The observation of decreasing oxygen redox through doping is more apparent for Sc compared to Mg. This result is in contrast to our previous observations on P2-Na 0.67 Ni 0.33 Mn 0.67 O 2 , where for a similar doping strategy (Na 0.67 (Mg /Sc) 0.1 Ni 0.33 Mn 0.67 O 2 ) the oxygen redox was found to show a greater reduction in the case of Mg doping. This might seem surprising at first but can be understood from the different dopant/Ni ratios present in both materials. In the previous study, we found that for a series of layered P2 compounds with different Mg/Ni ratios, the degree of O-redox became smallest for a Mg/Ni ratio of 1, while the degree of O-redox increased for ratios greater than or less than 1. In the present O3-NaMNMO (O3- To further elucidate the redox processes in the Sc-and Mg-doped materials compared to the undoped material, we performed density functional theory (DFT) calculations.