Non‐Flammable Electrolyte with Lithium Nitrate as the Only Lithium Salt for Boosting Ultra‐Stable Cycling and Fire‐Safety Lithium Metal Batteries

Abstract Lithium metal batteries (LMBs) attract considerable attention for their incomparable energy density. However, safety issues caused by uncontrollable lithium dendrites and highly flammable electrolyte limit large‐scale LMBs applications. Herein, a low‐cost, thermally stable, and low environmentally‐sensitive lithium nitrate (LiNO 3 ) is proposed as the only lithium salt to incorporate with nonflammable triethyl phosphate and fluoroethylene carbonate (FEC) co‐solvent as the electrolyte anticipated to enhance the performance of LMBs. Benefiting from the presence of NO 3 − and FEC with strong solvation effect and easily reduced ability, a Li 3 N–LiF‐rich stable solid electrolyte interphase is constructed. Compared to commercial electrolytes, the proposed electrolyte has a high Coulombic efficiency of 98.31% in Li‐Cu test at 1 mA cm −2 of 1.0 mAh cm −2 with dendrite‐free morphology. Additionally, the electrolyte system shows high voltage stability and cathode electrolyte interphase film‐forming properties with stable cycling performances, which exhibit outstanding capacity retention rates of 96.39% and 83.74% after 1000 cycles for LFP//Li and NCM811//Li, respectively. Importantly, the non‐flammable electrolyte delays the onset of combustion in lithium metal soft pack batteries by 255 s and reduces the peak heat release by 21.02% under the continuous external high‐temperature heating condition. The novel electrolyte can contribute immensely to developing high‐electrochemical‐performance and high‐safety LMBs.