All-solid-state batteries (ASSB) are considered as attractive further development of conventional lithium-ion batteries, since they are expected to deliver higher energy and power densities. So far, ASSB with inorganic solid electrolytes have not been applied in large-scale due to difficulties in processing, insufficient overall ionic conductivities, and high interfacial resistances between active material and solid electrolyte. In this investigation, the influence of stressing conditions on the scalable production of ASSB composite cathodes via a high-intensity mixer is investigated. The high-intensity mixer is supposed to circumvent the challenge of high interfacial resistances within an ASSB cathode consisting of submicron-sized active material LiFePO4, carbon black and solid electrolyte Li3InCl6. The mixing process is simulated employing the discrete-element-method, from which the stressing conditions acting on the particles are extracted and linked with microstructural observations and electrochemical data. These investigations show that the capacity of the ASSB increases with increasing specific energy input, which is, however, limited by a certain stress intensity determined by the rotational speed of the mixer. The increasing capacity of the composites can be explained by microstructural investigations, which show a comminution of highly cohesive LIC with increasing stress intensity thus resulting in an ionic bonding of the LFP particles. This not only leads to an increase in the capacity and thus also the partial ionic conductivity of the ASSB, but also to a reduction in the electronic conductivity due to a large number of finely dispersed insulating LIC particles. The LIC comminution also leads to an increase in the composite strength due to the breaking up of loose LIC agglomerates. By breaking up the elastic LIC agglomerates, the elastic fraction of the composite material increases with increasing stress intensity, which shows that the influence of LIC on the composite material increases with its degree of comminution. Overall, this study suggests that optimizing the stressing conditions during mixing can improve the performance of ASSB composite cathodes by influencing their microstructure and consequently their electrochemical and mechanical properties. This is particularly important for dry calendering of ASSB cathodes, where optimized dry-mixed ASSB powders could be used.