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Figure 2. Phase programming strategies toward high energy density cathodes. (A) Schematic illustration of phase programming for high-energy-density cathode materials; (B) Scanning transmission electron microscope (STEM) image showing single-layer Li₂MnO₃ superstructures embedded in an O₂-type structure^[40]. Reprinted with permission from Ref.^[40] Copyright © 2018 Wiley; (C) STEM image of disordered rock-salt material, corresponding FFT, and intensity color maps showing the distributions of both Li-rich (green) and transition metal-rich (red) nanoregions, as well as Li-rich regions alone^[41]. Reprinted with permission from Ref.^[41] Copyright © 2023 Springer Nature; (D) X-ray Rietveld refinement of layered V₂O₃ and polyanionic host phases; (E) High-resolution transmission electron microscope image of a heterostructure between two phases^[42]. Figure D and E reprinted with permission from Ref.^[42] Copyright © 2025 Royal Society of Chemistry. FFT: Fast Fourier transform.