Defect engineering of black phosphorene towards an enhanced polysulfide host and catalyst for lithium-sulfur batteries: A first principles study

Abstract

Although lithium-sulfur (Li-S) batteries are widely regarded as one of the most promising next-generation high energy density storage systems, their large-scale applications are seriously impeded by rapid capacity fading and poor Coulombic efficiency owing to the shuttling of lithium polysulfides (LiPSs) and irreversible discharge product Li2S. Here, by means of first principles calculations, we studied defective black phosphorene (BP) as a host material to realize high-performance Li-S batteries, including Stone Wales [SW(55-77)], single, and double vacancy [SV(5-9) and DV(5-9-5)] defects. Our results demonstrate that while BP has moderate adsorption energies towards LiPSs, the presence of defects could enhance the adsorption strength between LiPSs and BP because of increased charge transfer. Particularly, defective BP could strike a good balance between adsorption energy and integrity of LiPSs, which is beneficial to prevent the shuttling of LiPSs. Moreover, during the lithiation process, defective BP not only has narrow bandgaps but also decreases the dissociation energy of Li2S, facilitating the catalytic oxidation of Li2S back to sulfur. Therefore, it is highly desirable to fabricate defective BP to improve the reversible capacity and cycle stability of Li-S batteries.

First-Principles Investigation of the Anchoring Behavior of Pristine and Defect-Engineered Tungsten Disulfide for Lithium–Sulfur Batteries

“…The trend in the increase of the shortest distance with the decrease in the S concentration in LiPSs is correlated with the corresponding binding energies (see Figure ). Similar characteristic changes in bond lengths are also observed in other AMs. ,, Additionally, we analyze intramolecular Li–S bond lengths in LiPSs before and after adsorption and the data are included in Table . We found that the adsorption of the LiPSs on WS 2 causes an increase in the intramolecular Li–S bond length and this increase manifests stronger interactions of LiPSs with WS 2 .…”

“…The structural deformation of the adsorbed LiPS species is apparent, whereas WS 2 retains the structural integrity. The Li atoms in LiPSs remain close to the surface similar to graphene, MoS 2 , TiS 2 , blue phosphorene, Ti 3 C 2 S 2 , and black phosphorene but is in contrast to that seen in the borophene where S atoms remain closer to AMs. The feature of the stereo configurations of the adsorbed LiPSs can be attributed to differences in the net electronegativity values between the AM and the S in the LiPSs.…”

“…We consider a surface concentration of 4% for vacancy and O-substitution. Various defects in the context of polysulfide adsorption on AMs such as graphene, ,, silicene, black phosphorene, blue phosphorene, and MoS 2 have exhibited promising performances. We create the monovacancy defect by removing one sulfur atom, covalently bonded with three W atoms, from the surface, and denote as MV–WS 2 .…”

“…This either type of defects along with antisite, ad-atom, and grain boundaries is commonly observed in 2D materials, which can tune the electronic states of the materials. − For example, sulfur vacancy in MoS 2 results in an increased electron localization and n-type doping because of its electron-rich donor states in the band gap . The vacancies narrow the band gap by introducing midgap states and promote charge transfer between the surface and adsorbate molecules in favor of stronger binding . The substitutional defects introduce additional electronic states that can effectively augment the LiPSs’ adsorption behavior.…”

Two-Dimensional Materials to Address the Lithium Battery Challenges

“…Incorporating defective 2D materials into sulfur cathodes can prevent the polysulfides from disintegrating and have been widely investigated. − Experimental studies and density functional theory (DFT) calculations showed that the defect sites on 2D materials such as nitrogen-doping could prevent Li 2 S n diffusion and dissolution by introducing a strong synergistic effect on their adsorption. − Following the effect of structural defects in Li–S batteries, Liu et al . performed a study on a composite of sulfur with three-dimensional porous graphene aerogel (GA) decorated with defect-rich MoS 2 nanosheets.…”