Figure 2

STEM images of a three-phase coexistence region. (a) Crystal structure of the spinel Li₄Ti₅O₁₂ viewed from the [110] crystallographic direction, showing the separated Ti and O columns. Ti1 and Ti2 columns with different atom densities are represented by balls of different sizes. (b) HAADF and (c) ABF images and (d) ABF line profile of the Li₄Ti₅O₁₂ (Li4) phase. Scale bar is 1 nm. (e) HAADF and (f) ABF images and (g) ABF line profile of the Li₇Ti₅O₁₂ (Li7) phase. Scale bar is 1 nm. (h) HAADF and (i) ABF images and (j) ABF line profile of Na₆LiTi₅O₁₂ (Na6Li) phase. Scale bar is 1 nm. (k) ABF image of the half-sodiated Li₄Ti₅O₁₂ nanoparticle. In the ABF line profile, the contrast is inverted for a convenient visualization. Scale bar is 2 nm. (l, m) Line profiles that cross the Li7/Li4 (line A) and Li7/Na6Li (line B) boundaries, respectively. Reproduced with permission.²³