fig2

Figure 2. (A) XRD patterns of LFO, LFO-BF, LFO-24h, and LFO-BF-24h. The characteristic reflections of degradation products and LiF are marked; (B) FTIR spectra of the four samples, highlighting the changes in LiOH- and Li₂CO₃-related bands; (C and D) SEM images of LFO before and after humid-air exposure; (E and F) SEM images of LFO-BF before and after humid-air exposure; (G) C 1s and O 1s XPS spectra of LFO, LFO-24h, LFO-BF, and LFO-BF-24h. XRD: X-ray diffraction; FTIR: Fourier-transform infrared spectroscopy; SEM: scanning electron microscopy; XPS: X-ray photoelectron spectroscopy; LFO-BF: NH₄BF₄-treated Li₅FeO₄.