specifically, uncoated regions of current collectors often develop severe wrinkles while coated areas frequently exhibit undesirable corrugations. Although controlling material tension has long been considered an effective strategy to address these defects, improper tension management can paradoxically lead to foil rupture or increased wrinkling severity, both result in elevated production waste. To address that, this work first explores the connection between the front/back tension intensity and the wrinkle and corrugation of the electrode via experiments and an analytical model. Results indicated that coated area corrugations were primarily influenced by the differential tension between processing stages rather than absolute tension values. For instance, reducing tension differential from 5N to 20N led to a significant 34.2% reduction in corrugation tortuosity. However, excessively large tension differences caused linear increases in shear displacement (δ), exacerbating wrinkling in the uncoated regions. After that, a novel pre-calendering process was proposed by applying compressive loading specifically to the current collector foil via a modified upper roller. Experimental results demonstrated an optimal defect reduction was achieved with both improved surface uniformity in the uncoated collectors and reduced corrugation severity in the coated area.