First‐Principles Insights into the Role of Coordination Polyhedron Size on Mn Ion Migration within Li_2‐<i>x</i>MnO₃ Layered Cathode Material

Li‐rich cathode materials are promising cathode materials for lithium‐ion batteries. However, the Mn ion migration in Li‐rich cathode materials during charge–discharge cycles significantly impedes their practical application. In this study, a systematical investigation has been carried out to reveal the Mn ion migration mechanisms in Li 2 ‐ x MnO 3 by using first‐principles calculations. It is found that the Mn migration energy increases with increasing Li + extraction from Li 2 MnO 3 . Conversely, the Li Mn anti‐site formation energy declines with the extraction of more Li + from Li 2 MnO 3 . The migration energy decreases under the tensile strain along the c‐ and b‐axes. Further investigations reveal that the Mn ion migration energy is determined by MnO 6 coordination polyhedron. Specifically, a larger MnO 6 coordination polyhedron volume would result in lower migration energy, highlighting the coordination polyhedron size as a pivotal factor in the suppression of Mn ion migration. This study offers an in‐depth understanding of transition metal ion migration phenomena, providing theoretical guidance for devising strategies to mitigate Mn migration in Li‐rich materials.