Stable Cycling of Lithium-Metal Batteries in Hydrofluoroether-Based Localized High-Concentration Electrolytes with 2-Fluoropyridine Additive

Li-metal has been regarded as one of the most ideal anode material candidates for next-generation lithium (Li) batteries. However, the deployment of high-energy-density Li-metal batteries (LMBs) is hindered by growth of dendrites, low coulomb efficiency, safety concerns, and limited cycle life. Herein, a 2-fluoropyridine (2-FP) additive is introduced into the fire-retardant lithium bis(flfluorosulfonyl)imide (LiFSI) triethyl phosphate (TEP)/hydrofluoroether (HFE)-based localized high-concentration electrolyte (LHCE), which significantly enhances the cycling stability of LMBs. The 2-FP additive successfully forms a high-quality LiF-rich interface on Li-metal anode to enhance the mechanical strength and the Li+ diffusion kinetics of the solid electrolyte interface (SEI), and it greatly optimizes the Li-metal deposition process to improve the compatibility of the electrolyte with Li-metal anode. Based on the electrolyte, the LMBs exhibit excellent cycling performance of 1000 cycles and realize 90.8% capacity retention rate at 1C. In addition, the Li||Li cells show long-term cycling stability for 2140 h and the Li||Cu cells achieve a high CE of 98.81%.