Insight into the Vibrational and Thermodynamic Properties of Layered Lithium Transition-Metal Oxides LiMO₂ (M = Co, Ni, Mn): A First-Principles Study

Evaluation of the finite-temperature thermodynamic properties of the electrode materials generally helps to accurately describe the performance of Li-ion battery (LIBs). To know the characteristics of the layered lithium transition-metal oxides LiMO₂ (M = Co, Ni, Mn) comprehensively, herein, the vibrational and related thermodynamic quantities of these electrode materials are investigated by using density functional perturbation theory (DFPT). Local density approximation (LDA) and generalized gradient approximation with the Hubbard model correction (GGA+<i>U</i>) yield similar results, either for the phonon dispersion or for the thermodynamic functions. Among the three layered lithium transition-metal oxides, the vibrational and thermodynamic properties of LiNiO₂ is more close to that of LiMnO₂, while relatively far away from that of LiCoO₂, due to the same crystal structure of LiNiO₂ and LiMnO₂, which is different from that of LiCoO₂. In addition, the corrections of average intercalation voltage as a function of temperature for Li_0.75CoO₂ and Li_0.5CoO₂ are evaluated when considering the contribution of vibrational entropy. Since our theoretical results for LiCoO₂ agree well with those from experiments, we can provide the reliable thermodynamic data for the layered lithium transition-metal oxides