For TM i , the charge compensation mechanism for non-fully-ionised states is the same as for other n-type defects where Mn 4+ in the proximity to the defect site get reduced. Having tested a range of charge states, we found Mn 3+ and Mn 2+ but no Mn 4+ species in Mn i defect supercells, whereas all Ni species always exist as Ni 2+ in Ni i defect supercells. When q = 2, interstitial Mn and Ni exist in +2 oxidation states. Adding more electrons in the systems (q = 1, 0) led to the formation of more Mn 3+ . Interstitial Ni 2+ prefers to be in the 12d sites, identical to the preference for Li i . Interstitial Mn 2+ , on the other hand, prefers to be in the 4a sites (∼ 0.05 -0.15 eV lower in energy). This could be partly due to a size effect. The 4a sites have larger octahedral volume than the 12d sites (Table ). ).