Briefly, the nominal valence of the cations in NMC are Ni 2+ , Co 3+ , and Mn 4+ and the aqueous stable valences of these cations are Ni 2+ , Co 2+ , and Mn 2+ . This means that releasing a Co or Mn from the (001) surface of NMC would require additional reduction steps to the 2+ state, but the release of Ni 2+ from NMC would not. Both experiment and our model agree that higher oxidation state metals, such as Mn 4+ , were more resistant to surface release. We then found that enriching NMC with Mn created a population of Mn 2+ in the solid state, to maintain charge balance, and that this was more likely to be released than Mn 4+ . The opposite was true of Ni enriched NMC; more Ni 3+ and Ni 4+ were formed in the solid state to balance charge, and were less likely to be released from the surface than Ni 2+ . The DFT + solvent ion model was able to show how adjusting the composition of the NMC delafossite structure allowed for controlled release of metals from the surface of CMOs via an analysis that coupled the thermodynamics of vacancy formations to an understanding of oxidation states and chemical environment.