While the influence of volume fractions and microstructure on charge carrier transport is frequently investigated, the influence on the thermal transport properties is scarcely studied. Nonetheless, due to internal resistances (𝑅) within the solid-state battery system, Joule heating occurs during battery operation. This is of particular importance during fast charging, as the power of heating (𝑃) is related to the square of the applied current (𝐼) via 𝑃 = 𝑅 • 𝐼 2 . When the generation of thermal energy is faster than its dissipation, heat accumulates in the battery system leading to an increase of the battery temperature and the development of temperature gradients. This heating and temperature evolution within a cell can significantly impact battery performance, accelerate degradation kinetics and lead to at-times violent device failure. Particularly considering battery safety, thermal transport is known to play a critical role in conventional batteries. Even though solid-state batteries are often promoted as being safer than their conventional Li-ion counterparts, potential safety concerns should not be overlooked and carefully studied. Using thermodynamic models, Bates et al. showed, that under short-circuit conditions larger temperature increases are possible in SSB compared to batteries with liquid electrolytes. Furthermore, severe reactions and fire generation even under inert atmospheres were observed by Kim et al. when they exposed charged cathode composites to elevated temperatures above 150 °C. This is further corroborated by exothermic reactions that were observed between SSB-components in a differential scanning calorimetry study by Johnson et al. Especially regarding the thermal management design, thermal transport considerations for SSB pose an essential addition to the often-conducted ionic and electronic conductivity studies. Thermal transport investigations on various SE have shown that their thermal conductivities are low and show a "glass-like" temperature-dependence. Density dependent thermal transport investigations on sulfidic Li +30 and Na +31 conducting SE revealed further lowering of the thermal conductivity with porosity, leading to thermal conductivities in the range of liquid electrolytes. The low thermal conductivity of SE materials indicate that slow heat dissipation and potential thermal runaway warrant careful consideration.