Fig. 4: Chemical states and stoichiometry.

a–d XPS spectra for Li, Fe, S, and F for Li₂FeS_2−xF_x. e F/S, S/Fe, F/Fe ratios. f Bader charge of Li₂FeS₂ and Li₂FeS_1.7F_0.3. Red, green, yellow, and blue-balls stands for Fe, Li, S, and F atoms, respectively.