The development of reproducible process chains for cathode sheets of solid-state batteries (SSB) is a key challenge in the further development of SSB. Contact losses between active material particles and solid electrolyte particles, high porosities and degradation processes of the solid electrolyte lead to a decrease in electrochemical performance and to faster ageing of the SSB. To counteract this, targeted mixing processes can be used to homogenize the cathode premix, to coat active material particles with solid electrolyte or to comminute the solid electrolyte in order to increase the number of active material particles actively bound to the ionic network. In addition, dry coating of the cathode sheets following the mixing process can offer the advantage that no solvents are used that could have a potentially negative influence on the electrolyte. Furthermore, undesirable reagglomeration processes of electrolyte particles are avoided and energy and cost-intensive drying steps are omitted.

In this study, the influence of a premixing process of LiNi0.83Co0.11Mn0.06O2 (NCM) and Li6PS5Cl (LPSCl) in a planetary ball mill on the resulting microstructure of the cathode mixture and its influence on the dry coating of SSB cathode sheets is investigated. The premixing results show that a reduction in LPSCl particle size and the formation of composite aggregates is achieved with increasing rotational speed and mixing time. This leads to an improvement in the mean discharge capacity (20 cycles at 0.1C) from 100 mAh g-1 (mixed for 5 min at 200 rpm) to 160 mAh g-1 (mixed for 10 min at 600 rpm). However, excessive stress due to high collision energies during ball milling at 800 rpm and 1000 rpm, leads to reduced performance based on a decrease in the crystallinity of the solid electrolyte.

The results of the subsequent dry coating of premixed cathode materials with PTFE show that the premixing process in the planetary ball mill significantly impacts the performance of the final SSB cathode. However, the high compaction forces during calendering create more contact points between the solid electrolyte and the active material, leading to an even higher mean specific discharge capacity – 185 mAh g-1 for the mixture pre-mixed at 600 rpm and 170 mAh g-1 for the mixture pre-mixed at 200 rpm. Thus, the dry coating process can partially compensate for suboptimal premixing through high shear forces and additional compaction.