Sulfide solid electrolytes (SEs) are recognized as one of the most promising candidates for all‐solid‐state batteries (ASSBs), due to their superior ionic conductivity and remarkable ductility. However, poor air stability, complex synthesis process, low yield, and high production cost obstruct the large‐scale application of sulfide SEs. Herein, a one‐step gas‐phase synthesis method for sulfide SEs with oxide raw materials in ambient air, completely getting rid of the glovebox and thus making large‐scale production possible, is reported. By adjusting substituted elements and concentrations, the ionic conductivity of Li4‐xSn1‐xMxS4 can reach 2.45 mS cm−1, which represents the highest value among all reported moist‐air‐stable and recoverable lithium‐ion sulfide SEs reported. Furthermore, ASSBs with air/water‐exposed and moderate‐temperature‐treated Li3.875Sn0.875As0.125S4 even maintains superior performances with the highest reversible capacity (188.4 mAh g−1) and the longest cycle life (210 cycles), which also breaks the record. Therefore, it may become one of the most critical breakthroughs during the development of sulfide ASSBs toward its practical application and commercialization.

Sulfide solid electrolytes (SEs) represent one most promising technical routes to realize all‐solid‐state batteries (ASSBs) due to their high ionic conductivity and low mechanical stiffness. However, the poor air/moisture/water stability of sulfide SEs leads to completely destroyed structure/composition, reduced Li+ conductivity, and toxic H2S release, limiting their practical application in ASSBs. To solve this problem, a universal method applicable to all types of sulfide SEs is developed to realize water‐stable sulfide SE membranes, by spray coating a Li+‐conductive superhydrophobic protection layer with Li1.4Al0.4Ti1.6(PO4)3 (LATP) nanoparticles and fluorinated polysiloxane (F‐POS) via hydrolysis and condensation of tetraethyl orthosilicate and 1H,1H,2H,2H‐perfluorodecyltriethoxysilane molecules. The F‐POS@LATP coating layer exhibits excellent superhydrophobicity (water static contact angles > 160°) to resist extreme exposure (direct water jetting), because of its micro‐/nanoscale roughness and low surface energy. Moreover, ASSBs using the extreme‐condition‐exposed modified Li6PS5Cl membrane exhibit a reversible capacity of 147.3 mAh g‐1, comparable with the ASSBs using pristine sulfide membranes. The superhydrophobic Li+‐conducting layer is demonstrated to be an effective protection method for sulfide membranes so that they remain stable and functionable in extreme water exposure conditions, providing a new approach to protect all types of sulfide SEs and other air/moisture/water‐sensitive materials without sacrificing electrochemical performance.