Spontaneous Formation of Robust Hybrid Organic/Inorganic Interface for Advancing Lithium Metal Batteries

Designing a high-performance solid electrolyte interphase (SEI) is crucial for advancing lithium metal batteries (LMBs). Herein, we propose a hybrid SEI comprising a thin LiF top layer and a bulk layer of a conjugated-ring organic compound mixed with LiF via the self-limiting reaction between the 1-ethyl-3-methylimidazolium (EMIM⁺PF₆^-) additive and Li⁰ anode. This method enabled the lithium anode to afford higher current density. By combining 0.1 M EMIM⁺PF₆^- with 1 M LiPF₆ in the FEC/FEMC (fluoroethylene carbonate/methyl 2,2,2-trifluoroethyl ester) electrolyte, exceptional performance metrics were achieved, including high Coulombic efficiency (99.93%). The LMB with improved electrolyte can stand against ultrahigh energy density (7 mAh/cm²) and ultrahigh current density (5 mA/cm²) under an electrochemical window of 3.0 to 4.6 V. This study presents an innovative electrolyte design approach that enhances the performance of LMBs by promoting SEI formation through in situ chemical reactions.