To efficiently survey the large compositional space covered by the material combinations of Table , we use first-principles calculations, based on density functional theory (DFT), to probe their thermodynamic stability upon contact, often referred to as "chemical sta- bility". Knowledge of the interfacial phase diagrams enable us to identify the relevant degradation reactions that may occur upon contact between anolytes and catholytes. For example, to investigate the chemical stability of Li 3 PS 4 (anolyte) with Li 3 InCl 6 (catholyte), we evaluated the Li-P-S-Cl-In quinary phase diagram. Using DFT, we computed the stability of all elements, as well as binary, ternary, quaternary, and unknown quinary compounds within this phase field, at ambient temperature and pressure.