Accurate Binding Energies for Lithium Polysulfides and Assessment of Density Functionals for Lithium–Sulfur Battery Research

Abstract

Lithium–sulfur batteries have high theoretical energy density, but a better knowledge of their intimate structural details will be helpful in improving their conductivity and long-term cycling behavior. In order to identify the stationary configurations of lithium polysulfides (Li2S n , 2 ≤ n ≤ 8) formed in the charging and discharging processes of the lithium–sulfur batteries, ab initio molecular dynamics was employed to sample the configuration space of Li2S n , followed by optimization of structures by CCSD­(T)-F12b/aug-cc-pVDZ. Using the optimized stationary points, we have created the LiSAE38 benchmark database of atomization energies (AEs) of 38 lithium polysulfide isomers by using the higher-level WMS and W3X-L methods. In addition, the performances of 39 density functionals have been assessed against the benchmark AEs and the relative stabilities of Li2S n isomers. On the basis of the assessments with the def2-QZVP basis set, the PW6B95, B97-1, B3LYP-D3, TPSS, and DSD-PBEP86 density functionals are the most accurate for the AEs, whereas the mPW2-PLYP-D, DSD-PBEP86, PW6B95, HSE06, and PBEQIDH functionals are most accurate for the relative energies. Local functionals are of special interest because of their lower cost (faster timings in terms of computer resources) for large systems; among the tested local functionals, MN15-L and revM06-L are the most accurate for the calculations of relative stabilities.

Conductive metal‐organic frameworks: Recent advances in electrochemical energy‐related applications and perspectives

“…It mainly works based on reversible redox reactions between metallic lithium and sulfur with several intermediate products of lithium polysulfides (LiPSs; Li 2 S n , 2 < n ≤ 8) 94 . In general, the polar organic solvents are introduced as electrolytes to dissolve insulating lithium polymer to improve the sulfur utilization and rate capacity 94 . Conductive MOFs can be utilized as the sulfur hosts and conductive framework in LSBs, benefiting from its good conductivity, structural diversity, and high adsorption site density.…”

“…As another alternative technology, LSBs have attracted enormous attention owing to its low cost, the high theoretical capacity of approximately 1675 mAh/g and energy density of approximately 2600 Wh/kg 93 . It mainly works based on reversible redox reactions between metallic lithium and sulfur with several intermediate products of lithium polysulfides (LiPSs; Li 2 S n , 2 < n ≤ 8) 94 . In general, the polar organic solvents are introduced as electrolytes to dissolve insulating lithium polymer to improve the sulfur utilization and rate capacity 94 .…”

“…94 In general, the polar organic solvents are introduced as electrolytes to dissolve insulating lithium polymer to improve the sulfur utilization and rate capacity. 94 Conductive MOFs can be utilized as the sulfur hosts and conductive framework in Copyright 2019, Nature Publishing Group. 91 C, Schematic of a ZBCP-coated separator and the charge repulsion operation of the ZBCP layer.…”

Multi‐coefficients correlation methods

“…132 Recently WMS has been employed to investigate the energetics in lithium polysulfides (Li 2 S n , 2 ≤ n ≤ 8), which are the important intermediates formed in the operational cycles of the lithium-sulfur batteries. 133 Based on the WMS calculations, the LiSAE38 benchmark database has been developed for AEs in 38 lithium polysulfide isomers, and the new database has been employed to assess the accuracy of 39 density functionals. More recently, WMS has been applied to investigate the mechanism of CO 2 reduction reaction on a new silicon hydride based catalyst.…”

“…Furthermore, WMS has been shown to be accurate for the predictions of the barrier heights in the DBH24‐W4 database and the energetics of the strongly correlated cases involving the reactions of the Criegee intermediates with water . Recently WMS has been employed to investigate the energetics in lithium polysulfides (Li 2 S n , 2 ≤ n ≤ 8), which are the important intermediates formed in the operational cycles of the lithium–sulfur batteries . Based on the WMS calculations, the LiSAE38 benchmark database has been developed for AEs in 38 lithium polysulfide isomers, and the new database has been employed to assess the accuracy of 39 density functionals.…”