First-principles calculations of the solvent effects on magnesium polysulfides in magnesium-sulfur batteries

Abstract

Magnesium-sulfur (Mg-S) batteries have gained much attention in research community of rechargeable magnesium batteries (RMBs) due to the high energy density, safety, and low cost. The main challenge in the development of practical Mg-S batteries is the dissolution of intermediate magnesium polysulfides (Mg-PSs) in the electrolyte and their migration to the Mg anode, which results in the notorious shuttle effect. In this study, we combine static density functional theory (DFT) calculations and molecular dynamics (MD) simulations to explore the solvated structures of Mg-PSs with different solvents (THF, DOL and DME) and the reduction processes of solvated Mg-PSs, and the diffusion of S8 for the first time, helping to address the challenges of developing novel electrolytes for Mg-S batteries. Our results demonstrate the effect of solvents on the electrochemical reactions of S cathode in Mg-S batteries and could contribute to the advancement of efficient and high-energy Mg-S batteries.