Fluoro-Ether as a Bifunctional Interphase Electrolyte Additive with Graphite/LiNi_0.5Co_0.2Mn_0.3O₂ Full Cell

In this paper, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) is adopted as a bifunctional electrolyte additive, which is identified to effectively stabilize the surface for both graphite anode and LiNi0.5Co0.2Mn0.3O2 (NCM523) cathode within the graphite/NCM523 full cell. The overall electrochemical performances of the full cell are significantly enhanced with 3 wt % TTE additive in a conventional organic electrolyte. A combination of studies of scanning electronic microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectroscopy show that a uniform, compact, and stable solid electrolyte interphase (SEI) with improved mechanics on the graphite anode and an effective cathode electrolyte interphase (CEI) on the NCM523 cathode is developed. The electron-withdrawing C–F group contributes to the stable and compact surface film, which explains the electrochemical enhancement of the NCM523/graphite full cell.