2H,3H-Decafluoropentane Endorsed Localized High Concentration Electrolyte for Low-Temperature Lithium-Metal Batteries

Graphical A low-temperature localized high concentration electrolyte (LHCE) for lithium metal batteries is prepared using 2H,3H-decafluoropentane (HFC) as the diluent. The addition of the HFC diluent forms an anion-dominated solvation structure, enhances ion migration and desolvation kinetics at low temperatures, promotes the formation of an inorganic-rich solid electrolyte interface (SEI), and significantly improves the electrochemical performance of lithium metal batteries under low temperatures. A lithium-metal battery's electrochemical performance is affected by the kinetics of desolvation and ion transport at low temperatures. Here, we propose a low-temperature lithium-metal battery electrolyte. 1,2-Dimethoxyethane (DME) is used as the solvent, 2H,3H-decafluoropentane (HFC) as the diluent, and a high concentration of lithium bis(fluorosulfonyl)imide (LiFSI) as the solute. The addition of HFC diluent increases the number of anions bound to lithium ions and decreases the number of solvents in the solvation structure, which is conducive to the desolvation process at low temperatures. In addition, the anion-dominated solvation structure is conducive to the formation of an inorganic rich solid electrolyte interface (SEI), which effectively enhances the compatibility of LHCE-HFC electrolyte with lithium metal. The LHCE-HFC achieves ultra-high coulombic efficiency of lithium metal anode in Li||Cu batteries (99.31 %) and Li||Li batteries (1080 h) that have strong fluorine content in the interface. The Li||LiFePO 4 (LFP) cells provide a discharge-specific capacity of 92.1 mAh g −1 at 0.2 C at −20 °C and capacity retention of 89.6 % after 200 cycles.