Insight into sulfur vacancy-induced insulator to metal transition of Li2S

Sulfur vacancy-induced charge carrier trap is quite important for improving the insulating characteristic of Li 2 S. In this work, we apply the first-principle calculations to investigate the influence of sulfur intrinsic vacancy and sulfur vacancy concentration on the structure and conductivity of Li 2 S. Sulfur intrinsic vacancy is dynamically stable. Importantly, sulfur vacancy reduces the band gap of Li 2 S. The calculated band gap of sulfur intrinsic vacancy is 0.700[Formula: see text]eV. We suggest that the removed sulfur atom leads to Li-2[Formula: see text] state shift from conduction band to Fermi level and improves the charge overlap between the top of valence band (VB) and the bottom of conduction band (CB). The strong charge interaction of Li pairing atoms forms the Li–Li metallic bond. Finally, we predict that sulfur vacancy gives rise to the insulator to metal transition of Li 2 S. Our works open up a new possibility for improving the conductivity of Li 2 S.