Interfacial structure and electrochemical stability of electrolytes: methylene methanedisulfonate as an additive

The mechanism responsible for widening the electrochemical stability window of methylene methanedisulfonate (MMDS)-containing electrolytes compared to conventional carbonate electrolytes is suggested based on molecular dynamics (MD) simulations and density functional theory (DFT) calculations. We find that MMDS has a stronger reduction ability and higher affinity for the electrode surface than solvents, and these behaviors provide an important condition for priority decomposition of the additive. The addition of MMDS could reduce the probability of finding solvent-ion complexes at the electrolyte-electrode interface, which is especially beneficial for the stability of the solvent electrochemical window. This knowledge of the local electrolyte composition and structure at the surface plays a significant role in advancing our understanding of the relationships between interface structure and battery cycling performance, and expanding the operating windows of electrochemical devices.