Enhancing the Cycling Stability for Lithium-Metal Batteries by Localized High-Concentration Electrolytes with 2-Fluoropyridine Additive

Lithium (Li) anode has been considered to be one of the most promising candidates for energy storage systems due to its high theoretical capacity. However, the side reaction between Li-metal and electrolyte and its safety concerns are inevitable obstacles for the commercial applications of Li-metal batteries (LMBs). The cycling stability of commercial electrolyte, high-concentration electrolyte (HCE), and localized high-concentration electrolyte (LHCE) in LMBs are studied in this work. Furthermore, 2-fluoropyridine (2-FP) additive is used to significantly enhance the cycling stability of Li-metal in LHCE that contains triethyl phosphate (TEP) and bis(2,2,2-triflfluoroethyl) ether (BTFE). The most stable cycle performance (about 2100 h) of Li||Li cell and the highest coulombic efficiency (98.82%) in the Li||Cu cell can be obtained in the system of LHCE + 2-FP (1.2 M LiFSI + TEP/BTFE + 0.01 M 2-FP). Li||LiFePO4 cell with LHCE + 2-FP exhibits the highest initial discharge capacity of 149.14 mAh g–1 and the most excellent capacity retention rate of 98.52% after 455 cycles at 1C. Moreover, the system of LHCE + 2-FP can also invest Li||LiFePO4 cell with the best rate capacity.