Versatile Co 9 S 8 Nanocoating Stabilizes Prussian Blue Analogue Cathodes for Aqueous Sodium-Ion Batteries

Prussian blue analogues (PBAs) show great promise as cathodes for aqueous sodium-ion batteries but suffer from severe structural degradation and sluggish kinetics. Herein, we develop an atomic layer deposition-driven interfacial engineering strategy to construct conformal Co9S8 nanocoatings (3–6 nm) on cobalt hexacyanoferrate (CoHCF) cathodes. Multiscale characterizations and theoretical calculations reveal that this artificial cathode-electrolyte interphase enhances electrochemical performance through a tripartite synergistic mechanism: (1) thermodynamic stabilization, which suppresses Fe dissolution by 85% through elevating Fe vacancy formation energy; (2) mechanical buffering, which alleviates mechanical…