Virtual screening of two-dimensional selenides and transition metal doped SnSe for lithium-sulfur batteries: A first-principles study

Two-dimensional (2D) metal chalcogenides are promising sulfur host materials for lithium-sulfur (Li-S) battery owing to their abundance on earth and unique physicochemical properties. Although 2D metal sulfides have been investigated for applications in Li-S battery, selenides with higher conductivity than sulfides are scarcely studied. Herein, focusing on finding the optimal 2D selenide as sulfur host of Li-S battery, for the first time, a series of 2D selenides were screened in terms of adsorption capacity and catalytic effect on conversion reactions for lithium polysulfides (LiPSs) using first-principles approach. Among them, SnSe is the best performer with the LiPSs/S8 adsorption energies of -0.77 to -2.31 eV and lowers the free energy of overall S8 reduction reaction (SRR) by 2.31 eV. For further improving the performance of 2D SnSe, eleven transition-metal doped 2D SnSe (TM-SnSe) were constructed and show enhanced anchoring capability and catalytic effect, among which Ti-SnSe stands out with adsorption energies of -2.09 to -4.01 eV and SRR free energy decrease of 3.27 eV. The electronic and structural analyses unveil that the considerable interaction enhancement between Ti-SnSe and LiPSs/S8 comes from strong Ti-S bond and enhanced Sn-S bond. Combining with the experimentally mature synthesis of 2D SnSe and doping strategy, Ti-SnSe is of great possibility to be obtained and achieve great improvement for Li-S battery.