Metalization of Li2S particle surfaces in Li–S batteries

Abstract

The Li–S battery is the most promising candidate for future electric vehicles. The study of stabilities and conductivities of Li₂S nanoparticles, which are used as pre-lithiated cathode materials, is crucial for the development of Li–S batteries. Here, we investigate the atomic and electronic structures as well as stabilities of Li₂S surfaces and nanoparticles using density functional theory (DFT) and classical electrostatic models. We show that Li₂S nanoparticles have octahedral shape and consist of only (111) facets. At low concentrations of Li, the surfaces of nanoparticles are metalized non-polar Li₂S(111) surfaces. The metalization is found to be due to the depletion of valence bands of surface states. However, for higher concentrations of Li, the nanoparticle faces are insulator non-polar Li₂S(111) surfaces. This study suggests that Li₂S nanoparticles with (111) surfaces are very promising cathode materials for Li–S batteries.