Defective Phosphorene as a Promising Anchoring Material for Lithium-Sulfur Batteries

The lithium-sulfur battery, despite having considerable advantages, is still far from its practical applications, which is primarily caused by the dissolution of polysulfide clusters of lithium (LiPSs) into the electrolyte. Entrapping these LiPSs through integration of the anchoring material with the electrode is an effective approach to overcome this problem. In this study, density functional theory and ab initio molecular dynamics have been adopted to systematically examine the anchoring behaviors of two-dimensional phosphorene-based (monovacancy/oxygen-/sulfur-doped) materials, for all the intermediates of polysulfide. The defective sites provide strong adsorption for polysulfide clusters by generating firm chemical bonds together with van der Waals interactions. As a result, the intermediate discharge products could be thermodynamically stabilized on these defective substrates, against the local environment with virtually alike to initial configurations, which cannot be achieved with pristine phosphorene. Moreover, the emerging midgap states in the electronic structures of defective phosphorene and adsorptive systems improve the electrical conductivity of the defective-phosphorene-based electrode, alleviating the low rate capability related with pristine-phosphorene based batteries. It is illustrated that the anchoring ability of pristine phosphorene can be significantly improved by the defects, among which the monovacancy structure demonstrates superior performance for achieving long cycle life.