where ∆H f (LiMn 1.5 Ni 0.5 O 4 ) is the formation enthalpy of LMNO. The potential formation of Li-Mn-Ni-O competing phases imposes thermodynamic constraints on µ i , namely that the stoichiometric sum of µ i of a competing phase must not be higher than its formation energy. For example, to avoid the formation of NiO would require