Boosting Low-Temperature Performance for Lithium Batteries with Controllable Solvation Structure Electrolytes

Lithium metal batteries (LMBs) have attracted more attention for their high energy densities. Their applications are limited for the poor low temperature (LT) cycle performance and the growth of dendrite due to the root problems of high Li+ desolvation energy barrier and poor electrode/electrolyte interface. Here, an electrolyte was prepared using low dielectric constant solvents of ethyl acetate (EA), 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropylether (D2), and the high voltage endurance lithium salt lithium difluoro(oxalato)borate (LiDFOB), which exhibits high ionic conductivity of 1 mS/cm even at −50 °C and superior high voltage tolerance. Moreover, fluoroethylene carbonate (FEC) is further introduced to realize the temperature-responsive solvation structure, which induces an enriched inorganic solid electrolyte interphase (SEI) film and homogeneous lithium deposition. Therefore, Li∥NCM87 batteries not only deliver outstanding ambient temperature performance (89% capacity retention after 290 cycles) but also can operate at LT of −40 °C for 40 cycles with a stable capacity of 120 mA h/g. This work can enlighten the development and design of an electrolyte operating under extreme conditions.