Dual-Driven Cathode Electrolyte Interphase Regulation for Durable Sodium-Ion Batteries

Abstract The insufficiently protective cathode electrolyte interphase (CEI) remains a critical challenge for sodium-ion batteries, particularly under wide temperature conditions. Conventional CEI-forming additives rely on potential-driven decomposition during charging, leaving the cathode surface vulnerable before polarization. Here, we develop a dual-driven CEI regulation strategy using N-fluorobenzenesulfonimide (NFSI), integrating contact-driven preformation with potential-driven reinforcement. Upon contact with Na4Fe3(PO4)2P2O7 (NFPP), NFSI induces spontaneous interfacial redox reactions to generate a NaF-rich inner layer, while the intermediate NaNSI is subsequently oxidized to form an N/S-containing outer layer during charging. This bilayer CEI suppresses electrolyte decomposition, transition-metal dissolution, and interfacial degradation while improving Na+ transport. With 1.0 wt % NFSI, NFPP/Na cells retain 79.9% capacity after 500 cycles, compared with 45.8% for the base electrolyte, and maintain cycling capability from –20 to 80 °C. The strategy is further validated in other cathodes and NFPP||HC full cells, providing a programmable approach for durable sodium-ion batteries.