For Mn Li and Ni Li defects with a change in coordination (O h → T d ) at the defect site, we observe a strong preference of Mn and Ni species to adopt the lowest stable positive oxidation states (a closer charge to Li + ) for these element (i.e. Mn 2+ and Ni 2+ ) (see Table ). ) are favoured on the Li + site. In addition, the ionic radius of Mn 2+ in a four-coordination environment is 0.66 Å, which is closer to that of Li + (0.59 Å), compared to Mn 4+ (0.39 Å). 102 Literature studies 2,7,21,103 suggest the formation of Mn 2+ as a consequence of Mn 3+ disproportionation reactions. Mn 2+ are detrimental to performance as they easily dissolve in electrolytes leading to capacity fading. Li TM defects involve changing the coordination of Li (T d → O h ). We found that fully ionised Li - Ni is always the most stable charge state across all synthesis conditions at their self-consistent Fermi levels. In addition, the formation energies of Li - Ni are lower than Li Mn , indicating that Li + would preferentially form on the Ni sites over the Mn sites. Similar observations were found on Li-doped LMNO, where Li + sat in the 4b positions. This inevitably replaces some Ni 2+ , leading to reduced capacity.