Solid-state electrolytes for all-solid-state batteries (ASSBs) are intensively researched in recent years, due to the improved safety they offer compared to liquid electrolytes and because they may enable alternative electrodes . In 2018, Asano et al. reported that the ternary halides Li3YCl6 and Li3YBr6 have ionic conductivities of ~1 10 -3 S/cm and showcased ASSBs with coulombic efficiencies of 94% using (uncoated) LiCoO2 as the active material in the cathode composite. Since then, the material family Li3M(III)X6 (M(III)= Y, In, Sc, Lanthanides; X=Cl, Br, I)) and other halide solid electrolytes have gained renewed interest in the scientific community due to their favorable combination of ionic conductivity (~mS/cm) and high-voltage cathode compatibility. More recently, Zhou et al. reached a milestone in the development of ASSBs using a Li2InxSc0.66-xCl4 electrolyte. The ASSB with this electrolyte possessing a 210 -3 S/cm ionic conductivity and a 4.710 -10 S/cm electronic conductivity, reached 3000 cycles at 80% capacity retention when cycled between 2.8 -4.3V vs. Li/Li + using LiNi0.85Co0.1Mn0.05O2 as cathode (6.21 mg/cm 2 ) at 3C . Considering these promising results, further improvements and fundamental understanding of such electrolytes may accelerate the development of practical ASSBs.