Elimination of electrode corrugations via a two-step calendering process

Abstract

Calendering is a crucial process in the manufacturing of lithium-ion batteries electrodes. Corrugations occur frequently in the electrode during calendering, leading to challenges in large-scale and low-cost production of lithium-ion batteries in industry. An in-depth understanding of the formation mechanism of electrode corrugations during calendering process is essential to improve the process and eliminate the corrugations. To do so, compression and tension experiments were first performed to obtain the mechanical properties of the porous active material for electrodes. The Drucker-Prager Cap (DPC) model was calibrated based on experimental results, and employed to capture the plastic deformation of the active material in the calendering process. The current collector foil was revealed to be responsible for the formation of corrugations, which hindered the elongation of the calendered active material. Based on the elongation difference obtained, a novel two-step process introducing a pre-elongation step was proposed. In the pre-elongation step, the rolling pressure was determined by simulation to elongate the foil by 0.75 %, enabling the elongation of the foil to match that of the active material in the next step. By using this new process, the corrugations of the calendered electrodes were significantly suppressed without requiring large web tensions. The intensity of the corrugations was reduced by >60 %, which is of great significance to reduce the calendered electrode defects, scrap rates, and manufacturing costs of lithium-ion batteries.