Advancements in Dry Coating for Battery Electrodes: Scalable Extrusion Mixing for Control of Electrode Microstructure and Electrochemical Performance

Dry coating of battery electrodes is emerging as a promising alternative technology to the prevailing slurry coating and drying process widely adopted in the lithium-ion battery industry. 1,2,3 To date, the most energy-intensive step in cell manufacturing is the drying of slurry-coated electrodes, 1 and the adoption of dry coating aims to mitigate both the environmental impact and production costs associated with electrode production. Beyond environmental and economic concerns, producing higher mass-loading electrodes, a crucial aspect for increasing cell energy density, faces inherent challenges with the slurry-coating process: the drying of thick coatings often leads to issues such as electrode cracking and the formation of inhomogeneous electrode microstructures. Bühler and Empa have collaboratively developed and are in the process of scaling up a dry-coating manufacturing method. 4 Our process centers around the extrusion mixing of electrode components, followed by calendering of the dry mixture to produce the final electrode and direct lamination onto a current collector. In this presentation, we showcase the adaptability of extrusion mixing in inducing shear fibrillation of polytetrafluoroethylene (PTFE) binder, crucial for achieving the desired electrode microstructures (see Figure 1a and 1b). Furthermore, we demonstrate the capability of our dry-coating technology to produce high-mass loading electrodes with areal capacities of 5 mAh cm -2 or more (see Figure 1c). The presentation encompasses a thorough characterization of dry-coated electrodes, including their microstructure and electrochemical performance in lab-scale batteries. Key aspects, such as rate capability and capacity retention, are evaluated. A comprehensive comparison with slurry-coated electrodes, fabricated using identical active electrode materials, mass fractions, and mass loading, reveals that our dry-coated electrodes exhibit comparable performance to their slurry-coated counterparts. 5 The scalability of our dry-coating technology is underscored, highlighting the achievable throughputs necessary for gigafactory-scale production with a single extruder. References: 1 F. Degen, M. Schütte, Journal of Cleaner Production, 2022 , 330, 129798 2 B. Schumm, S. Kaskel, Next Energy, 2023 , 100009 3 Y. Lu, C.Z. Zhao, H. Yuan, J.K. Hu, J.Q. Huang, Q. Zhang, Matter , 2022 , 5 , 876–898 4 InnoSuisse Flagship project CircuBat 5 E. Quérel, V. Dolder, C. Hänsel, P. Stössel, C. Battaglia, in preparation Figure 1