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The development of high voltage electrolytes plays a critical role to achieve advanced lithium ion batter-ies with high energy density.Application of suitable electrolyte additives is a facile and effective way to achieve enhanced electrochemical performance at high voltage operation.In this work,2-(trifluoroacetyl)thiophene (TFPN) was investigated as a functional electrolyte additive for high performance lithium ion batteries using high-voltage LiCoO2 cathode.When cycled between 3.0 V and 4.4 V at 0.5 C,the capacity retention of the LiCoO2 cathode significantly increases from 33.2 ％-90.6 ％ by the addition of 0.5 wt％TFPN into the baseline electrolyte.Based on the measurements on impedance spectra and X-ray photo-electron spectra,the improved cycling performance is attributed to the preferential oxidation of TFPN on the cathode surface and thus form a protective layer to suppress the decomposition of both electrolyte solvent and lithium salt.This work presents that TFPN has great potential as functional additive for the development of high-voltage and high-energy-density lithium ion batteries.