fig7

Figure 7. HAADF and ABF STEM results of lithiated Nb₄W₇O₃₁ (0.8 V) confirming its Li⁺-storage sites: (A) atomic-resolution HAADF-STEM and (B) ABF-STEM images viewed along [001], (C) magnified ABF-STEM color image with inverted image contrast showing the positions of inserted Li⁺ ions (some examples are indicated by dotted circles and highlighted by white arrows). Unit cells corresponding to Structure A, Structure B, and Structure C are respectively highlighted by red, blue, and black squares in (A and C). For clarity, in (C), Nb/W and Li are shown in only one-quarter of each unit cell due to the symmetry of the P4 space group. Crystal structure models of (D) lithiated Structure A, (E) lithiated Structure B, and (F) lithiated Structure C corresponding to HAADF-STEM and ABF-STEM images.