Breaking the Solubility Limit of LiNO3 in Carbonate Electrolyte Assisted by BF3 to Construct a Stable SEI Film for Dendrite‐Free Lithium Metal Batteries

Abstract Lithium (Li) metal is regarded as a potential candidate for the next generation of lithium secondary batteries, but it has poor cycling stability with the broadly used carbonate‐based electrolytes due to the uncontrollable dendritic growth and low Coulombic efficiency (CE). LiNO 3 is an effective additive and its limited solubility (<800 ppm) in carbonate‐based electrolytes is still a challenge, as reported. Herein, using BF 3 (Lewis acid) is proposed to enhance the solubility of LiNO 3 in carbonate‐based electrolytes. The dissolved NO 3 − can be involved in the first solvation shell of Li + , reducing the coordination number of PF 6 − and EC (ethylene carbonate). In addition, the NO 3 − is proved to be preferentially reduced on Li metal by differential electrochemical mass spectrometry so that the decomposition of PF 6 − and EC is suppressed. Therefore, a SEI layer containing Li 3 N can be obtained, which exhibits high lithium‐ion conductivity, achieving even and dense Li deposits. Consequently, the CE of Li||Cu cell with BF 3 /LiNO 3 can be increased to 98.07%. Moreover, the capacity retention of Li||LiFePO 4 with a low N/P ratio (3:1) is as high as 90% after 300 cycles (≈1500 h). This work paved a new way for incorporating LiNO 3 into carbonate‐based electrolytes and high‐performance lithium metal batteries.