Figure shows the Ni K-edge and Figure shows the Mn K-edge spectra for these samples at different states of charge, i.e. at OCV, charge to 4.0 V, charge to 4.4 V, and discharged to 2.5 V. Apparently, the Ni redox is involved in the electrochemical reaction throughout the charging process for all three materials, as evidenced by the obvious shift in edge energies to higher values (see Figures ). The Sc-doped material shows the largest shift of the edge energy between the charged states at 4.0 V (blue curve) and 4.4 V (orange curve), followed by that of O3-NaNMO and O3-NaMNMO, demonstrating that the Sc-doped material shows the overall largest amount of Ni redox above 4.0 V. However, the undoped and Mg-doped materials both deliver a higher charging capacity than the O3-NaSNMO material in this regime. Moreover, the Mn redox is electrochemically inactive except in the case of the Sc-doped material because of the charge-balancing effect of the higher valence state of Sc 3+ vs the Ni 2+ that was replaced, see Figure . These results suggest that there is another redox process that contributes to the higher capacity in the undoped and Mg-doped materials above 4.0 V. The likely cause is oxygen redox, which has been found for many P-type Ni-Mn based layered oxides for SIBs. In addition, a comparison of the Ni Kedge XANES of the three materials at the fully charged state (4.4 V) is shown in Figure , where it can be seen that the edge energy of the undoped material is located at a lower energy compared to both doped materials. This implies that the two dopants can enhance the Ni redox activity, which is found to be greatest in the case of Sc doping.