Tris(pentafluorophenyl) silane (TPFPS) is tested as a film-forming agent for nickel-dopedmanganese spinel (LiNi0.5Mn1.5O4, LNMO) positive electrode. The surface film derived from the TPFPS-free electrolyte (organic carbonate-based one) is poorly passivating the high-voltage positive electrode to cause continued electrolyte oxidation and film deposition. It leads to an increase in the film resistance and thus electrode polarization eventually causing capacity fading. In contrast, the surface film derived from the oxidation of TPFPS prior to the carbonate-based solvents is highly passivating. As a result, additional electrolyte decomposition is suppressed to give a higher Coulombic efficiency for the Li/LNMO cells. In addition, insignificant film growth/electrode polarization allows a much improved capacity retention. (C) 2016 The Electrochemical Society. All rights reserved.