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Adsorption and Diffusion of Lithium Polysulfides over Blue Phosphorene for Li-S batteries

Abstract

Lithium-sulphur (Li-S) batteries suffer from capacity loss due to the dissolution of lithium polysulfides (LiPSs). While finding cathodes which can trap LiPSs strongly is a possible solution to suppress the “shuttle” effect, fast diffusion of lithium and LiPSs is also pivotal to prevent agglomeration. We report that monolayer blue phosphorene (BP), a recently synthesized two-dimensional material, possesses these characteristics as a cathode in Li-S batteries. Density functional theory calculations show that while the adsorption energies (Eb) of various LiPSs over pristine BP are reasonably strong (from -0.86 eV to -2.45 eV), defect engineering the lattice by introducing a single vacancy (SV) increased the binding strength significantly, with Eb in the range -1.41 eV to -4.34 eV. Molecular dynamic simulations carried out at 300 K showed that the single vacancies trap the Li atoms in the LiPSs compared to pristine BP. Projected density of states revealed that creation of an SV induces metallicity in the cathode. Furthermore, increase in the adsorption strength did not cause significant structural deformation, implying that the soluble large LiPSs did not decompose which is essential to suppress capacity fading. The energy barriers for LiPSs migration over pristine BP are minimal to ensure ultrafast diffusion, with the lowest diffusion energy barriers being 0.23 eV, 0.13 eV and 0.18 eV for Li2S4, Li2S6 and Li2S8, respectively. Furthermore, the energy barrier associated with the catalytic oxidation of Li2S over pristine and defective BP were found to be less than three times smaller than graphene, which suggests that charging processes could be faster by orders of magnitude. Therefore, BP with a suitable combination of defects would be an excellent cathode material in Li-S batteries.

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Publication details

The article was received on 14 Jun 2018, accepted on 03 Oct 2018 and first published on 09 Oct 2018


Article type: Paper
DOI: 10.1039/C8NR04868A
Citation: Nanoscale, 2018, Accepted Manuscript
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    Adsorption and Diffusion of Lithium Polysulfides over Blue Phosphorene for Li-S batteries

    S. Mukherjee, L. Kavalsky, K. Chattopadhyay and C. V. Singh, Nanoscale, 2018, Accepted Manuscript , DOI: 10.1039/C8NR04868A

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