Modulating Reversible Zinc‐Ion Storage via Interfacial Water Regulation Enabled by Pyrophosphate Layer on MoS ₂

ABSTRACT Before aqueous Zn 2+ can intercalate into two‐dimensional hosts, highly reactive water forces the ions to migrate as a [Zn(H 2 O) 6 ] 2+ complex rather than as bare ions. Upon reaching the interface, the instability of interfacial water further impedes ion transport, limits the intrinsic capacity, and further triggers side reactions that shorten cycle life. To decouple Zn 2+ storage from the deleterious influence of interfacial water, a coordination environment is engineered at the MoS 2 surface by installing a dense layer of pyrophosphate rich in PO 3 − groups. The terminal oxygens of PO 3 − chelate Zn 2+ in a low‐strain, multi‐dentate fashion, creating additional interfacial storage sites while simultaneously displacing coordinated water. The resulting interface stabilizes interfacial water while accelerating desolvation of hydrated Zn 2+ , lowering the intercalation energy barrier. Concurrently, the protons released from PPI stabilize interfacial water by establishing a local acidic microenvironment, which suppresses water decomposition and arrests ZnSO 4 (OH) 6 · x H 2 O nucleation at its origin. This dual‐function interfacial design endows the Zinc‐ion storage device with high capacity and exceptional structural stability over extended cycling.