Solvation Engineering to Break the Solubility–Stability Trade-Off in LiNO ₃ -Based Electrolytes for High-Voltage Lithium Metal Batteries

Lithium nitrate (LiNO3) can be preferentially reduced on Li metal to induce an inorganic-rich solid–electrolyte interphase (SEI) (e.g., Li2O/Li3N), making it an effective handle to regulate Li-metal interfacial chemistry. However, the extremely low solubility of LiNO3 in conventional low-donor-number carbonate electrolytes prevents LiNO3 from evolving beyond an additive, whereas high-donor-number solvents that dissolve LiNO3 typically suffer from insufficient oxidative stability at high voltages, limiting their compatibility with Ni-rich cathodes (e.g., NCM811). Herein, we developed a LiNO3-based electrolyte that simultaneously delivers high-voltage stability and high LiNO3 solubility via synergistic anion-coordination regulation using an oxazolidinone solvation platform, a tunable cosolvent, and a fluorinated dilution. Specifically, the introduction of TTE (1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether) increases the fraction of anion-paired species and strengthens NO3– coordination in the solvation sheath. This solvation reconstruction promotes the transition from monodentate to bidentate NO3– coordination, thereby favoring nitrate-derived interfacial reduction. The optimized electrolyte enables >3000 h stability in Li||Li symmetric cells, 97.64% average Coulombic efficiency (CE) in Li||Cu cells, and 83.44% capacity retention after 500 cycles at 4.3 V (1C) in Li||NCM811 cells, offering a practical design paradigm for LiNO3 electrolytes that combine high solubility with high-voltage stability.