Enthalpies of formation of layered LiNixMnxCo1–2xO2 (0 ≤ x ≤ 0.5) compounds as lithium ion battery cathode materials

Layer-structured mixed transition metal oxides with the formula LiNi Mn Co (0 ≤ ≤ 0.5) are considered as important cathode materials for lithium-ion batteries. In an effort to evaluate the relative thermodynamic stabilities of individual compositions in this series, the enthalpies of formation of selected stoichiometries are determined by high temperature oxide melt drop solution calorimetry and verified by ab-initio calculations. The measured and calculated data are in good agreement with each other, and the results show that LiCoO –LiNi Mn solid solution approaches ideal behavior. By increasing , i. e. by equimolar substitution of Mn and Ni for Co , the enthalpy of formation of LiNi Mn Co from the elements becomes more exothermic, implying increased energetic stability. This conclusion is in agreement with the literature results showing improved structural stability and cycling performance of Ni/Mn-rich LiNi Mn Co compounds cycled to higher cut-off voltages.