Lithium-ion batteries are an inevitable part of energy storage in our modern world. However, conventional lithium-ion batteries are expected to run into performance limits. To push battery performance beyond these limitations, it is critical to investigate alternative battery technologies. One particularly promising technology is solid-state batteries (SSB). By replacing separators and liquid electrolytes of lithium-ion batteries with solid-state ion conductors, the usage of Li-metal anodes and thus higher energy densities can potentially be enabled. Further advantages are increased mechanical stability, the absence of leakage and a potentially improved thermal safety. Solid-state batteries utilize composite electrodes, consisting of the electrochemically active material, the solid electrolyte (SE) and, if necessary, additives such as binders or conductive carbons, e.g., vapor grown carbon fibers (VGCF). In these composite systems, a sufficiently high ionic (𝜎 ion ) and electronic (𝜎 e ) conductivity, as well as balancing of the two transport quantities is of paramount importance to enable high electrode utilizations and to avoid reaction fronts during charging and discharging. On the one hand, charge carrier transport can be decisively influenced by varying the volumetric ratios of the electrode components given that the electrochemically active material and carbon additives are solely responsible for the electronic conduction, while the solid electrolyte exclusively conducts ions. With that, altering the SE content in composite anodes, such as Li4Ti5O12-Li7P2S8I-C or Si-Li6PS5Cl (LPSCl)-C , can facilitate changes in the effective ionic conductivity over orders of magnitude. Similarly strong correlations between effective ionic and electronic conductivity and the volumetric ratios of the composite components were found in cathode systems such as NCM622-LPSCl 12 , LiMn2O4-Li3InCl6 and S-LPSCl-C . On the other hand, the microstructure of the composite electrode can influence its effective conductivities. Froboese et al. demonstrated the influence of differently sized inclusions on the effective ionic conductivity of composites. Studies investigating the effect of changing active material particle sizes in NCM622-LPSCl and Si-LPSCl-C electrodes on the battery performance highlight the importance of carefully designing microstructures to improve electrode utilizations. In a similar manner, optimizing the particle size of the SE in LiNi0.83Co0.11Mn0.06 (NCM83)-LPSCl composites leads to better electrode utilizations due to a more homogeneous ion current distribution during battery operation. This emphasizes that both the active material and electrolyte particle size need to be considered in electrode design.