Oxygen Evolution in Overcharged LixNi1/3Co113Mn1/3O2 Electrode and Its Thermal Analysis Kinetics

The oxygen evolution behavior in overcharged LiNil/3COl/3Mnl/3Oz-based electrode was investigated by differ- ential scanning calorimetry and thermal gravimetric （DSC/TG）. Meantime, its thermal kinetic parameters were calculated by Kissinger＇s and Ozawa＇s method. As observed by DSC/TG, two exothermic peaks at 239 and 313℃ in washed cathode （4.6 V）, were attributed to two steps of oxygen evolution. More importantly, the temperature of its oxygen release processes decreased obviously compared with that charged to 2.8 V. Activation energy （E） for the first and second oxygen evolution, both of which were assumed closely to be the first order reaction, between 200 and 350℃ in Lio.2o4NilnCol/3Mnl/3O2-based electrode were calculated as 113.63 and 158.13 kJ.mo1-1, respectively and the corresponding Arrhenius pre-exponential factors （A） of 1.05 × 10^11 and 6.46× 10^13 s-1 were also obtained. The different energy barrier of such two steps of oxygen evolution should probably be ascribed to the different bond energy of M--O （M=Mn, Co, Ni）.