Electrochemical Properties and Gas Evolution Behavior of Overlithiated Li₂NiO₂as Cathode Active Mass for Rechargeable Li Ion Batteries

Electrochemical properties and gas evolution behavior of Li 2 NiO 2 are studied. In-situ gas evolution test of Li 2 NiO 2 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 Li 2 NiO 2 during phase transformation, while the severe gas generation results from the material decomposition of structurally unstable phase after the phase transformation. 3 wt% Al 2 O 3 coated Li 2 NiO 2 shows improved gas evolution properties.