Local Redox Reaction of High Valence Manganese in Li2MnO3-Based Lithium Battery Cathodes
Zihe Zhang, Shu Zhao, Boya Wang, Haijun Yu
Abstract
Li2MnO3 endows Li-rich layered oxides with a superior energy density; however, its electron transfer mechanism is still unclear. Here, the electronic and thermodynamic behavior of LixMnO3 (x = 0.5–2) is determined using first-principles computations. The cationic redox, anionic redox, and local electron exchange in Mn-O polyhedron are revealed. An obvious electron donation inclination of manganese is demonstrated when the Li+ content is low. Through ab initio molecular dynamics, high valence Mn6+ and Mn7+ are generated in the form of MnO4 tetrahedrons with structural transformation toward a disordered structure, controlled by the Li+ content and dynamic energy barrier. Furthermore, a local redox reaction between Mn6+ or Mn7+ and their surrounding oxygen atoms is elucidated. Consequently, a comprehensive understanding regarding the electron transfer in LixMnO3 is provided. Our results bring insight regarding the electron transfer mechanism in Li-rich layered oxide cathode materials and encourage further reconsideration and investigation into its redox mechanism.