Optimization of Edge Quality in the Slot‐Die Coating Process of High‐Capacity Lithium‐Ion Battery Electrodes

Abstract

Understanding and reducing edge elevations at the lateral edges are crucial aspects to reduce reject rates during electrode production for lithium‐ion batteries (LIB). Herein, different process conditions to reduce edge elevations at the lateral edges of water‐based, shear‐thinning coatings in the production of LIB electrodes are presented. The reduction of edge elevations is transferred from state‐of‐the‐art electrodes to high‐capacity electrodes. The developed process configuration greatly reduces reject caused by cutting off the edge areas in the industrial roll‐to‐roll process for electrode production. Compared with state‐of‐the art electrodes, the reject rate for high‐capacity electrode production is significantly higher because the edge geometry in crossweb direction of the electrodes is wider. An optimization can be achieved by a combined adjustment of the coating gap and the slot‐die angle to the substrate (angle of attack) to affect the pressure field in the coating bead. Therefore, a systematic investigation and optimization of these process parameters are presented. In addition, the investigation of the process stability of the coating is required. Based on this optimization, a reduction of edge elevations for high‐capacity electrode coatings (5 mAh cm−2) of 69% and ultrathick high‐capacity electrode coatings (7 mAh cm−2) of 48% is possible.

Challenges and Opportunities for Large‐Scale Electrode Processing for Sodium‐Ion and Lithium‐Ion Battery

“…It should be noted that a high viscosity at low shear rates is advantageous, as this limits particle movement (less susceptible to sedimentation). Towards higher shear rates (>10 s −1 ) the viscosity of the anode and the viscosity of the cathode slurries approach each other indicating a comparable suitability for slot‐die coating [10,33,58] . A further effect is that scrap rates due to edge elevations during electrode manufacturing can be minimized by slurries with a higher viscosity at low shear rates and shear thinning behavior [33,58–60] …”

“…Towards higher shear rates (> 10 s À 1 ) the viscosity of the anode and the viscosity of the cathode slurries approach each other indicating a comparable suitability for slot-die coating. [10,33,58] A further effect is that scrap rates due to edge elevations during electrode manufacturing can be minimized by slurries with a higher viscosity at low shear rates and shear thinning behavior. [33,[58][59][60] As suggested in the previous section, the different drying times may be compensated by increasing the solid content for SIB materials with a lower capacity than LIB materials.…”

“…[10,33,58] A further effect is that scrap rates due to edge elevations during electrode manufacturing can be minimized by slurries with a higher viscosity at low shear rates and shear thinning behavior. [33,[58][59][60] As suggested in the previous section, the different drying times may be compensated by increasing the solid content for SIB materials with a lower capacity than LIB materials. However, it can be seen from the determination of viscosity that an increase in solid content, with otherwise the same composition between LIB and SIB, leads to a further increase in viscosity.…”

Process and Drying Behavior Toward Higher Drying Rates of Hard Carbon Anodes for Sodium‐Ion Batteries with Different Particle Sizes: An Experimental Study in Comparison to Graphite for Lithium‐Ion‐Batteries

“…[36] This reduces the reject rate during electrode production. [37][38][39] Since the same solid content and the same electrode composition with the same CMC amount was adjusted, all three HC slurries for SIB and the graphite slurry for LIB show the same behavior for the viscosity at a shear rate above 100 s À1 . In the slot-die-coating process at state-of-the-art industrial coating speeds, typical shear rates in the coating gap are above 400 s À1 .…”

“…In the slot-die-coating process at state-of-the-art industrial coating speeds, typical shear rates in the coating gap are above 400 s À1 . [37,40] It is assumed that the processability, in particular toward faster industrial coating speeds, will be similar for all investigated slurries and the coating equipment for LIB anodes at pilot and industrial coating plants can be used for HC slurries for SIB without major changes or investments.…”