Overall, the DFT calculations support the finding that the capacity of the studied materials is dominated by Ni redox followed by oxygen redox. Some Mn redox is present in the Sc-doped material. Regarding the oxygen redox behaviour, two important conclusions can be drawn from the calculations. First, the oxygen redox is strongest in O3-NaNMO, followed by O3-NaMNMO, and O3-NaSNMO. Second, the oxygen redox activity in O3-NaMNMO is strongest for 'O bound to Mg'. Both findings agree well with the conclusions made from the experiments, this way supporting the proposed redox mechanisms.