Water-Stable Sulfide Solid Electrolyte Membranes Directly Applicable in All-Solid-State Batteries Enabled by Superhydrophobic Li+-Conducting Protection Layer

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 H 2 S 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 Li 1.4 Al 0.4 Ti 1.6 (PO 4 ) 3 (LATP) nanoparticles and fluorinated polysiloxane (F-POS) via hydrolysis and condensation of tetraethyl orthosilicate and 1 H ,1 H ,2 H ,2 H -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 Li 6 PS 5 Cl 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.