In general, this assessment shows that solid-state cathode composites are limited by their ionic conductivity that is <1 mS•cm -1 , while the electronic conductivity between chemistries spreads a wide range and can be optimized more freely by introducing electron conducting additives. Consequently, the search for higher conducting solid electrolytes, and the improvement of the solid electrolyte percolation in the electrode, are of highest importance for the development of solid-state batteries in outlook on application. This need for higher conducting solid electrolyte is further emphasized by the exponential loss in ionic conductivity (Figure ) when increasing the CAM volume fraction in the cathode that is necessary to enable high areal loadings. This additionally shows that good ionically conducting active materials should be explored, as they promise a softening of the loss in effective (ionic) conductivity when going to high volume fractions of active species.