Two-dimensional porous transition metal organic framework materials with strongly anchoring ability as lithium-sulfur cathode

Abstract

Lithium-sulfur (Li-S) batteries are regarded as promising candidates for energy storage devices due to their high theoretical energy density. An ideal Li-S batteries cathode should effectively prevent polysulfide dissolution in order to achieve longer cycle life and higher rate performance. Herein, a new 2D transition metal organic framework material, hexaaminobenzene-based coordination polymers (HAB-CPs), has been systematically investigated as cathode candidate materials for Li-S batteries. First principles calculations combined with the vdW interaction and solvent model reveal that V-HAB-CP has the best ability to hinder the shuttle effect of lithium polysulfides among the three polymers (V, Cr and Fe-HAB-CPs). Quantum conduction (G) and density of states (DOS) calculations indicate that HAB-CPs maintain excellent conductivity during the whole charging process. Moreover, a very small volume change (about 3.06%) of V-HAB-CP before and after the electrode reaction can well deal with the volume expansion problem of Li-S batteries. Meanwhile, the energy density reaches 808.465 W h kg-1 when the electrode reaction product is Li16S8/V-HAB-CP. Attributed to these benefits, V-HAB-CP is a suitable cathode material, which is expected to be used in future Li-S battery systems. The computational method adopted in this paper can provide a guidance for considering the influence of electrolytes on the Li-S batteries in the future and be widely used in other simulation calculations involving the solution effect.