Synergistic DFOB ⁻ /NO ₃ ⁻ ‐Regulated Solvation Enables Safe High‐Voltage Lithium Metal Batteries

ABSTRACT Achieving high‐safety, high‐voltage, and long‐life lithium metal batteries (LMBs) requires electrolytes capable of simultaneously stabilizing lithium (Li) metal and withstanding severe oxidative environments. Here we report an anion‐regulated electrolyte constructed by co‐optimizing lithium difluoro(oxalato)borate (LiDFOB) and lithium nitrate (LiNO ₃ ) in nonflammable triethyl phosphate. Combined theoretical simulations and experimental investigations reveal that the DFOB ⁻ /NO ₃ ⁻ dual‐anion synergy reconstructs the Li ⁺ solvation sheath from solvent‐dominated, solvent‐separated ion pairs into anion‐rich structure dominated by contact ion pairs and small‐sized aggregated clusters. This solvation transformation weakens Li ⁺ ‐solvent interactions, facilitates rapid desolvation, and induces preferential anion redox, thereby forming uniform lithium fluoride, lithium nitride, and B–O/F‐rich solid‐electrolyte interphases at both the anode and cathode. These robust, anions‐derived, and inorganic‐rich electrode‐electrolyte interphases suppress dendrite initiation, mitigate parasitic reactions, stabilizing high‐voltage LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (NCM811) cathode and improve interfacial Li ⁺ transport and de‐solvation kinetics. Benefiting from this synergistic solvation and interphase co‐engineering, Li||NCM811 cells with anion‐regulated electrolyte deliver 226 mAh g ⁻¹ at 0.1 C, retain 136 mAh g ⁻¹ at 4 C, and maintain 152 mAh g ⁻¹ after 500 cycles (0.5 C discharge). This work establishes anion‐regulated solvation as a scalable route toward safe, high‐voltage, and long‐cycling LMBs.