Under all conditions, V Ni is a high energy defect and, as such, has very low concentrations and is unlikely to act significantly as a nucleation site for oxygen dimer formation. However, the Li Ni defect can, under lithium rich and/or nickel poor conditions, be present in a concentration of approximately 1 in 500 nickel sites (0.18%) . Previous studies have shown that lithium migration from such sites into the lithium layer is facile, so there is no reason to suspect that delithiating these sites will be kinetically inhibited . After delithiation these defects will functionally act as V Ni and induce O -formation, driving bulk oxygen dimerization as outlined above.