Oxygen dimerization as a defect-driven process in bulk LiNiO2

To explore the possibility of oxygen dimerization — particularly the formation of molecular oxygen-like species — in the bulk of LiNiO2 lithium ion cathodes materials at high states of charge, we conduct a redox-product structure search inspired by recent methodological developments for point defect structure prediction. We find that delithiated Li1 – x NiO2 (x = 1) has good kinetic stability towards decomposition into molecular oxygen and reduced transition metal oxides, but that defects can act as nucleation sites for oxygen dimerization. These results help reconcile conflicting reports on the formation of bulk molecular oxygen in LiNiO2 and other nickel-rich cathode materials, highlighting the role of defect chemistry in driving the bulk degradation of these compounds.