Lithiation and Delithiation Processes in Lithium–Sulfur Batteries from Ab Initio Molecular Dynamics Simulations

Lithium–sulfur (Li–S) batteries are a promising alternative to the Li-ion technology due to their high theoretical capacity and low cost. Unlike intercalation compounds, the sulfur cathode undergoes a series of complex electrochemical reactions that give rise to substantial structural and morphological changes. Here, we report ab initio molecular dynamics simulations of the lithiation and delithiation reactions that are important in Li–S batteries. The lithiation is studied on two low-energy surfaces, (100) and (001), of sulfur (S8), whereas delithiation is studied on the (111) surface of lithium sulfide (Li2S). The effect of electrolyte is included by constructing interfacial systems between these surfaces and dimethoxyethane, a widely used liquid electrolyte. During both lithiation and delithiation, a layer-by-layer reaction pattern is revealed. The evolution of atomistic structure and reaction voltage during lithiation and delithiation is studied, and the microscopic reaction mechanisms are analyzed. D...