Fig. 3: Structure determination of Li_3.3SnS_3.3Cl_0.7.

Final Rietveld fit against a SXRD data, NPD data from b Bank 4 and c Bank 5 of Polaris diffractometer with I_obs (red dots), I_calc (black line), I_obs—I_calc (blue line), and Bragg reflections (black tick marks for Li_3.3SnS_3.3Cl_0.7, pink tick marks for Li₄SnS₄ (∼4 wt% (10 mol%)). This impurity could not be detected in the NPD patterns. d ⁶Li MAS NMR spectrum. The experimental spectrum (full line), total fit (dashed line), spectral deconvolution (dotted lines) and orthorhombic Li₄SnS₄ impurity⁴¹ (pink dotted lines) are shown. e The defect stuffed wurtzite average structure of Li_3.3SnS_3.3Cl_0.7 with Li1 (orange) and Sn (purple) occupying the tetrahedral site (grey) and Li2 the octahedral site (red) along with the polyhedral environments for f Sn and Li1 and g Li2. The hcp anion sublattice is shown by the mixed S (yellow) and Cl (green) sites. The combined refinement of X-ray and neutron diffraction data, where S and Cl have different scattering lengths⁷⁰, enabled precise anion site occupancy refinement without the assumption of full site occupancy. Bulk elemental analysis of Li_3.3SnS_3.3Cl_0.7 was performed using WDX and ICP-AES analysis (Supplementary Discussion) and confirmed the assumption required for the multiple source refinement of anion occupancies that S and Cl are the only elements occupying the anion sites.