Koç et al. reported the formation of LiCl as one of the decomposition products between Li 6 PS 5 Cl/Li 3 InCl 6 and Li 3 PS 4 /Li 3 InCl 6 interfaces, and hypothesized that the chemical instability of these bilayer interfaces caused the observed degradation in battery performance. The electrochemical performance was improved by adding a nanometer-thick layer of Li 3 PO 4 in between Li 6 PS 5 Cl (anolyte) and a composite positive electrode (Li 3 InCl 6 with NMC622 as active material, and binders). They thus inferred the stability of the Several observations can be made when comparing the chemical compatibility of the anolytes with the fluoride and chloride catholytes investigated here. (i ) Similar reactivity trends are observed for these two classes of catholytes. For example, Li 3 PS 4 and Li 3 PO 4 show the best chemical compatibility (out of all the sulfide and oxide anolytes considered here) with both chloride and fluoride-based catholytes. In contrast, sulfide anolytes show the highest reactivity with the In-containing Li 3 InF 6 and Li 3 InCl 6 catholytes. (ii ) For those bilayer separators predicted to react, we also find that the reaction products from fluoride catholytes are similar to those from chloride catholytes. We have demonstrated that LiCl is a major product in the decomposition reactions involving chloride-containing catholytes.