17 O MAS NMR spectrum and its deconvolution for charged Na 0.6 Li 0.2 Mn 0.8 O 2 (top). The data are fitted to a model with two unique O sites in a 63:37 ratio corresponding to the oxidized O ions in 2Mn coordination and the unoxidized 3Mn oxide ions (3:2 ratio), indicated by orange and green, respectively. The shift in the O-Mn spectrum on charging is due to interaction with the delocalized electrons that are located primarily on O-Mn 2 , not O-Mn 3. The calculated spin densities, (0), for the O-Mn 2 atoms in the charged material give better agreement to the NMR spectrum as HFX is decreased, tending towards a single value, indicating delocalization of the electron holes across these O-Mn 2 oxygen atoms. a 0 is the Bohr radius.
