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

摘要

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+U) 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 Li0.75CoO2 and Li0.5CoO2 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.