Affiliation:
1. Department of Physics Education, Kyungpook National University, Daegu 41566, South Korea
2. The Center for High Energy Physics, Kyungpook National University, Daegu 41566, South Korea
Abstract
Cathode materials undergo various phase transitions during the charge/discharge process, and the structural transitions significantly affect the battery performance. Although phonon properties can provide a direct clue for structural stability and transitions, it has been less explored in sodium cathode materials. Here, using the first-principles calculations, we investigate phonon and electronic properties of various layered NaMnO2 materials, especially focusing on the dependency of the Jahn–Teller distortion of Mn3+. The phonon dispersion curves show that the O′3 and P′2 structures with the Jahn–Teller distortion are dynamically stable in contrast to undistorted O3 and P2 structures. The structural instability of O3 and P2 structures is directly observed from the imaginary phonon frequencies, as so-called phonon soft modes, whose corresponding displacements are from O atoms distorting along the local Mn–O bond direction in the MnO6 octahedra. This is consistent with the experimental stability and a structural transition with the Jahn–Teller distortion at the high Na concentration. The orbital-decomposed density of states presents the orbital redistribution by the Jahn–Teller distortion, such as eg-band splitting in both O′3 and P′2 system, and the stability of O′3 and P′2 is not sensitive to the electron–electron correlation. Our results demonstrate the importance of phonon analysis to further understand the structural stability and phase transitions in cathode materials.
Funder
Korea Electric Power Corporation
Korea Institute of Science and Technology Information
Subject
General Physics and Astronomy
Cited by
2 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献