Fig. 5. Evaluation of the Li₂S formation via solid-state conversion.

a X-ray diffraction (XRD) pattern of solid Li mixed with solid S (in a molar ratio of 2:1) after different resting times at 25 °C ± 3 °C (red to blue solid lines). While the sharp S diffraction peaks decreased, broader Li₂S diffraction peaks evolved. The Li₂S peaks show a similar width as the Li₂S obtained from electrochemical discharge (black solid line). b The Scherrer crystallite size of the (111) peak is 7 nm for Li₂S obtained from electrochemical discharge and around 12.5 nm for Li₂S obtained by mixing solid S and Li. With increasing resting time, the Li₂S diffraction peaks grow, their width and the crystallite size remain constant. This is shown based on a Lorentzian peak fit of the form $I\left(2\theta \right)=BG+A/{\left(\left(2\theta -{2\theta }_0\right)/\sigma \right)}^2$.