High voltage positive electrodes for lithium ion batteries have suffered from continuous oxidation of the electrolyte during cycling, which largely offsets the benefits of high energy and power densities. In this work, the electrolyte oxidation and concomitant film deposition/dissolution behaviors were investigated on Pt electrode by using linear sweep voltammetry (LSV), electrochemical quartz crystal microbalance (EQCM), and X-ray photoelectron spectroscopy (XPS). Two characteristics were identified. First, film deposition is relatively unfavorable at higher potentials (>4.7 V vs. Li/Li+) because the oxidation products are mostly gaseous or soluble species. Second, the concentration of inorganic species decreases in the surface film as the potential increases, which is likely dissolved by HF or polar species. The dominance of gaseous or soluble products and the partial dissolution of the surface film, are two characteristics which hamper passivation of the electrode surface, leading to severe electrolyte oxidation at the high potentials. (C) 2018 The Electrochemical Society.