Central‐Atom‐Differentiated Solvent Chemistry Enables Anion‐Reinforced Solvation for Ultra‐Long Cycling Ah‐Level Sodium‐Ion Pouch Cells

ABSTRACT

Conventional carbonate‐based electrolytes for sodium‐ion batteries (SIBs) provide high salt solubility and high‐voltage compatibility. However, their inherent Na ⁺ solvation behavior and interfacial reactions remain largely governed by carbon‐centered carbonate motifs, making it difficult to concurrently achieve rapid Na ⁺ desolvation and durable electrode–electrolyte interphases under practical operating conditions. Here, we introduce a central‐atom–differentiated solvent chemistry by incorporating ethylene sulfite (ES) into a conventional carbonate electrolyte. The sulfur‐centered sulfite motif creates an oxygen‐donor environment electronically distinct from that of the carbon‐centered carbonate motif, thereby rebalancing solvent‐anion competition and promoting PF ₆ ⁻ participation in the inner Na ⁺ solvation sheath. The resulting anion‐reinforced solvation substantially lowers the Na ⁺ desolvation barrier. Concurrently, the distinct interfacial conversion chemistry of ES, combined with the enhanced anion participation, favors the formation of robust, inorganic‐rich interphases on both the cathode and anode. Consequently, a 2.34 Ah NaNi _0.33 Fe _0.33 Mn _0.33 O ₂ ||hard carbon pouch cell retains 81.29% of its initial capacity after 3500 cycles at room temperature (corresponding to over one year of continuous cycling) and maintains stable cycling across a 70°C operating window from −20°C to 50°C. This work demonstrates that differentiating solvent central‐atom chemistry provides a compositionally simple route to simultaneously regulate Na ⁺ solvation and dual‐electrode interphases for practical SIBs.