Figure 4
From: Amorphous iron phosphate: potential host for various charge carrier ions
Ex situ analysis by synchrotron X-ray diffraction (SXRD) and schematic of K insertion into amorphous FePO4. The black, red and magenta lines depict the SXRD patterns recorded for the ex situ electrode samples recovered from the (a) sodium, (b) lithium and (c) potassium test cells after the initial discharge, initial charge and second discharge cycles until 1.2, 3.7 and 1.2 V, 1.6, 4.2 and 1.6 V, and 1.5, 3.5 and 1.5 V, respectively. The blue line is the SXRD pattern of the pristine ns-FePO4 powder. The humps attributed to teflonized acetylene black used in the electrode fabrication are marked for easy identification. (d) Schematic illustration of the reversible amorphous-to-crystalline transition in amorphous FePO4 that occurs during the electrochemical K insertion.
