Nanoengineering of Li₂MnO₃ Domain Stabilizes Li-Rich Layered Oxides

Lithium-rich manganese-based layered oxides (LMOs) have emerged as promising cathode materials for next-generation high-energy-density lithium-ion batteries owing to their capacity derived from reversible oxygen anion redox reactions within the Li₂MnO₃ domain. However, their practical application is hindered by key challenges, including limited rate capability, progressive capacity fading, and voltage decay, primarily attributed to irreversible oxygen evolution and structural degradation during electrochemical cycling. In this work, we introduce a nanoarchitecture engineering strategy that leverages twin boundary formation to regulate the domain configuration of Li₂MnO₃ in LMO cathodes. Through comprehensive characterization─integrating atomic-resolution scanning transmission electron microscopy, synchrotron-based X-ray spectroscopy, and density functional theory calculations─we demonstrate that the engineered twin boundaries not only establish conductive networks and enhance lithium-ion diffusion but also effectively control the Li₂MnO₃ domain size distribution below 5 nm while preserving the honeycomb-type cation ordering. This synergistic modification mechanism significantly improves the reversibility of anionic redox reactions and reinforces the structural stability over prolonged cycling. Our findings offer fundamental insights into domain engineering of oxygen redox-active materials and establish a robust nanostructure design paradigm for advancing high-performance lithium-rich cathode materials.