Rational Design of Fluorinated Electrolyte to Achieve Fast Charging and Low Temperature Lithium-Ion Batteries

Abstract

Ethylene carbonate (EC) -based electrolytes are commonly used in commercial lithium-ion batteries. However, in extreme environments such as high power rates and low temperatures, their low lithium-ion migration number and high interface resistance seriously prevent the application of lithium-ion batteries in fast charging and high altitude environments. Here, we design a fluorinated electrolyte that achieves a balance between weak affinity and sufficient ionic conductivity by fluorinating low viscosity and low freezing point ethyl acetate (EA) to 2, 2-difluoroethyl acetate (DFEA), which can significantly improve the cyclic performance of lithium-ion batteries at high rates. The graphite anodes can form a low RSEI even at a high rate, which inhibits the irreversible Li deposition during the fast charging process. The NCM622||Li half cell assembled with the fluorinated electrolyte can also have a high reversible specific capacity of ~99 mAh g-1 and cycle stability at a high rate of 4C. High reversible capacity of ~50mAh g-1 and high capacity retention after 100 cycles at 0.1C at -20℃.