In Li-ion batteries, Li4Ti5O12 (LTO) has merits of an excellent cycling stability combined with a safe working potential of 1.55 V vs. Li+/Li at which no adverse side-reactions with the electrolyte are expected. Concerns regarding gassing of LTO, especially at elevated temperatures, have however recently been reported. In this work, LTO gassing behavior at 50 degrees C is investigated by in situ pressure and online electrochemical mass spectrometry (OEMS), allowing for both qualitative and quantitative analysis of evolving gases. H-2, C2H4, and CO2 are the dominantly evolving gases for ethylene carbonate (EC) based electrolytes. H-2 is mainly produced during the first charge step, while C2H4 is observed at lower potentials resulting from the reduction of EC. CO2 evolution mechanism is complex and is promoted at more anodic potentials. Passivating the LTO surface, e.g. by a proper coating, and/or exchanging the LiPF6 salt, may effectively reduce gas evolution, thus clearing the way for future use of LTO in energy storage applications at elevated temperatures. (C) 2015 The Electrochemical Society. All rights reserved.