Based on their electrochemical properties, sulfide, and oxide SEs are best employed as anolytes, whereas ternary halide SEs are well suited for catholyte applications. Several studies have claimed improved electrochemical performance of ASSBs using bilayer separators: Li 6 PS 5 Cl/Li 3 InCl 6 ; Li 6 PS 5 Cl/Li 3 YCl 6 ; LGPS/Li 2 ZrCl 6 . However, other investigations on similar bilayer based ASSBs have reported battery performance degradation enabled by specific SE pairings, such as Li 6 PS 5 Cl/Li 3 InCl 6 ; Li 6 PS 5 Cl/Li 3 YCl 6 ; Li 6 PS 5 Cl/Li 2 ZrCl 6 ; Li 3 PS 4 /Li 3 InCl 6 . This degradation has been linked to the chemical incompatibility of specific anolyte and catholyte combinations with the formation of interfacial decomposition products. From these studies emerges the need to identify chemically compatible SEs to form stable and practical bilayer separators.