This preliminary study investigates initial gas formation in Li[Ni0.4Mn0.4Co0.2]O-2 (NMC442) pouch cells with three different electrolytes: 3:7 ethylene carbonate : ethyl methyl carbonate (EC:EMC) w/ 1 M LiPF6 as the control, control + 2% prop-1-ene-1,3-sultone (PES) and control + 2% vinylene carbonate (VC). In situ volume measurements reveal three main features of gas evolution, an initial gas step, gas absorption, and a second gas step at higher voltage. Gas chromatography-mass spectrometry is employed to identify the gaseous compounds. This work illustrates the strong dependence of volume change due to gas evolution on additives, charging rate and temperature. (C) The Author(s) 2015. Published by ECS.