Breaking the Solubility Limit of LiNO 3 in Carbonate Electrolyte Assisted by BF 3 to Construct a Stable SEI Film for Dendrite-Free Lithium Metal Batteries.

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.