Novel heterocyclic solvent for high-performance lithium–metal and lithium–sulfur batteries

Abstract

Lithium–sulfur (Li–S) batteries are considered promising candidates for next-generation rechargeable batteries owing to their high theoretical energy density of 2600 Wh kg⁻¹ and the natural abundance of sulfur. However, their practical viability is limited by polysulfide dissolution, parasitic side reactions at the lithium anode, and sluggish sulfur redox kinetics, all of which result in rapid capacity fading and poor cycling stability. To address these challenges, we introduce 2-methylfuran (2MeF), a novel heterocyclic solvent with intrinsically weak solvating ability, into conventional ether-based electrolytes to rationally tailor solvation structures and interfacial chemistry. Spectroscopic and computational analyses reveal that the incorporation of 2MeF decreases the fraction of solvent-separated ion pairs while promoting contact ion pairs and aggregates, thereby strengthening Li⁺–solvent interactions. Electrochemical and interfacial characterization studies demonstrate that the optimized DOL:2MeF:DME formulation facilitates the formation of a thin and uniform LiF-rich solid electrolyte interphase on the Li anode and mitigates cathode passivation, resulting in homogeneous Li deposition and more reversible sulfur redox processes. Consequently, Li–S cells exhibit improved cycling and enhanced rate capability. This study underscores the critical role of solvent design in governing solvation chemistry and electrode interfacial stability, offering new insights into the development of sustainable, high-performance Li–S batteries.