Enhanced performance of a Li-ion rechargeable battery at low temperatures: Use of 3,3,3-trifluoropropyl acetate as an electrolyte additive

The addition of 3,3,3-trifluoropropyl acetate (TFPA) to electrolyte in a Li-ion rechargeable battery (LIB) provides a means for increasing the discharge performance at low temperatures as a result of the formation of a superior solid electrolyte interphase (SEI) on the graphite anode. For instance, the addition of 2 wt% TFPA to the electrolyte significantly increased the cycle stability and the discharge capacities at low temperatures (-10 degrees C) even at current rates of 3 C. The SEI films formed on the graphite anodes were characterized by electrochemical and spectroscopic techniques and by computational analysis. Although the formation of LiF on the anode has been recognized, present research revealed that the decomposition of TFPA on the anode surface resulted in the formation of an SEI layer consisting predominantly of organic fluorides. This layer suppressed the decomposition of the electrolyte resulting in a decreased anode impedance and an increase in cycle stability and discharge capacity at low temperatures. The application of 3,3,3-trifluoropropyl acetate (TFPA) as an alternative electrolyte additive, and cell performance at low temperatures (25 to -30 degrees C) were examined. The addition of TFPA improved the cell capacity and cycle stability even under a high current density (3 C) and low temperature (-10 degrees C). The TFPA underwent decomposition on the anode surface to form an SEI layer given that LiF that contained organic fluorides suppressed the decomposition of the electrolyte and the graphite anode.image