Phenyl TrifluoroMethane sulfonate as a novel electrolyte additive for enhancing performance of LiNi0·6Co0·2Mn0·2O2/Graphite cells working in wide temperature ranges

To optimize the electrochemical behavior of NCM-based high-energy lithium-ion batteries (LIBs) in wide temperature ranges, Phenyl trifluoromethane sulfonate (PTM) is demonstrated as the novel electrolyte additive to enhance the electrochemical behavior of LiNi0·6Co0·2Mn0·2O2/graphite cells at 25 °C, −20 °C and 45 °C. The cells with 1.0 wt% PTM-containing electrolyte deliver 80.6% capacity retention after 350 cycles at 25 °C, 73.4% after 100 cycles at −20 °C, and 82.6% after 300 cycles at 45 °C, which are significantly higher than that in standard electrolyte (STD), corresponding to 36.4% at 25 °C, 40.3% at −20 °C, and failure at 45 °C, respectively. According to density functional theory (DFT) simulations and quantitative calculations, the PTM preferentially reduces on the anode and oxidizes on the cathode to participate in the formation of solid electrolyte interphase (SEI) films. In addition, the scanning electron microscopy (SEM), Transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and other analysis suggest that the formed SEI films are thinner and more stable for the electrolyte containing PTM, and the formed SEI films effectively control the decomposition of carbonate-based electrolytes and greatly decrease the increased resistance during the cycle.