Slot die coating of lithium-ion battery electrodes: investigations on edge effect issues for stripe and pattern coatings
- 1.4k Downloads
An important step in the production of lithium-ion batteries is the coating of electrodes onto conducting foils. The most frequently used coating method in industry is slot die coating. This process allows the reproducible preparation of thin functional films at high velocities. A phenomenon that is often neglected in scientific studies and has attracted little attention, compared to film stability, is the inevitable presence of edge effects. Film elevations appear at the coating edges and at the start of each single patch during intermittent coating. These superelevations will cause problems at the downstream cell-assembling steps. In this study the influence of dynamic and geometric coating parameters on the shaping of coating edge effects was investigated. A quantitative measurement technique for edge profiles was developed and implemented. Film stretching has been identified in literature as a main reason for edge effects. We could show that varying the coating speed and the gap ratio did not lead to ideal edges, but affected the shape of the coating edges. The elevation height appeared to be independent from the varied process parameters, in the range of investigation. Also the gradient at the very edge of the film was not affected by these parameters. Only the edge width showed a disproportionately increasing trend towards higher applied gap ratios. The results indicate that the approach of film stretching is not sufficient to fully describe the cause of superelevations in lithium-ion battery coatings.
KeywordsLithium-ion batteries Slot die coating Edge effects Fat edges Film profiling
Part of this work has been supported in the frame of the project Competence E by the German Federal Ministry of Economics and Technology on the basis of a decision by the German Bundestag (Funding No. 03ET6016). The authors would like to thank all involved mechanics, assistants, and the student Conny Buerkin for their support work and building up the experimental set-up. We specially thank Valentin Wenzel (KIT-MVM-VM) for mixing support, Dr. Bernhard Hochstein (KIT-MVM-AM) for rheological measurements, and our cooperation partners at TSE Troller AG, Switzerland, for the technical support.
- 1.Nationale Plattform Elektromobilitaet (NPE), In: Bundesregierung, GG (ed) Zweiter Bericht der Nationalen Plattform Elektromobilität. Nationale Plattform Elektromobilität, Berlin, 2011Google Scholar
- 2.Thielmann, A, et al., “Produkt-Roadmap Lithium-Ionen-Batterien 2030.” In: Fraunhofer Institute for Systems and Innovation Research ISI (Karlsruhe) (ed) Technologie-Roadmapping am Fraunhofer ISI: Konzepte – Methoden – Praxisbeispiele. Fraunhofer-Institut für System- und Innovationsforschung ISI, Karlsruhe, 2012Google Scholar
- 5.Linden, D, Reddy, TB, Handbook of Batteries, 3rd ed. McGraw-Hill Professional, New York (2001)Google Scholar
- 6.Buchmann, I, Batteries in a Portable World. Cadex Electronics, Richmond (2001)Google Scholar
- 8.Cohen, ED, Gutoff, EB, Modern Coating and Drying Technology. Wiley, New York (1992)Google Scholar
- 9.Schmitt, M, et al., “Slot-Die Processing of Lithium-Ion Battery Electrodes—Coating Window Characterization.” Chem. Eng. Process. Process Intensif., 68 32–37 (2013)Google Scholar
- 10.Cavadini, P, et al., “Investigation of Surface Deformation During Drying of Thin Polymer Films Due to Marangoni Convection.” Chem. Eng. Process. Process Intensif. (2012, in press)Google Scholar
- 11.Schmidt-Hansberg, B, Sanyal, M, Klein, MF, Pfaff, M, Schnabel, N, Jaiser, S, Vorobiev, A, Müller, E, Colsmann, A, Scharfer, P, Gerthsen, D, Lemmer, U, Barrena, E, Schabel, W., “Moving Through the Phase Diagram: Morphology Formation in Solution Cast Polymer–Fullerene Blend Films for Organic Solar Cells.” ACS Nano, 5 (11) 8579–8590 (2011)Google Scholar