Changes in structure and stability of lithium polysulfides encapsulated in carbon nanotubes: A DFT study

Abstract

• Carbon nanotubes (CNTs) can act as possible anchoring channels to immobilize soluble lithium polysulfides. • The interior of CNTs can accommodate lithium polysulfides and suppress the shuttling effect. • Electrostatic interactions between CNTs and lithium polysulfides are responsible for the stability of these complexes. • Confinement of lithium polysulfides inside CNT weakens the bonding between Li and S. • Incarceration inside CNT destabilizes the Li 2 S molecule and helps in the conversion kinetics. Lithium-sulfur (Li S) batteries are emanating as the next generation alternatives for rechargeable batteries. However, the loss of capacity and self-discharge due to the dissolution of lithium polysulfides hinders their practical applications. In this study, we performed density functional theory simulations to explore the importance of carbon nanotubes (CNTs) as possible anchoring channels to immobilize soluble lithium polysulfides (Li 2 S 2n , where n = 2,3, and 4). We quantitatively investigated the interplay between confinement effects and interaction energy of Li 2 S 2n species with CNT to address the shuttling effect. Our results demonstrate that the interaction between CNTs and lithium polysulfides is governed by electrostatic interactions. Based on the interaction energies, Charge transfer analysis, and density of states, we found that CNTs facilitate the immobilization of Li 2 S 2n . Results obtained from this study will provide useful guidelines to improve the performance of Li S batteries.