While our findings suggest minimal water presence near the graphite and sodium metal electrodes, it remains imperative to investigate the probability of water decomposition on these electrodes, as it may significantly impact the electrochemical stability window. To achieve this, we examine the energetic favorability of water reduction (see Eq. 4) on the electrode surface by selectively breaking two O-H bonds from two adjacent water molecules (see section 2 for more details). Our investigations exclusively consider the water molecules within the partly desolvated contact and solvent-separated ion pairs directly adsorbed onto the surface, as they represent the most stable water-containing adsorption complexes before water decomposition (see Fig. ). Positive reaction energies obtained from Eq. 2 in the presence of graphite (∆𝐸 ",-= 3.6 𝑒𝑉) indicate the unlikelihood of water reduction at the interface between the examined WiS electrolyte and inert graphitic electrodes, aligning with the stability objectives in WiS electrolyte design. In contrast, calculations in the presence of the highly reactive sodium metal surface yield relatively large negative decomposition energies (see Fig. ), indicating a strong tendency for water reduction. Thus, if water molecules reach the layer covering the sodium surface, they are likely to undergo reduction, leading to the formation of sodium hydroxide and hydrogen gas (see Fig. ). This process can ultimately compromise the electrochemical stability and impact battery performance. Therefore, it is crucial to achieve a water-lacking SEI on the sodium metal electrode when using a WiS electrolyte. Based on the insights derived from our present investigation and the findings of our previous study , this objective can be effectively pursued by increasing the salt concentration to a sufficiently high level where both free water molecules and free ions are absent in the bulk electrolyte. In such a system, water can only access the electrode surface as part of solvation shells around contact and solvent-separated ion pairs. However, these structures exhibit minimal tendency to approach the sodium metal surface (see Fig. , panels e and g), thereby effectively reducing the probability of water decomposition on the sodium metal electrode. On graphite, the adsorption process may lead to the formation of an interfacial layer comprising intact anions, cations, and water molecules, all maintaining a vertical distance of at least 2.9 Å from the surface layer. This suggests a purely electrostatic nature for the corresponding solidelectrolyte interactions, which could potentially compromise SEI stability in the absence of robust chemical interactions. However, the presence of large aggregates within the WiS electrolyte can improve the stability of the SEI by involving multiple anions in the SEI formation. The corresponding triflate anions tend to adsorb onto the surface with their C-S bonds nearly perpendicular to the surface, potentially forming a brush-like interfacial structure.