Fig. 2. Morphological and structural characterization of the MoO_x electrode.

(A and B) SEM images of (A) the polished Mo foil and (B) SEM image of the MoO_x electrode. (C) Cross-sectional SEM images of MoO_x electrode. (D) SEM images of the contact surface between MoO_x flakes and inner Mo foil. (E and F) TEM and high-resolution TEM (HRTEM) images of the delaminated MoO_x flakes, respectively. The inset in (F) shows the corresponding selected-area electron diffraction (SAED) pattern. (G) Acquired energy-dispersive spectroscopy (EDS) elemental mapping of MoO_x flakes. (H) Raman spectrum of MoO_x electrodes. a.u., arbitrary unit. (I) Crystal structure of α-MoO₃, representing the layered structure and three types of oxygen anion. (J) ESR spectra of MoO_x and MoO₃. Inset: Digital photographs of MoO_x (left) and MoO₃ (right) powders. Photo credit: Hongwei Sheng, Lanzhou University.