However, despite the relative stability of the dimercontaining structures compared to the oxygen-holecontaining structures, none of the structures containing dimers are more stable than that of the R 3m-NiO 2 system, marking a departure from the behavior of lithiumrich systems. This can be seen as a logical progression from ribbon ordering in certain lithium-rich (or sodiumrich) cathode materials, that delay the onset of bulk molecular oxygen degradation relative to the more typical honeycomb-ordered lithium-rich structures . This implies that, despite the thermodynamic preference for phase segregation of bulk NiO 2 into rock salts and gaseous oxygen, the pristine layered system is kinetically stable towards this decomposition process . Oxygen redox is unlikely to drive transition metal migration, potentially explaining the significantly lower first-cycle hysteresis noted in LiNiO 2 relative to lithium-rich systems despite spectroscopic signatures of oxygen dimer formation . Instead, vacant sites in the nickel layer are likely to act as nucleation points for oxygen dimerization.