Fig. 2: Crystal structures and lattice vibrational modes.

a Synchrotron powder XRD patterns of Li₂FeS_2-xF_x, \(x\) = 0–0.4, with \(\lambda\) = 0.61992 Å converted to the Cu_-K_α radiation of 1.5406 Å. b SAED patterns of Li₂FeS_2−xF_x for \(x\) = 0 and 0.3. c Fitted Raman spectra of Li₂FeS_2−xF_x, \(x\) = 0–0.4.