Fig. 6: 7Li NMR spectra before and after lithiation.
a 7Li NMR spectrum recorded for the collapsed oxysulfide phase (Sample 1) and b after its electrochemical lithiation (i.e. after discharge down to 0.5 V (vs. Li/Li+) corresponding to the intercalation of 1.75 equivalents of Li; see Fig. 4d) and c after chemical lithiation (i.e. after addition of 1.5 equivalents of n-BuLi; see Supplementary Fig. 22). Each spectrum was deconvolved (black line: observed, red line: fit) into Gaussian or Lorentzian peaks and their hyperfine shifts were interpreted in terms of the Li local structure as well as the Mn2+/Mn3+ ratio. Sidebands of the peak at 0 ppm (due to diamagnetic impurities) are labelled with a asterisk (*). See Supplementary Fig. 26 for the whole spectra. d Three possible local environments around Li. Black thick lines highlight connectivity between Li and four nearby Mn2+/3+ cations. Mn2+/3+ cations are either sandwiched symmetrically by S2− anions at apexes of tetrahedra, or asymmetrically by S2− apexes and S2 dimers. In the latter case, charge transfer from S2 dimers to Mn leads to stronger Mn-S-7Li interactions.
