Stable Operation of High‐Voltage Sodium‐Ion Batteries via Cathode Interphase Reconstruction with Competitive Anion Coordination Chemistry

Abstract High‐voltage sodium‐ion batteries (SIBs) have significant application prospects in low‐cost energy‐storage systems. However, their performance is limited by sluggish Na + desolvation kinetics and the formation of an unstable cathode‐electrolyte interphase (CEI) in traditional electrolyte systems. This study introduces an anionic competitive coordination strategy in which SO 2 CF 3 − from sodium trifluoromethanesulfonate (NaSO 2 CF 3 ), with delocalized electron structures, preferentially occupy the inner layer of the Na + solvation sheath, replacing traditional sodium salt anions and solvent molecules to construct a highly dynamic solvation microstructure. This novel solvation structure facilitates Na + ion desolvation and induces the formation of a thin and robust CEI rich in sulfur/fluorine‐containing organic and inorganic species by regulating the interfacial decomposition pathway, thereby ensuring interfacial stability at a high voltage of 4.4 V. As a proof of concept, the optimized electrolyte effectively mitigates the structural degradation of high‐voltage cathodes such as NaFe 1/3 Ni 1/3 Mn 1/3 O 2 and Na 3 V 2 (PO 4 ) 2 O 2 F and simultaneously enhances their rate performance and cycling stability. Furthermore, NFN||hard carbon full cells incorporating the optimized electrode exhibit excellent cycling stability under a high mass loading. This study establishes an innovative electrolyte design paradigm that overcomes interface failure issues in high‐voltage SIBs by precisely regulating the CEI composition and structure via anionic coordination chemistry.