Exploring steric and electronic effects in tailoring lithium-ion solvation using engineered ether solvents through molecular dynamics simulations

Abstract

Lithium-metal batteries, owing to their remarkable energy density, represent a promising solution for future energy storage needs. However, the widespread adoption of lithium-metal batteries has been impeded by the inherent instability that exists between lithium metal and traditional liquid lithium electrolytes, initially designed for graphite anodes in lithium-ion batteries. Recent insights underscore the efficacy of electrolyte engineering as a strategic avenue to realize the potential of lithium-metal batteries. A notable approach involves the fluorination of solvent molecules, particularly those of the ether class. Nonetheless, a comprehensive understanding of the various factors governing solvent molecular design remains elusive. Here, we examine four solvents derived from 1,2-dimethoxylethane (DME) via molecular dynamics simulation. These solvents are engineered with the introduction of additional alkyl groups or through fluorination. We particularly scrutinize two critical facets: steric effects, arising from the incorporation of bulkier alkyl chains, and electronic effects, originating from fluorination. Our inquiry delves deeply into the stability, ion transport characteristics, and solvation behavior exhibited by these five distinct solvents. Our study underscores the profound impact of adjusting the steric and electronic attributes of solvent molecules on Li+ solvation behavior. This, in turn, influences the coordination strength and the mode of association between Li+ and solvation sites within the first solvation shell, providing key insights into the disparities in ion transport properties within electrolytes.