Unveiling the Local Strain-Induced Structural Degradation Mechanisms in Li Excess Manganese Cathodes

With the growing demand for high-capacity rechargeable batteries, continuous advancements in cathode materials are imperative. Among the candidate materials, Li-excess Mn-rich (LMR) cathodes, known for their superior capacity compared to traditional cathodes, are gaining attention for commercialization. However, Li₂MnO₃, predominantly used in LMR cathodes, undergoes structural degradation in the voltage plateau region, and its atomic-level mechanisms have not yet been precisely elucidated. Herein, we use first-principles density functional theory calculations to investigate the process of structural change and redox mechanisms of Li₂MnO₃ induced by local strain. Our studies suggest that local intrinsic strain significantly influences changes in redox mechanisms, Mn migration, and the formation of O–O dimers. Furthermore, the process of structural collapse due to strain was further confirmed through ab initio molecular dynamics calculations. As a final step, we observed the collapse process until all of the Li ions were completely removed from the structure. Our results, considering the effects of local strain, integrate existing degradation mechanisms of Li₂MnO₃ and provide advanced understanding and new insights for its improvement.