Influence of fluoroethylene carbonate as co-solvent on the high-voltage performance of LiNi1/3Co1/3Mn1/3O2 cathode for lithium-ion batteries

In this work, the electrochemical performance of LiNi1/3Co1/3Mn1/3O2 cathode is investigated under high voltage with fluoroethylene carbonate (FEC) as co-solvent for lithium ion battery. Charge/discharge tests show that the cycling and rate performances of LiNi1/3Co1/3Mn1/3O2 are dramatically improved at high voltage operation when ethylene carbonate (EC) is replaced by FEC in electrolyte solution. After 100 cycles between 3.0 and 4.6 V (vs. Li/Li+) at 0.2C rate, the capacity retention of LiNi1/3Co1/3Mn1/3O2 with FEC/dimethyl carbonate (DMC) (1/4, vol.%) solution is 82.7%, while the EC-containing electrolyte is only 41.3%. The effects of FEC on the high-voltage performance and the surface properties of the LiNi1/3Co1/3Mn1/3O2 cathode are characterized by electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). It is found that FEC as co-solvent participates in the formation of protective surface films on the LiNi1/3Co1/3Mn1/3O2 cathode, which efficiently suppresses the decomposition of the electrolyte, prevents the severe structure destruction and improves the cycling stability and rate capability of LiNi1/3Co1/3Mn1/3O2 electrode under high voltage.