Electrochemical properties and gas evolution behavior of Li2NiO2 are studied. In-situ gas evolution test of Li2NiO2 cell shows that large amount of gas is evolved during the first delithiation process at two characteristic potential levels of about 3.6 V and 4.13 V vs. Li/Li+ for small gas and severe gas generation, respectively. In-situ XRD and EXAFS analyzes reveal that the small gas generation is related to the bulk structural collapse of Li2NiO2 during phase transformation, while the severe gas generation results from the material decomposition of structurally unstable phase after the phase transformation. 3 wt% Al2O3 coated Li2NiO2 shows improved gas evolution properties. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.105206jes] All rights reserved.