fig2

Figure 2. Structural and surface chemical characterization of the HS-LFP (A) XRD patterns of the HS-LFP, S-LFP, LFP and FP, together with the corresponding PDF references; (B) TEM image of the HS-LFP catalyst; (C) HRTEM image of the HS-LFP catalyst and enlarged lattice-fringe image from the selected region, showing an interplanar spacing of 0.327 nm corresponding to the (102) plane of a FePO₄-related structure and the disordered region; (D) HAADF-STEM image of the HS-LFP catalyst, the blue dashed circle highlights representative isolated bright contrast features assigned to highly dispersed Fe-related sites; (E) High-resolution Fe 2p XPS spectrum; (F) High-resolution O 1s XPS spectrum. S-LFP: Spent LiFePO₄; LFP: LiFePO₄; XRD: X-ray diffraction; FP: FePO₄; TEM: transmission electron microscopy; HRTEM: high-resolution transmission electron microscopy; HAADF-STEM: high-angle annular dark-field scanning transmission electron microscopy; XPS: X-ray photoelectron spectroscopy.