A reliable design of production processes for the manufacturing of lithium-ion battery electrodes requires a deep understanding of the interdependency of processes, the resulting electrode microstructure and the influence on the cell performance indicators, like energy density, cycle life and aging. In the present study, the focus lays on the calendering process during which the electrode coating is compacted with the aim of adjusting uniform electrode properties such as mechanical, electrical and electrochemical behavior. Compaction of the electrode coating affects the pore structure and therefore has a crucial influence on the electrical and electrochemical behavior of the cell. Consequently, process and machine parameters have to be adapted in order to generate electrode structures optimized for a desired application. To meet this target, an in-depth understanding of how the calendering process affects the electrode structure beyond the simple reduction of porosity and further how the calendering process itself is affected by the preceding process steps like dry or wet mixing is mandatory.

Thus, the focus of the presented work is to investigate the interdependency between the dry mixing process step and the subsequent calendering process by correlating powder properties adjusted via the dry mixing with the machine behavior during the calendering as well as the resulting coating density. The impact of the calendering process on the electrode microstructure and its correlation with electrode properties by developing process-product-property functions, regarding the above mentioned criteria, is an additional focus of the presented study.

Therefore, powder mixtures of NMC622 with carbon black were created under varying the dry mixing intensity and thus adjusting the carbon black agglomerate size. The created powder mixtures were comprehensively characterized, e.g. particle size distribution and powder conductivity, and then used to build up electrodes which afterwards were compacted to different coating densities. The correlation between the powder properties and the calendering behavior shows a higher compaction resistance with decreasing carbon black agglomerate size. Whereas reducing the carbon black agglomerate size leads to lower electrical resistivity and therefore strongly impacts the C-rate capability.