Trace Dual-Salt Electrolyte Additive Enabling a LiF-Rich\nSolid Electrolyte Interphase for High-Performance Lithium Metal Batteries

The composition and physiochemical\nproperties of the solid electrolyte\ninterphase (SEI) significantly impact the electrochemical cyclability\nof the Li metal. Here, we introduce a trace dual-salt electrolyte\nadditive (TDEA) that accelerates LiF production from FEC decomposition\nand improves the LiF distribution, resulting in earlier LiF precipitation\nand the formation of a LiF-rich SEI on the Li anode. TDEA at a millimolar-level\nconcentration was found to alter the morphology of deposited Li, suppress\nLi dendrite formation, and increase the cycling time and operating\ncurrent density for Li anodes. Li∥NCM811 full cells using TDEA-based\nelectrolytes exhibited approximately two times longer lifespan than\nthose without additives. Additionally, the TDEA-based electrolytes\nenabled a high energy density of 347 Wh kg<sup>–1</sup> for\n500-mAh pouch cells, maintaining stable cycling over 180 cycles under\nstringent conditions (N/P = 1.26 and E/C = 2.2 g A h<sup>–1</sup>). Our findings suggest that the proposed TDEA strategy offers a\npromising path to achieving high-performance Li metal batteries.