Weak-Solvating Carboxylate Ester Electrolyte Enables Hybrid Interphase via Cooperative Additives toward Wide-Temperature Sodium Metal Batteries

Fast Na+ transport and durable interfacial stability remain challenging for wide-temperature Na- metal batteries. To address these issues, we developed a synergistic solvation-interphase regulation strategy by integrating methyl propanoate (MP) with a combined VC/NaDFOB additive pair. MP modifies the Na+ solvation sheath and facilitates Na+ desolvation, while VC and NaDFOB cooperatively generate a mechanically robust hybrid organicinorganic interphase. This coupled regulation enables enhanced ion transport and interfacial stability over a broad temperature range. The EC/EMC/MP + VC/NaDFOB electrolyte exhibits an ionic conductivity of 2.52 mS cm–1 at –40 ̊C and an increased Na+ transference number. Na||Na3V2(PO4)3 cells retain 96.5% of their initial capacity after 1000 cycles with an average Coulombic efficiency of 99.98% at room temperature. At –20 ̊C, the cells deliver 69.4 mAh g–1 for over 900 cycles, corresponding to 82% of their room-temperature capacity. This work establishes a practical solvation-interphase regulation approach for wide-temperature Na- metal batteries.